Tandem mig welding Help?

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Hey !I am hoping I might find some advice here about some weld issues I am having and am hoping I can nip these problems in the butt once and for all. I don't know if this forum has any members with robotic welding experience? I am going to take my time and try to explain the situation in detail so you can understand fully whats going on. I wish I had pictures to really show whats happening but alas I do not.First let me say I am NOT an expert in GMAW welding processes ( I am very knowledgeable when it comes to resistance welding). None the less at the production facility I work at some people would consider me one of the go-to guys. I am actually not very proud of this! I have been successful at improving many of the robotic welding machines at my plant and have learned much through trial and error. I feel that welding is a science not MAGIC (and as such good welding procedures can be taught) and the whole superhero mentality at my plant really drives me nuts. But thats a whole other story...Ok I have this machine with 4 fanuc tandem welders using lincoln powerwave equipment. I have fixed so many problems with this machine i could write a novel on it.One of the biggest problems is that no one is in control of the process! technicians from all 3 shifts tend to play around with the weld data and travel speeds. e.g. Slowing down the robots and turning up the wirefeed After a lot of work (and password protecting the robots) I was able to get good consistant welds for a while until everybody learned the password. My next solution was now just to memorize the settings and put them back to what the were when someone changes them. That has worked till now. anyways right now my welds are getting holes in them...What happens is when there is a problem with the weld the other techs slow down the robots and turn up the wirefeed.This slows down the line which is no good (we need 800 parts a shift)Also the extra wirefeed results in more spatter which causes a varety of faults from broken diffusers to stuck cylinders etc...This is also no good because it affects production.The parts are about 5mm/0.196in thickthe the way the parts mate up looks like A.and the parts are slightly curved like B.The parts fit up is pretty good but the parts can be a bit oily at times.right now I have the robots running at 70 IPM one wire the lead is set up for Gmaw the trail is gmaw pulsed. the schedules are right now at ;wfs          = 300 IPMvolt / trim = 26 / 1.0(I could give a a more detailed description of the settings if needed)Ok so this was good for a while (provided the robot was programmed well and people weren't background editing the robots) but lately we have been getting holes in the welds.I have had this problem before when there were problems in the wirefeed system, or too much gass flow(long story), or a poorly programmed robot.But right now I can't seem to get rid of the problem no matter what I do. I haven't changed the torch yet because the holes show up on  different robots and in different spots I do know that people keep playing with the set up data and any weld parameter they can get their grubby little fingers on.If you watch it while it welds it looks like the lead wire loses its arc so if I turn up the trail  WFS I can make the holes occur less but not eliminate them. I kind of want to find the definitive cause of this problem because playing with the data leads to more weld spatter and more downtime. I want to fix this problem so the other techs can go back to being lazy instead of f****ng up my welds I also am sick of the welders tan any ideas?The only difference in the process now from when we had good consistant welds is that our gas (argon/ co2) does not come from a bulkpack but from a tank outside the plant. Even then these problems didn't start when we initially made that change.thanks sorry bout the long explaination DOOMHEAD
Reply:I have wanted to work with the Lincoln tandem MIG system, must be a lot of fun when you get her going right.  As you clearly state, the whole mess is simply out of control!I hope your company is not fabricating anything safety critical.  Robots with tandem MIGs are not trivial, where is the management, supervision, QA dept., does the President know what's going on?Who originally developed the welding procedure?Aren't the original settings written down any where?  If guys are messing with the wave form on the PowerWave, things can go bad in a heart beat.How about getting a Lincoln rep. out to your site, or sending samples to Lincoln for suggestions on parameters?One thing for sure, you have to absolutely ensure that the techs are not changing the weld settings.  I know it's not any fun for the techs, they want to have a hand in making the welder work, but as you already realize, you will never solve your problems with a helter skelter shot gun approach.  Change one thing at a time.I worked in a situation like your's, and fought a porosity problem like yours.  In high production MIG welding, enough changes without you knowing it, you don't need people purposely changing the process.  How do you find the change that is causing the problem when everything changes several times a day?You indicate a porosity problem started when you changed from bottled gas to a bulk system.  I suggest you leak test every single pipe joint in the delivery system, from the bulk tanks, through the mixer, to the end of the torch, whether soldered, brazed, welded, or threaded.  Any leak can aspirated air into the system.  Check all valves, the flow meter, everything up to the nozzle on the end of the torch.  Try to plug off flow at the nozzle to pressurize the torch and any plumbing after the gas solenoid valve, so you can check this area for leaks.  Once you know there are no leaks, you can start looking things that screw up your gas flow like excess spatter buildup in the nozzle, improperly assembled torch components, excess draft from a fume exhaust system, contamination from a previous process, etc.Hum, sometimes the parts can be oily?  Oil = hydrocarbon = main cause of porosity in the world's welds.Where are you located?  Sounds like you may want to hire an experienced welding engineer.
Reply:Thanks That helps a bit unfortunatly I don't have the authority to hire any one I have recommended that we hire a weld engineer but that will never happen. The environment where I work is pretty messed up. ( funny, we're a major tier 1 supplier too  ). What you said about changes is exactly right. I've had the most success when I password protected the fanucs and only I was able to modify any parameters. I had the robots running clean @ 70 IPM with less than 5% rework (1000 parts a shift). But I am just a technicion too not the boss and after a while the other tech's learn the password. Our quality dept doesn't know anything either lol they are a joke. We have the same problems with our resistance welds but obviously deficiencies in that process arn't noticed as easily.Having said that, The tandem process is pretty cool! and thx for the advice.cheers
Reply:Now that the welders have learned the password, change the password and let the supervisor (who can discipline the welders) know that code prevents any changing of the parameters.   I can tell you, unless you make an example out of the first chinga who finger-jack's the program,  you're never gonna have the process under control.  That's just the sad truth of it.I r 2 a perfessional
Reply:Are you ISO Cert'ed?If you are tier one, I'm sure you are.Your plant should have an ISO/QS coordinator, or maybe even committee. Rest assured, if ISO or QS is in play at your plant, someone most definitely cares about people making undocumented, untested adjustments to the process or process-equipment!It may just be a matter of finding the right person who both cares about this (Realistically EVERYONE "should" care) and has the power to do something about it.I've been through what you are talking about many times and it's no fun. I can tell you that until you get a handle on these guys making these adjustments, you will be fighting a loosing battle.I still get put in this trick bag once in a while and It's always a battle. Iv'e tried everything short of violence!(I do wanna see if breaking someones fingers will do the trick though)Oh.....Sorry about that rant.....I think you must have hit a nerve.....now where did I put those little white pills?????Patrick
Reply:You neglected to say what transfer mode you were running on the first lead, or what wire size and gas mix.  These are important factors.  The voltage is excessively high for short-circuit transfer, which could be the cause of the spatter.  You could also be in globular transfer which might also cause bad spatter.  At 5mm thickness, you should be able to run straight spray transfer.  I don't see the need for pulse on the second lead unless the weld is out of position.-Heath
Reply:Thanks all You are keeping me sane!I am glad to see I have sympathizers I honestly think out plant is going to $%&. We are ISO Cert'ed but most departments just forge the documents to pass the audits. I.E. maintainance logs etc...NO one cares and our supervisors are useless. (one of the people randomly changing weld settings is one of the supervisors and he is usless). We have a 1-800- employee hotline I wonder if I should call that? Anyway I care because I've put a lot of effort into improving this machine (that came from a plant that went out of business) I've found if I can get it running good then the guys leave it alone and don't play with the settings.so with that said...>>You neglected to say what transfer mode you were running on the first >>lead, or what wire size and gas mix. lead: spray, trail: pulsed spray0.45 and ArCO2  (we mix it at the plant 92/8%)robots travel @ 70 IPMEquip 1 volts is 26 with WFS of 295 (lead)Equip 2 trim is 1.0 with WFS of 295 (trail)>>These are important factors. The voltage is excessively high for >>short-circuit transfer, which could be the cause of the spatter. The spatter is not too bad until Someone starts playing with the weld settings Up till now I always changed the settings back to what was giving me good welds. But again I've had no formal training in GMAW and appriciate any advice, tips, etc..Right now I am getting big holes in my welds. I actually think it may have to do with Pulser's point about gas... Anyway I found out today that there is a leak in our argon tank but it looks like no one is going to do anything about it.I asked the supervisor if they checked the gaslines for leaks and he said yes and there were none then 30 minutes later I found out about the leak in the argon tank when I asked him about it he just said "oh that leak maintainance knows about it." Anyway If they didn't pay so well I'd be out of this place thanks again for all your advice it helps!
Reply:I'm assuming that the holes that you are referring to is porosity in the weld, in which case, that would definitely indicate a problem with shielding gas.  You'll need to get that fixed before you can evaluate any other factors.Using .045 at 26 volts near 300IPM seems excessive for your material thickness.  I'll wager that you're running that hot to get the deposition rate up and keep the travel speeds high.  That's great for productivity, but it's going to make it more difficult to optimize your process.I don't personally have any experience with tandem GMAW and can't offer much advice beyond my limited academic understanding of the process.  You might try reading the following document from Lincoln which does include some limited details about tandem GMAW and GMAW in general.  What you have is a job for a welding engineer, but without one, I suspect you could probably slog through it and get things working well.http://content.lincolnelectric.com/p...ture/c4200.pdf-Heath