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Old 09-23-2006, 06:40 PM
cab cab is offline
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Need Sheet Metal Welding Help

All,

Well after my emabarassing attempt to weld an "aluminum" fender I got a used steel fender and started practicing today. After spending a couple of hours on this I have a LOT of questions (please bear with me), but first here is my setup and my practice panel:

Millermatic 135 welder
C25 gas
Wire - most of the work was done with solid .024 wire, but towards the end I switched to Harris "twenty gauge" brand wire in .030 diameter

Panel - A used flate model fender (24 gauge)

The task - Cleaned paint off a section of the fender (both sides - it was pretty dang clean), cutout a patch with a 3" cutoff wheel, and attempted to weld that same patch back in (see pic).

Now for the questions:

1. Welding wire bunch up - As I weld I'm experiencing issues where the spool of welding wire bunches up feeding into the hose. I actually switched to the Harris .030 wire primarily because I hoped it would help alleviate this (it did to a degree). Any tips to alleviate this?

2. Welding wire and spool - The welding wire is so loose on the 10lbs spool it wants to come "unravelled" if it isn't under enough tension. Any tips for alleviating this?

3. Weld "blob" build up - While I was welding I often got a lot of wire blob on top of the sheet metal - leading to a LOT of grinding. Is this just a matter of having too much wire speed?

4. Sometime it would seem like the wire was feeding, being consumed, and then feeding some more with a "pop....pop....pop" sound (i.e. pops far apart) - is this a "too slow" wire-feed condition? (Note: I was doing a lot of experimenting with settings).

5. Penetration - As I ground my welds down, I noticed that as I got closer to the base sheet metal level several of my welds didn't have good penetration and were really just sitting "on top" of the sheet metal. Is this a "voltage" issue (i.e. too little)?

6. Wire tip - When you pull the trigger should the mig wire already be in contact with the panel or should it be a millimeter or two away from the panel?

7. Panel gap - As you can see from the pic (hopefully) I had a pretty good gap al the way around the panel, and in a few places the cutoff wheel got away from me and left a bigger gap. Are my gaps "way big" as compared to what you guys usually have (note: I found it pretty difficult to get them any smaller with the cutoff wheel). The larger gaps were really difficult to close up. Do you weld across the gap or parallel to it trying to build up the edge?

Thanks guys - I know I'll think of 5 more questions as soon as I hit Submit!
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Old 09-23-2006, 07:05 PM
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Old 09-23-2006, 07:48 PM
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1) Is your wire dirty and have any rust? Surface flash on the spool from sitting will bind in the gun liner. If the wire is dirty, spool off wire until it's clean or install a fresh spool. If you're settings are wrong for voltage, the wire can stick to the tip and it will "ratsnest" like this too. Are you using the correct contact tip for the wire size installed?

2) Tighten the spool tension nut a the center hub of the wire spool. This needs to be tight enough that the spool stops turning without coasting when you let off the trigger.

3) Blob build up. You may not have enough voltage and wire speed. Take time to tune up the settings on a scrap the same thickness. Take an hour or so and just tinker with wire speed and voltage while making tacks to the scrap. Listen to the sound, that will tell you lots about the setup. Turn the panel over after an adjustment and check for penetration. If it's throwing off too many sparks voltage is too high. If the handle is pushing back, it's not enough voltage.

4) Check if you have adequate tension for the drive wheels. There is a tensioner adjustment above the grooved wheel. The wire should be able to push back against the torch without slipping. It should be loose enough that it won't ratsnest in the machine if it doesn't arc right away. Check you wire speed and voltage settings. Those numbers in the door are starting points. You will need different settings for different line voltage or materials. Also make sure your ground clamp is solid and close to the weld. Keep "stick out" the same for each weld once you find settings that work. Stick-out has considerable effect on weld height and penetration. Cut the wire for a fresh sharp cut before each cold tack. Your cutters/pliers should be right there all the time.

5) Penetration is a function of wire speed, voltage, stickout and time. All of those need to be the same for each and every weld once you have working settings. You can vary one and make up for it with the other. For instance, less stickout will make up for lower voltage to some extent. So work on repeatability for stick out, timing and your settings.

6) I snip the wire fresh. Then I hold it 1/10" or so from the work and pull the trigger. I stop when the tack is hot enough to get penetration. Then I stop while it cools to dull red, step over just about 1/2 tack and burn in the next one. The second needs slightly less time because the panel is now hot. After a series of these are connected, I stop and let it cool. Fix heat warp and grind and finish connected tacks before the panel twists too much. Once you have it flat, connect some more segments. Skip around the panel and always keep an eye on the shape.

7) Your panel gap is making the work difficult. Large gaps encourage burn through at one or the other panel when heat flows to only one panel. Ideally, the gap is smaller than your MIG wire so it can't slip through the gap. Fit for minimum gap by fitting a patch panel that is as close to the same size as possible. If you have penetration issues, run hotter, more voltage, longer time, less stick out or bevel the edges.

I don't find those butt welding clamps ideal. I have a set that I don't use. They set too large a gap. You can hold the panel in place long enough to tack down with masking tape or magnets. Just keep the magnets distant from the arc. Don't forget the patch and the panel need to be in the same plane. If one is higher than the other, it will grind thin when you finish it later on.
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Old 09-23-2006, 07:57 PM
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1. Welding wire bunch up - As I weld I'm experiencing issues where the spool of welding wire bunches up feeding into the hose. I actually switched to the Harris .030 wire primarily because I hoped it would help alleviate this (it did to a degree). Any tips to alleviate this?

Make sure you keep your whip as straight as you can, if the liner is old it can cause the wire to drag and “bunch up”

2. Welding wire and spool - The welding wire is so loose on the 10lbs spool it wants to come "unraveled" if it isn't under enough tension. Any tips for alleviating this?

It should have enough tension on the spool that you can turn it but as soon as you stop it stops turning.

3. Weld "blob" build up - While I was welding I often got a lot of wire blob on top of the sheet metal - leading to a LOT of grinding. Is this just a matter of having too much wire speed?

Not enough volts, turn up the volts and then play with your wire speed.

4. Sometime it would seem like the wire was feeding, being consumed, and then feeding some more with a "pop....pop....pop" sound (i.e. pops far apart) - is this a "too slow" wire-feed condition? (Note: I was doing a lot of experimenting with settings).

This could be related to your number one question. If the wire isn’t moving evenly then it could cause this.

5. Penetration - As I ground my welds down, I noticed that as I got closer to the base sheet metal level several of my welds didn't have good penetration and were really just sitting "on top" of the sheet metal. Is this a "voltage" issue (i.e. too little)?

Too cold again turn up the voltage

6. Wire tip - When you pull the trigger should the mig wire already be in contact with the panel or should it be a millimeter or two away from the panel?

It shouldn’t matter if its touching or not, I have heard that cutting the wire at a sharp angle so it has a sharp point can help make it start faster but I just cut mine off and pull the trigger

7. Panel gap - As you can see from the pic (hopefully) I had a pretty good gap al the way around the panel, and in a few places the cutoff wheel got away from me and left a bigger gap. Are my gaps "way big" as compared to what you guys usually have (note: I found it pretty difficult to get them any smaller with the cutoff wheel). The larger gaps were really difficult to close up. Do you weld across the gap or parallel to it trying to build up the edge?

Those gaps are pretty big for that thin of sheet metal. You need to keep the gaps as little as possible or none at all. With gaps that big you are going to have a lot of warpage as the metal shrinks. Keeping tight butt joints will help with that issue.
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Old 09-23-2006, 08:06 PM
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I'm in the same boat as you with trying to teach myself how to use my Hobart 140. When I tried thinner wire and went to .025 I had the same problem with the bunch-up in the hose to the gun. I kept thinking it was the tip or the tension on the feed wheels and really felt stupid when I finally noticed what it was. May not be the problem you have but I found that the inlet to the gun liner/hose was not pushed in as far as it could be up next to the feed wheels. The thumb-screw had loosened and the gun hose had pulled away far enough that there was too much unsupported gap between the feed wheels the the gun liner/hose. Might want to check that.

[QUOTE=cab]All,

1. Welding wire bunch up - As I weld I'm experiencing issues where the spool of welding wire bunches up feeding into the hose. I actually switched to the Harris .030 wire primarily because I hoped it would help alleviate this (it did to a degree). Any tips to alleviate this?
QUOTE]
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Old 09-23-2006, 09:05 PM
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Guys - THANKS! This is great info.

On items 1 & 2 - I just checked my spool and indeed the nut was loose. In addition (Mak) the whip actually FELL OUT at one points so I think it is fair to say it was also slowly moving away from the wheel contributing to the bunch up. I've cinched it in there now. So hopefully that will help with items 1 and 2 (along with keeping the whip straighter). The welder is new, and so is the wire although I notice the .024 wire that I used at first is shiny copper, but the new Harris "twenty gauge" brand .030 wire is black/grey - is that normal?

I'll try out all of the other suggestions tomorrow (as best I can) and am sure I'll have more questions. Thanks again - your input is invaluable!
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Old 09-24-2006, 01:55 AM
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You definitely need to at least switch tips between .024 and .030.
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Old 09-24-2006, 07:25 AM
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Cab, Store your "Twenty Gauge" away until you get this under control. First thing is DON'T get discouraged! No one can just pick up a welder and take right off with it so what is happening to you is "normal" and if you keep at it this will soon "click" and it will then seem easy The advice you have gotten should help a lot and about the only other thing you might want to check now would be the tip location in relation to the nozzle. If the tip is set back inside the nozzle too far it can cause problems so it should be about flush with the end and in fact I prefer to have the tip stick out past the lip of the nozzle just slightly. Also, as has already been pointed out, don't forget to snip the wire before starting each weld because the little ball that forms on the end of the wire when you stop welding does not conduct very well and can cause the wire to make contact with the work piece without starting the arc, this will cause the wire to push back and can be the cause of several of the problems you have mentioned.
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Old 09-24-2006, 09:26 AM
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I did switch the tips so I am good there, and thanks for the tip positioning advice Oldred - that was one of the questions I forgot to ask!
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Old 09-24-2006, 09:58 AM
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Mig welding thin sheet metal has definately got a longer learning curve than thicker stuff. I like using a brass or copper backup plate under butt welds. Aluminum works too but has a tendancy to get a little in the weld when using a mig. Close fitup and using .023 wire will save you alot of aggravation.

I have heard from several people who have used this ESAB 'easy grind" wire on sheet metal that it is worth finding. I have not used it myself,(i TIG most all my sheetmetal), but it might bear mentioning here.

The esab website page is not very informative, but i have come across mention of the following additional info.

I've been told it is easier to grind down,(guess that's why they call it that, duh), softer, so it doesn't put such a hard weld line and can be hammered flatter without splitting the base metal like if you use the e70s6 wire, and it can be used over moderately dirty joints ,such as would be encountered in doing auto body work or stuff that gets fitted and then not welded immediatly.

I wonder if it would work different than the cored harris 20 gauge wire you are using? I just looked at that wire on the harris website and it looks intriguing

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Last edited by powerrodsmike; 09-24-2006 at 10:10 AM.
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Old 09-24-2006, 11:07 AM
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Mikey, The best part of the Twenty Gauge is that is easy (after a bit of practice) to get a weld that does not need grinding I have tried the "easy grind" wire and it is indeed "easy" to grind and welds nice however although it may be strong enough for sheet metal body panels it is too soft to have much strength and I am sure it will get used somewhere that it should not. I know this is operator error but it is going to happen just the same.
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Old 09-25-2006, 10:33 PM
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I finally want to say

I've seen this several times on here and finally want to say: It is most important to practice, to get a fender is great, BUT
when you cut out a piece to practice on you must butt up to two edges only to practice. Everyones' cuts, including mine, are usually made with a blade or wheel that leaves too wide of a gap all around. Remember when you are patching you are cutting a new piece to the "exact" or near exact size as the "hole" so its tight all around. When you practice you can only get two adjacent sides tight. All the practice'ers are making the same mistake. gaps are too big for beginners let alone experienced welders. You can grind down your "clamps" ($5 for 6-8 at HF.) to .025 or .030 from about .040 as purchased. If you are careful you can do this on the side of your grinder or sanding station or by hand. But tape or a friend will let you get butt tight or but tight or as a frogs....never mind.
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Old 09-26-2006, 07:27 AM
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Bart, Good point. Also a beginner should start the practice on something thicker, like 1/16" to 1/8", until they get the feel of it and learn to control the arc, there is no sense in trying to learn how to lay down a decent bead and having to contend with burn through at the same time. Once they learn how to control the welder instead of the welder controlling them they can move on to the thin stuff and deal with the burn through and warpage without having to learn how to simply weld at the same time.
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Old 09-26-2006, 08:05 AM
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The easy grind wire is good stuff and I've used a few spools in the past with better weld flow and easy hammering and grinding. I tried the 20 guage stuff and was very dissapointed with dirty welds and no benifits that I can see, the wire is now used for anything but welding.
.030 wire works better in my machine than .023 and provides better starts.

I've found many welding suppliers online that offer wire for general manufacturing that I'd bet would be similar the the easy grind being a mild steel with a lower strength rating than the auto industry specd stuff I use now. I need to order some up and give it a try. When working outer body sheetmetal on these old mild steel cars the softer welds sure are nice. Frames and structural strength areas definately need the stronger welds though. ramble, ramble, Bob
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Old 09-26-2006, 08:37 AM
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Bob, Not sure how anyone can get "dirty" welds with the Twenty Gauge and I am very puzzled by why you could be having problems with it since this is by far the most forgiving wire I know of to weld with. As far as the advantages of using it there are several most notably it's ability to weld extremely thin stock and a VERY smooth clean bead. I have been a professional welder for 38 years and I have burned literally miles of wire of deferent types and after finding the Twenty Gauge we began to use it exclusively on the very thin duct panels that was built in my shop because even the .023 had burn through problems due to the metal thickness, I would put the Twenty Gauge up against ANY wire I have ever used and believe me when I tell you I have used a lot. This wire is really good stuff and can make body panel welding much easier especially for beginners due to it's low heat requirements which means far less burn through and warpage problems. I agree that the "Easy" grind wire works well and my only complaint is that it is not strong enough to use for much else but body panels and you know what will happen with people being people and all
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