MIG Mystery

[Leecapri83]

Hi
I'm hoping someone can shed some light on a dilemma i'm in. I've been tasked with replicating a product that i have been assured is mig welded. I have tried laying a weld on the external edge and then grinding/linishing back but once the part is powder coated it shows up any witness marks and highlights any changes in the edge profile.

Really what i'm hoping for is if anyone can tell me is if this standard is possible and it's my own skill set that needs improving or if there is another type of welding/grinding that i'm not aware of that could be the solution.

Thanks in advance for any help or just taking the time to read this.
Please find pictures attached.
Lee

 

[HughF]

we used to build stuff like that all the time at the sheet metal shop with mig on 2mm carbon steel... The grinders skill is what results in a good job. You need fibre discs and a flexible backing pad, then a decent DA... We then used trike tank, spray etch, powder coat.

 

[Kent]

Spend a year doing hardly anything but grinding like many of us did as teenagers and it's easy!
Best I can say is take to square on both flats before you try for the radius
I should do it with a hard stone type wheel then diminishing grades of cloth type sanding discs on a hard then soft backing pad
Expect to add an odd blob of weld here and there during taking the thing down

 

[HughF]

we used fibre discs all the way down then finished with the DA

 

[BrokenBiker]

i have not long been on a job for my company to a supplier that makes boxes for us from 2mm ali and stainless that then go on to be powder coated.

the technique i used was to use a low grit sanding disc to rough the weld down, then a 120 grit disc on a DA sander to get the weld down flush and buff the whole part ready for coating. out of the 380 we did there were 6 that came back and you could clearly see the swirl marks through the powder coat. you need to do a bit of sanding, play the light and look at it from every angle, the radius will take a while to get right, but after doing it a few times it should be simple. also a scotchbrite pad will help get some of the harder to reach areas (if there are any).

all parts we were processing we tig welded as they had deemed mig unsuitable for the task.

 

[Ewok]

Best I can say is take to square on both flats before you try for the radius

Agreed. Then put a even 45deg on the corner and ONLY then round that off - same regime when woodworking.

 

[Leecapri83]

A massive thankyou for all the replies. I've just purchased a DA sander so i'm going to persevere with the finishing side of things in view of the advice given above.
Thanks again.