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Robot MIG Weld Problems






www.weldreality.com

Written by Ed Craig.
ecraig@weldreality.com

Robot Weld Solutions and Weld Tips.


If you are a robot programmer, it helps in a confused
industry to have a sense of humour,

 




FOR FOUR DECADES, THE LACK OF INDUSTRIAL ARGON MIG GAS MIXES AND LACK OF MIG WELD PROCESS CONTROL EXPERTISE, WAS THE REASONS WHY THE JAPANESE MADE TERRIBLE MIG WELDS AND THEN MADE TERRIBLE MIG EQUIPMENT:

Japan is a country that has had few industrial gas plants. Argon MIG gas mixes in Japan have een a rarity and when available were and still are very costly. For decades Japan utilized mostly straight CO2 gas for it's MIG welds and the result was globular, erratic weld transfer that should have made any QA weld personnel cringe.

In the last four decades, North America played sales games with it's MIG gas mixes and occasionally produced gas mixes that actually helped optimize MIG welds. In contrast, during 1950 - 1990, Japan had minimal experience with attaining optimum quality MIG Spray Transfer welds and these welds were the most widely utilized welds made in manufacturing plants in North America and Europe.

Few Japanese auto plants had been able to produce optimum manual or automated quality MIG welds and we in the North American weld business saw the results of this when the Japanese delivered their robots and weld equipment to North American auto plants in the 1990s, It's important for weld personnel to keep in mind that if you used Japanese MIG equipment in the last two decades you were using equipment that typically was inferior to Miller / Lincoln / ESAB. Today in 2010 the Japanese MIG equipment is better than the earlier units, and with pulsed MIG equipment the cost effective Asian built OTC Daihen equipment is superior to
most North American pulsed MIG equipment.

Please note. The Pulsed MIG process is not required for most steel welds. Optimum MIG manual or automated weld quality and productivity for the majority of steel welds is attained with much lower cost, more durable, easier to use and maintain MIG equipment using the traditional short circuit and spray transfer modes, and it does not matter if that MIG equipment utilized was purchased in 1960 or 2010.

The global lack of weld process cobtrol expertise has always effected MIG weld equipment selection and also the weld process logic that has been presented in automated MIG weld equipment software. When it comes to evaluating robot MIG weld software, Japanese and North American
weld logic were rarely similar.

 



 

ROBOTS AND WELD EQUIPMENT PURCHASE CONSIDERATIONS:



BEFORE YOU PURCHASE THAT ROBOT.... Those small to medium weld volume shops that are looking to purchase and introduce robots to MIG weld their steel and stainless applications, should give consideration to the following;


[] When you examine each robot manufacture's product don't get caught up with the robot bells and whistles and fancy electronic pulsed MIG power source with it's glossy page weld benefits and ridiculous 1 billion wave forms. Today in 2013 I see no real world weld benefits from the pulsed MIG process for most steel and alloy steel welds,

[] When an integrator or a company that makes robots advises your organization to use pulsed MIG for a steel or alloy steel application, remember pulsed MIG is typically not necessary, and the pulsed mode in contrast to the traditional spay transfer mode from much lower cost MIG equipment developed and in use since the 1950s, will produce inferior weld fusion and inferior arc stability.

[] The complex electronics required in the pulsed MIG equipment offer minimal weld quality - productivity benefits but these electronics will be a costly concern for both your purchasing and maintenance departments.

[] Pulsed MIG will rarely achieve the weld deposition rate potential (weld speeds) that can be attained by the MIG spray mode

[] In comparing robots from different robot manufacturers, examine the simplicity and length of time required to both program a common part and especially the time required to make weld changes to different welds. Typically Japanese robots have been much slower to program than Swedish, more logical ABB robots and if you are not a believer let ABB show you..

[] In comparing robots, examine the ease in which the MIG wire feed, voltage or pulsed parameter changes are made and how these important parameter are viewed and monitored.

[] In comparing robots, examine the logic layout of the welding program soft ware as this feature can be both frustrating and time consuming.

[] Examine the calibration accuracy between the robot pendant and power source weld data, Note most are not calibrated correctly.

[] In comparing robots, examine the robot's automated TCP capability and repeatability.

[] Examine the ease or complexity of making touch sense and through the arc robot tracking changes. Also carefully examine how effective and consistent these valuable features are.

[] Examine the accuracy and repeatability of the robot with the positioner utilized.

[] Examine the complexity of programming the robot to work with secondary equipment such as the positioner and torch cleaning stations.


[] Examine the robot instruction literature, the technical support, the training available and service capability. Most important, figure out during your initial discussions with the integrator or robot company, who's' supplying the most bovine faecal matter.

[] For those low to moderate volume, difficult to weld parts with a few small welds, it's important to always remember, that a blind robot with limited dexterity can never produce the weld productivity or quality that a manual welder can produce.

[] Never purchase a robot without a guarantee in the purchase contract that stipulates the robot will produce four hours worth of weld production meeting the production quantity requirements with no down time and no more than 2% weld rework.


Assume no one in the weld shop is an expert on robot best weld practices and robot weld process controls, and then think of the insanity in spending all that money on the costly robot - weld equipment, and yet your organization has not considered spending a few dollars on the weld process control training that can optimize the robot weld quality and productivity..



 

 

Don't look to the auto - truck industries to lead the way
with robot good weld practices and process controls.



ADVICE ON AN AUTOMOTIVE, ROBOT TIG APPLICATION:


This weld report deals with the robot TIG auto welding issues. The parts required approx. 15 precise small tack welds. The tacked parts were later brazed, The TIG welds were made with a Fanuc Arc Mate 100 robot, and a Lincoln 350 amp "pulsed" square wave power source.

The welding issues at this tier one part supplier were extensive. For more than a year they had struggled to attain a production rate of only 40% of what they desired. The tack welds were frequently missing, arc starts issues were extensive, and the tack weld locations would leak. After I rectified the problem, I wrote the following report to the plant management.
By the way if you want to automate TIG welds and you have not been to www.tiptigusa.com, you are missing a great process.





THE ROBOT YOU MAY BE CONSIDERING TO PURCHASE MAY WORK WELL IN AN AUTO PLANT WHERE WHERE THEY RARELY CHANGE THE WELD PROGRAMS, AND THE DAILY POOR INCONSISTENT ROBOT WELD QUALITY AND PRODUCTIVITY IS ADDRESSED BY ROBOT PERSONNEL WHO WILL PLAY AROUND WITH THE WELD DATA, OR FROM ADDING MANUAL WORKERS TO THE END OF THE ROBOT LINE TO FIX THE EXTENSIVE WELD REWORK. HOWEVER THIESE SAME ROBOT MAY NOT MAKE THE GRADE IN A WELD JOB SHOP THAT'S SERIOUS ABOUT WELD QUALITY CONSISTENCY, WELD REPEATABILITY, EASY
AND FAST ROBOT PROGRAMMING CAPABILITY.

IF YOU WANT A GREAT COMPARISON OF CONFUSION VERSUS ROBOT WELD LOGIC, COMPARE THE SOFTWARE = HARDWARE DIFFERENCES BETWEEN A JAPANESE PANASONIC OR MOTOMAN ROBOT, AND THE MORE LOGICAL SWEDISH SOFTWARE - HARDWARE USED IN ABB ROBOTS.

BY THE WAY, ON APPLICATIONS WITH A LARGE AMOUNT OF WELDS, I BELIEVE THAT IN CONTRAST TO JAPANESE ROBOTS THAT IT
CAN TAKE 30 TO 50% LESS TIME TO PROGRAM THOSE WELDS WITH AN ABB ROBOT.

TO REVIEW THE IMPORTANT ABOVE JOB SHOP CONSIDERATIONS, SIMPLY SEND YOUR PARTS TO COMPANIES THAT SUPPLY THE ROBOTS AND LET THEM GIVE YOU THE PROGRAMMING AND WELD RESULTS IN A VIDEO.

.




With robot welds, the quality & productivity opportunities are only
limited by a manager's - engineer's process control knowledge.





ROBOTS AND WELD ISSUES




YOUR COMPANY PURCHASED A $100,000 ROBOT CELL, AND YET NONE OF YOUR EMPLOYEES
HAD ROBOT MIG WELD BEST PRACTICES & PROCESS CONTROL EXPERTISE, COSTING $500.



ANY OF THE FOLLOWING 15 REASONS WOULD INDICATE THAT A COMPANY
LACKS MIG WELD PROCESS CONTROLS AND BEST PRACTICES EXPERTISE.

[1] If you have robot weld rework is more than 2% of your parts.

[2] If your robot cells have a ROBOT DOWNTIME per shift, of more than 15 minutes per-robot.

[3] If you use gas shielded Flux Cored wires for welding clean carbon steels < 3/8 in the flat and
horizontal welding positions.

[4] If you utilize any three part gas mixes for MIG welding carbon steels or thin gage stainless.

[5] If you utilize Metal Cored wires
for MIG welding carbon steels or for thin gage stainless.

[6] If you weld carbon steels and you use any MIG gas mixes containing oxygen.

[7] If you purchase your primary weld supplies from more than one supplier.

[8] If your purchasing manager is involved in the selection of your weld consumables.

[9] If the person who has full responsibility for the robot welds works in the maintenance department.

[10] If your company allows robot operators or anyone other than the programmer to make welding parameter changes to the robot program.

[11] If the changes made to the robot welds are not immediately verified through macro samples,

[12] If there is no pre-weld qualification, weld parameter and weld manufacturing instructions posted
on the walls of the robot cells.

[13] If there is no method to verify the weld amps - volts - WF for each weld with that recommended on the weld map charts that are supposed to be posted on the out side of the robot cell for easy verification,

[14] If your manual welders doing the repairs or simply manual welds daily use a whipping, skipping or weave actions with their MIG guns.


[15] If you use pulsed MIG and don't understand the implications of each pulsed parameter adjustment.

ALL OF THE ABOVE ARE COVERED IN MY TRAINING PROGRAMS....





THE AUTOMOTIVE ROBOT TIG APPLICATION:
This weld report deals with robot TIG welding issues that were occurring on one of the big three cars. The parts required approx. 15 precise small welds and the the parts weld seams were later |brazed. The TIG welds were made with a Fanuc Arc Mate 100 robot, and a Lincoln 350 amp "pulsed" square wave power source. The weld issues at this tier one part supplier were extensive. For more than a year they had struggled to attain a production rate of only 40% of what they desired. The tack welds were frequently missing. Arc starts issues were extensive, and the tack welds would leak. After I rectified the problem, I wrote the following report.

If you want the highest weld quality attainable TIG manual or robot welds and you are not using TIP TIG, you are not using the correct process. Check out tip tig at www.tiptigusa.com.







"Robots and Programmer Weld Process Control Expertise".



A question from an HR manager at a manufacturing facility that utilizes MIG welding robots

Ed. What type of "MIG Weld Process Control Expertise" should we expect when we hire a new a robot programmer
who will be in charge of our MIG welding robots?

Answer. Your anticipations in 2013 to hire a person with robot weld process control - best practices expertise should be low as less than 1 in 10 persons who program MIG robots will have the necessary expertise.

[] It would be beneficial if the robot programmer was able to do the following. Lets say the weld application is a Robot MIG welded common, carbon steel, automotive part. The parts welded are 2 to 2.5 mm thick with gaps up to 1.5 mm. Most of the welds are fillet welds. The programmer is informed that the last time your company welded similar parts, weld burn-through issues were prevalent. With this in mind the programmer should know without "playing around" where to instantly set all the optimum robot weld parameters, wire feed, amps, volts travel speeds and be able to provide the best practice solutions necessary to rectify the weld issues. The programmer should be able to justify and explain the benefits of the weld transfer mode, weld gas and weld wire size selected and the programmer should be able to train the cell operators to recognize arc sounds that indicate weld faults.

A robot programmer should have the capability without playing around and without"reference to a weld text book"
to instantly;

[] Provide the most logical weld process and mode of weld transfer, short circuit, spray or pulsed and be aware of the optimum complete parameter working ranges for the wire size utilized.

[] Provide if using pulsed, expertise on the wide variety of pulsed parameter adjustments.

[] Provide the maximum robot weld travel speeds for each weld.

[] Provide weld voltages for each weld that will minimize weld spatter.

[] Be aware of how to minimize the effects of the weld heat on the part and how to prevent weld burn through.

[] Provide the optimum robot weld start / stop data.

[] Be aware of the robot MIG gun technique which can effect the arcs and welds.

[] Provide weld data that compensates for gaps or part alignment discrepancies.

[] Provide weld data that ensures consistent weld fusion.

[] Be aware of the weld deposition rates that can be attained and their influence on robot weld travel rates and the weld cost,

[] Be able to educate the fixture manufacturers and designers of welded parts on how to design for good weld ability


[]
Be able to answer my MIG weld questions.


A SMALL PRICE FOR KNOWLEGE: To train your robot personnel with all of the above data will cost your organization approx. $400 and you will find it my manual or robot process control training resources.

 


     

     

    Can you Relate to the Following?

Robot parts with unacceptable "weld gaps". Thanks to manufacturing managers and engineers that don't know how to do their job, weld gaps are the number one problem for "robot" MIG welds. Management and designer and engineers frequently forget that manual MIG welders can use "adjustable skills" to compensate for weld gap variations. With robot welds, it takes sophisticated programming, and sometimes complex joint sensing controls to provide solutions to weld gaps.

It's a fact that in most automotive - truck plants, that too many weld part dimension tolerances are not in accordance with the part design. The acceptable dimensional weld gap tolerances for optimum, gage MIG robot welds would typically 0.060m (1.6mm). This dimension is acceptable even for thin gage metals up to 0.060. For parts less < 0.060, the weld gaps should be no larger than the gage thickness. For fillet welds on parts > 3/16, there should be no reason that the gaps should be no more than 0.020. What's ironic, is the dimensional weld gap tolerance are rarely known by the designers or manufacturing managers.






    To compensate for the common oversize weld gaps on the thin parts, the automotive manual welder who rarely touches their power source controls, develops "reactive welding skills." The welder can increase the welding wire stick-out to compensate with a weld current reduction. In contrast the robot can use these practices or utilize weld weaves or different weld schedules to compensate for the gaps. This subject covered here.


     



You will frequently see "long MIG wire stick outs over one inch" ( > 25 mm) used in automotive - truck part plants.
Welders working with thin exhaust parts with excess gaps will often use a long MIG wire stick out of one to three inches (25 to 75 mm). The reality is that any company that allows manual MIG welders to weld with more than >25 mm wire stick out, is a company waiting to be sued for poor weld quality. When welding with long wire stick outs, the weld integrity is no longer an issue as the welds will have more in common with poorly placed chewing gum.

The practical solution to welding gaps. Place a little focus on providing training for manufacturing engineers and supervisors so they can build the stamped welded parts in accordance with the part design dimension tolerances.





Poor designed oversize weld slots as shown in this car seat, cause robot weld and part strength issues. I have yet to meet a designer of auto - truck parts that understood the requirements for optimum robots MIG welds.

 

For those designers, engineers, managers, technicians or supervisors who
have an interest in MIG weld process control knowledge and requirements,
I recommend they take a look at my MIG self teaching and training resources.




THE WELD PROCESS EXPERTISE NECESSARY TO ESTABLISH ROBOT WELD BEST PRACTICES - PROCESS CONTROLS, IS FOUND IN MY ENGLISH AND SPANISH MIG SELF TEACHING AND TRAINING RESOURCES.

Note the poor design dimensions of the above car seat slot welds. The slots required for the lap weld are too wide and the short erratic weld length is only attached to one side of the slot. Any slot wider than 4 mm on gauge parts will reduce weld productivity (larger welds = slower weld speed), increase weld burn through potential and reduce the weld strength. Design such as above are an indication that the designer of these parts did not understand the MIG process.

Note with robot weld lengths less that 18 mm, its difficult to define the weld quality attained as the robot in a very short period has to communicate three sets of weld data, start - weld - stop, these welds require that the programmer have good weld process control - best practice knowledge..

PROCESS CHOICES FOR SHORT WELDS: To optimize short weld lengths, or avoid weld burn through on common 1.6 to 2.5 mm gauge parts and optimize the robot weld productivity, you could could utilize high short circuit parameters, moderate pulsed parameters or low spray transfer parameters. If as a weld programmer you look at the above common part, and you don't know the optimum weld parameters for each of the weld transfer modes mentioned, it's time to examine your value to your organization.


 






For decades, the USA had a short supply of good robot welding fixture builders.

How many robot fixtures have you seen which do not allow optimum MIG gun access or optimum MIG gun angles?

How many fixtures have you seen that have clamps that don't hold the parts with sufficient rigidity, or the clamps are too difficult to open?

How many fixtures have you seen that are sensitive to weld spatter and need rework after being in operation for a few days?

How many fixtures have numerous manual operated clamps when a simple pneumatic control would open all?

For thin gage welds, you could reduce those weld burn through issues, if the fixture designer would think "heat sink" and add highly conductive alloys to the clamps and fixture in the weld vicinity. Weld part designers should communicate with fixture designers and both these individuals should communicate with the robot programmer.



    A common management influenced issue in many manufacturing plants that have purchased MIG robots is "ineffective communication between all the parties involved in the robot weld projects"




Other issues that can effect robot welds.

Incorrect size MIG wires utilized.
In too many instances
, welders and robots are using MIG wire diameters which are too large and require too high weld current for the part thickness, weld joint or weld gaps. This is a common problem in automotive plants, and the bottom line it's a reflection of the lack of weld process expertise from the managers and engineers that made the consumable selections.

Incorrect robot weld data selected.
The robot weld data is frequently selected by intergrators and robot programming individuals who lack in-depth MIG weld process control expertise. The weld data while sufficient to get the robot up and running rarely provides optimum quality or productivity.

Unnecessary equipment bells and whistles in the robot cells,
In 2013, the majority of MIG welding robot cells are using unecessary, sophisticated electronic pulsed MIG power sources
l. This equipment is typically recommended by salesmen and purchased by people who believe in salesmen. Less than two percent of MIG welds will require expensive and complex pulsed welding equipment. The prime reason this unnecessary welding equipment is purchased, the purchaser is frequently over optimistic that more costly the weld equipment will compensate for a plants general lack of manufacturing controls and MIG process expertise.


Innapropriate weld responsibility:
It's too easy in the auto industry to find management that places the responsibility for the robots and weld process controls with mechanical or electrical engineers, These are engineers who typically have never struck a MIG arc and lack weld process control expertise. If the individual responsible cannot operate a process and equipment at it's highest efficiency potential, then they should not manage it till they receive adequate training.

The same management will not think twice about allowing the maintenance electricians and millrights to make weld process changes which negatively effect the weld quality or productivity. This is a plant which is ignorant to the product liability consequences of inconsistent weld quality. Maintenance should be in on Saturday and Sunday doing preventive PM. They should not be allowed to make any "unqualified inexperienced process changes" which can negatively affect the so called pre-qualified weld data. If maintenance have to make changes, the management solution is simple, ensure these individuals have effective MIG best practices - process control training.





Panasonic Robot Concerns.


FOR SIX WEEKS, THE PANASONIC ROBOT TEAM COULD NOT GET
THE PANASONIC ROBOTS TO PRODUCE TWO SIMPLE EXHAUST WELDS.

 



For me, it was another one of those annoying Japanese, Panasonic robot applications. Thanks to the Panasonic engineers, and their obvious lack of understanding simple weld application requirements, we had another simple weld application made complex for the robot end user.

After six weeks, the Panasonic engineers and Panasonic robot integrator could not get their robot to consistently place two small controlled welds, 15 mm in length. The welds were made on a carbon steel rod to a thin gage galvanealed part exhaust bracket. The exhaust hanger bracket was poorly designed by engineers at Honda however was weldable. The Panasonic robot personnel had given up on the project and left the plant and the part supplier had five days left before production was supposed begin. For the rest of the story click here.





HOW FAST OR HOW SLOW SHOULD THAT WELDING ROBOT GO?

Most robots for two decades have been under utilized, and from a weld speed perpective they rarely weld at their weld speed potential. In contrast many other robots are welding at speed which are too fast producing welds with innsufficient weld fusion.

The robot weld speeds can be influenced by;
[a] the wire size or gas selected,
[b] the shape of the part, the part thickness, or the part surface,

[c] the parameters or weld mode selected are not optimum,
[d] using pulsed when they should be using spray.
[e] using short circuit or globular, when they should be using pulsed or spray,
[f] perhaps its the fixture design, the part design, the joint type, part thickness or ridiculous gaps,
[g] maybe the weld size could be reduced.


In my MIG and Flux Cored Weld Process Control self teaching - training resources you will find all the information required for optimum robot weld speeds for all your applications. In my management book I provide unique research infomation that i carried out, that allows robot weld speeds in the 40 - 80 inch/min range.




I had to deal with numerous Motoman Robot Weld issues.

The following is an E mail sent to me March 2001. At the persons request, I have deleted his and his companies names.

Ed, we are on our 4th generation of Motoman robots, and I didn't think they could get any worse, however I was wrong.

I simply would not recommend the new UP/XRC Motoman robots to anyone. We have had nothing but problems with them.


Motoman has a real problem with the encoders in their motors, and we have replaced everyone at least once. In addition, I have a servo pack or motor go out on an average of once per week. They are also having wire harness problems with the insulation prematurely wearing out. I have had to replace four so far, and we have only been running since August. We have also had to replace 13 boards in the main processor. They are saying that the Panasonic power sources are creating noise in the unit and taking out the boards, but we are not really buying it and neither is Panasonic. Now, let's compare this to our Canadian facility which uses mostly Fanuc on the same lines designed to produce the same product. I spoke with their technical manager last week and he has not had any warranty claims since startup. If you total up what would have been my repair expense, if the robots were not under warranty, I would have spent in excess of $175,000.00.

2003. Motoman also produced a sad excuse for a weld power source to be used with it's robots.

Notes from Ed: From 1985 to at least 2000, the majority of the global pulsed MIG equipment produced did not have the electronics necessary to provide controlled pulsed MIG transfer and with common steel and alloy steel welds this equipment often caused more weld quality = productivity - down time issues than it resolved. Unfortunately the weld equipment manufacturers forgot to tell the welding industry this simple fact. For more info evidence link here.

If you company used Motoman robots, it's unfortunate that you may have purchased the MotoArc 350 MIG weld equipment. If you were welding thin gauge steel parts with this power source and you wanted poor to mediocre, inconsistent, globular type short circuit welds, you purchased the right equipment.





A nightmare MIG power source.

If you wanted to produce poor to mediocre, inconsistent, globular type
short circuit welds, purchase the above Motoman MIG power souce.



MORE MOTOMAN ISSUES. REMEMBER AN IMPORTANT TOOL IN THE ROBOT CELL IS THE MIG POWER SOURCE, AND NOT ALL THE MIG POWER SOURCES WERE CREATED EQUAL:

At two separate plant locations during 2003, I had issues with the Motoman weld equipment. In Aug. 2003 it was my unfortunate task to optimize a large welding cell that utilized Moto Man UP6 robots with the MotoArc 350 welding equipment. I had no issue with the robots except the poor TCP controls and the length of time required with programming. I did witness and identify poor power source response time and erratic welds from the 350 MIG equipment. The root cause of the weld problems were generated from the new Motoman 350 weld equipment. In one robot cell the 350 unit was was so erratic it had to be replaced. With the other cell the 350 unit provided poor arc starting characteristics, inconsistent, erratic weld transfer and the required weld voltage range was excessive resulting in globular type transfer instead of controlled short circuit .


Later in 2003 I was asked by one tier one auto supplier of thin parts to help them resolve their numerous robot weld issues. The parts being welded were carbon steels, 0.045 (1.2 mm) thick. The weld wire was 0.035 (1 mm). The weld mode selected was short circuit. I noted again with the MotoArc 350 MIG equipment that at the required low wire feed short circuit wire feed settings, that the minimum stable weld voltage required from this equipment was 1.5 to 3 volts higher than that required from CV MIG equipment with more suited Volt - Amp Slope Curves. The required, higher weld volts from the Japanese MIG equipment caused in low to medium weld current applications, (gauge welds), erratic spatter producing, globular transfer. Also the additional required voltage provided higher weld energy which added to the "weld burn through potential on parts 1 to 2.5 mm.

Please Note: In the land of the rising sun, the relationship between MIG equipment optimum slope curves and weld transfer modes and argon mixes was not well understood in 2003 and I doubt that in 2013 that most Asian MIG equipment companies have yet to figure out how to design an optimum MIG power source.

Question: Ed we are using a Motoman robot with the MotoArc 350. We are welding 1 to 2.5 mm carbon steel parts, and 1.2 mm is the most common. We use argon with 5% oxygen and the short circuit with an 0.035 wire. Some of the welds are subject to weld burn through and we need to use weld settings around 100 amps with 13 volts. We don't like the short circuit weld performance from the Motoman power source at 100 amps with this equipment and when we set the MotoArc equipment at the 0.035 pulsed mode the weld performance is not optimum any suggestions.

Answer: With this MotoArc welding equipment, use the 0.035 (1mm) wire but change the setting on the pulsed control panel to the"0.030 pulsed steel setting" and you will get reasonable pulsed weld results in this parameter range. By the way this was a logical short circuit application but then you would have needed a decent power source to get short circuit with minimum weld spatter. Regards Ed.

 

 

 

 

If you paid for pulsed MIG equipment, this is likely what you got.

Erratic Volt - Amp performance with optimum weld settings.


FEW WELD SHOPS RECOGNIZED THAT FROM THE 1980s TO 2000, THE ELECTRONICS IN THE PULSED EQUIPMENT COULD NOT MEET THE DEMANDS TO CREATE CONSISTENT, STABLE PULSED WELD TRANSFER.




IF MANAGEMENT DOES NOT TAKE RESPONSIBILITY AND OWNERSHIP OF THEIR ROBOTS AND WELD EQUIPMENT, THEY SHOULD EXPECT WELD QUALITY - PRODUCTIVITY ISSUES.

Your company purchased a costly robot cell, yet because those that managed the robot purchase did not stipulate the correct questions on the PO, the robot integrator did not apply the appropriate tests to prove that the robot could consistently produce, optimum weld quality - productivity. Or perhaps your company did stipulate the correct questions on the PO and the robot integrator was simply incapable of the task.

From lack of essential calibration issues, to poor arc command response times and erratic poor performing MIG weld transfer modes, for more than two decades the major robot manufacturers like Motoman - Panasonic - Fanuc - Cloos and ABB selected MIG welding equipment that was the root cause of many of the global robot weld quality and productivity issues that were common throughout the weld industry. However the good news for the robot and weld equipment manufacturers, was thanks to the general customer MIG weld process ignorance which was especially common in auto - truck plants, few company managers using the poor performing weld equipment recognized the real root causes of many of their weld issues. Therefore few managers or company owners took legal actions against the robot and weld equipment suppliers for their weld quality cost issues and production losses. The common robot weld problems I had to deal with;


[] Poor power source characteristics.
[] Slow power source to robot communication.
[] Poor weld parameters selected.
[] Poor choice of consumables.
[] Poor robot / weld equipment calibration.
[] No best practices or process controls.
[] Lack of weld process expertise by all involved.


Weld quality and productivity responsibility starts in the front office.

When I visit a plant I work with the robot programmer. After a quick assessment of the weld issues, I would then make the robot weld program changes necessary to compensate for the parts, weld or robot equipment inadequacies. My process changes always improved the weld quality and increased the weld production. After I create the new weld programs and check the welds, I then provide the process control training. As managers and engineers are supposed to be responsible (few are), I insist that all
management, engineers and supervision involved with the welds take part in the training.

When making robot changes, its frustrating to see with specific robots how slow those program changes are being made especially with Japanese robots. Keep in mind, I have worked with every possible global robot type. If you are a "job shop making frequent new robot weld programs" I firmly believe that the ABB robots thanks to the joy stick control and logical Swedish weld soft ware, will require with parts that have many welds, typically 30 to 60% less robot programming times

EVEN ONE OF THE WORLD'S LARGEST ENGINEERING COMPANIES ABB,
AND ESAB A GLOBAL WELD EQUIP MANUFACTURER DID NOT KNOW WHAT THEY WERE DOING.

As some of you are aware I was the North American weld manager at ABB robots. While I had much admiration for their robots ABB also had issue with the MIG weld equipment it utilized. ABB got together with ESAB to integrate an Erratic MIG weld power source into the ABB controls. The ESAB equipment marriage would result in the first robot system produced in which the weld power source and robot control would become a single unit. When the ESAB / ABB robot controls arrived in North America in late 1990's, I was responsible for testing the weld equipment and found numerous major weld issues with the ESAB equipment. The
ESAB power sources had unsuitable slope dynamics for most MIG welds and irrespective of the optimum weld data used,
the results were unstable, inconsistent, poor quality welds especially on parts > 3 mm. Even though the power source was built into the robot control, the weld parameter change response time was too slow dramatically impacting the control of weld starts / ends. The bottom line was the power sources sold by ESAB for the ABB robots was better suited to manual stick welding than for optimum robot MIG welds. The sales personnel at ABB could readily see the ESAB weld issues in the test lab. My blunt advice to the salesmen " if you want to get and keep your robot business, recommend the robots with Miller Delta Weld Equipment". ABB sold the units with the poor ESAB weld equipment to the USA industry and other users knowing the power sources were substandard.

WHY DIDN'T THE GLOBAL WELD SHOP CUSTOMERS COMPLAIN
ABOUT THE ROBOTS AND MIG WELD EQUIPMENT?

The majority of the ABB / ESAB weld power source units were typically sold in the auto plants that had little understanding of the weld process requirements for optimum MIG weld quality / productivity. Remember these were the companies that are used to and have through ignorance always lived with both manual and robot MIG weld quality - productivity issues. And lets face it, managers, engineers and supervisors who lack MIG process control expertise will think it's natural for their weld personnel to play around with the robots and MIG weld data. When you get a chance, visit the MIG equipment sections of this site to read about the sub standard performance of pulsed MIG weld equipment from 1980 to 2005. It's 2013 and while electronic advances are making vast improvements in PULSED MIG equipment performance, there is still little justification for this costly, difficult to maintain equipment and I still weekly see many of the same old problems.









More ABB Robots and the ESAB
Arcitec MIG Power Source Issues.






Poor Robot MIG Welds on Ford
6061 Aluminium Car Seats.

 

During 2000, I was requested by an engineer at VAW a tier one supplier, to evaluate the weld performance of their ABB robots and ESAB Arcitec weld equipment. This plant produces extruded aluminium parts. The aluminium welded car seats were for manufactured for Ford. The car seats and parts required small welds which were made on thin gage 6061 aluminium. Since the installation of the robot cells, continuous production of optimum weld quality parts has been impossible as a result of the weld issues documented in the following report. The weld reject rates averaged sixty percent and the robot down time per hour averaged 20 to 30 minutes. To see the rest of the ESAB Arcitec story, click here.


 


SOLUTION TO A CO
MMON ROBOT MIG PROBLEM.
"INCONSISTENT ARC STARTS"




Info like this in Ed's Robot Training Program..




Weld Question:
Ed, we frequently have poor robot arc starts on our MIG spray transfer, carbon steel or stainless weld applications. Often the arc does not initiate. We weld carbon steel parts 3 to 5 mm thick. The typical fillet weld size is 3/16, (5mm). For the 3/16 fillets we use an 0.045 (1.2mm) wire set at 450 in./min. The weld travel rates vary from 40 to 60 in./min. The gas used is an argon - 5% oxygen gas mix and the weld / start volts vary from 24 to 25 volts.



Answer. The part thickness you weld and the 3/16 fillet weld size requirement allows " higher than normal manual weld travel rates". Weld speed affects the weld voltage used, the faster the speed the lower the weld volts. Two things here are effecting your weld start issues. The argon - oxy gas used requires" lower weld voltages" than the more common argon 10 - 20% C02 mixes. As the fast weld speeds require "lower weld voltages" and the gas requires lower weld volts "therefore the weld voltage you are using is lower than normal for the high wire feed rate delivered".
For starting the arc with the high wire feed used with the 045 wire, you typically would require 28 - 30 volts. Examine your other options below.

Robot Arc Start Solution: Just because you are welding with a high wire feed rate for the weld does not mean you have to use a high wire feed rate at the weld arc start. You could reduce the 0.045 wire feed rate at the arc start to a low spray rate of 370 ipm instead of the 450 ipm. This would require a lower start voltage of 26 to 28 volts. This action not only improves arc starts, it will reduce wire burn back potential and stop over size welds at the start.

Robot Arc Start Solution: For a spray weld ensure the arc delay time is sufficient for the arc ignition. Typically 0.2 to 0.4 seconds. Remember robot micro times are rarely accurate, if you don't hear your arc start data the time you selected is typically not effective.

Robot Arc Start Solution: The larger the weld the longer the arc ignition delay time. The smaller the weld the shorter the ignition time. On gage applications I rarely use ignition delay times

Robot Arc Start Solution: Ensure the pre-flow gas time is sufficient. Without gas ionization arcs don't exist

Robot Arc Start Solution: If you don't want to build up a glob on the end of your weld wire, remember that good arc start data requires good end weld data. Optimum weld end data ensures the completed weld wire stick out is minimum and there is no ball of weld on the wire tip.


We are touching a miniscule amount of the process control - best practice
data that I provide for approx. $400.
Ed's Resources.









Lincoln Pulsed MIG Equipment and Robot Axle Weld Cracks.





2000: If you want to make your weld manufacturing life more expensive, more complex and less meaningful than it needs to be, you could have listened to a salesman and purchased a Lincoln Power Wave for your robot or manual MIG applications.

It was 1999 or 2000. My weld task appeared simple. A tier one, axle manufacturer located in Michigan ordered two robot systems to weld truck axles. The company I worked for ABB, supplied the robots. The robot cells would provide one million axles annually. When the robot cells were complete, as per the contract, ABB was required to provide a few thousand welded axles as part of the robot cell run off. Little did we know about the serious axle, Weld Cracking issues
that were about to occur. For the rest of the story click here.

 



The Lincoln Powerwave and Ford, robot frame MIG welds
on the world's best selling trucks.


When you utilize so called sophisticated MIG power sources with robots, and
your organization lacks weld process expertise you get unnaceptable welds like above.

 



There were 6 major issues with the Ford robot frame "pulsed welds" made at a USA tier one supplier. The welds were made with an 0.052 (1.4 mm) MIG wire and a Lincoln Power Wave. Can you look at the welds and identify the process issues? Could you instantly provide the data to correct these sad Frame welds. All the process control data you need for optimum robot weld quality and productivity for any application is available in my low cost, CD training programs.

 

Robot weld issues because sometimes in robot cells, "TIME accumulates.

For robot welding small fillet / butt welds < 3/16 (< 5 mm) in size, it's often beneficial to use "No Arc Ignition Delay Times". A robot ignition delay time in combination with arc weld start delay time and the pre flow gas time can create too much of a delay at the weld start leading to a larger weld usually in the first 9 mm at the start, (look in the photo above). Remember the times put into that robot program our rarely accurate and can be much higer or lower than the programmer expects.

For two decades the timing issues have been an issue with all robots and needs more consideration from both the robot / MIG equipment manufacturers. Some robot manufactures believe their robots will provide the controls necessary for the weld starts and stops, while in contrast the MIG equipment manufactures believe their power source should provide these controls, it's been this way for two decades, Ying versus Yang, and screw the weld shop.

In contrast with larger welds as typical on parts > 5 mm, the longer the arc start times and pre-gas flow required. To establish the weld puddle with welds larger than 5 mm, an ignition delay time of 0.3 to 1 second. is typical. if you cannot hear the start time data change to the weld data your times are innefective.

Aluminium welds require long start delays, this is necessary to break up the aluminium surface oxides.

Note. In robot cells, often at weld starts, the most troublesome robot weld is often the very first weld, or a weld made after a long weld pause. The problem occurs because the welding wire is "cold", electrons travel better when the wire is hot. For this situation you may benefit from using a shorter wire stick out at these program points. Always have a least 2 robot arc re-strikes programmed for all welds.


Optimum Robot Spray Start Data for carbon steels with 0.035 (1mm) wire welds on parts > 4 mm. For the 0.035 spray weld arc start, set the wire feed at 500 in./min with 27 to 30 volts. This recommendation purposely utilizes low spray transfer wire feed rates, settings which require "minimum spray volts". The low wire feed rate and moderate (not too high) voltage is the best combination for weld start data. This weld data not only provides optimum arc starts it also reduces the potential for wire burn backs to the tip at the arc starts.


There are many factors that influence robot weld profiles at arc starts and at arc ends and these with the resolutions are addressed in all my robot weld process training
books. resources.

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Robots and MIG equipment. Premature Interface Communication.

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Motoman - Fanuc Robot Weld Question.

Ed I am a weld consultant. I came across a weld problem with Fanuc and Motorman robots. At the plant I was assisting there was a Fanuc robot which was 5 years old and it was utilizing a Lincoln Power Wave power source. The plant also had a Motorman robot which was brand new and the power source was a Miller Invision 11. The weld problem was notable on both 3/16 - 1/4 fillet, stitch welds. The welds were 2 to 4 inches in (5 - 10 cm) length and it would appear that 50 to 75% along the weld length the weld appearance would change. Ed what do you think is happening?


Answer. What do you expect from North American designed MIG weld equipment that is trying to communicate with the land of Japan.

I believe you have a case of what I would term as PRC (Premature Robot Cmmunication). The poor interface with this equipment between the robot and power source has left it's mark on your welds. Instead of the robot going to the end of the weld and "instantly" bringing up the pre-programmed Weld End / Crater Fill data, your robots like many of us are premature and bring up the weld end data too soon. Try this, place an additional robot program point about 3 mm from the end of the weld and make sure you complain to that robot company or integrator as this is their SOFTWARE - HARDWARE issue, not yours..


There are many factors that influence robot weld profiles at arc starts / arc ends and these are addressed with many solutions in all my robot weld process training books. resources.

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STAINLESS MIG GAS SELECTION AND ROBOT MIG WELDS;

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Robot Weld Question:


Ed, we robot weld 300 series stainless. The parts are 1.8 to 2.5mm used in an exhaust manifold. The parts have inconsistent fit and gaps. We have been using an 0.045 (1.2mm) wire with a 90% helium - 7,5% Ar - 2.5% CO2 tri-mix with short circuit. Many of the welds are lap welds with gaps and we often find the extremes like either lack of weld fusion
or weld burn through and always distortion. Are we using the correct consumables and which pulsed MIG equipment, would you recommend for this application?



Ed's Weld Answer:


First, stop wasting money on that useless Helium Tri-mix. This gas mix which requires the highest weld voltage along with other things is adding to your weld burn through - distortion issues. See my two part weld gas recommendations in the MIG gas section at this web site. The choice of 0.045 wire on these applications was not correct, the 0.035 wire with higher weld current density - and low to high current short circuit current capability would have been fine. However with this stainless thickness range, this is one of the few welding applications that can justify the use of pulsed MIG.

Reference the pulsed power equipment and consumables. I like the performance and price of OTC pulsed MIG equipment. Use the pulsed mode with an 0.045 wire, and use a simple but honest two part gas mix of 98 argon 2% CO2 which is suited to both pulsed MIG and short circuit. I developed this argon CO2 mix for the North American weld industry back in the 1980s, when I worked for AGA. The weld reality is most gas distributors are simply selling commodities they dont understand and they are either ignorant about the 2% CO2 mix, or they are happy that you are paying a premium for your poorly selected tri mix....

Using the pulsed mode will in contrast to short circuit provide superior weld wetting for the sluggish stainless thicker gage welds especially those welds > 2 mm. The higher pulsed wire feed rates than short circuit should also allow you higher weld travel rates than the short circuit welds which will decrease weld burn through and lower the weld cycle times and decrease distortion.

Remember when welding less than 14 gage or gage parts with gaps you can always switch back the weld transfer mode to short circuit. The argon CO2 mix will again benefit the short circuit as it will reduce weld burn through. As for that poor fit and inconsistent weld gaps in your parts I have a simple solution, fire the engineer responsible for those parts.


There are many factors that influence weld gas selection. If you visit the MIG gas section at this site you will note that I developed three of the major gas mixes sold in North America. Appropriate MIG gas selection without salesmanship is in all my Robot Weld Process Control Training Resources.

 

 

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Drive Roll Groove Question: Ed I believe you need different guide rolls for different MIG wire types, what's recommended?. Thanks for the site, JH. Manchester UK.?

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Ed's Answer on MIG Drive Rolls:

[] For solid hard wires use a Vee Groove rolls built for the wire OD. Two large rolls are just as effective a four smaller rolls. Note for MIG welds there is no MIG weld that should ever require using a wire diamter smaller than 0.035 (0.9 - 1mm)

[] For flux core wires use a Vee Groove with at least onE roll providing a serrated surface to improve the grip. Watch you do not apply too much drive roll pressure to these wires.

[] For aluminium wires use a U Groove with smooth surface again don't use excess drive roll pressure. With aluminium ensure minimum gaps between the inlet, drive rolls and outlet guides to avoid buckling. If using a regular MIG gun use a rigid plastic liner and when possible use a maximum gun length of 10 - 12 feet.


Note: The best MIG gun length for any difficult weld wire is a 10 foot length. What is the value of the free information that you are reading? Will you improve your companies weld quality - productivity and career prospects with the process control - best practices knowlege such as this? Visit Ed's Resources.

 

 

 


Robot Programmer asks a weld $alary Question.


03/23/2000: Ed, I have been working with robots for almost ten years. I am a highly qualified robot programmer. I have extensive MIG weld process expertise based over 20 years of MIG experience. As you are aware there are many career opportunities available to me at this time, particularly in plants that supply auto - truck, robot welded parts.



I have been looking at many different job opportunities mostly in the auto / truck industry. When I go for a job
interview, I usually find the plants will have numerous robot weld issues. All the plants I visit employ engineers
who obviously do not have the expertise to address the daily, costly, robot or weld issues. I know that I can improve their weld quality - productivity and have a big impact on these companies, however, and here's my gripe. When it comes to the salary offered no one offers to pay me more than they pay their entry level engineers who seem to have little influence on improving anything. The bottom line the salary offered is typically not much more than they pay their manual welders who work few hours overtime. By the way as a salary individual, the only time
I can make "major changes" to the robot programs is on the weekends. So on Saturdays and often Sundays, when the managers and engineers are at home, I get to work without over time pay alongside the hourly paid trades people who get time and a half. Rrgards and thanks for what you do. Mike James.

Ed's Reply: Mike lets face it. when you work for management that do not understand what you do, your remuneration and responsibilities will reflect this. The salaries today offered to the few, experienced robot arc weld programmers (programmers with process control expertise) in North America are not much different than 25 years ago, and in reality are a sad reflection of how out of touch the majority of engineering and manufacturing managers are from the real world requirements for optimized weld automation. Lets face it, to figure out how much your management will understand what you do daily is to take a look at the common two paragraph simple, job descriptions or perhaps like many technicians you wont have a job description. In automotive plants, where managers and engineers waste so much time daily running around putting out fires that they cause, you will typically find that weld quality and productivity responsibility is rarely clearly defined. In too many manufacturing plants that do a large amount of welds, hands off managers and engineers tend to shy away from weld process and equipment ownership.

It's a global weld reality that few manufacturing or HR managers are familiar with the expertise levels necessary for optimum robot arc welding process optimization. From a weld career perspective, If I was in your shoes and looking to improve my job satisfaction, increasing my salary and quality of life. I would look outside the auto industry to industries which offer a higher calibre of management for example manufactures of medical equipment or valves.

Today many companies use robots in the medical, defence, electronic, power and oil industries. With these companies in contrast to the automotive industry, you will typically find a more relaxed, intelligent approach to manufacturing, with better wages, shorter hours and less dead wood management.



 

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YOUR JOB DESCRIPTIONS ALAWAYS DEFINES THE EXPERTISE OF YOUR MANAGEMENT:

In many manufacturing plants where minimal focus or understanding is placed on the expertise necessary to attain optimum, consistent weld quality and productivity from a robot, all you have to do is examine the job descriptions to figure out the management awareness.

IF A JOB DESCRIPTION AND RESPONSIBILITY IS CLEARLY DEFINED FOR HIGH TECH INDIVIDUALS, THE WELD QUALITY - PRODUCTIVITY RESPONSIBILITY, ACCONTABILITY AND SALARY WILL TYPICALLY BE AS IT SHOULD BE.

For those technicians or engineers who understand how their daily functions have a great impact on the weld quality / production attained, and you are frustrated but wish to stay with your knuckle head employer, my message to you is simple, educate your peers as to what you do and show your managers with weld production and quality data the money you daily save your company. As for that working Sat - Sun for free, be a man take pride in your expertise and learn to say no when you think its relevant.

Remember in today's bean counters world, if you don't show the beans saved you have little value.

To help those mangers who wish to put things right and feel the need to actually manage what they are responsible for, I recommend my "Management Engineers Guide to MIG" book and CD resource

 




NEW TECHNOLOGY IS OFTEN NOT BETTER.




A Robot plus the Lincoln Power Wave
and Street Lamp automated weld Issues
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Hey folks you may not like the message, but you know you won't get this kind of info from your local weld equipment mfg or supplier. More practical robot weld data to follow I can write this stuff forever, but what the heck why can't you miss a dinner and invest in my books or in my self teaching CD training resources that way you have acess to the real valuable info that I don't provide at this site.

If you were going to set a robot to weld inside a sophisticated vessel or container, I hope you would not set the MIG weld data like that shown in the ABB robot photo below. Remember for code quality welds that we now also have TIP TIG which provides superior weld quality and productivity than regular manual and automated Hot and Cold Wire TIG. TIP TIG is very compatible with robots and weld automation. (www.tiptigusa.com).

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The Excess Spatter Window (a spatter window should be set for all welds)
reveals poor MIG weld parameter selection.

This company purchased good robots but lacks MIG weld process control expertise



MIG WELDS AND CONTACT TIP ISSUES:


 

082007. E-mail:

Hello Ed. I recently purchased your "Management and Engineers Guide to MIG Welding book". The 600 page book is everything I had hoped it would be...and then some! The company I work for has a handful of welding engineers scattered throughout North America. Over the past few months I have had a growing number express satisfaction with using 0.030 tips with 0.035 wire robot welds. My issue is this, no one has given me a specific engineering or scientific reason for the contact tip change. Simply, "So-and-so told me to try it. It works for him so I do it to." (I believe the idea originated with a suggestion from one of the consumable sales reps.) This concerns me. I foresee a number of problems including increased uneven tip wear, restricted wire feed, spatter blockage issues, etc and I don't see where current flow would be influenced significantly.

Am I missing something? By the way Ed, thank-you for having the motivation and courage to make this kind of information available. I have not yet come across an opinion from you that I did not share or a concept I did not admire. Regards. Fraser Rock.
Weld Eng:

Ed's Reply: Fraser: Thanks for kind words. For the five decades I have worked with the MIG process I have never had to use smaller tips unless there was something wrong with the wire diameter or the tip bore dimensions, and in theses situations, i would change the supplier of the consumables. I have found in many plants that a common issue like this is usually a "distraction or crutch" for plant people (including engineers) who frequently lack the ability to get to the real root cause of their daily weld issues.


Most robot contact tip issues typically result from wire burn backs, poor weld start and end data, incorrect wire stick outs, poor parameters or wire cast - helix issues. A contact tip bore needs to be approx. 0.008 to 0.01 larger than the max wire diam. When you purchase smaller tips than those recommended it's important to remember that with today's inconsistent weld wire quality, the weld wire OD is inconsistent and could be on the plus side. No contact tip should be put on a robot without the robot operators or weld personnel manually running the weld wire through the tip. If the wire and snags, the wire is too large or the tip is too small. If the wire is manually fed through the tip and makes consistent, unrestricted contact, it's fine. If the tip bore is not the correct size, (check with drill gauge), change your contact tip manufacturer, Remember that many of the contact tips sold in North America are made in China and you will find that like most Chinese products, the tip bore dimensions are often all over the place. If the MIG wire OD is too big, change the wire manufacturer and for god's sake get rid of weld distributor that provides you with these poor quality products.

As for those so called weld engineers. For the last decade, there has been in North America many weld quality issues with offshore manufactured, substandard weld consumables. The role of an engineer is not to provide BS or add to the numerous weld shop myths, but to get to the root cause of all welding issues. Regards Ed:

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E-mail:

Question: Ref MIG wire burn backs to the Gun Tip.


Ed, we are one of the largest producers in North America of automotive Shocks. I would say that our robots on average weld 200 to 400 parts per-shift. In each robot cell we average 2 to 5 wire burn backs per shift. The burn backs require that we frequently replace the contact tips. As the down time and time required to rectify the problem takes an average of 5 to 10 minutes per burn back you can imagine the production and weld quality consequences. What is the primary cause of this common robot problem, why does this not happen as frequently with manual welders, and are there practical solutions?



Ed's Answer: There are many factors that influence weld wire burn backs and this is one of the prime causes of robot down time. These issues are easily resolved To quickly get to the root cause of all your contact tip issues, attain Ed's Robot Weld Process Control Training Resources.

By the way I had one robot technician tell me the other day that he could not purchase my robot weld process control resources because his Tier One company that had paid over a hundred million dollars for it's robot weld line refused to pay the $390. Its a shame that a company that is likely loosing millions annualy with robot weld quality - productivity issues thinks like this. It's also a shame that the young engineer that likely spent at thousands on his weld education will not invest a few huindred dollars in attaining the real education he really needs so he can get away from those managers that have their head in the sand...

 

 

The so called MIG weld benefits from Special
Alloy Contact Tips for Robot Welds?

Ed contact tip issues is a prime cause of robot down time at our plant. We make steel auto / truck shock components. I figure each shift we are loosing 40 to 60 minutes of robot production per- robot cell due to the contact tip issues. We had a saleman tell us about his companies special alloy tips and their influence on tip longevity. My question is should we be doing more work on tip evaluation?


Signed Simon, a frustrated robot weld tech.

Ed's Answer. Thanks to different alloy additions to copper of course some contact tips will offer different properties that can affect wear or conductivity, however and you can take this to the bank, the alloy composition of the tip is rarely relevant to the contact tip life. A larger, thicker contact tip does enable less weld heat to form in the tip in contrast to thinner tips. The real issue in most robot weld cells is to first recognize the root cause of the contact tip failure.
You will find that most of the contact tips being replaced are due to wire burn backs and to weld spatter blocking the tip bores.

WHY LET ONE DOLLAR ITEM EFFECT WELD QUALITY AND PRODUCTIVITY?

Every robot operator should start each shift with a new, $1 contact tip and again replace the tip immediately after lunch. Each Technicain or Engineer responsible for the robots should at least twice a week, check the contact tip bore diameters and the quality of the tips purchased. The complete check list and my seven step program to prevent costly robot down time is item 4 and you know where that is. As for the special alloy tips if you continue to purhase them, give me a call, I have a bidge I can sell you in Brookyln for less than a $100.

Note: By the way, I created a patent on ceramic - Cu tips, and those tips were designed to allow extended MIG wire stick outs. This enables higher wire feed rates (faster weld travel rates) with lower MIG weld current.. These are two real world weld benefits for robot gauge welds. but don't go looking for them..


Robots and Gas Flow Issues.

Question.
Ed I'm having a hard time keeping flow meters from "blowing their lids" in my plant. We've run both ESAB and Rexarc flow meters and over time they are both failing. At the start of the weld the solenoid opens letting the gas flow into the flowmeter...pegs the BB out on the top of the unit then settles to the set flow rate. I have tried snubbers and I have tried placing the FM before the solenoid. We have 50 psi of 90%AR - 10%CO2 coming down from ceiling to each weld cell. Then provide a 10-15 ft flex hose to the solenoid. The flow meter is hard plumbed to solenoid, then 4ft flex to 8' Torch bundle. Do I need to rearrange? Is this common? Surely not! FYI, we have 2000 arc starts/day on these FM's, some last 4 months, others last 4 days! Should I remove the FM altogether and get a set calibrated orifice like at www.okcc.com? I did turn down my pressure leaving my gas mixer to 40psi but all FM's are calibrated at 50psi, so it throws off my readings. (Help)..



Ed's Answer. Most MIG gas flow meters have the pressure regulated at 20 to 30 psi. I would install a pressure gauge at your outlets and lower your gas pressure to 20 - 30 psi. The only concern for MIG gas flow is the flow rate coming out of the MIG gun nozzle, and the robot operators should chaeck this at the start of each shift. This flow rate should be 30 - 35 cuft /hr.

 

 

 




Question. WELD POROSITY:

Ed we have an extensive porosity issue with our robot welds would appreciate your thoughts on the subject.


MIG WELDS AND POROSITY: What is weld porosity, it's a cavity, pore or many discontinuities that form in a weld from a gas and metal reaction. The porosity can trapped in the weld or at the weld surface. The porosity is typically round in shape but can also be elongated. The primary cause of porosity in auto - truck plants is lubricants on the parts and the result of fast weld speeds and poor weld data.


ROBOTS AND MIG POROSITY.
When you find the robot weld porosity occurs on each part at the same location, and it's not at the weld start or the weld end, examine the robot movement and see if the robot arm is causing a restriction of the gas flow line. Also it's common with robot cells to see a severe gas flow restriction due to the narrow orrifice gas line connections. In a robot cell it's critical that at the start of each shift that the cell operator measures gas flow as it "exits the gun nozzle". If the porosity is at the weld start or stop increase the gas pre flow and post flow times.


ALIGNED OR RANDOM WELD POROSITY. The common causes of localized or aligned group of gas pores with random distribution. If the weld surface is clean this porosity is typically a result of part contamination. If the weld surfcae is oxidized (grey) then look to insufficient gas flow issues. Also small weld lengths and small fast freeze welds and arc blow will contribute to this porosity

ELONGATED WELD POROSITY. (Wagon Tracks). This porosity is typically found parallel to the weld axis. This classic porosity is evident when moisture is found in the gas shielded flux cored wires, (a too common issue). The pores rise to the suface of the welds, (usually in the weld center) and before they can pass into the solifying flux cored slag, the ores which can be large and small will form a rough line typically called Waggon Tracks. Increasing the flux cored wire stick out and increasing the wire feed rate will help. Storing wires in a dry environment also reduces potential. If however this is a common problem with the FCA wires change your FCA brand and change your supplier. The bottom line, avoid weaves and adding arc and weld energy decrease the weld cooling rate and should produce less porosity.

LARGE PORE WELD POROSITY. If weld surface is clean and does not look oxidized, the large pore MIG and FCAW porosity is usually a result of excessive gas flow. Gas turbulence occurs with gas flow greater than 40 cuft/hr and is especially prevelant in Vee - j groove welds.. If weld surface is grey and dirty, the cause is otfen a result of insufficient gas less than 20 cuft /hr. Gas flow must be measured at the gun nozzle.

 




 

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The apathetic management at this tier one company, allowed the selection of an oversized 0.052 (1.4mm) MIG wire for the robot frame gauge welds.



This hydro formed Ford Trucl Frame weld is more than a bad weld,
it's an indication of poor management and a weld process out of control.



Can you identify the root cause of cold truck frame welds?




A manager, engineer, supervisor or robot technician that had weld process control expertise would look at the above robot welds on the big three hydro formed truck frames, and instanly know what the weld issues and resolutions were.

The above tier one, Ford frame, globular welds with evident lack of weld fusion are not the fault of the robots or the over priced Lincoln Power Wave MIG equipment utilized. These and the other similar globular welds on the truck frames were the result of inexperienced, hands off managers and engineers who selected oversize MIG weld wires and used undertrained robot personnel to provide thousands of welds that jepodized the structural integrity with some of the world's most expensive truck frames.


 

Fanuc and Lincoln Power Wave.


and 2004 Ford 500 Cradle / Frame Welds.




Date 23. July 2004.
2004 Ford 500 Cradle / Frame Welds..
This report is a condensed review (changed with a little added humour too keep things sane) of a Ford robot weld line used to MIG weld the Ford 500 steel cradles and sub assemblies. I evaluated this new robot line to establish the root cause of the many weld issues that were impacting the cradle and frame robot weld quality and production.


This mid west, Ford plant purchased approx 100 Fanuc robots with Lincoln Power Wave weld equipment. The weld wire type was E70S-6, and size 0.045 (1.2 mm). It was notable the the Fanuc robots at this plant did not have automated TCP controls or any weld joint tracking equipment. The hourly production range was 60 to 70% of it's goal, and the daily weld rework was > 40%.

When purchasing robots for an auto or any high volume manufacturing facility, it's important that the management and engineers responsible do a weld risk assessment and that they understand how the parts or the robot equipment selected can impact either the weld quality or production. It was evident at this Ford plant that the manufacturing management and engineers responsible for the robot welds had little expertise or interest in owning the processes or the equipment that make their profits.

Note: With robot MIG welds, the primary concerns with common auto truck parts welding 2 to 4 mm is the attainment of acceptable and consistent weld fusion. Its a sad fact that on steel parts > 2 mm, one in three or four welds in the auto industry will typically will reveal marginal or lack of weld fusion. In contrast the weld concerns for parts less than < 2 mm, is typically to avoid weld burn through.

The Ford plant provided numerous welds on steel parts < 2 mm. On these parts the MIG weld burn through risk potential was high, and it was compounded by the poor weld data, oversized weld wire, unnaceptable part dimensional issues, plus lack of ability for the robots to track the weld joints, no control of the robot Tool Center Point (TCP), along with management and engineering process ignorance.

As the Ford plant ramps up to try and attain its 100% robot production goal, thanks to the apathetic engineering involved in producing stamped parts to the design dimensions, the reality is that it's unlikely that the part dimensions will improve, (most welded part dimension issues increase with amount of stamped parts provided). Therefore the weld issues, unless radically addressed will increase daily.

I found In this plant, that lke many, the weld consumable selection was influenced more by the purchasing department than by knowleable engineers, just as the robot and weld equipment selection for this plant has had more to do with salesmanship than it did with weld - robot engineering logic.



 



 
 

THE IMPORTANCE OF ROBOT TCP CONTROLS.

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THE FORD PLANT WAS LOOSING 20 - 30 MINUTES PER-ROBOT HOUR PRODUCTION LOSS BECAUSE THE FORD MANAGEMENT AND ENGINEERS LACKED THE BASIC KNOWLEGE NECESSARY TO ORDER THE CORRECT EQUIPMENT AND IMPLEMENT EFFECTIVE WELD BEST PRACTICES AND PROCESS CONTROLS:

Part dimension ACCURACY and TCP controls are critical when welding thin gage applications. The thinner the gage, the greater the weld gap sensitivity. Thin gage requires smaller welds which require faster weld speeds that require stable joint dimensions.

Torch Control Point (TCP), apart from maintaining the robot program point accuracy of the wire to work, also enables an altered program to be put back to the original approved program. In this Ford facility, with the robot cells purchased, there are no means for accurately checking the robot TCP, and you will find programmers constantly making changes to the welds, none of which have anything in common with the original so called pre-qualified weld program.

While I was at this plant, the plant typically was loosing slightly over 20 minutes/hr of robot down time. The lost production from the 33 robots in opertion (33 x 20 minutes = 660 min/ hr) The bottom line was each hour the plant was loosing > 30% of its production.

Note: On robot welded parts with gaps or inconsistent dimensions, to compensate, you typically have to be able to place "oversized weave welds". Over sized welds not only decrease weld travel rates, they can increase the weld burn through potential, especially on the 1.5 - 2 mm parts. To avoid weld burn through with the larger welds, aggressive weld weaves are beneficial, the plant programmers made no use of the weld weaves in any of the robot programs. Unfortunately with the numerous weld burn through issues, the resulting holes in the parts were disrupting the weld arcs, causing the weld wire to end up with excess length (excess wire stick out) which was a root cause for poor arc start and for the contact tip issues.


To minimize the potential robot weld issues that will occur, the Ford plant management needs more focus on the implementation of best robot weld practices and knowlege about process controls (cost a whopping $400 at this site).


 

FORD AND THE LINCOLN PULSED MIG EQUIPMENT.

2004: For more than two decades, the major MIG equipment manufactures have been developing and promoting pulsed MIG equipment for "steel applications".

When so called engineers have to rely on "sales advice" for technical answere they get what they desreve. The Lincoln pulsed equipment purchased for your robot weld lines has undergone years of development, yet still in 2004 provides "poor arc stability" along with arc length sensitivity. The pulsed arc length sensitivity makes the pulsed mode unsuitable for most of your high weld speed steel applications. It's ironic that the weld equipment your company purchased has cost >50% more than the available superior, stable, traditional CV equipment that could have been used. The pulsed weld equipment purchased will also likely cost three times as much to repair and you will need to keep more spare equipment than normally would have been required with traditional, more durable CV equipment.


FORD AND T
HE PULSED MIG AND HIGH SPEED WELD CONCERNS:

When using an 0.045 (1.2mm) MIG wire and pulsed welding on the cross members, to attain the desired minimum weld travel rate of 45 ipm, on the 1.6 mm lap welds, the MIG weld wire has to have a "very short arc length" and virtually make contact with the weld surface. This required wire to work contact not only disrupts the pulsed transfer, it causes extensive weld spatter which negatively impacts the contact tip life. The weld spatter is also contaminating your fixtures causing part assembly and fit issues.

When establishing the Power Wave pulsed trim voltage, (the arc length) with this high speed pulsed application, if the pulsed weld voltage (arc length) is set to a none weld spatter condition, (requires increased arc length), the pulsed weld transfer and instability at 45 - 50 ipm weld travel rates will cause "skip welds" (missed welds and weld blobs on the parts).


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Typically with this 2004 pulsed MIG power source technology, when pulsed welding we need a sufficient arc length to enable the pulsed MIG weld drops to form and transfer across an arc gap without making a short circuit contact with the work and with the wire tip. With the Lincoln pulsed MIG equipment selected the desired minimum arc length required for optimum pulsed weld transfers is detrimental when pulsed welding thin gage parts using 0.045 wire at the "high weld speeds". If logic and ownership had been applied by the Ford engineers, the weld equipment and the robots would have been tested before the purchase order was produced for the equipment and also the PO contracts should have stipulated that the weld quality - productivity goals be produced at least for 4 hours before the robots and weld equipment was delivered to Ford.

The thin gage parts also limit the allowed pulsed wire feed rates which limit the Lincoln Power Wave pulsed frequency utilized. The low pulsed frequency with the large wire diameters and a weld which for 50% of its time is at a background current of less than 100 amps resulted in an unstable weld transfer mode unsuited to high weld speeds on the Ford 500 cradle welds.

The robot, high speed skip weld issues at the Ford plant are the same pulsed weld issues that every wheel manufacturer and torque converter manufacture has had to deal with for almost two decades. Another ironic fact is when you use the Lincoln pulsed equipment in the traditional spray transfer modes which provides improved arc stability is the weld decision maker may not be
aware that the slope influenced performance of the traditional spray mode from the pulsed MIG equipment is typically inferior to the lower cost traditional CV equipment.

To attain high robot weld speeds with weld transfer stability, I recommend the pulsed mode should be replaced with the more stable, less arc length sensitive "spray transfer mode". While the spray mode runs hotter than the pulsed this is not a concern for the welds on lap welded parts in which the two parts combine for > 2mm. The the weld heat can be reduced through the use of
smaller MIG wire diameter such as an 0.040 or 0.035.


Note: Remember this time period is 2004 for pulsed MIG equipment, and although I had been describing these and similar pulsed issues on this site for at least seven years, managers and engineers in the auto industry were happy to get advice from the people who made and sold the equipment. Poor performing pulsed equipment was something companies like MIller. ESAB and Lincoln
did not discuss in public. There is not be the same pulsed MIG electronic and weld transfer concerns with most of the pulsed equipment sold > 2006.


CONCLUSION FOR THE FORD PLANT: I could waste my time and show you the numerous list of weld issues and the resolutions I provided for this plant. An ironic point also is Ford spends millions every year on training for robot weld applications such as this, and it's clearly evident that the management lack the technical ability to figure out the training that will attain the results they desire. I would hope that one day an intelligant, pragmatic Ford executive that sits in his ivory tower and does not have ego issues will read this stuff and will then come to the conclusion of where the responsibility lies and what has to be done.

 

 

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As I wrote the above Ford report, I was also involved with a tier one company that was using 0.052 (1.4 mm) weld wires on Ford truck frames that were typically 2 to 4 mm thick. This company was also using the same Lincoln pulsed MIG Lincoln equipment. They also went through the consequences of the pulsed arc instability, and they were unable to use high spray parameters required as a result of management selecting an oversize 0.052 wire.

As they could not dial in the required MIG spray parameters, the robot programmers at the plant unknowingly dialled in lower "globular parameters" which started to cause all types of production and quality problems, (see frame plant report at this site).The globular transfer caused over 80% weld rework. The globular drops on the wire tips also caused extensive robot down time.

A reasonable question that could be asked was which idiot at the Ford and Tier One company ordered the oversize 0.052 wire, and dont be surprised if the answer was found not in the management offices and engineering departments (no process ownership) but was found in the purchasing department.

July 30-04. E Mail to Ed. Ref Miller Pulsed MIG issues,



 

Miller Accu-Pulse / Auto Axcess Issues.

 

Ed: Your description of arc sensitivity with high speed pulsed welds is exactly what I am experiencing with our robots and the new Miller Accu-Pulse process / Auto Axcess.

The new auto bumpers we are welding are thin gage, 1/16 (1.6mm) HSLA and we have weld heat martensite concerns.

To minimize the weld heat into our parts, I tried to weld above 40 IPM with the Accu-Pulse using Miller's recommended weld settings we could not do the welds due to weld skipping and arc instability.
We went to an 0.035 wire and could not get the travel speeds so we changed back to 0.045 wire (1.2mm) wire and had to run the pulsed arc with the arc length buried in the part. The small arc resulted in extensive weld spatter, also the part could not handle the pulsed weld transfer and with the resulting high weld heat we had weld burn through holes all over the place.

With the disappointing Miller pulsed weld equipment results. we took your advice and changed the weld transfer mode to CV, using high circuit with the 0.045 wires. We are attaining 40 IPM travel rates and I have no spatter of any consequences on the parts. Also we are having no arc stability problems with the short circuit.m I hate to admit it but this is is another pulsed failure in my book. I am also pissed of at the fact that we could have got these short circuit weld results from much lower cost CV weld equipment without all the costly head aches.


Regards from a fan but a frustrated robot tech... G.S.



 



BEST WELD PRACTICES SHOULD NOT INCLUDE PURCHASING MANAGERS.


 

I can understand why third world country weld shops get uptight about weld
consumable costs, however in many North American auto - truck plants engineers should not have to worry about saving pennies on it's MIG wire costs.

Bigger MIG wires require less drawing so they do cost less than smaller diameter wires. Bigger weld wires also require higher weld current which typically depending on the size will not be suited to the gauge parts.

It's a sad reality, that with the common hands off, lack of ownership managers - engineers that are found in too many auto - truck plants, that a purchasing manager rather than a qualified engineer may decide on the MIG wire diameters and gas mixes selected for the robots or manual welders.


A typical auto cradle may today use approx. 1 to 2 lbs of weld wire per cradle. So the purchasing manager can save 20 to 30 cents a cradle by recommending an 0.045 or 0.052 wire instead of the 0.040 or 0.035 wires. When we use the correct wire diameters, we can optimize the weld heat, the weld quality and the productivity and therefore minimze weld rework. So while the purchasing manager is trying to save a few cents per part the robots daily churn out a robot weld production of typically less than 60% with 20 to 70% weld rework.


Question. Ed I read above that the Ford people were not using weaves on the robot cradle welds. When should we consider weld weaves.

Three important weld benefits are attained from the weld weaves on gage parts;


Answer: "Controlled weld weaves" avaialble ifrom automated applications enable

[1] Reduce weld burn through potential.
[2] Help compensate for gaps.
[3] Helps compensate for part dimensional deviations.
[
4] Help control fusion


THIN PARTS AND WELD WEAVES.
Typically weld weaves which slow down weld production are a good tool for poor part design, poor fixtures and poor parts, all of which are a refection on the expertise of the engineers responsible.
Weld weave requirements and weld weave types are discussed in my robot process control, best practices, self teaching and training resources.

 

 

 


 
This manager is a common reason for the lack of robot
best weld practices and process controls in his plant.





How unqualified individuals and inflated egos influence welds:


THESE COMPANIES HAVE INFLATED WELD PROCESS CONFIDENCE, WHY?
BECAUSE THEIR PARTS ARE EASY TO WELD.


At North American auto - truck parts plants, companies such GM, Ford Honda, Toyota and Chrysler and of course Tier One companies such as Magna which is one of the world's largest suppliers of auto - truck components, when the robot welded parts are typically >2 mm, some times the robot MIG welds will be a very simple task, especially when those companies utilize a combination of good manufacturing practices that result in part fit that actually meets the design, dimensional specifications, and use fixtures designed by engineers who actually understand the automated weld requirements of the job they are paid create the fixtures for. With this rare combination, the weld burn through risk would be very low and therefore the weld quality and productivity potential is often at a reasonable (but rarely optimum) level. The reader at this site should also be aware that in most automotive plants >95% of the welds produced are not subject to a macro weld evaluations and typically a great portion of those welds would reveal serous defects like lack of fusion and excess porosity. It should therefore come as no surprise that in this manufacturing environment that you will often find that many executives, managers, engineers and technicians will have an inflated ego on their abilities to manage and control robot welds. The sad reality in this environment is that the majority of the robot technicians making the daily weld changes will typically have minimal robot MIG weld Process Control - Best Practice expertise.

HOW IMPORTANT IS PROCESS LNOWLEGE TO YOUR CAREER OR TO THE PLANT YOU WORK AT:

If GM, Chrysler and Ford and the other major auto - truck manufacturers were capable of managing essential mfg.. processes such as robot MIG welding, painting and stamping cost efficiently, then there would be no need for tier one suppliers. With these major manufacturers, controlling costs means, cutting people, reducing wages or benefits, shutting plants or getting government or state loans, a great portion of their profits is derived from decreasing the prices made for their parts from their suppliers. With the primary part suppliers, in contrast profits are made when daily production - quality goals are consistently attained within budgets, and if the suppliers cannot bring their process costs down annually, unlike the big three, the suppliers will eventually be driven out of business.

I have visited a few of the Magna plants and talked with many
young robot technicians who typically had one to four years of robot weld programming expertise. I found that many of the rookie robot weld warriors while enthusiastic about their careers, had unwarranted swollen egos about what they knew. These guys, (women tend not to have the ego problems) had made a decision sometime in their short life that they knew all the weld knowledge they required, therefore had nothing to learn from someone like me. By the way, this was at a time I was considered a process control expert with 40 plus expertise, which was (the reason I was invited to the plants. It's a sad situation when a manufacturing generation is happy to get by with a little knowledge and when technicians, supervisors, engineers and managers with a few years under their belt decide they no longer need to further their very limited weld process control education with the world's most important welding process.

IF YOU EVER FEEL IN YOUR CAREER THAT YOU HAVE NO MORE TO LEARN, YOU DON'T BELONG IN THE ENGINEERING OR SCIENCE FIELDS, YOU WOULD BE BETTER SUITED TO WORKING IN A DONUT SHOP.
E Craig 2013.

I don't blame the young technicians I bumped into at Magna for there unwarranted ego's or their sad know it all attitudes, after all my generation raised too many of these young buggers to believe that no matter what their performance is, it's all good, and therefore there is little need for them excel. Lets face it, to excel would mean that they would require a depth of knowledge that actually requires some intense study and they would also have to ask questions from old farts like me.

I have great respect for the founder and owner of Magna who I believe at one time must have been a great tool maker, (likely the reason Magna consistently produces good stampings). However it's been my experience from the 1000 plus companies that I've provided weld production - quality improvements for, that when that large manufacturing corporations allow hands off, middle management who usually don't understand the meaning of process ownership, to enable their workers, supervisors, technicians and engineers to get by with minimal process expertise such as that found around the MIG process, which is a critical process that typically generates a good portion of their companies profits, then it's not rocket science to figure out that Magna, as with many of it's tier one predecessors, eventually pay an unnecessary premium for the parts it produces. Those premium may be derived from;
[a] Paying for overpriced automated and weld equipment that provides costly, unnecessary bells and whistles, as found on overpriced pulsed MIG equipment. These are the products which are usually influenced by someone in sales.
[b] The general lack of understanding of weld process controls and the lack of best practices expertise means the welds will not always be established to achieve a robot's full weld or quality production potential. In too many auto plants it takes two robots to do the work of one. If a robot spends more than 10 minutes downtime each shift it's under utilized.
[c] Weld rework may be generated that increases the part costs. Anything above one percent rework is not acceptable.
[d] Weld quality issues could involve future recall and liability cost consequences.

L
ets face it, and this logic applies to any weld shop, if a company purchases a robot and there is not one person on the weld shop floor or one supervisor or manager can tell the deposition rate potential for a common weld or the cost of a simple, yet common 3/16 (4.8mm) fillet weld, how can that costly e equipment or process be maximized?

We all know there are a few good robot technicians that have extensive MIG weld process controls and best practices expertise, (I have trained many), however and managers don't like to hear this, these guys are the minority. For those robot weld programmers, technicians, supervisors, engineers or managers that figure they don't need robot process or best practice expertise, try the following fundamental, yet important MIG process control test, and after the test ask your self, "is this info important to my company and to my career
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MANAGERS - ENGINEERS - SUPERVISORS AND TECHNICIANS, TO AVOID ROBOT WELD PROBLEMS, IT'S LOGICAL YOU WOULD WANT TO TAKE OWNERSHIP AND BE ACCOUNTABLE FOR THE PROCESSES AND AUTOMATED EQUIPMENT USED IN YOUR ORGANIZATION.


THE PROBLEMS DREQUENTLY START AT THE ROBOT INTEGRATOR: It's a reality that with the major auto / truck companies that many of the robot weld issues are caused before the robots get to the plants.

WHY WOULD ANYONE IN THE AUTO - TRUCK INDUSTRY ORDER A ROBOT WITHOUT FIRST HAVING THE ROBOT AND FIXTURE SUPPLIERS PROVE THEIR PRODUCTS AND CONSUMABLES CAN CONSISTENTLY PRODUCE;

[a] FOUR HRS PRODUCTION MEETING THE WELD PRODUCTION CYCLE TIME AND WITH NO MORE THAN 5 MINUTES DOWN TIME,

[b] FOUR HRS PRODUCTION WITH NO MORE THAN 1% WELD REWORK.

[c] ALL PARTS WITH 100% QUALITY WELDS, (ALL WELDS FULLY FUSED WITH ACCEPTABLE POROSITY LEVELS).

As mentioned, it's not uncommon to find the robot weld issues that result from the selection of oversized MIG weld consumables and poor performing weld equipment and fixtures. Many times the robots will not be calibrated correctly or lack essential options which are necessary to deal with the parts. The robots, weld equipment, fixtures and consumable selection is often influenced by project engineers (mechanical or electrical engineer), or by purchasing individuals that don't understand the MIG process and it's automated needs. Other issues will arise from managers who have to ask a salesmen about a weld issue.
Add the above issues that result from inexperienced weld decision makers and then throw in the pot manufacturing engineers that lack the ability to provide stamped or formed parts that meet the design dimensional specifications. Finally add to the mix, inexperienced, hands off manufacturing managers who do not believe or understand process and equipment ownership and you have a city called Detroit and you have global plants that will never know the cost of a weld, will never figure out their real robot weld production potential, and certainly will never attain their real weld cost, quality and productivity potential.



 

Read how Chrysler management wastes
millions through corporate weld decisions.
 

 



Ed teaching his grandson, so one day he won't
have to Ask a Salesman from Lincoln "how to make a weld"



KEEP SMILING AND DON'T GET PISSED OF AT THE MESSAGER



 


E-Mail. Weld Question From: Dave.

Subject: Robots and Mig weld conduit?

Ed we are trying to find the best conduit to go from the spool to the robot mounted wire feeder. We have tried various types, larger hollow plastic with a strain reliever at the robot, (too rigid, found that it destroyed the quick connect at the feeder), a more flexible steel braided inner with a rubber coating and no strain reliever (found that the conduit broke at the quick connect prior to the wire feeder). Any advise that you could give us on this topic would be greatly appreciated.

I passed this on to my buddy Greg Smith.

From Greg: Dave, I read your E-mail and I think I understand your problem. I was wondering which wire feeder you were speaking of (Lincoln, Miller etc.). If using the PW455 welder with the robotic Lincoln feeder, you should be using the A-1LN Inlet Adaptor along with the A-4 Quick Disconnect Fitting from Wire Wizzard.

If using the Miller Feeders, use the A-1A-C Inlet Adaptor with Quick Disconnect on the feeder. The quick disconnect fittings should not be sticking out off the back of the feeder but should be flush mounted to the castings. If this is not the case that may be why you broke your quick disconnect fittings.

My company has most of the MIG wire drums up on a Mezzanine above the weld cells. We are using the the EC-5 Blue Polymer Conduit with A-16F5 Self Threading connectors on each end. We run this about 15 - 20 ft out of the drum and down into the cell behind the robots. We then go into a A-14BK Bracket Kit and come out into the High Flex Black Conduit that is steel wound on the inside and rubber coated on the outside. The part number of the black conduit is FC-H. We then use a A-10C-H-SR Strain Relief Connector on each end of the black conduit and this conduit is typically about 8-10 ft long into the robot wire feeders. All the stuff we use is again provided by Wire Wizzard
out of Jackson MI. You may need to contact your local distributor. In the past we used some black rubber conduit from "Electron Beam"
and found that it did not hold up as well as the stuff Wire Wizzard has If you are using a side mount spool kit on the robots, the FC-H steel rubber coated conduit should be all you need about 6 ft long. We do not use any side mount spools here but the conduits must be the correct length so as to not pull down too hard on the back of the feeder. Your conduits may be slightly too short causing excessive downward pulling and damaging the Quick Connector. One other option is that Wire Wizzard also has a Standard Duty Black rubber conduit FC-S which should go with a A-10C-S Compression connector and ferrule. This conduit has a smaller ID than the FC-H and should not be as heavy. They make a strain relief for this conduit as well A-10C-X-SR if you need it. Because you have experienced troubles I would probably use the "Standard" conduit instead of the "Heavy Duty" stuff. We have not experienced any problems like you described, but again we are not using side mount spool kits. If you don't have a Wire Wizzard catalog, call them and get one sent to you. They are also on the web at www.wire-wizard.com. Good luck and feel free to call me if you have additional questions.

Gregg W Smith
Weld Engineer
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E-mail. Oct 2008: Ed I sent you this E-mail because I have
come to a questionable snag with my pulsed MIG equipment. I have the MIG equipment set in the spray mode. I am welding on 5/16” carbon steel material. My weld settings are set to spray transfer (29 volts 500 wire speed in/min).

When making a 3/16” fillet weld with the 0.035 (1mm) wire I have noticed that at the end of the weld is very concave, and the weld surface has what I have been taught to refer to as a “fish eye” I am not sure if this is the right term for this problem.

The attached photo will show you what I am referring to. When coming to the end of my weld I back over the weld about ¼” instead of just stopping. I don’t pull my nozzle away before I let the trigger go, so I don’t think this issue is caused due to the length of the stick out. My gas is set to 35cfh argon/CO2 mix.

Could you please advise what may be causing this poor finish is this just cosmetic or an issue that needs to be addressed? If this is an issue that needs to be addressed could you please explain the proper procedure for fixing. These parts are under extreme vibrations and some stresses Vertical / Horizontal and Lateral. Thank you.T Eason.

.

Ed's Reply. Two things going on here.

[1] First your weld picture indicates both poor side wall fusion and undercut which are more of an issue than your crater defects. As you are using spray parameters the lack of fusion could be a result of your weld speeds are too fast. Also the weld surface looks like it was wire brushed yet the mill scale has been left. (I don't know this for sure) however if any weld shop has a concern about weld mechanical properties, you don't MIG weld over mill scale as it impeads the
fusion.

[2] A fish eye is typically a pore evident in a failed weld, and
the bright shiny appearence in the pore indicates the presence of hydrogen, so you dont have a fish eye. The defect you show has more to do with a stupid pulsed power source that has a built in defect. This is a a commom classic issue with pulsed equipment in which the machine so called controlled weld end or wire burn back parameters are set too high, (more evidence that pulsed equipment manufactures don't correctly test the equipment they build.) I see this defect all the time in pulsed equipment in robot cells. At the end of the weld, a high voltage spike is applied for the wire burn back, and this spike causes a suck back effect in the arc leaving that classic hole in the crater. In many instances if you examine with magnification you will find micro shrinkage cracks around that hole and with your fatigue concerns, this defect has to be ground out and the crater filled in.

My MIG process control training resources deal with this issue and provides the process solutions, It's ab ironic point that this defect would not occur on a lower cost traditional CV power source.


 

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After twenty years in the weld shop with a little process expertise, you finally may be able to afford an indoor toilet.


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ROBOTS AND WELD CRATER CRACKS.

The cracks are usually in the center of a concave crater that formed at the termination of the weld.
The weld crater has insufficient strength to resist the solidification stresses imposed by the base
metal.

Cause: Improper weld robot end - crater parameters and robot techniques at weld termination.

Solution. Ed's Robot Process Control Book deals with weld start / stop issues and optimum robot
data that prevents these problems..


ROBOTS AND LONGITUDINAL WELD CRACKS.


A crack running in the direction of the weld axis found in the base metal HAZ or weld center.

Cause: If the longitudinal weld crack is in the weld center, typically the weld is too concave creating a
weak weld that has insufficient strength to solidify without tearing itself in the last place to solidify, i.e.
the weld center.

Cause: Longitudinal crack in base metal. Typically results with too much weld heat is applied
from oversized wels resulting in a part in which the weld imposes more stresses than
the hot base metal can handle.

Solution limit horizontal fillet welds to 6 - 7 mm and flat fillets to 10 mm


ROBOTS AND TRANSVERSE WELD CRACKS.


A crack running into or through the weld or welds, transverse to the weld axis direction.
Cause: Due to poor weld metal selection, (welds with lower than necessary ductility and strength). Also from welds with incorrect weld chemistry or undersize welds with minimal weld fusion, can occur as hot or cold cracks:


ROBOTS AND ROOT / THROAT WELD CRACKS.


Definition: A longitudinal crack located in the weld throat area. Cause: Typically a hot crack
that results from transverse shrinkage weld stresses during the weld solidification. Usually a
result of a concave weld or highly restricted fillet weld joint, especially when the parts are thicker
than 6 mm.


ROBOTS AND TOE WELD CRACKS.


Definition: A crack that is seen in the base metal and begins at the toe of the weld. Cause: Transverse shrinkage stresses. Indicates a brittleness problem in the heat affected zone. Preheat helps and with a robot you could
change the weld sequence so more heat is put into the part before the weld is made.

Remember when making repairs on MIG cracks, completely grind out the defect. Its a shame that in many auto / truck plants that they simply make weld repairs on top of these serious weld defects, (a management issue and a corporate liability issue). Another common problem in these plants is the MIG weld wire size used for the repairs. Weld repairs should be made with a small wire diameter. As most weld defects are small you want a weld wire that can provide high, concentrated, localized weld energy that will provide weld fusion without over welds. An 0.035 wire is much more suitable for weld repairs than the 0.045 or 052 wires most welders are given.




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This is simply a partial look at MIG robot issues. For the most comprehensive data ever written on
Robot Process Controls, and Management Weld Process Controls follow this Robotic MIG Welding link.

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If you are part of the weld industry it pays to have thick skin and maintain a sense of humor.




Extensive MIG weld equipment issues in the MIG and pulsed MIG sections

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Email Ed Craig at ecraig@weldreality.com   -  Phone Eastern Time. USA.