More info on the Wire Stick Out (ESO) influence on burn-backs.
When the robot weld starts, the robot control sends a signal to the power source to open the contactor to provide current to energize the weld wire. When the wire makes contact with the work, the wire feed should be feeding forward with full inertia. The current arrives at the wire tip before the wire feed has it's full inertia and momentum and torque from the feeder. The high start current available during the wires contact with the work causes a short circuit that can melt the MIG weld wire back to the tip.

The MIG wire stick out at a weld completion is controlled by the "wire burn-back control data". The wire stick out at the weld completion should always be kept as short as possible. The wire burn back should be set so the wire stick out is approx. 3 - 6mm from the end of the nozzle. A normal nozzle to work distance should 1/2 to 3/4 (12 - 18 mm) depending on the welding circumstances. With these settings you allow a gap between the wire tip and work.

Remember. At the robot weld start, there should be sufficient wire to work distance of 4 - 6 mm to ensure the wire is feeding forward before the wire makes contact with the work.

 

 

 

Contact Tip Stick - Outs.

For almost twenty years, the standard robot MIG gun produced in North America and Europe had the contact tips located either flush with the gun nozzle or sticking outside the nozzle by approx. 3mm. The lack of understanding of the influence of Wire Stick Out (WSO) and resulting poor contact tip placements were simply a result of the robot weld process ignorance by the gun manufactures and the robot integrators. Both of these contact tip positions caused numerous robot down time and productivity issues with the world's most common MIG weld transfer modes, spray and pulsed.

If MIG equipment manufactures show little understanding of the MIG process, It should be no surprise that the MIG gun manufactures and the robot integrators who delivered their robot guns with the contact tips sticking outside the gun nozzles simply did not know better. Also someone needs to ask why for decades, did the MIG gun manufacturers classify their MIG guns for use with straight CO2, when less than one percent of the MIG welds were carried out with straight CO2.

At most of the plants I visited that were using spray transfer on parts > 3 mm, the robot MIG guns would be welding with the contact tip stuck outside the nozzle and numerous contact tip issues would be occurring. I would tell the people on the floor to take a hack saw and cut 3 to 6 mm off the contact tips.

It should not have taken a rocket scientist to figure out that if you stick a contact tip too close to that spray weld, with the high weld parameters, the high weld heat and spatter will increase the potential for contact tip issues.

As for that pulsed MIG weld, if the contact tip extends outside that nozzle that typically means less wire to work distance is available to create that stupid little weld drop. A drop that needs a greater arc gap than spray, so the pulsed droplets can transfer uninterupted across the arc gap without being in contact with both the wire tip and work.

Many factors influence arc start with robots. All MIG robot programmers should be aware of the factors that effect arc starts, and be aware of optimum start welding parameters of each available mode of transfer and for each wire diameter used. All the data you need is in my books and training resources.

How many companies are aware that pulsed MIG welding is much more prone to wire burn back then traditional MIG weld spray transfer?.

The primary reason there is a contact tip concern with many pulsed weld power sources and robots, is with the pulsed process there are electronic time factors and weld wire arc length requirements necessary to create and transfer a pulsed weld droplet, a weld drop that typically provides no carbon steel weld benefits.

For a spatter free pulsed weld transfer, the pulsed weld droplet has to cascade across an arc gap into the weld without contacting the wire tip and weld at the same time.

If a pulsed weld drop makes contact with the work and wire at the same time an explosive short circuit in the pulsed weld drop will occur. The pulsed drop short circuit explosion will cause spatter and possibly disrupt the controlled formation of the next weld drop. These issues (which can typically be heard in the arc sound) can effect the weld and fusion consistency. This situation gets worse as the wire feed rates increase.

The pulsed MIG mode requires a longer arc gap than that is necessary for spray transfer, two to three times the length. The longer arc gap means a shorter wire stick out from the end of the contact tip. The shorter wire stick out increases the potential for wire burn backs. Want a 100 pages of why pulsed can cause weld issues you won't get this data from Lincoln, Miller or ESAB, you will get it from my 600 page "Managers and Engineers Guide to MIG book"


A common automotive plant oproblem. Plants which allow robot welds with oversize contact tips, or contact tips that have excessive tip bore diameter wear. This results in erratic current transfer from tip to the MIG wire?

 

When you understand WSO you can often increase your robot weld speeds in the range of 50 to 100%.

 

My Management Engineers book has over 600 pages on how to consistently control both manual - robot weld quality. This book also shows you how to increase traditional MIG robot weld deposition rates (faster weld speeds) in the range of 50 to 100% If you want best practices - process controls for MIG and flux cored welds, this is it. ."Management Engineers Guide To MIG"

 

The weld speed rates for fillet welds are obviously first determined by the weld size which influences the required weld deposition rate. Another restriction is the weld fusion requirements. Travel too fast with that robot and irrespective of the weld current or weld mode utilized you will have a weld fusion issue. The weld surface condition, the weld length and the shape of the steel (round components are more sensitive to lack of fusion than plate), will also influence the weld speed and weld fusion.

 

 

Poor welds on frames and axles and we should also have concerns for the shock welds:

Many years ago a major USA shock manufacturer called Monroe, requested my assistance as they could not get their robot MIG spray welds on their shock bracket welds to qualify for a Chrysler "shock load test spec"

The Chrysler engineers required the bracket welds on the shocks absorb at least a 13,000 lb test load. After robot welding the steel brackets with 5 mm fillet welds on the shocks that were only 2 to 3mm thick, Monroe found that their shocks bracket welds would fail prematurely, typically in the 7000 to 9000 lb range.

While the Chrysler weld specification for the shock bracket welds required that the welded brackets pass a test load of 13,000 lbs, it took me less than two days of welding and testing on the shock bracket welds to reveal that any test load of less than 19,000 lbs, indicated lack of weld fusion in one of the four bracket welds.

There were three reasons that the shocks could not meet the minimum shock weld test load requirements,

[1] the robot spray transfer welds were made on "cold rolled round parts",

[2] the robot weld speeds for the small weld lengths were "set too high",

[3] the robot weld lengths on the brackets "were to small".

After I figured out the weld problems, I changed the weld wire size to a smaller wire which increased the weld current density. I reset the spray parameters, extended the shock bracket weld length by another 3 mm. After my changes, the shocks bracket welds failed at an average load test of 21,000 lbs.

How fast, how slow should the robot go?

If all MIG welds were evaluated for the internal weld fusion, there would be more focus on the weld speeds utilized. Many robots today are either welding too fast or too slow. A common problem is that the MIG wire size may be wrong, or maybe it's because pulsed, globular or short circuit is being utilized when spray would be superior. Maybe the weld issue is the part design, joint type, part thickness or ridiculous gaps many auto / truck companies present to the robot weld cell. Optimum weld speeds for all applications and weld compensation data for potential weld issues are covered in my books.

ROBOTS & WELD SPEEDS.
Many companies who purchased pulsed MIG equipment for their robot cells, may have had high robot weld speeds and high weld production expectations. The majority of weld decision makers who purchased the MIG equipment for the robot cells were under the impression that with the new, sophisticated, pulsed MIG equipment, that their Multi - Wave Form, Pulse on Pulse, AC - DC, Fuzzy Weezzy, Remote Wireless Controlled, $13000 MIG power source, that they can now 'weld faster" with more production that that possible with a conventional MIG power source on applications > 3 mm.

The MIG robot weld speed reality is this. The low cost MIG equipment that has delivered MIG spray transfer since the 1950s has always provided the fastest most stable MIG weld speed potential on carbon, low alloy and stainless steels parts > 3 mm. Note in Australia using my MIG process control resources, companies are making spray welds in the 15 - 25 lb/hr range. Few weld shops in North America, when using MIG have attained over 16 lb/hr.

When welding carbon and stainless steels under 1/8 (3 mm), if you have the right pulsed MIG equipment, pulsed MIG can provide higher weld speeds than short circuit welds. Conventional spray is typically too hot for these applications.




The following are a few MIG Spray Transfer weld facts:

For those of you that believe the pulsed equipment is depositing more weld or delivering faster automated weld speeds, on applications > 4 mm, compare what you are achieving with this weld reality.

[1] With low cost, traditional, durable CV MIG equipment, spray transfer when used on parts > 4 mm, weld deposits in the range of 8 - 25 lb/hr are being utilized. On these applications, the pulsed MIG mode can not deposit more weld metal than spray transfer. The typical, stable pulsed spray deposition range is 8 to 14 lbs/hr.
,
[2] Using conventional weld practices, the typical spray transfer "robot or automated, common, 1/4 (6 mm) fillet welds" made on parts > 5 mm, are made at weld travel speeds of 18 to 23 inch/min. On these parts pulsed cannot provide faster weld speeds.

[3] When welding the common 3/16 (5 mm) fillet welds, the typical weld deposition rates with an 0.045 (1.2mm) wire using spray transfer will be 10 to 12 lbs/hr. The automated weld speeds for this weld should be in the 40 to 60 inch/min range. With extended wire stick outs, (information in Ed's "Management Engineers MIG" book) I have produced these 3/16 fillet spray welds at robot weld speeds up to 85 ipm. On these parts, the pulsed process will not provide faster weld speeds, however the pulsed mode can if required provide lower weld heat (lower distortion) than that which results from spray.

One of the very few limited Pulsed MIG weld benefits: The pulsed mode when used and set correctly, on steel applications less than 1/8 (<3 mm), can provide higher weld deposition rates than short circuit or globular transfer. As short circuit is a poor choice, pulsed MIG is also a logical choice for < 3 mm aluminum applications.

 

 

THE TOO COMMON Weld Magazines and Weld Equipment - Consumables Bias:

I have had 30 articles published in global weld / engineering magazines. The weld magazines of the 1980s have little in common with those that are in place today. Today when you read about weld process, consumable or equipment articles and recommendations in the North American weld magazines, you will too often find a strong, marketing influenced bias in the article which adds to the never ending BS we find in too many weld shops. The reality is as advertising revenues shrink annually, most weld and related magazines get the majority of their advertising revenues from the companies that provide the majority of their weld articles.


E-mail. Nov. 2004. Hi Ed. It's Matt Finn. I spoke with you on the phone a couple of weeks ago. Well contrary to the beliefs of my co-workers I must say your concepts on GMAW were well worth trying. Your story of reading weld literature articles and finding they are too often not factual, inspired me to do the same and in the last three years, all I have done and continue to do is read from a variety of welding resources. In the past few weeks, I have focused my study on the "hands-on" practical aspect. It's amazing what you learn from having your nose in the arc rather than observing from out side the robot fence.

After reading your books and getting hands on experience, I now fully understand how and why Globular transfer is not a reliable mode of transfer, especially when utilizing it for high travel speeds (50- 70ipm range). Tonight I was able to figure out how you were able to achieve over 70 ipm when welding in spray mode. I went snooping around the plant and found an old style of diffuser that was shorter than our common ones. I then took your advice from your Management Engineers book and cut about a quarter inch off the end of a contact tip. With having the tip well recessed in the nozzle, this allowed for a longer than normal wire stick out which decreased the weld amperage but still maintained the weld current within the spray range.

The longer MIG wire stick out, permitted me to run higher WFS (higher deposition rates) without the extra amperage that would cause unwanted weld heat defects such as burn through or undercut. The weld spatter that resulted with the longer WSO was minimal and the spatter was easy to remove. Also the recessed tip and diffuser were spotless. After trying your ideas on attaining high deposition high speed welds in your "Management Engineers MIG book" it now makes sense. Thanks Ed for your extensive web site and your weld process expertise.
Matt Finn. USA.

 

 

When asked for his opinion on Spray transfer versus Pulsed MIG, a chap called Albert might have said the following.

"Constant weld energy attainable from CV spray transfer
is a logical requirement for constant weld fusion".

 

The three most important aspects of any weld, are the size, the weld fusion and quality attained.

[] With more than 90% of all MIG welds there is no evaluation of the weld fusion attained.

[] Every weld shop that MIG welds should be aware that the primary weld concern with most steel and stainless welds over 3mm is to attain sufficient weld fusion in a consistent manner.

[] In contrast, a primary MIG concern with most steels under 2 mm is avoid weld burn through and distortion.

PULSED MIG AND HOT CRACKS: A common concern you will find with high deposition rate pulsed welds. When pulsed is used in the high, "stable spray transfer wire feed range", the pulsed MIG arc is influenced by the high pulsed Hz and high peak current required. This combination often provides a highly agitated pulsed arc that results in a narrow, high velocity plasma. This high velocity pulsed plasma can provide a digging effect resulting in crater problems and narrow weld penetration profiles that can lead to hot, center weld cracking.

Ed made the following manual spray transfer weld with a $250 traditional MIG CV power source using an 0.045 (1.2 mm) E70S-3 MIG wire, set at 450 ipm. (1 - 2 o'clock), approx. 12.5 lb/hr. These deposition rates are extended with increased WSO.

 

What's that $6000 - $12000 Pulsed MIG power source going to achieve?

To attain the open arc spray transfer for carbon steel or common stainless steels, an argon mix is required along with a specific minimum amount of weld current (> 200 amps 035. > 255 amps 045), the wire feed rate and the voltage for each electrode wire diameter selected. The resulting spray weld stream is protected from the atmosphere by the spray plasma, (the ionized, white, bell shaped cloud).

The spray transfer arc plasma not only conducts the weld current, the plasma with argon mixes also shrouds the electrode wire tip. In contrast, when using straight CO2, the arc plasma occurs "under the weld droplet being formed. This plasma supports the weld drop as it forms and grows till eventually it drops off the wire tip in an erratic manner. The CO2 plasma is the reason you cannot get spray transfer from straight CO2. It's also the reason the CO2 content is limited to approx. 20% in argon mixes. See MIG gas mixes if you want to cut through gas salesmanship and read more practical gas data.

When a plant MIG welds bombs for the Airforce, you would think some manager, engineer or supervisor at this defence contractor's plant, would know the difference between a MIG short circuit and a MIG Spray transfer weld.

In manufacturing, the real weapons of mass destruction is often a result the management process apathy thats found in the engineering department that make products.

Many years ago, a well known US military defence contractor wanted to me to optimize the bomb lug welds that attached the cylinder shaped bombs to the underside of the fighter planes. My weld focus was to improve the MIG weld fusion that was being attained between the thick bomb lugs and the heavy wall (1/2 - 1 inch ) bomb casings. The MIG weld process improvement were really necessary as when I checked, the majority of the bomb lug welds being daily produced at this plant, revealed that the majority of the lug welds had more than 50% lack of fusion.

The first thing I found at the bomb plant, was their was no qualified weld management or supervison, just a bunch of military type engineers and white shirt managers that thought they were managing a parade ground. The welders who did not know better were utilizing poor MIG weld practices and using both the MIG short circuit and globular weld transfer modes. Using these two low energy MIG weld transfer modes that were more suited to 14 gage welds than the 1/2 to 1 inch parts welded, it was simply impossible to get the weld fusion desired for the lugs. To rectify this companies weld issues, I had a choice between the use of pulsed MIG or spray, (they had recently purchased new pulsed MIG equipment). After I produced the pulsed and spray welds at the same wire feed rates to maintain production. For both processes I set optimum weld parameters. The weld macro weld tests clearly indicated that the spray transfer mode had to be the first choice to provide the consistent weld fusion necessary. By the way I knew this would be the result before i welded. I simply did the two weld mode tests to show the engineers that the solution to their weld problems was always with the old equipment thay had and they did not need to take the sales reps advice and purchase the pulsed MIG equipment. After the weld tests were done I provided training for both the workers and managers and that was that.

Power point from my Robot MIG Process Controls Training Program

 

 

More SPRAY Fundamentals. The argon mix plasma that envelops the MIG wire tip, allows the weld droplets (transition) or stream to transfer axially, in a stable manner. If more than 20% CO2 is utilized the plasma is lowered under the droplets, supporting the drops till they grow and erratically transfer when they succumb to gravity Note: In this video shot the spray transfer is in the transition zone found between short circuit and spray. This zone results is a distinct controlled weld drop that looks very like a pulsed weld. The spray plasma also enables stable transfer of the electrons as they transfer from the negative work, weld cathode spot locations, to the positive anode areas located on the electrode wire tip. While the negative electrons are driven upwards to the positive wire tip by the weld voltage, the positive larger gas molecules are driven downwards to the negative work. The electrons on there way to the wire tip collide with the larger mass, gas molecules. The electron and gas molecule collision causes the gas molecules to split (ionization) adding more free electrons and protons in the arc plasma, this increases the plasma ionization energy. The electron and gas molecule collision increase the MIG plasma arc conductivity and the energy.

Spray transfer and the effects of Mill Scale on the welds:

The mill scale on that hot rolled plate surface to be MIG welded may be a poor electrical conductor causing electron reduction and arc instability. The electron conductivity of spray transfer is influenced by both the mill scale thickness and mill scale composition.

Mill scale acts as an insulator which can impede the electron flow from the cathode spots on the weld surface as they travel to melt the MIG wire tip. As mill scale increases the weld energy is reduced and to sustain the open arc, the MIG weld voltage has to be increased. Mill scale melts at a higher temperature than the base metal and typically the welds become more sluggish.

If you make a spray transfer weld on carbon steel without mill scale, and then without changing the weld voltage, make a spray weld on a part with mill scale, the welder would note the arc distance from the wire tip to the weld has reduced. The arc length reduction is a result of a decrease in electron conductivity, less electrons = less energy to melt tip of MIG wire and the wire gets closer to the weld. The shorter arc length often results in the MIG wire running into the weld, displacing the weld causing weld spatter. To reduce the weld spatter would require that the welder increase the weld voltage to increase the arc length. As we don't teach welders this simple fundamental fact we end up each day spending millions removing excess weld spatter.

Even with the correct voltage, the higher melting temperature mill scale can affect the weld fusion - porosity potential and frequently these welds will solidify in a convex shape with a roll over at a fillet weld toe. The influence of mill scale and the process requirements to compensate for the sluggish welds and spatter control, is another reason why weld personnel would benefit from my weld process control training resources.

The influence of the MIG arc on the steel mill scale.

An intense, consistent high energy arc as found with a spray transfer weld is more beneficial than pulsed MIG with it's fluctuating peak to back ground current when dealing with mill scale issues.

In contrast to pulsed MIG, the CV spray arc will;
[a] assist in maintaining consistent electron flow adding to arc stability,
[b] assist in the removal of surface contaminates,
[c] provide superior wetting for a sluggish weld,
[d] provide consistent weld fusion.
[e] provide less weld porosity

TThe sluggish MIG welds made on heavy mill-scale parts will often result with unacceptable or marginal side wall weld fusion. In contrast to pulsed MIG, when using optimum spray transfer weld parameters with argon - 15 to 20% CO2, the spray plasma arc intensity is much more "constant" and the average energy generated is typically greater than that attained from the pulsed welds made in their optimum parameter range.

With pulsed MIG, the plasma is influenced by the peak to low background current variations and the weld current and voltage fluctuations which are common from the electronic pulsed MIG equipment. Also pulsed MIG often utilizes low energy gas mixes like argon oxygen or argon 5 - 10% CO2 which also decrease the weld energy.

Weld Voltage and Weld Current Stability?

2004: While testing Japanese and Americam pulsed MIG equipment, we had this oscilloscope graph made of a carbon steel "pulsed MIG weld" set at optimum weld parameters. As the graph below indicates, when using one of the most costly, popular and sophisticated pulsed MIG power sources sold in the USA, that weld current and voltage instability is the norm.

 

 

Above pulsed MIG voltage and current, note difference below..


In contrast below, this graph is regular spray transfer taken at the same time from
a CV MIG power source that cost 1/3 the price of the pulsed power source.

Steels or Aluminum, Spray always more Stable.

 

 

The influence of the MIG plasma shape and intensity:

Spray transfer produces a bell shaped plasma. The wider the plasma in the cathode spots area, (the work - weld surface), the greater the weld area that benefits from the MIG plasma surface cleaning attributes and the greater the arc stability.

In contrast to spray, the pulsed process typically provides a narrower plasma that fluctuates with the changes from peak to back ground current. As you increase the pulsed welding parameters to traditional high spray transfer wire feed levels, when welding steels > 5mm, the pulsed plasma zone which is influenced by the "high frequency, high peak pulsed weld current" can become intense. Typically the excess high peak current can result in an intense pulsed plasma that's conical and narrow in shape. The resulting narrow intense plasma configuration can cause an arc digging effect that may result in deep narrow weld penetration. These pulsed MIG welds may produce,

[a] narrow weld beads that depending on the application can produce (hot center weld cracks),
[b] excess undercut,
[c] frequent crater cracks.


MIG spray, allows a shorter (less sensitive) arc length than pulsed MIG:

The shorter arc length (wire tip to weld surface distance) allowed by spray transfer can provide a highly localized, intense plasma configuration that is very beneficial for the weld stream transfer on robot high speed steel welds, and also beneficial on high deposition welds, large size welds or when welding plate with surface contaminates such as mill scale.

< 2005: How many of you have used pulsed MIG for high speed welds >30 ipm, and found the weld transfer was inconsistent and the welds were skipped. Just about every auto - truck wheel or torque converter manufacturer found this problem with their costly pulsed MIG equipment, yet these manufactures continued to utilize and purchase the pulsed weld equipment that caused the issues.

The Pulsed MIG mode requires a longer arc length: For the uninterrupted formation and transfer of a pulsed weld drops across the open arc, the pulsed MIG mode requires a longer arc length than traditional spray transfer. The bottom line, depending on the weld surfaces the weld settings and pulsed equipment utilized, the pulsed mode on many welds can be arc length (voltage) sensitive. This sensitivity upsets the pulsed weld droplet transfer causing arc instability (often evident in the arc sound produced). In contrast, the traditional spray mode in which the metal transfers in a stream can utilize much shorter arc lengths and the continuous weld stream is hardly affected by minor arc length variations. The arc length sensitivity is an important point as it affects;

[a] Shorter, less sensitive arc lengths allowable with spray transfer improve arc stability when welding at a high speeds.

[b] Shorter less sensitive arc lengths allows longer wire stick outs which reduces wire burn backs to the contact tip.

[c] Shorter less sensitive arc lengths are beneficial when welding on mill scale or coated metals.

MIG Gas influence on Mill Scale:

When spray transfer welding on troublesome mill scale applications, a high energy MIG gas mix such as argon with 15 to 20% CO2 is recommended. The 15 to 20% CO2 gas mix in contrast to a lower CO2 mix, or argon oxygen mix, enables higher weld voltage to be used and promotes higher energy at the cathode locations on the plate or weld surface.

Note While at AGA, Ed and his friend John Lowery, were the team that introduced the gas mix argon - 20% CO2 to the USA. In the following years many of the weld distributors who were making this gas mix were putting too much CO2 in the cylinders. With this in mind Ed lowered the CO2 content and then introduced to the North America the argon - 15% CO2 gas mix.

What makes CO2 gas unique? The CO2 plasma provides unique "gas dissociation properties". In the MIG arc. The CO2 molecules break down from CO2 to CO and O2. When these molecules get close to the cooler weld surface the CO - O2 molecules form back to CO2. This gas dissociation, "molecular change" adds energy to the weld.

In contrast to argon with 5 - 10% CO2, and tri mixes containing argon - CO2 - oxygen, the 15 - 20% CO2 typically requires 1 to 2 extra weld volts to sustain the arc. The extra voltage and CO2 arc dissociation properties improves the electron flow, improves the arc stability and enables additional weld energy for improved weld fusion and lower porosity.

For those companies that use argon oxygen mixes, or the heavily marketed, useless three part mixes containing argon - CO2 - oxygen on carbon steel applications that have mill scale, (applications >3/16), they should realize they are jeopardizing the weld fusion potential and increasing weld porosity potential.


The oxygen and low CO2 in many argon tri-mixes, results in a spray transfer plasma in which low to medium weld energy is generated in the outer periphery of the plasma. This results in finger or nipple shape weld profile. As the narrow finger weld solidifies rapidly this increases the opportunity for weld porosity to form especially in the finger shaped weld root. It's very common for this defect to show up in ultrasonic evaluation or with x-rays on fillet welds on parts > 5mm.

In contrast to what some weld gas sales rep may tell you, two or three component gas mixes containing oxygen can result in welds with greater potential to create;

[a] weld porosity,
[b] welds with lower weld energy, resulting in inferior weld fusion profiles,
[c] less gas in the cylinders than that attained with argon 15 - 20% CO2 mixes.

For extensive weld gas data see my weld gas section, or better still, invest a few dollars on yourself and purchase one of my welding books. My " Management Engineers Guide to MIG" has over 600 pages on how to control all MIG and flux cored welds.
Note Ed was a key writer of the USA AWS "MIG Gas Specifications".


E Mail. July 05.

Ed. It looks like we are just starting out on a new Chrysler project welding a galvannealed product. Galvanneal NS 6000 D series 44a. According to the Chrysler weld specification, with MIG we would be allowed to use a solid carbon steel ER 70S-3 MIG wire, however they require a 75 argon / 25 CO2 gas mixture for this application. I think Chrysler takes the cake on this MIG gas selection. By the way if our engineers had selected galvanized material, according to the Chrysler spec we would have been forced into using the terrible Lincoln self shielded FCAW process.....Is the Chrysler weld engineer from this planet? What I also don't understand is the fact that they are specifying a coated material, and then we are still required to e-coat the part. I wonder what the reasoning is behind double coating the cradles.....I'm sure they don't even know.

Regards GR. Tier One Supplier.

Ed's Answer:

For more than a decade there was no rationalization for most of the weld logic that came out of Chrysler Corporate engineering offices. The choice of the 75-25 CO2 gas restricts the use of spray transfer that could be used on robot welded parts over 0.080. The 75/25 gas will instead be the cause of weld spatter or weld burn through. As for the use of the self shielded wires, no one knows why the Chrysler corporate engineer still insists on the world's worst electrodes for coated materials. The weld engineer made this decision for Chrysler its cost them millions in weld rework and lost production and he has to much of an ego to admit his recommendations were wrong. As for the double coating, it makes no sense. What would make sense is this industry could coat many (not all) parts after welding. All those involved with welding are aware that irrespective of the coating type, the weld destroys the coating in the weld area, therfore from a corrosion perspective the weld areas are the wekest links. As I have said on numerous occasions on this site don't look for weld logic and weld reality when dealing with the Chrysler coporation.

Want to know how to reduce "cracks" or Arc Blow.

Minimum Spray Transfer weld current with argon > 10% CO2 Mixes.

Many welders and robot programmers are not aware of the minimum weld current or minimum wire feed rates necessary to attain optimum spray transfer. Its therefore not surprising to frequently find welders or robots welding with globular transfer and creating a weld spatter mess.

When welding carbon steels with the 0.035 (1 mm) wire, and a 15 to 20 CO2 mix, to achieve spray transfer, a minimum weld current of > 185 amps is desired.

For the 0.045 (1.2mm) wire and the 15 to 20 CO2 mix. To achieve spray transfer, a weld current approximately > 255 amps is desired.

These minimum spray transfer weld current settings are reduced with lower CO2 mixes,
or when those useless two or three component argon mixes containing oxygen mixes are used.

There is an optimum MIG Wire Diameter for every application thickness.

As I have mentioned at least 600 times, the auto / truck industry is one industry that for decades has been notorious in it's selection of unsuited MIG and flux cored electrode diameters for welding steel applications < 6mm.

Few companies understand the weld wire, weld mode, weld current, weld size, weld travel rate and part thickness relationships. For those individuals that want to proffesionally manage the MIG and FCA weld processes, this is an extensive part of my books and weld process control training programs.

2013: Did you ever consider why, after at least four to five decades of making MIG welding equipment and welding consumables, that Lincoln, ESAB, (Linde), Miller or Hobart did not put practical MIG weld parameter information on their MIG wire packages or along side the relevant MIG wire feed or power source parameter controls?

I believe the reasons the MIG welding electrode wire manufacturers never provided their weld customers with practical, cost effective MIG or flux cored welding data on the wire boxes, is because they did not employ management or engineers that had figured out the simple relationships that exist between the few required wire feed and voltage settings necessary for the majority of all the common global MIG and flux cored applications. To overcome their focus on weld process controls I developed the "Weld Clock Method".

In the weld equipment and consumable distributor industry, sales and real world data were often far apart. The incredible lack of MIG and FCA weld process expertise that prevailed from the world's largest weld consumable manufacturers and thousands of distributors is not that unusual. As we all are aware just because you make something does not necessarily mean you are an expert in it's use. The sad issue today for the self taught global weld industry, after 50 years of weld misinformation, too many weld shop still rely on these same companies for weld advice.

Note: In the 1980s in a marketing program I set up at AGA in Cleveland. I introduced MIG weld wires which were enclosed in boxes in which I had printed all the short circuit and spray weld settings required for any applications with the 0.035 and 0.045 wires. With Airgas and Liquid Carbonic, I created simple two part SteelMiX and StainMix gas mixes, and then I put the labels on the cylinders that again provided all the possible optimum MIG settings.

Note: Ed got the GM management - engineers to stop using the nasty self shielded flux cored weld wires for the CORVETTE body welds, and then trained the GM workers on how to use the MIG process on the same application. Keep in mind, this was after MIG had been available for four decades. This shows that in the automotive industry, you can always hope that sanity will prevail. By the way, I would like to thank the Corvette racing team for making me there unpaid MIG weld consultant..

The MIG process celebrates 50 years as being the world's most utilized weld joining process yet, how many of you have watched weld equipment and consumable reps "play with the weld parameter controls" during a demonstration of MIG equipment, weld wires, gas mixes or those E71T-1 flux cored consumables?

For an experience you may not enjoy. Next time you visit a Fabtech or AWS weld show, ask the Lincoln - Miller - ESAB - Panasonic rep the following technical question. Look for someone demonstrating pulsed MIG, then ask them to do a 6 mm vertical up, carbon steel or stainless fillet weld on > 1/4 (6mm) plate. After the weld, look the rep in the eye and ask how his pulsed wire feed rate compares weld deposition wise with an 0.045 (1.2 mm) E71T-1 wire set at a feed rate of 400 in./min. The weld you view and the answers you receive to this fundamental simple weld question will show you how little or how much is known by the so called weld equipment or consumable experts.

The sales reps promoting pulsed weld equipment at the AWS or Fabtech trade shows may extol the virtues of their weld equipment benefits, however, the bottom line is those benefits may dwindle quickly when you take a real look at the inconsistent arc characteristics and then provide a realistic comparison of their process or equipment against other processes, mode of weld transfers, equipment and consumables.


Before weld personnel provide an opinion on a welding process or weld consumable, they should have all the facts on the processes and consumables that compete with their process or consumables. And of course if they were a true professional they would then provide an answer without product or process bias.

 

The Harley management did not know the meaning of process ownership.

 

When Ed established the robot welds for Harley bike frames, he resisted the use of the pulsed mode (at that time arc instability issues with the pulsed equip.) and turned to low spray transfer. Ed set 3 simple weld schedules for the more than 50 welds required on the frames.

Note on Harley lack of management: At the main Harley Bike plant, I sat in on a meeting in which two weld engineers and nine robot personnel discussed for more than two hours a robot MIG weld spatter problem on a bike gas tank. At the end of two hours, the problem was unresolved. Thanks to the Harley "hands off" management approach, I was not allowed to speak at this meeting. The management were afraid I would upset the Harley sensitive workers. For me, that meeting was a sad engineering situation. This American company with it's global brand reputaion indicated that it's combined mangement and engineering resources could not resolve a simple weld voltage issue that should have taken two minutes to resolve.

How many global production man hours are lost daily with inexperienced weld team meetings having discussions on robot weld issues which with a little weld process expertise would take a few minutes to resolve? Ed Craig. 1985.

If you want a quick evaluation of the weld process expertise in your shop, ask three of your welders or the weld shop supervisor to tell you the 0.045 (1.2mm) wire feed position in which the start point occurs for spray transfer. You may be surprised at the diverse incorrect answers provided for the world's most popular wire size and the world's most utilized weld transfer mode.


If you think your weld personnel fully understand the weld process they make a living from, why not give them my MIG weld process control quiz?

 

 

"Play Around". No managers or engineers should allow these two words to be used for any manufacturing process that is critical for an organization.

The good news is the common lack of MIG and flux cored weld process expertise can be quickly eradicated in any weld shop. First managers have to put their focus on the root causes of their weld issues and always remember that quality - productivity responsibility and product liability starts in the front office, not on the factory floor.

HANDS OFF WELD MANAGERS AND ENGINEERS WON'T MIND WHEN THE PURCHASING MANAGER MAKES WELD PROCESS - CONSIMABLE DECISIONS.

When purchasing personnel make weld consumable or equipment decisions, the management supervisors & engineers should resign.

Throughout the weld manufacturing industry and especially common in the auto - truck industry, "purchasing managers" and other inexperienced personnel are frequently involved in weld consumable and weld equipment selection decisions.

Perhaps your company has a purchasing manager that found out that "bigger weld wires cost less than smaller wires and therefore recommended the large wires which resulted in a "weld wire cost savings".

When selecting the correct MIG wire diameter, the optimum weld current compatibility of that wire with the part thickness, the weld transfer mode and weld size are the prime considerations for consumable selection. Selecting the optimum MIG wire diameter requires MIG weld process expertise. For those companies that are utilizing wire diameters that are too large, most of the welds produced with the over sized weld wires will be in the globular mode the weld productivity, costs and weld repair consequences will be extensive.

It's a fact that more than 75% of the MIG and flux cored robot applications welded in the North American auto and truck plants, are using weld consumable sizes and types that are not optimum for the welding applications.

To Ed Craig. Sept 2004.
E-Mail.

Question: Ed. Our company is a US based, Japanese auto parts manufacturer. We use Japanese robots to MIG weld 1 to weld 3mm steel parts. We use the pulsed MIG process, argon gas 10% CO2 mixes, and 0.045 weld wire. We use Japanese MIG wires equivalent to AWS E70S-6. The manager wants to reduce robot-welding costs. I am currently writing a cost justification calling for a change to a MIG wire manufactured in North America -- possibly an 0.035-in. wire. Our company engineers, however, insist on sticking with the imported Japanese MIG wire which costs approximately $0.50 more per pound than the equivalent USA MIG wires. These engineers also inform me I cannot change the wire size or type since the code states this wire is an essential weld variable. Am I correct that according to most codes, as long as both wires are E70S-6s, they are interchangeable and therefore a none essential weld variable?

Ed's Answer:

Essential weld variables are three words that may carry some weight in an organization that welds within the boundaries of codes such as API or ASME. However from a common sense perspective these three words should never be used within the boundaries of an automotive plant and especially in your plant.

First, irrespective of the codes or weld procedures in place, as long as the plant uses argon mixes there will be no negligible influence on steel weld mechanical properties, whether the MIG wire is American or Japanese E70S-3 or E70S-6. Both these MIG wires are qualified for argon mix use. Second, if the company changes the wire size, it's logical to redo the weld procedure.

Importing costly MIG wires into the USA a country that has the world's largest MIG wire manufacturer makes as much sense as exporting USA coal to Newcastle UK. Any US or Japanese auto-manufacturing company that throws money out the window by importing expensive Asian MIG weld wires needs a new plant and engineering manager.

It makes little sense to be concerned about so-called essential weld variables when the pulsed-equipment manufacturers are making radical E –Prom changes to their weld equipment every few months. Each new robot line brought into your plant has pulsed equipment that may have little in common with the pulsed-weld equipment purchased two years ago.

Weld procedures have little meaning when the weld equipment used is either changing or inconsistent and lets face it the majority of robots sold do not have proper calibration between the robots, power sources and wire feeder. It also makes little sense to worry about essential weld variables, when every day some robot technician in your organization is probably making unqualified weld changes to the robot data. And most important, why worry about essential weld variables when the parts you produce will likely suffer from dimensional issues that afftect the weld fit and weld gaps.

It's rare in auto - truck manufacturing plants that strive for manufacturing autonomy to see effective weld practices or effective robot weld process controls implemented. It's even rarer to find engineers in this industry who have in-depth weld process control expertise. This of course leads to the weld consumable cost discussions and distractions from the real weld issues.

To have an impact on a plant's weld costs forget about saving pennies on consumables and start out with an evaluation of the “weld deposition rate potential” and the real-world weld efficiency of the robots. Evaluate the robot's downtime and the robot weld rework generated. Compare these numbers with the information attained in my robot-weld-process-control book. Check out the high weld-speed benefits of a 0.035 or 0.040 in. wire on parts less than 0.080 in.

The engineers and managers who want you to use the Japanese weld wire do so because they fear process change. My solution would be to fire all the engineers and managers involved.

For decades the best MIG weld wire for the auto and truck
industry is of course the one they rarely use.

Weld Question: We weld carbon and stainless steel parts 3 to 5 mm. What's the best MIG electrode size for spray transfer robot applications? Our key weld requirements are;


[a] Attain consistent optimum side wall weld fusion.

[b] Attain welds speeds above 40 ipm.

Answer: Considering the weld current compatibility with the part thickness and desired weld size, the following is a logical choice of MIG wire size selection.

[a] Robot - Manual Spray welds on steel / stainless parts 3 - 5 mm. If available, the first choice MIG wire diameter would be the 0.040 (1.1mm) MIG electrode wire. If the 0.040 wire is not available, use the 035 (1mm) wire. Wires smaller than 0.045 provide superior small weld puddle control and the spray current range of these wires is better suited than 0.045 wires.

E-mail March 2007.
Ryan Good. Dana Corp.

Hey Ed:
Just thought I would drop you a line and let you know that in the beginning of April, thanks to your advice, we will be working on switching over the 5th Dana plant to an 0.040 MIG wire and using the spray transfer mode instead of 0.052 globular mode we were getting with the Rapid Arc (Lincoln's pulse MIG program). Thanks Ryan.

 

 

A reason the 0.045 (1.2mm) weld wire is an optimum choice with spray transfer, for applications > 3/16, > 5mm is the "weld current required and control of the weld fluidity". This is a prime reason the 0.045 MIG wire is superior to the higher current 0.052 and 0.062 (1.4 - 1.6mm) wires. The 0.045 wire also can provide spray transfer at typical current of 250 - 380 amps. For the 0.052 and 0.062 wires to out perform the weld deposition rate of the 045 wires, the larger wires would have to use well over 400 amps, this higher weld current promotes excess weld fluidity and is hard on both the weld equipment and welder's skin. When welds are produced over 400 amps the resulting high weld heat and fluid welds can cause undercut. The hot welds will also react with the atmosphere and form oxides increasing weld porosity potential, especially on multi-pass welds. Also high weld current can promote grain growth and weaken the steel adjacent the welds. The excess weld heat can also lead to hot cracks in the base metal especially when welding high strength steels or highly restrained weld joints.

High spray weld current > 400 amps can cause excess weld fluidity creating a challenge for a manual welders, especially when producing single pass horizontal fillet welds larger than a 1/4 > 6mm.

A horizontal 5/16 (8 mm) fillet weld provides a manual welding challenge. Maintaining weld puddle control, avoiding undercut, and at the same time ensuring consistent side wall weld fusion are three of the prime reasons the 5/16 (8 mm) fillet weld is usually the maximum horizontal fillet weld size allowed. This is also why robots should when possible weld large fillets in the flat position.

When robot welding in the "flat positions" rather than the horizontal position, and the parts are >5/16 thick, an 0.052 (1.4mm) MIG wire is beneficial and this wire will cost less than the 0.045.

Lets see, the electrode size recommendations should provide an optimum spray transfer current range which is compatible with the part thickness welded and allow control of the weld fluidity and oxidation.

This is an interesting approach to weld wire selection and weld process control. Weld current compatibility with the part thickness means the electrode selected can use the high end of it's optimum operating parameters without concern for an agitated arc plasma and a turbulent weld puddle. Using current compatible with the part thickness means no concern for over heated, oxidized welds or weld burn through. The welding parameters will allow high wire feed rates resulting in optimum weld deposition rates and maximum weld travel rates for the weld consumable utilized.

Weld Current Compatibility with the Part Thickness.

 

In my book, extensive written data has been provided on the subject of SMAW (stick welding) reference, electrode diameters, weld current and part thickness requirements. I focus on this subject for the MIG process and I have written more on this subject than any other global welding source. The selection of the correct MIG wire diameter and stick out is an essential consideration for attaining both optimum, robot / manual weld quality and productivity.

E-Mail from Shawn.

Question: Ed on our robot application we have a multi-process, pulsed MIG - short circuit - spray power source. We weld auto thin gage steel parts from 1 to 4 mm with an 0.035 wire. Is there a defining line when we should switch from one weld transfer mode to another?

Answer:

Shawn this is a great question.

[] For robot applications < 0.070 I would use short circuit before pulsed. The short circuit mode is an arc on / arc off weld transfer and therefore provides less potential for weld burn through, especially if weld gaps are involved.

[] For applications 0.070 to 0.150, pulsed MIG fits the bill and will typically allow the use of higher wire feed rates than short circuit, however if gaps greater than 0.060 occur remember to set the parameters to short circuit. .

Robot welding on parts > 0.150 to 4 mm, take your choice of spray or pulsed. If using spray use an 0.035 wire at the transition point.. If the welds are is too hot consider pulsed and an 0.045.

Every weld decision maker should know this. Weld Amps and Welder Appeal.

The optimum spray current that provides ideal weld puddle control with the 0.045 MIG wire is typically found between 250 and 380 amps. Managers, supervisors and engineers should be aware that welders do not like the weld heat generated from spray transfer once the weld cycle time is more than a few minutes and the weld current typically passes 360 amps as required with both the 0.052 (1.4mm) and 0.062 (1.6mm) wires.

Often when using the large diameter wires, and this applies also to >0.062 and larger flux cored wires, you will find that too keep the manual weld heat at a comfortable welding level, the welder will set the large wires at a low current = low wire feed setting. Few weld supervisors check a welders wire feed settings, and even fewer understand the potential weld deposition rates and weld costs that can be attained.

What about large welds? When welding steels > 3/8, multi-pass welds are required. The best approach to multi-pass fillet - groove welds is to make each weld pass the equivalent of a 1/4 (7mm) fillet. This enables the best control of the weld fusion and stringer weld speeds that minimize oxidation. The weld wire that provides the best control of a 1/4 fillet is an 0.045 wire. The bottom line, the large wires rarely provide deposition benefits and typically produce more weld smoke and spatter than attained with the more manageable, smaller 0.045 MIG wires.

I hope you are not still taking notes as that proves like me that you don't have a life.

Invest in yourself and consider one of my books or training resources. This book is my robot - manual MIG self teaching process control book. It's available in both English and Spanish. The book has 170 pages with 170 MIG questions all directed at weld process control and weld parameter selection simplification through the easy to leran weld clock method.

For your weld shop training needs you would purchase three items. This self teaching book, a unique CD power point program and a video. These are the most practical weld data resource your weld personnel will ever learn. Welders, robot programmers, robot operators, QA personnel, weld supervisors, managers and engineers, all will benefit from this valuable weld process resource.

It's important that all weld personnel who make weld decisions be of "one weld mind set". Click here for the training info.


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If you are just entering the weld profession, you will be glad to know that
weld renumeration in 2014 is just about where it was 25 years ago.

MIG Spray Section Two. [] Robot wire burn backs and arc start problems cause extensive down time. Find the solution. [] Find out how to deal with galvanized welds. [] Recognize the different types of weld porosity, and the root causes. [] Find out why some Lincoln - NS and Hobart MIG wires may be part of your weld problems. [] Find out why you have stop your welders using STICK weld techniques with the MIG process. [] Learn both the visual and sound approach to setting optimum MIG welds.

Ed's now Em's Self Teaching - Training materials.