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

MIG Welds and Robot Weld Tips.

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

A little reality: : Japan is a country that for almost five decades had few industrial gas plants. Argon MIG gas mixes were a rareity and when available very costly. In this time frame, when MIG welding, Japan utilized mostly straight CO2 gas. Four decades after the second world, this nation had minimal experience with attaining optimum quality MIG Spray Transfer welds, which were the most widely utilized welds in North America.

 

Process expertise will effect process logic and the software.

Remember when it comes to evaluating robots and MIG weld software, Japanese Weld Logic and North American & European are not be the same.

Where as Japan used electronics to compensate for it's lack of argon mixes, it's important for weld shops considering the purchase of a MIG welding equipment or a robot to remember, at the end of the day, for five decades, optimum MIG weld quality and productivity has never required sophisticated electronics..

ROBOT 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 1 billion wave forms. Stay focussed on the practical weld capability of the equipment in robot cell.

[] When an integrator advises you to use pulsed for that steel application, remember it's typically not necessary and may not be the optimum weld transfer 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.

[] In comparing robots, examine the ease in which 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, who's' supplying the most bovine fecal 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.

REMEMBER, 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 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, 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 ROBOT AND A MORE LOGICAL SWEDISH ABB ROBOT WITH IT'S PRACTICAL REAL WORLD WELD PROGRAM FEATURES. BY THE WAY I BELIEVE IT TAKES 30 TO 50% LESS TIME TO PROGRAM A WELD PART WITH AN ABB ROBOT, IN CONTRAST TO ANY
JAPANESE ROBOT.

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

ROBOTS AND WELDING ISSUES



THE FOLLOWING 13 REASONS WILL INDICATE YOU
LACK PROCESS EXPERTISE AT YOUR FACILITY.

[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 robots 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 or parameter data 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.

Why not visit the Management / Engineers section
for robot weld process controls

ROBOT ARC WELDING SAFETY

Ensure the safety system of your robot cell is compliance with the revised ANSI/RIA R15.06 standard. Compliance to ANSI is voluntary, however note, OSHA inspectors and lawyers involved in robot safety issues may reference these standards when evaluating the robot cell safety. For more safety data visit the RIA web site www.RIA.comh.

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 tack welds. The tacked parts were later brazed, The TIG welds were made with a Fanuc Arc Mate 100 robot, and a Lincoln 350 amp "pulsed" square wave power source.

The welding issues at this tier one part supplier were extensive.For more than a year they had struggled to attain a production rate of only 40% of what they desired. The tack welds were frequently missing, arc starts issues were extensive, and the tack welds would leak. After I rectified the problem, I wrote the following report.

.

 

 

"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 be able to justify and explain the benefits of the weld gas and weld wire size selected. The programmer should also know without "playing around" where to instantly set all the optimum robot weld parameters.

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.

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

Provide the robot weld wire feed speed or weld current setting for the wire selected.

Provide the maximum robot weld travel speeds.

Provide a weld voltage which will minimize weld spatter.

Be aware of how to minimize the effects of the weld heat on the part.

Provide the optimum robot weld start / stop data.

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

Provide weld data that compensates for gaps.

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.

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 optimize 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.

 

Motoman Robot Concerns?

The following is an E mail sent to me March 2001, I have deleted
the name of the person and companies 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

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 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 equipment , use the 0.035 wire but change the setting on the pulsed control panel to the "0.030 pulsed steel setting" and you will get good pulsed weld results in this parameter range. Regards Ed

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. 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 around 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
"job description" or the 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 ownership. Its a global weld reality that few manufcaturing managers or HR personnel are familiar with the expertise levels necessary for robot arc welding process optimization. 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 your hands off managers the money you save your company. Remember in todays bean counters world, you have to show the beans saved. To help you on this trip I recommend my "Management Engineers Guide to MIG" book and CD training program.

 

 

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.

Answer: Robot arc start issues are addressed in all my process training resources. Note. The part thickness you weld and the 3/16 fillet weld requirement allows " higher than normal manual weld travel rates". Speed affects voltage.

The MIG gas mix selected will also influence the arc starts. When you use a low energy argon oxy gas mix or tri mixes that contain oxygen, these mixes in contrast to an argon >15% CO2 mix will require lower weld voltages to sustain the spray arc. High speed welds = low voltage for the weld + low voltage for the gas = insufficient voltage for the arc starts. If you are in this section you will benefit greatly from my robot process control training book.

The high weld speed (low voltage) that's possible with a 3/16 (5mm) fillet, and a low energy gas mix (low voltage) will influence the required spray transfer "welding voltage". In these circumstances typically 24 to 26 volts is required for the high, 450 in/min wire feed rate used. This low spray transfer "weld voltage" of 24-26 would typically not be sufficient for consistent arc ignition on colder wires at a wire feed rate of 450 ipm.

 

[a]Arc Starts: For the 3/16 fillet welds and the 045 wire,if using the spray transfer wire feed rate of 450 ipm ensure your actual robot start voltage is in the range 28 to 31 weld volts.

[b]Arc Starts: 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.

[c]Arc Starts: 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 dont hear the start data its typically not effective..

[d]Arc Starts: 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

[e]Arc Starts: For fillet welds smaller than 3/16, ignition delay time can build up excess weld at the starts

[f]Arc Starts: Ensure the pre-flow gas time is sufficient.

[g]Arc Starts: 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

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 PowerWave. 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.

Robot Ignition Delay Times in the Robot Start Data?
For robot welding small fillet welds <3/16, its often beneficial to use "no
ignition delay time". The ignition delay time in combination with arc start delay time and pre flow gas time can create too much of a delay at the weld start. The delay or robot start pause can result in a weld build up for the small welds especially in the first 9 mm of weld.

The larger the weld, the longer the arc start time required. To establish the weld puddle with welds larger than 3/16, an ignition delay time of 0.3 to 0.8 sec is typical.
Aluminum welds require long start delays to burn through the alum surface oxides.

Note, the most troublesome robot weld is often the very first weld, or a weld made after a long weld pause. The problems occur because the welding wire is "cold", electrons travel better when the wire is hot. For this situation you may benefit from a shorter wire stick". Always
have a least 3 robot arc re-strikes programmed for all welds.

Optimum Robot Spray "Start Data" for Carbon Steel .035 (1mm) Wire.
For the 0.035 (1mm) "spray transfer" arc start, set the wire feed at 500 in./min with 28 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.

 

 

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 PowerWave 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 half way to 75% along the weld length the weld appearance would change, what do you think is happening?

ANSWER. What can you expect when North American designed weld equipment is trying to communicate with the land of Japan.

I believe you have a case of "premature robot communication" The poor interface 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 preprogrammed 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.

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 the USELESS helium tri-mix which is adding to your burn through issues. See the weld gas recommendations in the MIG gas section (MIG DATA) of this web site. Also 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 could create lack of weld fusion issues on the
thicker gage parts.

Reference the pulsed power source, a North American Miller Invision (sells for less than $4000), 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 . 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 swith back to short circuit. The argon 2 oxy or CO2 MIX will again benefit the short circuit and reduce weld burn through.

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 aluminum wires a U groove with smooth surface again don use excess drive roll pressure. With aluminum 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.

 

A Robot the Lincoln PowerWave Street Lamp 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.

 

 

A Fanuc Robot TIG Weld Situation

 

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.

 

 

Excess weld spatter caused
by poor parameter selection .

Good Robots, 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: Thank-you for having the motivation and courage to make this kind of information available. I have not yet come across an opinion 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 who frequently lack the ability to get to the real root
cause of their daily weld issues. Most 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 , 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 contact its fine. If the tip bore is not the correct size, (check with drill gauge), change your 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 poor quality products and provides bad advice. There is the possibility is the tips you purchase are made in China or Timbuktu. There are many quality issues with off shore, substandard weld consumables. Good luck. Ed:

How to prevent 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?.

The most common occurrence of burn-backs,

Wire burn backs at a "weld starts". At a weld start the wire may not have enough forward feed momentum, yet weld wire may have enough current to snap of the wire or cause the wire to weld itself to the tip.

Wire burn backs "during the weld". The second cause of burn-back is when the MIG wire
is restricted in the liner, or the tip, or from lack of sufficient wire tension from the drive rolls. These problems frequently result in a wire burn back which can melt the end of the contact tip. It can occur the arc start or during the a weld. When welding with a robot using an 0.035
(1mm) wire, sometimes the robot arm over twists the gun cable restricting the wire. This is noted when the burn back consistently occurs at a specific weld.

Why the common wire burn-back problem occurs. Many factors other than wire feed issues can influence a wire burn back.

[1] Wire stick out length.
[2] Robot program arc start data.
[3] Use of globular transfer.
[4] Lack of shielding gas.
[5] Wire restriction.
[6] Poor wire feed.

The following weld data is found in my books:

Wire stick-out influence on burn-backs.
As the robot starts an arc, the robot control sends a signal to the power source to open up the contactor to energize the wire. When the wire makes contact with the work, the wire feed should be feeding forward with full inertia. In some instances the high start current melts the wire before it can be fed forward at its full speed.

Many robot personnel are not aware of the influence of the wire burn back data on welding issues. They may set the "wire burn back" data in the weld program so the wire stick out is 1/2 at the weld completion. This means the stationary 1/2 of wire sticking outside the nozzle can make contact with the grounded work before the wire is fed forward at full momentum. The
high current through the wire as the wire short circuit occurs cab disintegrate the wire and can melt it back to the contact tip end.
The wire stick out at a weld completion is controlled by the wire burn-back control data. The wire stick out should always be kept as short as possible. The programmer should set the wire burn back so the wire stick out is approve a 1/4 from the electrode tip at the weld completion. The optimum contact tip position for spray or pulsed spay is with the tip recessed inside the nozzle about 3 to 4 mm. With the gun nozzle set at 1/2 to 3/4 the 1/4 wire stick out will result with wire to work distance of approximately 3/8. This distance is beneficial in allowing the wire feed some forward momentum before contact with the work. (A normal nozzle to work distance should 1/2 to 3/4 depending on the circumstances).

Tip Stick-out. Up to two years ago the standard robot MIG gun produced in North America had the contact tip located either flush with the end of the nozzle, or "sticking 2 to 4 mm outside the nozzle". I used to go in plants and tell the people on the floor to cut 6 to 9 mm of the contact tips. The robot gun manufacturers were not aware that their nozzle tip design was one of the great contributions to robot tip problems. Of course if you stick a tip close to a spray weld its going to increase the potential for burn back to the tip, and the super heat will increase the
weld spatter that will adhere to that tip.

Burn backs caused by the utilization of the erratic globular transfer process. This high spatter process provides weld drops that attach to the contact tip and restrict the wire feed delivery so the weld wire burns back to the tips. In the auto / truck industry this is a prime issue as some process ignorant engineer selected a weld wire too large for the gage application, causing the use of weld data that produces globular transfer.

Arc start data influence on wire burn backs. If the weld parameters utilize high weld voltage. During the arc start, as a result of the power source slope output, a large amount of current is available as the wire makes contact with the work. With the wire contact, the power source volts drop and the current out put rises dramatically. The higher the weld voltage used the higher the available current for the wire short circuit. For arc starts with a robot we do not need to use the same weld data for the start data. For the start data use a lower spray, pulsed or short circuit wire feed setting this requires a lower voltage setting that restricts the available current for the arc start. This data provided in earlier paragraphs.

All MIG programmers should be aware of the low end optimum welding parameters of each available mode of transfer for each wire diameter, its all in my books.

Time and gas influence on arc starts. At a weld start, its critical for good arc starting to have the weld gas flowing before the arc is initiated. Poor arc starts occur if there is not sufficient gas, remember its the arc plasma ionized gas which assist the conduction of electrons across an arc gap.

A robot offers many timed functions that a manual welder does not have to deal with. Arc ignition times, arc delay time etc. With many robots the different arc timed functions can accumulate. The arc ignition time may combine with the gas pre-flow time which may combine with the time in which the robot examines the arc ignition before it allows the
weld to commence. The accumulation of time results, the robot maybe stationary too long at the weld start.

Time is a critical factor for both arc ignition and ensuring the weld is fully fused at the weld
start. With thin gauge metals to minimize "over weld size" at the start, and reduce weld burn through potential which frequently occurs at arc starts, you need to reduce the arc start times
to a minimum. However one timed item is important "gas pre-flow time". For good arc starts always ensure there is sufficient gas pre-flow, the bigger the weld the longer the arc ignition and gas pre-flow times and as mentioned for smaller welds visa versa. When welding thin gauge, on many robots a flying start may be available in which the gas pre-flow is switched on before the robot gets to the arc start.

Contact tip positions and arc starts. Too many robots have poor contact tip positions and this greatly affects wire burn back for ideal settings get the books. Ensure for spray applications that the contact tip is recessed at least 3/16 to a 1/4. For short circuit applications an ideal tip position is flush with the end of the nozzle

Pulsed welding is much more prone to wire burn backs then the traditional MIG mode. The primary reason there is a concern with pulsed, is with pulsed there is a time factor required to create the pulsed drop on the wire tip. For spatter free weld transfer, the weld drop created per- pulse has to be able to cascade across an arc gap to the weld without making contact
with the wire tip and weld at the same time. If contact occurs, the weld drop would explode causing spatter. In contrast to spay transfer, the pulsed mode therefore requires a longer arc gap, (distance between wire tip and weld). The longer pulsed arc gap means a shorter wire stick out from the end of the contact tip, which means increased potential for wire burn backs. More ROBOT info my books.

 

 

2004. Pulsed weld made with a Lincoln Power Wave

.

This ridiculous tier one weld is not the fault of the robot or the over priced Lincoln PowerWave, it is the fault of the hands off, managers and engineers. This frame weld 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. These welds are simply a reflection of apathetic process management and engineering. It's easy to fix weld problems like this, that is if you can find manufacturing managers who are sincere about finding out the real root causes of their daily robot weld process issues.

Robots and Gas Flowmeter Issues.

Question.

Ed I'm having a hard time keeping flowmeters from "blowing their lids" in my plant. We've run both ESAB and Rexarc flowmeters 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 flowrate. 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.

WELD 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. Whe 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 restiction due to the narrow orrife 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 ( waggon 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 ofen a result of insufficient gas less than 20 cuft /hr.

An 0.052 (1.4 mm wire) robot MIG wire was selected
for this 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 the engineer responsible,what would you do to rectify the situation?

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 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.

After eight long Bush years, with a little process expertise you may
be able to afford an indoor toilet

 

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.

MIG 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 shape of the tip is rarely relevant, thicker 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. The vast majority of contact tips require replacement due to the following;

[a] Wire burn back due to poor robot weld start / end data.
[b] Use of oversized wires causing the use of globular weld transfer. The large globular droplets quickly block the contact tip bore.
[c] Spatter caused by poor weld parameters.
[d] Wire cast or helix issues.
[e] Tip in wrong position or nozzle to close to weld.
[f] Pulsed or spray parameters that create a short wire stick out.

The resolutions to eliminating all major contact tip problems are spelled out in my robot process
control training book, click here

Contact Tip Facts. Copper has been the material of choice for many decades, primarily because, after silver, it displays the second best electrical conductivity amongst all metals.
Due to it's face centered cube crystalline structure, pure copper is naturally ductile. Copper for contact tips is strengthened by a number of strengthening mechanisms including cold work, solid solution, precipitation hardening and dispersion strengthening.

The most popular and inexpensive copper alloy used in North America for contact tips is CDA C12200 (P deoxidized copper). Precipitation hardening alloys such as C18100 (Cu-Cr-Zr), C18200 (Cu-Cr), C17510 (Cu-Be) have been common for high performing tips since generally they tend to have higher physical wear performance than C12200. Unfortunately, as most strengthening mechanisms, precipitation-hardening can compromise the electrical conductivity of copper. Plant experience with these alloys has been mixed; however keep in mind most plants do not correctly analyze the root cause of the tip problems and even fewer plants will take the logical process corrective actions.

This is simply a partial look at MIG robot issues s. My books and Robot Process Control training CD resources will give you everything you need to resolve any robot weld issues. For the most comprehensive data ever written on Robot Process Controls, and Management Weld Process Controls follow this Robotic MIG Welding link.

Remember you are part of the weld industry,
so keep thick skin and maintain a sense of humor.

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