strange issue welding body panels

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PostPosted: Sun Jul 04, 2021 6:09 pm
Im replacing some panels on my 64 Chevy, My mig machine has worked fine with the original metal and the sheet I made patches with. When I try to weld the new tail lamp housing panel to the bed side the welder will not penetrate the new panel. I have a cheap machine run on 220 power and I have turned it up to where it burns through the original metal. I have moved the ground to the new and old sides of the weld. nothing works for penetrating the new panel. I put the new panel on the bench and by itself I get penetration with no issue. As soon as the new panel touches the truck, no penetration. I often back the steel with aluminum to help fill bigger gaps and that is exactly what the panel looks like after trying.
I am an experienced welder mostly on heavy duty equipment so sheet metal is kind of new to me but it has been going fine until I got to the new panel.
Anybody had this issue before?

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PostPosted: Mon Jul 05, 2021 8:17 am
Is the new panel actually steel?
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PostPosted: Mon Jul 05, 2021 9:50 am
Yes its steel, magnet sticks, I put a couple of tacks on it when on the bench and no problems. I have been attempting to weld flange to flange by drilling a hole on the bed side flange and tacking through the hole onto the new panel flange. After thinking about it for a day I think I will try a bigger hole or even cutting a small section from the old flange to make sure I am penetrating the new flange first. Got my fingers crossed



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PostPosted: Mon Jul 05, 2021 1:06 pm
The New Panels being re-popped for this older stuff is many times Made in China where they use less than quality steels to stamp the panels from, and its thinner than original in most cases as well.

What machine are you using? what settings? volts? wire speed? gas flow? wire size?
Are you trying to BUTT weld or Over lap the two pieces?
Not all machines work with same settings but you probably know that.
I am sure you also know as an experienced welder but Both sides of each piece being welded needs to be super clean no rust paint oil or grease a wipe with Acetone helps.

I have run into problems Sanding metals clean myself, Sanding Grinds impurity's into surface. I Wire wheel all pieces smooth after sanding especially if I am Tig welding it.
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PostPosted: Tue Jul 06, 2021 6:45 pm
My machine is a cheapy from Harbor Freight but it has been working fine for me. The heat settings are 1-6 so who knows. I have been up and down with the settings with no luck. I have butt welded a number of patches without a problem. The panels have flanges to the inside (originally spot welded) and I have been attempting to drill holes in one panel and then tack through the hole onto the new panel and melt back to the panel with the hole. I wont have a chance to try again until this weekend and I have a new plan of action. I will cut small pieces from the old panel to get more exposure to the flange on the new panel. I think now what is happening is as soon as I have an arc the old panel absorbs it. If I make sure I am arcing the new flange first I should be able to melt back to the old easier. Hopefully



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PostPosted: Wed Jul 07, 2021 12:13 pm
Check out this Video
https://www.youtube.com/watch?v=aoTFcYw_qwc

Listen to the Sound of the weld you want your machine to sound like this when welding!
Watch your STICK OUT!!!!!! Watch the ANGLE of the Torch while welding!!!!! and again listen! you want that Sizzle sound once you get it your close Stick out is critical !!!!
To close = BAD!, TOO Far out = BAD!!!!! I shoot for 1/4" - 3/8"
Torch Angle again is critical lay down to much =BAD!, To Hi = Bad!
You want your torch angle to be around 35 Degrees.
Always Push the bead when you can it is a little harder to learn but better to learn this way.
Dragging the bead can be done BUT is harder to make sure you have a Good bead penetrating.

What wire are you running ????? what size????

What Gas and what Gas pressure are you running?
I Run a 80/20 Steel mix set mine up flow to 20 cfh min occasionally a little more if its breezy in shop. Or what thickness metal and wire size type of material.

I have never played with the Harbor Fright machines, I like to shy away from most Harbor fright junk. Almost every thing I have ever bought their needs repaired or modifications to work.
Everlast builds a Good cheap import with a warranty they stand behind and service center in the USA for repairs. and the machines have a decent Duty cycles.
https://www.everlastgenerators.com/
May I suggest? https://www.everlastgenerators.com/prod ... i-mig-275s

I don't like click setting machines myself, I like to be able to fine tune Power voltage/Amps and wire speed to get that Sound.
There are charts you can go buy that get you close for settings but are only a Guide to get you close you need to be able to control power and wire speed on a Mig to get that perfect Sizzle sound.

Was this a new machine or was it purchased used ?
If used possible wire liner may be contaminated? rust, oil, dirt, may be possible it had aluminum wire ran through it as well. Aluminum will contaminate the liner.

Another possibility Most cheap imports come with the cheapest accessories possible Ground clamp are usually junk for most part you can try to upgrade your clamp to a Good heavy duty one like this:
https://www.harborfreight.com/400-amp-w ... yUQAvD_BwE

I am not suggesting the one from Harbor fright but posted it as an example of the type of clamp to look for.
Your local welding supply where you buy gas should have a Good name brand made of solid copper or Brass. When I get a New welder the first upgrade I do is a new Heavy duty Ground clamp! right off the Batt before ever even turning the machine on for first time.
Next is upgrading the Gas Regulator, Torch and Leads in that order as again The MFG's Put these machines out there with the cheapest accessory's possible to increase there bottom line profits while they will work most welders consider the supplied stuff cheap junk for most part.

Using a Heat sink OR a Backing plate:
I am guilty of doing this myself although I use Copper NOT Aluminum i am not saying alum cant be used I just don't use it.
I have since stop using any sort of backing plate as They absorb heat away from the weld bead requiring a higher setting. and back side of bead usually looks like sugar from lack of penetration from lack of heat and no Gas shielding.
Even the slightest gap in free air allows shielding gas to get through to the back side with a Backing plate it cant get in there.

Using a Backing plate is practiced by many and sworn too as the way to do it by many.
I myself don't use it unless I absolutely have to, I find free air welding to be better providing a Better weld bead on the back side, What the bead looks like on the Back side of the weld is more important than the side you see.

Welding Thin sheet metal is NOT easy to do or to learn definitely! Its a hard skill to master! It takes a lot of practice! I learned to weld with Gas almost 40 years ago Then Jumped into a Mig for sheet metal on cars as It was said to be the way to go for cars sheet metal. so I bought one Only to Cuss it till I learned how to use it correctly, BUT I still wasn't happy with my welds so Then I jumped into Tig welding and I cussed that till I learned to use the machine correctly Only to go Back to using Gas!
Gas and Tig are best for Thin sheet metal hands down, Mig has its place But for sheet metal panels gas is the way to fly the Bead is so soft and easily Malleable for beating the bead flat and working the heat warp-age out. Tig is too but it has a Harder bead than Gas in my opinion Tig's main advantage is Pinpointing the Heat of the weld bead and not affecting the panel as much.
This is Tig: Gas Has a much Larger heat effected zone.
Image


Good DC only Tig starter machine for steel only, with High freq start less than $500
It will do all the Thin stuff you want.
https://www.everlastgenerators.com/prod ... rc-160isth
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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PostPosted: Wed Jul 07, 2021 8:16 pm
rustybart wrote:My mig machine has worked fine with the original metal and the sheet I made patches with. When I try to weld the new tail lamp housing panel to the bed side the welder will not penetrate the new panel. I have a cheap machine run on 220 power and I have turned it up to where it burns through the original metal. I have moved the ground to the new and old sides of the weld. nothing works for penetrating the new panel. I put the new panel on the bench and by itself I get penetration with no issue. As soon as the new panel touches the truck, no penetration. I often back the steel with aluminum to help fill bigger gaps and that is exactly what the panel looks like after trying.


I've been following this thread and keep coming back to this. If you can lay a bead on each panel separately then the issue is not with the welder (machine, not person). You say you're an experienced welder so I'll accept it's not an issue relating to technique, at least for now. Of course, all the basics like clean surfaces, removed coatings, galvanising etc. are givens.

If the problem only occurs when you have the new panel on the vehicle then about the only possibility I can see is that you have some kind of strange electrical flow path happening like a ground loop. Put yourself in the position of that excited little electron who's just been zapped down the wire and out the end of the gun. Now he just wants to find the shortest and easiest way home. Why would that not be via the new panel?
Chris



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PostPosted: Thu Jul 08, 2021 10:54 am
NFT5 wrote:
rustybart wrote:My mig machine has worked fine with the original metal and the sheet I made patches with. When I try to weld the new tail lamp housing panel to the bed side the welder will not penetrate the new panel. I have a cheap machine run on 220 power and I have turned it up to where it burns through the original metal. I have moved the ground to the new and old sides of the weld. nothing works for penetrating the new panel. I put the new panel on the bench and by itself I get penetration with no issue. As soon as the new panel touches the truck, no penetration. I often back the steel with aluminum to help fill bigger gaps and that is exactly what the panel looks like after trying.


I've been following this thread and keep coming back to this. If you can lay a bead on each panel separately then the issue is not with the welder (machine, not person). You say you're an experienced welder so I'll accept it's not an issue relating to technique, at least for now. Of course, all the basics like clean surfaces, removed coatings, galvanising etc. are givens.

If the problem only occurs when you have the new panel on the vehicle then about the only possibility I can see is that you have some kind of strange electrical flow path happening like a ground loop. Put yourself in the position of that excited little electron who's just been zapped down the wire and out the end of the gun. Now he just wants to find the shortest and easiest way home. Why would that not be via the new panel?


My exact thoughts as well
BUT he says he is experienced and says its a Click type Harbor freight special.
Most Pro experienced welders would avoid using such a machine on a job like this at any cost!

Like I said being an el'cheapy welder I bet the ground that it came with is one of the problems. The other is whats not said! or not explained. Fit up, cleaning, wire type & size, Gas used, settings on the machine.

I have seen metals that are Magnetized and or Magnets being used to Hold pieces together or used to hold such things as his Aluminum backing cause the problems he is having! drawing the Bead away from the intended weld ask me how I know?

Magnets and welding are not a good combo not saying it cant be done But I haven't had great success using them ever! Use Clamps, Screws or Clecos.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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