It has been quite a few years since I have mig welded and I have a question/concern on what I have seen regarding a welding practice.
The type of material being used is 6 x 4 x 1/4 wall rectangular tubes. The joint type involved one tube being welded 90 degrees to the other. There are two vertical welds required, one is a horizontal fillet and the other is an underneath (bottom) fillet weld. The welding practice that I question/concern are the vertical welds. What I saw being preformed on the vertical welds with the mig welder was:
The welder would pull the trigger on the mig gun in the vertical weld joint for about a second, release the trigger on the mig gun for about a second, while the trigger is released the mig gun is moved to a new position about .05 inch to .1 inch above the last trigger pull in the weld joint, the trigger on the mig gun is pulled again for about a second. This process is repeated until the vertical weld is completed.
Can you advise me if the is a good practice for welding using this method.
Thanks.
Nice. I think i know that guy.....
The technique is called "triggering"
Is the technique valid?
Depends on the intended service of the part, the skill of the welder, the parameters he is using and more.
Is it possible to make a sound weld (compliant with code) with this method? Yes...
Is it likely.. Not very...
I would half to agree, would it be a practice i would recommend, depends like you said, would it be great for sheet steel for distortion control, yes, Structural steel because u can't vertical weld, no.
Good, bad or indifferent, I have used this method on aluminum with a spool gun to reduce heat when the joint heats up to near the point of loosing it.
Compliant with a code ehh?
I guess you could classify it as pulse welding, but documenting it would be tricky. Then he technically would have to pulse the complete member unless they call out a different procedure for the remaining joints.
Ok... You got me.. I was thinking about mechanicals..
Could you trigger and get root and sidewall fusion...?
Pass a fillet break and macro? Yes,
but I don't know about consistancy.
Generating a WPS I diddn't think about :)
Yes, you could trigger a root in and get complete penn and side wall fusion. Just have to have the right parameters to start off and keep your steps pretty close together. It's all about the steps and trigger pull on off time. lol I've seen fillet weld breaks that wern't triggered, but where whipped, break and look like something a sproket would ride in because there whips were to far apart. Pretty interesting to see. Sometimes I wish I had a camera all the time so I could put all that stuff in a file and save it for class.
One advantage of triggering is being able to set your parameters at a range suitable for all positions. The settings that would work for flat overhead and horizontal would be too hot for vertical up. And even more so the settings that work for welding vertical up would be too cold for other positions.
So with higher heat settings it would become necessary to trigger the gun. As to whether this is good ir bad, it depends on tbe service and settings.
I actually failed a test at a company on 3/8 plate because I didnt trigger. I decided that that wsd not the place for me to work.
I have triggered some but prefer to set the machine for the joint being welded. Some machines have a dual setting and thats kibda nice.
Gerald Austin
Weldingclassroom.org
Gerald, darn this is the first I've heard any thing out of you for a long time. Really good to hear from you again.
We actually have qualified procedures that discribe "Triggering" as a method of distortion controle.
Hey Ron,
I've been staying busy with working during the day, teaching two nights a week, and working on a couple of websites for welding stuff. Usually by the time I see a post here I may be able to help with, many of the great contributors here have already responded.
Its very humbling to read some of the great content here.
That is interesting about the triggering. Do you indicate a min or Max on/off time?
Also, do you just employ the triggering vertical or in other positions?
I really enjoy playing with a mig gun. I would love to hook one up on a 3d printer type setup. Another topic though.
Have a great day.
Gerald Austin
Weldingclassroom.com
Shane,
WELCOME TO THE AWS WELDING FORUM!!
I have seen the 'triggering' method used since the 70's successfully on alum and carbon steel. But as has been cautioned, it must be properly applied. Material grade, thickness, part application upon completion, on/off time sequences, and many other factors come into play.
When thought out, this is just the forerunner for 'Pulsed' systems in use today. Only it was operator controlled as to frequency and other operating perameters. Now they are all machine controlled and can then be qualified by testing to assure their successful useage.
I would also go one step further, I have seen welders use it with SMAW when welding over a blow out. Not recommended by me. I prefer to go down in amps, use smaller electrodes, and keep building up the edges and lettting them cool some to 'butter' the parts until I can make the proper weld. It is accomplished in this case by momentarily braking the arc, letting the weld pool cool slightly and then restriking the arc for another brief shot of filler. Again, proper useage with many variables to consider. Granted, there is no trigger or footpetal here, only the manual manipulation of the electrode. Basic principle is the same.
Have a Great Day, Brent
Hello Shane;
I have seen this done and done it myself. Usually it was used on some light gauge steel to keep distortion to a minimum or the fitter maybe cut the wrong side of the line. I would trigger a short arc stringer in and cover with flux core. I would grind the other side and finish with flux core. This was heavy structural work. Sometimes at a cosmetic spot , on say a shaker skid corner, I would trigger the cover plate on as to not have to grind a lot if any at all. Also, it depends on welder skill as has been said. I have seen some new welders who couldn't run short arc up or down. But as they went on, the time between triggers got longer till they were running the whole joint without triggering. Just takes practice. I wouldn't like to see the method you mentioned on every joint, but it has its place and uses; in my opinion at least. You know what they say about those though.
Have a good one;
Matt
Are you performing this work to a particular code? I have never heard of triggering as a mode of metal transfer for GMAW in any code. Mode of metal transfer is typically an essential variable for GMAW so be careful if you are doing code work. Check the PQR to see how the procedure was qualified and if they put down triggering for a mode of transfer.
How would that change mode of metal transfer? You'd still be using GMAW semi-auto with short circuit transfer. There are issues with GMAW-S regarding starts and stops. I doubt this (triggering) could be proven as a consistent quality process in all positions.
Since no parameters were given I guess I jumped the gun on assuming mode of transfer. With that being said, the mode of transfer would still be any of the common GMAW transfers.
By saying what you just said would also make GMAW-P not a mode of metal transfer either then because GMAW-P is basically just the machine turning spray transfer on and off for you.
You might be on to something..... GMAW Intermittent Arc Transfer....
Yup, never heard of it in any code I've worked to. Hopefully he isn't building to a particular code. Although I think the new addenda of the Farm code might have something in there though.
Seems to me a technique is valid IF one qualifies the procedure. Write it up and test it, right?
Stringer,
I tried to think about it as being code compliant by going the technique route, but technique consists of such elements as, Stringer or Weave, Orifice or nozzle size, method of cleaning, method of back gouge, Oscillation, tube to work distance, Multiple or single pass/side, single or multiple electrodes, electrode spacing, manual or automatic, peening, use of thermal processes. There is never anything about triggering and probably for good reason because I would have to say that turning the arc on and off manually would be classified as a mode of metal transfer. Pretty much like GMAW-P, except that the machine does it consistently for you and it's easy to document and keep consistent in production for GMAW-P. When qualifying a GMAW procedure one must list the mode of metal transfer because it is an essential variable. Triggering is not a documented or proven mode of metal transfer. The only way now that I could see to circumvent the system would be to classify it as pulse for mode of metal transfer. Then document your pulses per second, on/off time, and peak volt/amps + travel speed etc etc. However, I would not want to touch that with a ten foot pole because the consistency in production would be next to impossible to supervise. This procedure wouldn't be very cost effective either because it would be very slow. Engineering would also get pissed because they will have to remember to call out 2 GMAW procedures for one attachment point that has vertical and horizontal seams. I'd say the maintenance would probably want to burn this procedure as well someday because it would be very hard on the equipment. That's just my $.02 though.
Kix
Kix
I think you are all trying to over engineer this method of welding! This method of ‘Triggering’ as you call it is used in every fab shop/site that has access to any form of MIG machine! It is effectively a lot of stop/starts, where in any code prohibits this? If the machine is set up for dip transfer or spray transfer, as per wps, it will not change whilst ‘Triggering’! It is quite possible to perform a weld that is code compliant whilst using this technique!
True, Kix, I've never even seen the word triggering until this thread, but I've been doing it whenever I felt like it for 30+ years although little of my mig work has been to code. I suppose it would be a form of pulse as suggested in the literal sense and the measurement and enforcement would be difficult.
