TIP TIG Welding is always better quality than TIG and 100 to 500% faster with superior quality than TIG - MIG - FCAW.

Robot Weld Tips.

It helps if you are a robot programmer,
that you have a sense of humour,

THE LACK OF A MIG GAS MIX IS THE LOGICAL REASON WHY THE JAPANESE MADE TERRIBLE MIG WELD EQUIPMENT: Japan is a country that has had few industrial gas plants. Argon MIG gas mixes in Japan have been a rarity and when available were and still are very costly. For decades Japan utilized mostly straight CO2 gas for MIG welds and the resulting commom globular transfer, high spatter welds would have made any QA weld personnel cringe. In the last four decades while North America played sales games with MIG mixes and produced MIG 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 which were the most widely utilized welds made in manufacturing plants in North America and Europe.

Few Japanese had been able to produce optimum manual or automated quality MIG welds and we in in the North American weld business saw the results of this when the Japanese delivered their robots and weld equipment to North American 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 OTC Daihen equipment is superior to most North American pulsed MIG equipment.

Please note. Pulsed MIG 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 low cost, more durable, easier to maintain MIG equipment using traditional short circuit and spray transfer, and it does not matter if that MIG equipment utilized was purchased in 1970 - 2010.

 

The lack of weld process expertise effects weld equipment
selection and the weld process logic presented in automated weld software.
When it coms to evaluating robot MIG weld software Japanese and
North American weld logic are rarely the similar.

 

ROBOT WELD CONSIDERATIONS:

For those small to medium weld volume shops, that are looking to introduce robots to MIG weld
their steel and stainless applications, 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. Unless you are going to use Pulsed which in many instances will produce inferior steel welds than regular spray transfer, the electronics in the pulsed MIG equipment will only be a costly concern for your purchasing and maintenance departments.

[] When an integrator or robot company advises you to use pulsed for that steel application, remember it's typically not necessary and it will not produce the most consistent weld fusion. Pulsed MIG will rarely achieve the weld deposition rate potential that can be attained by the older 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 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.

[] In comparing robots, examine the logic layout of the welding program soft ware.,

[] Examine the calibration accuracy between the robot pendant and power source weld data.

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

[] Examine the ease 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, training and service capability, and 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.

THE ROBOT YOU MAY BE CONSIDERING MAY WORK WELL IN AN AUTO PLANT WHERE THEY RARELY CHANGE THE WELD PROGRAMS AND THE DAILY POOR INCONSISTENT ROBOT WELD QUALITY IS ADDRESSED BY WORKERS PLAYING AROUND WITH THE WELD DATA AND ADDING WORKERS TO THE END OF THE ROBOT LINE TO FIX THE EXTENSIVE WELD REWORK. HOWEVER WILL THIS SAME ROBOT MAKE THE GRADE IN A WELD JOB SHOP THAT'S SERIOUS ABOUT WELD QUALITY, WELD REPEATABILITY, EASY ROBOT PROGRAMMING AND FAST PROGRAMING CAPABILITY.

IF YOU WANT A GREAT COMPARISON OF CONFUSION VERSUS WELD LOGIC, COMPARE THE DIFFERENCES BETWEEN A JAPANESE PANASONIC OR MOTOMAN ROBOT AND A SWEDISH ABB ROBOT . BY THE WAY, I BELIEVE THAT IN CONTRAST TO JAPANESE ROBOTS IT CAN TAKE 30 TO 50% LESS TIME TO PROGRAM A WELD PART WITH AN ABB ROBOT. THIS STATEMENT REQUIRES THE APPLICATION HAVE MORE THAN A FEW WELDS AND THE BOTTOM LINE TO REVIEW THIS IMPORTANT JOB SHOP CONSIDERATION SIMPLY SEND YOUR PARTS TO COMPANIES THAT SUPPLY THE ROBOTS AND LET THEM GIVE YOU THE RESULTS.

With robots, the weld opportunities are only
limited by the management's imagination.

ROBOTS AND WELDING ISSUES



YOU PURCHASED A ROBOT WITHOUT WELD PROCESS CONTROL EXPERTISE?

THE FOLLOWING REASONS WILL INDICATE YOUR ORGANIZATION LACKS WELD PROCESS CONTROL EXPERTISE.

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

[2] If you utilize three part gas mixes for carbon steels or thin gage stainless.

[3] If you believe you have to use Metal Cored wires to weld your carbon steel parts.

[4] If you utilize flux cored wires for welding clean carbon steels < 3/8 in the flat and horizontal welding positions.

[5] If you weld carbon steels and you use mixes containing oxygen.

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

[7] If the person who has full responsibility for the robot welds is in the union or in the maintenance department.

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

[9] If your purchasing personnel make decisions on the weld consumables selected.

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

[11] If your manual welders daily use a whipping action or weave action with their MIG guns.

[12] If your robots have a ROBOT down time per shift of more than 15 minutes per-robot.

[13] If you use pulsed MIG and don't know how to provide optimum pulsed parameter adjustments.





THE AUTOMOTIVE ROBOT TIG APPLICATION:This weld report deals with the robot TIG welding issues on one of the big three cars. The parts required approx. 15 precise small welds and the the 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 welds would leak. After I rectified the problem, I wrote the following report.


If you want the highest weld quality attainable TIG welds with a robot 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 Expertise".

A question from an HR manager at a manufacturing facility.

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. It would be beneficial if the robot programmer was able to do the following. Lets say your application is a Robot MIG welded carbon steel automotive part. The parts 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 solutions necessary to rectify weld issues. The programmer should be able to justify and explain the benefits of the weld 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.

Provide if using pulsed, expertise on the wide variety of pulsed parameters.

Provide the maximum robot weld travel speeds.

Provide weld voltages which will minimize weld spatter.

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

Provide the optimum robot weld start / stop data.

Be aware of the robot MIG gun technique which can effect the arc and weld.

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 answer the MIG weld quiz section of this site weld questions.

All the above data will cost your organization approx. $400 as it's addressed in all my robot process control training resources.

THE WELD PROCESS CONTROL EXPERTISE NECESSARY FOR ROBOT WELD PROCESS
CONTROL IS FOUND IN MY ENGLISH |AND SPANISH MIG / ROBOT TRAINING RESOURCES.

Reference the 2 - 2.5 mm steel application discussed above. Anyone who has picked up my process control training CD, or read my books would be aware of the relationship between the part thickness, the weld current and the optimum weld wire diameter and gas mix.

To avoid weld burn through on parts 2 - 2.5 mm and optimise the robot weld productivity, you could could utilize pulsed or spray transfer. With spray transfer we would typically utilize 220 to 240 amps. The MIG wire best suited to this current / application would be an 0.035 (1mm) wire. The reason the 0.035 wire is optimum sor spray, is this wire has a typical spray range of 200 to 300 amps, in contrast to 0.045 wire requires at minimum >255 amps.

To attain the 240 amps with the 035 wire, we would set a wire feed rate of approximately
500 in./min. To minimize weld burn through with the spray transfer we would use a low energy spray gas mix such as argon with 5 to 10% CO2. This wire and gas selection reduces weld burn through potential on this thin part while providing excellent, spatter free weld quality with weld deposition rates of approx. 9 to 10 lb/hr We would expect a robot travel rate of 40 to 60 ipm.

 

Panasonoic Robot Concerns.

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

For me it was another one of those annoying Japanese, Panasonic robot applications. Thanks to the Panasonic engineers, "we had another simple weld application made complex". After six weeks the Panasonic personnel and Panasonic robot integrator could not get their robot to consistently place two small 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.

Motoman Robot Concerns.

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

Ed, we are on our 4th generation of Motoman robots, and I didn't think they could get any worse, but I was wrong. I simply would not recommend the new UP/XRC 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.

Later in 2003 I assisted one auto supplier of thin parts with his numerous robot weld issues. The parts were 1.2 mm thick, the weld wire was 0.035 - 1 mm. The weld mode selected was short circuit. I noted again with the Motor Man 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 to 3 volts higher than that which would have been required with the traditional North American CV equipment. (Slope and optimum MIG equipment weld transfer mode performance was not well understood in Japan at this time).

The required, higher weld volts from this inferior Japanese MIG equipment caused ERRATIC "globular transfer" and the additional voltage provided higher weld energy which added to the "weld burn through potential" on the thin parts being welded.



Question: Ed we are using a Motoman robot with the MotoArc 350 pulsed power source. 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 12-13 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 and Motoman could rarely claim with this equipment that it had great MIG welding equipment.
Regards Ed.





July 31 - 2010. E-Mail From Craig Jennings.
Managing Director Motoman.
E-mail is craigsjennings@aol.com

Ed I read what you have to say on your web site about robots and welding. Your site is your personal play ground to "pontificate on your out of date opinions about products you have no current capability to form an opinion on". To say ABB robots can take 30% to 50% less program time than Japanese robots is simply uneducated and reflects on your lack of experience with anything but ABB, (who I think let you go in one fashion or another). I dare you to publish this post.
Craig Jennings.

Reply from Ed: Jennings this site has take over 10000 hrs to develop and over ten years to build. In this time period the site has simply reported info from others and data from my own experiences. As few global robot and weld equipment companies provided product recalls or informed their customers about their equipment problems this web site makes no apology to you or anyone else for reporting facts. Your E-mail reveals much about your self and how little you know about what I do for a living. I don't believe you have looked at more 1/10 of this site's content. Your company makes robots and sells turnkey cells and the bottom line in contrast to a decade ago, today there is only subtle differences between your self and all your competitors products.

A little more of my pontification. If you had put a little depth into reviewing this web site you would have found that my expertise is the "control of the processes that are attached to your robots". As for my expertise. Possibly you are not aware that I have close to 40 years weld process control experience. I have written three books on the subject and published over 1/2 million words and 30 weld process control articles. From a hands on perspective, the robot welds I produced in the 1980s are superior to the majority of the robot welds produced today. I believe I am the only person in the industrial world that has successfully set robot pulsed MIG welds for boiler header tube welds, (I did this ten years ago when pulsed MIG equipment had poor performance). This all position multi-pass application is worth a mention as it has always required the highest skilled manual TIG welders to meet the all position x-ray ASME requirements. In 2008 I patented a new approach to automated MIG clad welds for a company that has clad 80% of the boilers in North America. And for the auto industry Ford 150 - Corvette - Harley, (read this site) and be aware that Chrysler contracted with ABB to pay them approx. $300.000.00 for two weeks of my service to fix their robot weld issues.

For more than two decades the major weld equipment manufactures and robot manufacturers like Motoman - Panasonic - Fanuc and ABB were the root cause of many robot weld quality / productivity issues suffered by the welding industry, yet thanks to global manufacturing weld apathy, few companies sued your organizations for the production, rejects and quality losses incurred. In this time period in ten different countries I worked with robots that are older than 20 years and also worked on brand new robot installations. I was called to fix weld issues and optimise welds that unfortunately the weld equipment, robot manufacturers and robot integrators could not fix. I would have thought a well dressed, ivory tower hands off executive like your self would appreciate someone not on your pay roll cleaning up your mess and doing your job for you.

Many of the common robot weld issues I worked with were a result of the MIG equipment and robot controls. Common problems. Poor power source characteristics - poor power source to robot control communication - slow weld power source communication - poor weld parameters - poor choice of consumables - poor robot / weld equipment calibration - lack of process expertise by all involved. When I visit a plant a robot programmer is typically provided and I will then make the weld program changes necessary to compensate for the weld or robot equipment inadequacies and typically optimise the weld quality and increase the weld production. After I create the new weld programs I then provide the training and insist that all management and supervision involved take the process control training as sold on this site. My frustration with robot programming speeds comes from my experiences when making those robot program changes and keep in mind I have worked with every possible robot type. After doing this for decades I stand by my statement that if you are a "job shop making frequent new robot programs" the ABB robots thanks to the ABB joy stick and logical Swedish weld soft ware will on jobs that have require many welds can dramatically reduce the robot programming time typically required by Japanese robots. And Craig what am I doing at age 64. Well I am still fixing the robot weld problems and recently I bought the world's most advanced multi-purpose weld technology "TIP TIG" to North America.

I am shocked that a leader of a global organization such as yours would have the time to write this "dare you to print" childish E-Mail and also to place some subtle innuendo about my departure from ABB. As the weld manager at ABB Robot Weld Division, (a company no longer in business) I clashed with ABB management in the 1990s when their marketing guru (a man who who knew about welding) with out discussion with me, signed a multi-million dollar agreement in Sweden with ESAB to integrate ESAB Arcitec weld power sources into the ABB controls. This equipment marriage would result in the first robot system in which the a 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 products and found numerous major weld issues with the equipment. The power sources had unsuitable slope dynamics for MIG and irrespective of the weld data used this resulted in 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 slow dramatically impacting the control of weld starts / ends. The bottom line was the power sources sold by ESAB 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". The bottom line Jennings, I clashed with another manager that could not accept or own up to the fact that he had made a stupid major costly decision. As your executive type is aware, marketing managers carry a big stick and this manager had one simple objective and that was to get rid of me and they eventually he succeeded. ABB sold the units to US industry knowing the power sources were substandard. The units were typically sold in the auto accounts that had little understanding of the requirements for optimum weld quality / productivity. These were companies that think it's natural for their weld personnel to play around with weld data every few hours. As for your "I dare you" , what do you want me to do "double dog dare you?". As this site repeats many times, "management who will not take responsibility for their words and deeds, management who lack the ability to educate themselves in the products they profit from, management who simply will not take ownership of their own problems has been for decades a major global issue".

Regards Ed Craig. Oct 4. 2010.

ABB Robots and
Arcitec Power Source Issues.

Robot Welds on Ford
6061 Aluminium Car Seats.

During 2000, I was requested by an engineer at VAW a tier one supplier to analysed the welding performance of their ABB robot and ESAB Arcitec weld equipment. This plant produces extruded aluminium parts. The aluminium welded car seats were 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 due to the issues documented in this report. Weld reject rates averaged sixty percent and the robot down time per hour averaged 20 to 30 minutes. To see the rest of the story, click here.

 

 

SOLUTION TO COMMON ROBOT MIG PROBLEM.
"INCONSISTENT ARC STARTS"

Weld Question: Ed, we frequently have poor robot arc starts on our 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 requirement allows " higher than normal manual weld travel rates". Weld speed affects weld voltage used.
Two things here are effecting your weld start issues. The argon - oxy gas used requires" lower weld voltages" than the more common argon C02 mixes. Fast weld speeds also require "lower weld voltage" and the weld voltage you are using is lower than normal. For starting the arc with the high wire feed used you typically would
require 28 - 30 volts. Examine your other options below.

Arc Start Solution: Just because you are welding with a high wire feed rate does not mean you have to use a high wire feed rate at the arc starts. You should reduce the 045 wire feed rate at the arc start to a low spray rate of 370 ipm. This will require a lower start voltage of 26 to 28 volts. This action will reduce wire burn back potential.

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 if you don't hear the start data it's typically not effective..

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

Arc Start Solution: Ensure the pre-flow gas time is sufficient.

Arc Start Solution: Good arc start data requires good end weld data to ensure the wire stick out is minimum and there is no ball of weld on the wire tip



There are many factors that influence robot arc starts and for approx. $400
these and all other weld issues are are addressed in all my robot weld process training resources.



Lincoln Power Sources and Axle Robot Weld Cracks.



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 application.

1999 - 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 cell would provide one million axles annually. When the robot cells were complete, as part of 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 weld cracking issues that were about to occur. For the rest of the story click here.

Robot Frame Welds.

There are 6 major issues with these robot frame "pulsed welds" made at a tier one supplier with an 0.052 (1.4 mm) wire and a Lincoln Power Wave. Can you identify the issues and could you provide the data to correct them. All the process control data you need for optimum robot weld quality and productivity is available in my low cost, CD training programs.

Weld Ignition Delay Times in the Robot Start Data.
For robot welding small fillet / butt welds < 3/16 (< 5 mm) in size, it's often beneficial to use "no ignition delay time".
A robot ignition delay time in combination and confusion with arc start delay time and 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. For two decades this has been an issue with too many robots and needs more consideration from the robot / MIG equipment manufacturers. Some robot manufactures believe their robots will provide the controls necessary for the weld starts and stops while the MIG equipment manufactures believe their power source should provide these controls. Its been this way for two decades, Ying versus Yang and good luck for the weld shop.

In contrast the larger the weld > 5 mm on the application, the longer the arc start time and pre-gas flow required. To establish the weld puddle with welds larger than 5 mm an ignition delay time of 0.3 to 0.8 sec is typical.If you cannot hear the start time data it;s usually not effective.

Note: Aluminium welds require long start delays to burn through the aluminium surface oxides.

Note. 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 Steel .035 (1mm) Wire Welds > 4 mm. For the 0.035 (1mm) "spray transfer" 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 / arc ends and these are
addressed in all my robot weld process training books. resources.

 

 

Robots and Premature Interface Communication.

 

Robot Weld Question

Ed I am a weld consultant and I have found 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 PRC (Premature Robot Communication). 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 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 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.

Robot Question: Ed we have synergic MIG equipment which has voltage sensing leads, (VSL). In our maintenance department there are several views as to where the leads should be attached in our mult-robot MIG weld cells.

ANSWER: I think the following sketch provides the VSL data you need.

STAINLESS MIG GAS FOR ROBOT MIG WELDS;

Robot Weld Question: Ed, we robot weld 300 series stainless. The parts are 1.8 to 2.5mm components used in an exhaust manifold.
We have been using an 0.045 (1.2mm) wire, a 90 helium tri-mix with short circuit. Many of the welds are lap welds with gaps and we often find the extremes of either lack of weld fusion or weld burn through. What do you recommend for this application?

Weld Answer: First, stop wasting money on that Useless Helium Tri-mix. This gas mix along with other things is adding to your burn through issues. See the weld gas recommendations in the MIG gas section (MIG DATA) of this web site and by the way to use short circuit with 0.045 wire on these applications was not the correct wire size choice 0.035 would have been optimum. This is one of those unique welding applications that can justify the use of pulsed MIG. Regular spray transfer would be too hot and short circuit will result in lack of weld fusion issues on the thicker gage parts.

Reference the pulsed power source, an OTC or North American Miller Invision (sells for less than $5000), this is all you need. Use the pulsed mode with either an 0.045 wire or an 0.035 (1mm) wire and a simple but honest two part gas mix of 98 argon 2 oxy or 2 CO2, (I developed this mix many years ago). Using the pulsed mode will in contrast to short circuit provide superior weld wetting for the sluggish stainless thicker gage welds. The lower weld energy (lower than spray transfer) pulsed mode will bridge the gaps better than short circuit and provide superior weld fusion. 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 the cycle times and may decrease the distortion.

Remember when welding less than 16 gage you can always switch back to short circuit. The argon 2 oxy or CO2 mix will again benefit the short circuit and reduce weld burn through.

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.

DRIVE ROLL GROOVES: Ed I believe you need different guide rolls for
different MIG wire types what's recommended. JH. Machester UK.?

Ed's Answer:
[] For solid hard wires use a vee groove built for the wire OD.

[] For flux core wires use a vee groove with at least on 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 a U groove with smooth surface again don 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 hard plastic liner and a maximum
gun length of 10 feet.

Robot Programmer asks a weld $alary question. 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 automotive 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 welding issues. All the plants I visit employ many engineers who obviously do not have the expertise to address the costly robot or weld issues. I know that I can improve the weld quality and have a big impact on these companies welding productivity. 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 anything. The bottom line the salary offered is typically not much more than they pay the manual welders who work 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 I work without over time pay alongside the hourly paid trades people who get time and a half. While we fix the robots the higher paid engineers and managers sit at home with their families.

Ed's Reply:The salaries today offered to experienced robot arc welding programmers in North America are frequently a sad reflection of how out of touch engineering and manufacturing management is from present day weld automation reality. I agree with you that many of the higher paid engineers are more comfortable in front of a computer than in a robot cell. I also agree that most semi-skilled welders and robot operators working overtime can earn as much or more than the technician or engineer responsible for the costly robot line.

Part of the primary compensation issue for high tech welding individuals, may relate to a companies "lack of a real world job description". Weld process accountability and weld productivity responsibility are typically not clearly defined in many manufacturing plants in which managers shy away from process and equipment ownership. It's a global weld reality that few manufacturing managers or HR personnel are familiar with the expertise levels necessary for robot arc welding process optimisation. If I was in your shoes I would look outside the auto industry. Many companies use robots in the medical and electronic industries and there you will typically find better wages, shorter hours and less dead wood management.

 

 

In many manufacturing plants, minimal focus is placed on the real expertise necessary to attain optimum weld quality productivity from a robot, and unfortunately the majority of manufacturing managers do not provide appropriate robot job descriptions. IF A JOB DESCRIPTION AND RESPONSIBILITY IS CLEARLY DEFINED FOR HIGH TECH INDIVIDUALS, THE SALARY AND APPRECIATION 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, my message to you is simple. Educate your peers as to what you do and show with data your hands off managers the money you daily save your company. Remember in today's bean counters world, if you don't show the beans saved you have little value. To help you on this trip I recommend my "Management Engineers Guide to MIG" book and CD training program.

 

A Robot. The Lincoln Power Wave.
Street Lamp Weld Issues

Hey folks you wont get this kind of info from your local weld supplier. More practical robot weld data to follow, but what the heck why can't you miss a dinner and invest in my books or in my self teaching CD training programs. The robot training resources will within a very short period of time give your employees all the weld process expertise they need.

 

 

 

 

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

 

 

Excess weld spatter caused
by poor parameter selection .

Good Robots. Lack of weld process control
expertise and poor parameters.

CONTACT TIP ISSUES:

08/07 E-mail:

Hello Ed.

I recently purchased your "A Management and Engineers Guide to MIG Welding". The 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. My issue is this, no one has given me a specific engineering or scientific reason for the 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?

Ps: 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.

Welding Eng.:

Ed's Reply: Fraser: Thanks for kind words. 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 burn backs, poor start and end data, incorrect wire stick outs or wire helix issues. A contact tip needs to be approx. 0.007 to 0.01 larger than the max wire diam. Keep in mind the wire will expand slightly during welding. 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 frequently on the plus side. If robot operators or weld personnel manually run the wire through the tip and it 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 its fine. If the tip bore is not the correct size, (check with drill gauge), change your contact tip manufacturer. If the 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. There are many quality issues with off shore, substandard weld consumables and there is the possibility that the tips you purchase are made in China or Timbuktu. The bottom line is your weld engineers need to get a life and put their focus where it belongs Good luck. Ed:

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 with our robots that weld 200 to 400 parts per-shift, we average 2 to 5 burn backs per robot per shift. This requires 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 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?.

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

 

MIG Special Alloy Contact Tip MIG weld Question.

Ed contact tip issues is a prime cause of robot down time at our plant. We make steel auto / truck shock components. I figure we are loosing over one hour of robot production per- robot due to the contact tip issues. I have read about special alloy tips and their influence on tip longevity and seen different tip profiles. My question is should we be doing more work on tip evaluation? Signed 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. The alloy composition of the tip or the shape of the tip is rarely relevant however a thicker tip (less heat) is typically better than thinner. The real issue in most weld shops that utilize arc welding robots is to first recognize the root cause of the contact tip failure.

2004. Pulsed welds made with a Lincoln Power Wave

These ridiculous tier one welds are not the fault of the robot or the over priced Lincoln Power Wave, these weld issues are the fault of the hands off, managers and engineers. These frame welds simply points out that when it comes to robot MIG welding, it takes much more than over priced MIG weld equipment or the pulsed MIG process to make a good MIG weld.

Robot welds like these are common in the auto / truck industry and are simply a reflection of apathetic management and engineers. It's easy to fix weld problems like this, that is if you can find manufacturing managers / engineers who are sincere about finding out the real root causes of their daily robot weld process issues.

Robots and Gas Flow meter 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 having the FM before the solenoid. We have 50 psi of 90%AR - 10%CO2 coming down from ceiling to each welder(automation). Then provide a 10-15 ft flex hose to the solenoid, FM 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 outlet and lower your gas pressure to 25 psi. Then check the gas flow output delivered from out of each gun nozzle. Set this flow at 35 cuft /hr.

WELDS AND POROSITY: Weld porosity, a cavity discontinuity that forms from a gas 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.


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

CLUSTER WELD POROSITY. A localized group of pores with random distribution.
Causes. Arc blow, gas flow inconsistency, intermittent material or wire contamination, poor weld parameters or technique.


PIPING WELD POROSITY. The pore length is longer than it's width. Often in fillet welds the pore is seen working its way from the root towards the weld surface. Typical porosity when using argon oxygen mixes on parts >6 mm. Increase weld energy, slow weld speed avoid weaves.

ALIGNED WELD POROSITY. Linear porosity, an array of round pores in a line. Typically caused from contamination in the metal or electrode. Add energy use arc to break up surface ahead of weld.

ELONGATED WELD POROSITY ( wagon tracks). Typically found parallel to weld axis. Classic porosity when moisture is evident in gas shielded flux cored wires. Increasing the flux cored wire stick out and increasing the wire feed rate will help. Baking flux cored wires and storing wires in a dry environment also reduces potential. For MIG welding slow weld speeds, make welds larger, avoid weaves, add
energy to decrease weld cooling rate.

SCATTERED WELD POROSITY. Porosity scattered randomly throughout the weld or welds. If the weld surface is gray and looks oxidized it's typically insufficient gas flow. If the weld surface looks as
clean as normal the scattered porosity is usually caused by part or electrode contamination, or weld
data that causes the weld to freeze too rapidly

LARGE PORE WELD POROSITY. If weld surface is clean and does not look oxidized, the large pore
MIG / FCAW porosity is usually a result of excessive gas flow, gas turbulence with gas flow greater than 40 cuft/hr. If weld surface dirty the cause is otfen a result of insufficient gas less than 20 cuft /hr.

An 0.052 (1.4mm) MIG wire was selected
for this robot frame weld. This was a poor choice
made by the tier one corporate engineer.




Can you identify the root cause of cold welds and lack of fusion from this robot weld?.
Apart from firing those responsible, what would you do to rectify the situation?

Fanuc / Power Wave Welds.

Ford 500 Cradle / Frame Welds.

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

The Chicago location purchased approx 100 Fanuc robots with Lincoln Power Wave weld equipment. The weld wire was E70S-6, 0.045 (1.2 mm). The Fanuc robots at this plant do not have automated TCP controls or weld joint tracking equipment. which reduced the hourly production by appprox. 30%. The weld wire size selected was too large and not appropriate, for the gage parts and weld rework was > 40% and the pulsed MIG power source used is a poor / costly choice which has added > $300,0000 of unnecessary cost to the cradle robot line.

In evaluating specific robot welding issues at this facility, it's important that the unique robot weld risks be understood for the welded parts under discussion, its something manufacturing management and engineers should have an interest in yet few do.

With robot MIG welds, the primary concerns with common parts welding 2 to 4 mm is the attainment of "acceptable and consistent weld fusion", while the concerns for welding parts less than < 2 mm, is typically to avoid weld burn through.

Note: On steel parts > 2 mm, one in three or four welds in the auto industry end up with lack of weld fusion in some part of the weld.

The Ford Chicago plant provides many welds on steel parts < 2 mm. On these parts the MIG weld burn through potential is at a high level and the part dimensional issues plus robot TCP deviations were compounding the the burn through issues. As this Ford plant ramps up for it's robot weld production, it's unlikely that the part dimensions will improve (most welded part dimension issues increase with amount of stamping provided) and this combined with the lack of the automated TCP controls from the robots, will ensure that the weld issues, unless addressed will increase in proportion to the weld production attained.
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 to achieve this the management and engineers in this plant should be the first in line for the process control training required.

The selection of inappropriate MIG weld consumables and inferior weld process modes has for two decades created major weld issues in the Big Three plants. As the robot steel parts decrease in thickness < 2 mm, the weld quality / productivity consequences of poor weld consumable / and weld transfer mode selection really becomes evident. In your plants weld consumable selection often has more to do with a purchasing decision cost reduction decision rather than a logical weld engineering decisions, just as robot and weld equipment selection for this plant has had more to do with salesmanship and costs than it did with engineering logic.

THE IMPORTANCE OF ROBOT TCP CONTROLS . The following weld data will assist the plant in establishing best weld practices for the cradle parts < 1.8 mm.

30 MINUTES PER-HR PRODUCTION LOSS FROM NOT ORDERING THE CORRECT EQUIPMENT:

Part dimension and TCP control will always be critical when welding gage applications. The thinner the gage, the smaller the required welds and the greater the degree of weld / joint accuracy. TCP control also enables an altered program to be put back to the original program with minimal deviation of the gun to the work. In this facility, in 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 program.

This plant was typically loosing 20 minutes of robot (down time / lost production from 33 robots 33 x 20 660 min/ hr from 1980 min/production/hr) due to program weld point adjustments and related contact tip issues.

Also on the parts with gaps or inconsistent dimensions, you typically have to be able to place "oversized welds" to compensate and of course over sized welds will 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 the robot programs. Unfortunately with weld burn through, the resulting holes were disrupting the arc causing the weld wire to end up with excess length which is a root cause for arc strike / contact tip issues.

THE LINCOLN PULSED POWER SOURCE SELECTION.

For almost two decades, the MIG equipment manufactures have been developing and promoting pulsed MIG equipment for "steel applications".

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 purchased also 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.

PULSED MIG AND HIGH SPEED WELD CONCERNS: When using an 0.045 (1.2mm) MIG wire and pulsed welding the cross members and similar seam lap welds, to attain the desired minimum weld travel rate of 50 ipm, on the 1.6 mm lap welds, the MIG weld wire has to virtually make contact with the weld surface. This "wire to work contact" not only causes extensive weld spatter which will impact the tip life. The weld spatter also gets on to the fixtures causing part assembly / fit issues. When establishing the pulsed trim voltage (arc length) with the high speed pulsed applications, if the pulsed weld voltage (arc length) is set to a none weld spatter condition, the weld transfer and instability at 50 ipm will cause "skip" welds (missed welds / weld blobs).

Typically with this present day power source technology, when pulsed welding we need a sufficient arc length to enable the pulsed MIG weld drops to form and transfer without making a short circuit contact with the work and wire tip. With the Lincoln pulsed MIG equipment 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".

The thin gage parts limit the allowed pulsed wire feed rate which limits the 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 unsuited to high weld speeds on the Ford 500 cradle welds. The robot, high speed skip weld issues you have at the plant are the same pulsed weld issues every wheel manufacturer and torque converter manufacture has had to deal with through for the last two decade. 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.

Note to managers: It's a logical practice to check out weld equipment before you purchase it.

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 the parts > 2mm as the the weld heat can be reduced through the faster weld speeds and the selection of a smaller MIG wire diameter such as an 0.040 or 0.035 wire.

Note: Remember this is 2004 pulsed equipment and although I saw the pulsed issues on numerous occasions and documented them at this site, poor performing pulsed equipment was something companies like MIller. ESAB and Lincoln did not discuss in public. There is not be the same electronic and weld transfer concerns with most of the pulsed equipment sold > 2006.

July 30-04. E Mail to Ed,

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. Our new auto bumpers are thin gage, 1/16 1.6mm HSLA and martensite concerns. I tried to weld above 40 IPM with the Accu-Pulse and could not do to weld skipping and arc instability. We went to an 0.035 1 mm wire and could not get the travel speeds. We changed to 0.045 (1.2mm) and had to run the pulsed arc with the arc length buried in the part, this resulted in extensive weld spatter also the part could not handle the pulsed weld heat and we would have holes all over the place. With the disappointing pulsed weld results we now use high end short circuit CV with the 045 wires and are attaining 40 IPM travel rates. I have no spatter on the part and have no arc stability problems with the short circuit. I hate to admit it but this is is another pulsed failure in my book. I could get these short circuit results CV power source for half the costs..
Regards G S.

BEST WELDING PRACTICES. WIRE DIAMETER SELECTION. As I write this report one of your competitors is utilizing 0.052 1.4 mm weld wires on Ford frames 2 to 4 mm. This company is also using the same pulsed Lincoln equipment as you. They also went through the consequences of the pulsed arc instability, and they were unable to use spray with the large weld wires. The programmers at the plant unknowingly dialled in lower "globular parameters" which are causing all types of production and quality problems, (see frame plant report at this site).The globular transfer caused over 80% weld rework.

The choice of an 0.045 wire for short circuit and spray welds that will be made on parts less than 2 mm is also an inappropriate choice.

The Chicago facility and the cradle welds will benefit from stable spray transfer and a smaller wire diameter than 0.045 (1.2mm) Lets take a moment to look at the MIG weld current compatibility with standard gage thickness used at the cradle facility.

[] With robot, single pass "butt" welds on 1.6 mm cradle parts, we typically would be in the short circuit mode, welding at 170 - 200 amps. Lap welds do allow higher weld current, however the butt weld data shows the part compatibility with the weld current utilized.

[] With the cradle 1.8 mm parts, the butt weld current would be increased to approx. 220 amps. For any application that uses a weld current over 200 amps we would want to use the high deposition, stable spray transfer mode. Butt welds on 2 mm parts could be robot welded using 240 - 260 amps.

An 0.045 wire requires a minimum of 250 - 260 amps to attain stable spray transfer. As many of the welds you produce require less than 260 amps it makes no sense to use a consumable that will simply cause weld burn through on many of your parts. The bottom line it's imperative the plant uses an 0.035 or 0.040 wire. The common 0.035 wire will go into spray around 200 amps.

BEST PRACTICES AND WELD WIRE COSTS.

I can understand why third world countries get uptight about weld consumable costs, however in many North American auto plants weld engineers should not have to worry about the $1 a pound MIG wire costs. As bigger wires cost less, in many auto plants purchasing managers rather than engineers may decide on the wire diameter selected. 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. In this case changing the weld wire to a smaller wire will dramatically improve both the weld productivity and quality, but hey, why worry about a daily, lousy robot production of 60% with > 40 % daily weld rework, when the purchasing manager can save 20 cents a part.

YOU ARE NOT LIKELY TO USE WELD WEAVES IF YOU DON'T UNDERSTAND THE ROBOT MIG WELD BENEFITS ATTAINED FROM WELD WEAVES:

THIN PARTS AND WELD WEAVES. The plant was not using weaves in any of the robot cells. The plant should consider when required, the use of weld weaves for specific problem welds. The weld weaves should comprise of amplitude that creates a narrow, high speed oscillation in the weld centre. This weld weave oscillation will not impact the potential weld speeds, it will however cause the fast freeze thin welds to thin out and provide slightly wider weld coverage.

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

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

If you are reading this today a few years will have passed since it was written. Do you see any similar issues in your plants? Hopefully this tongue in cheek weld article will assist some UN-blinkered auto / truck manufacturers to give a little more consideration to weld process and equipment requirements. If you want to spend less time trying to put out the weld shop fires that daily spread through too many weld shops, managers, engineers and technicians and any weld decision maker involved, all need to walk the same path to weld process optimisation, in other words for god's sake get some process control MIG Welding training.

 

SOME REASONS FOR THE COMMON LACK
OF BEST WELD PRACTICES AND PROCESS CONTROLS.


How unqualified individuals and
inflated egos influence welds:

INFLATED WELD PROCESS CONFIDENCE FROM PARTS EASY TO WELD.
At many North American auto / truck parts plants, when the robot welded parts are >2 mm, thanks to good part fit and the low weld burn through risk, and the simple fact that few of the welds will have an internal weld evaluation, you will often find that the managers, engineers and technicians at the plants have an inflated weld process confidence and ypically they also have minimal weld process expertise. Along with the unwarranted weld confidence it's not difficult in these plants to find managers and engineers who do not believe in weld process ownership. Also you won't have to look far to find young technicians with 24 months robot weld expertise These rookie warriors will often have swollen egos and with their attitudes they will have decided they no longer need to further their very limited weld process education. So many programmers figure they don't need robot weld process expertise yet the majority would have a difficult time with this fundamentalMIG process control test .

THE WELD PROBLEMS START OFTEN BEFORE THE ROBOTS ARRIVE: It's a reality that with the big five auto / truck companies and their suppliers, that many of the robot weld issues are caused before the robots get to the plants. It's not uncommon to find weld issues that result from the selection of oversized MIG weld consumables and poor performing weld equipment and fixtures. The consumable selection is often influenced by project engineer (mechanical engineer), or a purchasing manager, individuals that rarely understand the MIG process. Other issues will arise from project mangers listening to salesmen and the delivery of erratic pulsed weld equipment or robots and fixtures loaded with bells and whistles let lacking in essential components that will benefit the application. Add the weld consumables, equipment and people issues together and to this team, throw in manufacturing engineers that lack the ability to provide parts that meet the design dimensional specifications. Then mix in an inexperienced, hands off manufacturing managers who do not believe in process ownership and you have the symptoms for a plant that will never meet the daily production and quality potential that the costly robots could have delivered.

SOUND MANAGEMENT DECISIONS CREATE SOUND WELDS.

It's obvious that many of the people who today make robot weld and cell recommendations are simply not qualified and as we all know, many of the robot weld problems we find today in the auto / truck industry are influenced by manufacturing decisions and specifications that have their roots in corporate offices.
See Chrysler management wastes millions through corporate weld decisions.

Ed teaching his grandson so he won't
have to Ask a Salesman or Lincoln How!

KEEP SMILING, AFTER ALL IT WAS YOUR
DECISION TO BE IN THE WELDING INDUSTRY.

E-Mail. Weld Question From: Dave.

Subject: Fw: 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.

Thanks Again Ed!

I passed this on to my buddy Greg Smith.

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 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. (866) 584-7281 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

E-mail. Oct 2008: I am emailing you because I have come to a questionable snag with my pulsed MIG equipment. I have the equipment set in the spray mode. I am welding on 5/16” carbon steel material, my 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, the weld flattens out and 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 the weld picture indicates poor side wall fusion. As you are using good spray parameters the lack of fusion is likely a result that the weld surface was wire brushed and the mill scale has been left. If you are concerned about fatique properties you don't MIG weld over mill scale. Grind the weld area before welding, I am sure you will see a difference in the weld appearence. As for the crater and crater hole.

[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. You do have a pulsed power source that has a built in defect. This is a a commom classic issue with pulsed equipment in which the machine controlled end parameters or 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, the high voltage spike applied for the burn back 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 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 provide process solutions, however you would be well served to send the power source back to the company who manufactured it. It's ironic that this defect would not occur on a lower cost traditional CV power source.

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ROBOTS AND CRATER CRACKS.
Found usually in concave crater left 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 termination robot parameters and robot technique.
Solution. Ed's Robot Process Control Book deals with weld start / stop issues and optimum data for these problems..

ROBOTS AND LONGITUDINAL 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 poor programming and too
much weld heat is applied resulting in a part in which the weld imposes more stresses than
the hot base metal can handle.

ROBOTS AND TRANSVERSE 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 WELD ROOT / THROAT 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 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 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 035 wire is much more suitable for weld repairs than the 045 or 052 wires most welders are given.

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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with the personnel in those front offices.

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