Customised Spot Welding question?

[richg1]

Hi,

I have a question regarding a custom spot welding application: Is it possible to spot weld through the thin edge of a sheet metal (~3mm) rib standing perpindicular to a mating flat sheet (~0.5mm)? (See attached pic)

And the sheets may be pre-galvanised!

My experience with RSW is limited so not sure if this idea is technically feasible.


As a follow up question, with this application could the spot weld be ganged, ie n-welds along the rib per cycle?

Thanks, Richard

 

[MintJulep]

I won't say that it can't be done, but I've seen lots of stuff held together with spot welds and I've never seen anything like that.

If it could be done, I think it would be worthless in fatigue.

 

[richg1]

Hey MJ,

I agree that the weld strenght would be vlow, but think that can be compensated for by a number of welds along the rib length. What I've shown in the image is a small section of a larger part.

Had another thought that similar to stud welding a V-shaped projection could be on the rib to improve the weld creation?

 

[MintJulep]

Have you looked into linear friction welding?

 

[richg1]

I think in this application (which I haven't fully explained, company IP, etc) friction welding wouldn't work. I need the workpieces to remain very well aligned during the operation.

Plus the final part is big-ish - car body panel size...

Will probably see about running some sample parts on a spot welder just for the hell of it...

 

[CoryPad]

You should consider a different welding technique, such as laser, electron beam, friction, friction stir in a local condition or as a seam. There are resistance seam welding techniques that use rolling electrodes. For any of these welds, contact with the bottom sheet looks like a better idea.

 

[gtaw]

I am thinking along the lines of richQ1.

A projection along the bottom edge of the butting (vertical)member so that the projection makes point contact with the nonbutting (horizontal) member. The current would be forced through the localized point of contact. There would be some shunting effect from adjacent points of contact and adjacent welds, but that can be offset by controlling the amperage.



Best regards - Al

 

[ornerynorsk]

Can you brake form a 90 degree lip and weld face-to-face? The whole assembly will be much stronger and stiffer. Personally, I don't think your weld as-drawn is going to be worth much other than as a temporary tack to hold position.

 

[richg1]

A bit more information...The actual, part, is slightly curved. The aim was to use the bottom edge of the rib as a laser cut or custom guillotined profile to provide the support without having to stamp or rollform the support. The welds along this length would hold the 0.55mm sheet in place.

It's just one of a few ideas and I was interested in whether this was even feasible. The general consensus and some of the manufacturers I've spoken to seems to be 'no'...

(ps. 30m should read 30mm)

 

[ornerynorsk]

Can you tab and slot, or just tab, in order to have a good spot weld surface. Short tabs will still allow your radius, but won't have a full weld seam along the length of the part. Just a thought.

 

[richg1]

Not a bad thought and something I'll probably try as well.

The downsides I can see are the 0.55mm sheet being very thin and I really need the face opposite the ribs to be smooth. So would need post-weld linishing and a touch up with paint. But still it might be feasible and still automated for high volume.

Thanks