Written by Ed Craig.
Robot Welding 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
were and still are very costly. For decades Japan utilized mostly straight
CO2 gas for it's MIG welds and the result
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
utilized welds made in manufacturing plants in North America
Few Japanese auto plants had been able to produce optimum manual or automated quality MIG welds and we in the North
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
than the earlier units, and with pulsed MIG equipment the cost effective Asian built OTC Daihen equipment is superior to
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
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
weld logic were rarely similar.
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
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
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
with the integrator or robot company, who's' supplying the most bovine faecal matter.
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
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.
THE ROBOT YOU MAY BE CONSIDERING TO PURCHASE MAY WORK WELL IN AN
AUTO PLANT WHERE WHERE THEY RARELY CHANGE THE WELD PROGRAMS,
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
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.
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
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.
robots, the weld quality - productivity opportunities are only
limited by a manager's or engineer's weld process control knowledge.
AND WELDING ISSUES
YOUR COMPANY PURCHASED AN $80,000 ROBOT CELL AND YET DID NOT HAVE EMPLOYEES
THAT HAD ROBOT MIG WELD BEST PRACTICES & PROCESS CONTROL EXPERTISE, COSTING $400?
ANY OF THE FOLLOWING
15 REASONS WILL INDICATE YOUR ORGANIZATION
WELD PROCESS CONTROLS AND BEST PRACTICES EXPERTISE.
If you have robot weld rework is more than 2% of your parts.
 If your robot cells have a ROBOT DOWNTIME per shift, of more
than 15 minutes per-robot.
 If you use gas shielded Flux Cored wires for welding clean carbon
steels < 3/8 in the flat and
horizontal welding positions.
If you utilize any three part gas mixes for MIG welding carbon steels or thin gage stainless.
 If you utilize Metal Cored wires for MIG welding carbon steels or for thin gage stainless.
 If you
weld carbon steels and you use any MIG gas mixes containing oxygen.
 If you purchase
your primary weld supplies from more than one supplier.
 If your purchasing manager is involved in the selection of your weld consumables.
 If the person
who has full responsibility for the robot welds works in the maintenance
 If your company allows robot operators or anyone other than
the programmer to make welding parameter changes to the robot program.
 If the changes made to the robot welds are not immediately verified through macro samples,
 If there is no pre-weld qualification, weld parameter and weld manufacturing instructions posted
on the walls of the robot cells.
 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,
 If your manual welders doing the repairs or simply manual welds daily use
a whipping, skipping or weave actions with their MIG guns.
If you use pulsed MIG and don't understand the implications of each pulsed parameter adjustment.
ALL OF THE ABOVE IS COVERED IN MY
ROBOT WELD PROCESS CONTROL PROGRAM....
AUTOMOTIVE ROBOT TIG APPLICATION: This
weld report deals
with robot TIG welding issues that were occurring on one of the
big three cars.
parts required approx. 15 precise small welds and the the parts weld seams were
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
of what they desired. The tack welds were
frequently missing. Arc starts issues were extensive, and the tack welds would
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
last time your company welded
similar parts, weld burn-through issues were prevalent. With this in mind the programmer should know
around" where to instantly set all the optimum robot weld parameters, wire feed, amps, volts travel speeds and be able to
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 wire size selected and the programmer should be able to train the cell operators to recognize arc sounds that indicate
A robot programmer should have the capability
and without"reference to a weld text
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.
if using pulsed, expertise on the wide variety of pulsed parameter adjustments.
the maximum robot weld travel speeds for each weld.
weld voltages for each weld that will minimize weld spatter.
aware of how to minimize the effects of the weld heat on the part and how to prevent weld burn through.
the optimum robot weld start / stop data.
aware of the robot MIG gun technique which can effect the arcs and welds.
weld data that compensates for gaps or part alignment discrepancies.
weld data that ensures consistent weld fusion.
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
able to answer my MIG weld
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.
Oversize weld slots in this car seat, cause weld and strength results.
I have never met a designer of auto - truck parts that understood
the requirements for optimum MIG weld results.
For those designers, engineers, managers, technicians or supervisors
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.
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.
SIX WEEKS, THE PANASONIC ROBOT TEAM COULD NOT GET
THE PANASONIC ROBOTS TO PRODUCE TWO
SIMPLE EXHAUST WELDS.
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.
and Robot Weld Concerns.
following is an E mail sent to me March 2001.
At the persons request, I have deleted
his and his
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.
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.
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.
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.
If you wanted to produce poor to mediocre, inconsistent, globular type
short circuit welds, purchase the above Motoman MIG equipment.
MORE MOTOMAN ISSUES. REMEMBER THE MOST IMPORTANT TOOL IN THE ROBOT CELL
IS THE POWER SOURCE, AND NOT ALL MIG POWER SOURCES ARE CREATED EQUAL:
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 .
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
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
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.
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.
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 OF STABLE, CONSISTENT PULSED WELD TRANSFER.
IF MANAGEMENT DOES NOT TAKE RESPONSIBILITY AND OWNERSHIP OF THAT 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
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.
Welds on Ford
6061 Aluminium Car Seats.
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
the installation of the robot cells, continuous production of optimum weld quality
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
SOLUTION TO A COMMON
ROBOT MIG PROBLEM. "INCONSISTENT ARC STARTS"
Info like this in Ed's Robot Training Program..
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
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
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.
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
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.
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.
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
Start Solution: Ensure the pre-flow gas time is sufficient. Without gas ionization arcs don't exist
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 Equipment and Robot Axle
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
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.
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
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.
have a least 2 robot arc re-strikes programmed for all welds.
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
in all my robot weld
process training books. resources.
Robots and MIG equipment. Premature Interface Communication.
Motoman - Fanuc Robot
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
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
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
with many solutions in all
my robot weld
process training books. resources.
MIG GAS SELECTION AND ROBOT MIG WELDS;
Ed, we robot weld
300 series stainless. The parts
2.5mm used in an exhaust manifold.
The parts have inconsistent fit and gaps. We have
been using an
(1.2mm) wire with a 90% helium
- 7,5% Ar - 2.5% CO2 tri-mix
with short circuit. Many
lap welds with gaps and we often find
like either lack
or weld burn through and always distortion. Are we using the correct consumables and which pulsed MIG equipment, would you recommend
for this application?
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
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.
|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
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
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.
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
many career opportunities available to me at this time, particularly in plants
that supply auto - truck, robot
I have been looking at many
different job opportunities mostly in the auto / truck industry. When I go for
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.
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
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.
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.
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.
Robot plus the Lincoln Power Wave
Street Lamp automated weld Issues.
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.
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).
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
MIG WELDS AND CONTACT
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
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.
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.
Fraser Rock. Weld
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:
Question: Ref MIG wire burn backs to the Gun Tip.
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
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?
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.
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.
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..
Gas Flow Issues.
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.
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.
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.
|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.
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.
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
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.
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.
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:
dimension ACCURACY and TCP controls are critical when welding thin gage applications.
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
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,
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,
weaves are beneficial, the plant programmers made no use of the weld weaves in any of the
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.
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 THE 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).
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.
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
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
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.
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
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.
30-04. E Mail to Ed. Ref Miller Pulsed MIG issues,
Miller Accu-Pulse / Auto
Your description of arc sensitivity with high speed pulsed welds is exactly what
experiencing with our robots and the new Miller Accu-Pulse process / Auto
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.
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.
WELD PRACTICES SHOULD
NOT INCLUDE PURCHASING MANAGERS.
can understand why third world country weld shops get uptight about weld
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.
important weld benefits are attained from the weld weaves on gage parts;
Answer: "Controlled weld weaves" avaialble ifrom automated applications enable
Reduce weld burn through potential.
 Help compensate for gaps.
Helps compensate for part dimensional deviations.
 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
weld practices and process controls in his plant.
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.
Lets 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.
MANAGERS - ENGINEERS - SUPERVISORS AND TECHNICIANS, TO AVOID ROBOT
WELD PROBLEMS, IT'S LOGICAL YOU WOULD
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
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.
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
Weld Question From: Dave.
and Mig weld conduit?
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
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"
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
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
carbon steel material. My weld settings are set to spray
transfer (29 volts 500 wire
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 dont pull my nozzle away
before I let the trigger go, so I dont think this issue is caused due to
the length of the stick out. My gas is set to 35cfh argon/CO2 mix.
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
things going on here.
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
mechanical properties, you don't MIG weld over mill scale as it impeads the
 A fish eye is typically a pore evident in a failed
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.
twenty years in the weld shop with a little process expertise, you finally may be able to
afford an indoor toilet.
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
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..
AND LONGITUDINAL WELD CRACKS.
crack running in the direction of the weld axis found in the base metal HAZ or
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.
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:
AND ROOT / THROAT WELD CRACKS.
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.
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.
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.
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.
This is simply a partial look at MIG robot issues. For the most comprehensive data ever written on
and Management Weld Process Controls follow
this Robotic MIG Welding link.
you are part of the weld industry it pays to have
thick skin and maintain a sense of humor.
MIG weld equipment issues in the MIG and pulsed MIG