MIGing on my car project :/

[conor1n]

Hey guys

I'm looking for a bit of feedback on some welds I did on my car at the weekend.. The welds seem a bit high and i'm wondering why. I was using the Smart MIG feature on the welder and dialled it in to the correct thickness. You can still tweak the wire speed so I kept it to the lower end.

It's all 1mm steel.

If you look at the first three pics, you can see a cut that I welded back together. It seems ok, I think, but the weld was a bit high, was it? Also, all the welds have the dimples in it.

For reference, what I have been doing is building up the 3 skins that had rotten and bringing them back together. First pics shows how they were after cleaning up the rust.

This is where things went a little downhill.. You can see the spots are a little high, and with dimples. I was using the same settings as earlier but they seem higher. What was strange is that there was decent penetration, sadly know pics on the other side.

Oh and I played around on some random bits of same thickness steel and got seemingly better results. I have been using the spot timer set to 1 second and about 20/25 CFM of gas.

It all looks like bird poo to be, tbh and I want to nail it all down before going any further.

Thoughts?

I started off drilling a couple holes to be able spot weld and add a bit more strength.

Spot welds seen from top.

Underside .. You can see some penetration. Is that enough?

Then... a final piece I have put on.

I spot welded on both sides like this.

 

[conor1n]

..Also.. I prefer the look of the red ringed weld as oppose to white. What's the difference?

 

[frank horton]

Conor
it's always dif to weld car panels, then add the crusty rusty cr@p between.....
I found when spotting or slightly longer welds is to slow the wire speed down...keeping the same amps....
Just to the point of it melting / blobbing as the wire touches the metal.....
this way it gives u a flatter blob almost to the point where very little grinding is needed....also it melts the underpanel and gets the top panel around the hole edge....even tho I use a 6mm drill for the holes I start at the middle and then work around the hole...plus I use .6wire........but u can use .8...it's just whats in the machine at the time for me....
I also found if u need to drill a spot weld hole and the panel behind is a bit rusty NOT crusty a squared off drill bit in a battery drill is used to scour the second panel.....that way u have a chance of getting the wire to melt into the second panel....

Unless ur lucky it takes a good while to get experience on welding basically c@arp.......

My last big car welding job was on a Citroen DS.....replaced all the panels u could buy plus made a whole lot more....
think the job was around 200hours.....thats just welding and prepping....only painting the new panels and repairs....
then the car went back to Amsterdam.....

 

[conor1n]

Conor
it's always dif to weld car panels, then add the crusty rusty cr@p between.....
I found when spotting or slightly longer welds is to slow the wire speed down...keeping the same amps....
Just to the point of it melting / blobbing as the wire touches the metal.....
this way it gives u a flatter blob almost to the point where very little grinding is needed....also it melts the underpanel and gets the top panel around the hole edge....even tho I use a 6mm drill for the holes I start at the middle and then work around the hole...plus I use .6wire........but u can use .8...it's just whats in the machine at the time for me....
I also found if u need to drill a spot weld hole and the panel behind is a bit rusty NOT crusty a squared off drill bit in a battery drill is used to scour the second panel.....that way u have a chance of getting the wire to melt into the second panel....

Unless ur lucky it takes a good while to get experience on welding basically c@arp.......

My last big car welding job was on a Citroen DS.....replaced all the panels u could buy plus made a whole lot more....
think the job was around 200hours.....thats just welding and prepping....only painting the new panels and repairs....
then the car went back to Amsterdam.....

That's good advice. I think that even the slowest speed on the smart mig was too fast.

I may play around with the manual mig and see how I get on. I do believe that welding thing metal on car panels is an art in itself, on top of the regular welding skill.

I did read somewhere that for light panels it can be better to run hot but in and out quick.

 

[decca]

For spot welds I was told turn the amps up, start in the middle and circle around to the edge of the top panel. I also uses spot weld mole grip type clamp with a bit of brass sheet in to act as a backing plate to prevent blowing through. On the seams try to overlap the welds.

it will look nicer.

 

[123hotchef]

..Also.. I prefer the look of the red ringed weld as oppose to white. What's the difference?

View attachment 300108

The white ringed welds are too cold.

 

[tom2207]

most of the weldings too cold , I like a 7mm hole to close spots , if possible get a copper backer in there and turn up the power ,,, it just takes a bit of faith ,,, I dont do the start in the middle of the hole though ,, I weld from the 3 o clock position to 6 then 12 then 9 ,,, sort of in a swirl , by starting at three you get the edge melted and heat transfer into the middle , then a bit of a swirl , ,, really any way you like , but then across to the other edge and slightly back to the middle to finish ,, give it a go . works for me and I weld a lot of rust, well ok not rust but certainly not stuff that you need to wipe with acetone .

 

[Myles1970]

Hi Conor. From what I can ascertain, there's many different schools of thought when it comes to welding car bodywork. There are a few varying factors apart from volts and wire speed that can influence your success. In my limited experience, I have found that keeping my volts and wire speed at the slightly higher end of the scale while keeping my "on" times short seems to work well. Those "dimples", I'd always presumed were part and parcel of the mig process.
Having access to both sides of the metal (for cleaning) will also make a difference, as will snipping the nib off the mig wire between welds.

As for plug welds, I've found most success from starting on the top layer, moving rapidly in a reducing circular motion. When I tried filling from the center, the top layer seemed to burn back, leaving me chasing holes.

I've so far stayed within areas where I can access both sides of the metal (mostly) so I can check the penetration and make good where required.

I also start any repair section with tacks, roughly 1" apart, returning to each one with an overlapping tack (or four for floor work) on the next pass. ie. I'll point the wire at the circumference of the previous tack..... If I'm doing four in a row, I wait until just before each one stops glowing red before pulling the trigger on the next one

When I do panels, I'll do the same, but I'll grind them level using the power file, in between each tack. Supposedly otherwise the previous weld would soak up the heat, meaning less penetration. I ain't done panels yet though so don't quote me

I think there's a lot to be said for the reliability of your equipment. I'm using a rusty old 2nd hand hobby welder with a Chinese torch. If you're using quality equipment, you should be able to get more predictable results

 

[a111r]

Good to see you got stuck in!
The first weld pictured looks OK, as you did grind the metal clean. That dirty, old stuff needs the heat, though, for decent penetration - if you can't / won't chop it out.

I'd say ditch using the stitch timer, as with inconsistent material it's 'bit by bit' and you need to get the feel, manually - of how far to go 'till it blows through.
Stick with it and you'll nail it, with a couple more hours experience.

This is a good thread as it's unusual for someone new to MIG to start a DIY resto. with such kit (Rebel 215) and it shows that synergic / smart control is no 'magic bullet'!

 

[daedalusminos]

Definitely look like they're lacking in penetration, but there's more to be learnt from the back side of a butt joint than the front. On 0.9mm, I set a 1mm gap between parts and you should get almost as much bead on the reverse as the front.
I tend to do short (5-15mm) beads rather than spots but move around or allow to cool to prevent too much heat build up. Photos below show a floor pan tacked in place...note the gap gets a bit wide towards the camera but still bridgeable. Haven't got a undressed pic of the front but 2nd photo shows undressed reverse.

 

[conor1n]

Thanks for the input every body.

Yes, it feels like the welds are a bit cold alright. I imagine the arc wasn't long enough to make a proper puddle, reality. It remind me of soldering electronics years ago, and how you would end up with a convex meniscus instead of concave if it didn't get hot enough.

Thanks for all the input on various techniques too.. welding really is another one of these skills that you just need to practice, practice, practice.. then practice a little more.

It also interesting as pointed out about the Smart Mig. It's probably a good feature for general settings but I guess it was my adding the spot timer which messed things up... or on the other hand.. even a numpty like me can mess up the settings on something that is pre-set for you LMAO!

I'll be at it again this weekend and i'll turn up the heat.

 

[Nick DV]

As ever, you'll always get great advice here, but if you want some simple techniques using basic tools, look at this bloke