Twisty

[Welderpaul]

Big lid come back from the galvanisers this morning, 1700mm ish square with a 90mm turndown. Fabbed from 4mm plate. Has stiffeners welded on the inside corner to corner. Lid is diamond pressed corner to corner. Obviously the heat from the galvanising process has mad a mess of it. The 4mm has pulled away from the stiffeners where its not welded, creating a load of 'bubbles' on the sections between the corner to corner creases. Cutting the welds between the plate and the stiffeners does not release anything.
Need to get this sorted asap, as we have a load more riding on this 'sample'.
Time is also of the essence.
Reckon if the stiffeners are cut off, and the creases are re-pressed that it will straighten it up. The stiffeners would then have to be rewelded back in to stop the thing wobbling around.

 

[Seano]

Bet there was a few choice words there then Paul..... how you gonna get round it...?

WcW

 

[Hitch]

What have they done to it!
Pressing a diamond once the edges are folded like that might give you problems...youd probably need to cut the corner welds aswell.

Hows about- upside down on some dunnage, all round the edges, then a pallet of steel, resting on a small block right in the centre(cut the welds that would be verticle if there is any, and the far ends of the stiff's)drop the forks down, then use the tilt to push it down further if req'd...Weld the verticle ones and the ends with some force on it
Worth a shot, seeing as youll need to cut half the bars off anyway
Doubt anything will get it perfect though.


Trouble is its stretched, but not evenly.
Wonder if it would have made much difference going upto 5mm?

 

[Welderpaul]

Problem is its so springy, even with the weight on, and welding up while the weights on, i still think it will spring back, thats why i was querying repressing the diamonds again, the bubbles are on the crease lines, and either side of them - hoping that the repressing would straighten everything out.

 

[steve202]

Could the stiffeners be welded all the way along?

 

[chunkolini]

Oh Joy of Joys, this must make a great start to the week.

Do you get anycome back from the galvanizers or is at your own risk?
It also explains why galvanisers have always told me to go away whe asked if they could galv' one of my big fishes. I can see that the tension and bends in all that thin stock might be a problem

Keep us posted as to how it goes.

Chunko'.

 

[Welderpaul]

Scrap skip i think. Might have a go at it tomorrow.
It's own risk i'm afraid. I've seen 10mm plate do the same. All depend on how its fabbed, stresses in the material and introduced during manufacture.
The joys of being a fabricator

 

[Drains]

You any good at heat-shrinking Paul? Might be worth a try - an hours chancing it instead of straight in the bin...

I can do it on section, but i've never got the hang of it on sheet - I always make it worse.

 

[craigthewelder]

I had some 8mm durbar come back from the galvanisers this morning and it had done pretty much the same thing. A bit of heat and a big hammer and it doesn't look to bad now..........

 

[craigthewelder]

Looking at the pics a few more stitches on the stiffeners would probably help. Which galvanisers did you send it to??

 

[Welderpaul]

Looking at the pics a few more stitches on the stiffeners would probably help. Which galvanisers did you send it to??

Yeah, i was trying to reduce the amount of welds to give the material room to flex, the stiffeners are there more to prevent to whole lid wobbling side to side than stopping it twisting. The warping probably wouldnt be too bad if there were no stiffeners on it.

 

[KTMMICK]

Just a thought could you not make the stiffeners separate and bolt them in after galvanising. No other Company who gets the job is going to have any less problems. Just explain it like that to the Customer. Honesty is the best policy.

 

[Welderpaul]

It's in the skip now. Try again.

 

[Hitch]

Im not wholely convinced by MK2 myself, will be interesting to see what happens. Stitching braces onto the flat sheet?

 

[Welderpaul]

I know your not The advice from 2 sets of tinbashers, plus the galvanisers is not to diamond press. Make up as normal, with a 50 x 10 flat bar bracing 'square' in the centre, with diagonal braces as before. More welds between braces and lid this time.
Galvanisers reckon they can do a quick dip as well to reduce the amount of heat that goes into it.
Weight is an issue, otherwise you'd have been struggling with 6mm into the break!

 

[Hitch]

Fair enough!

Air cool instead of water quench will probably make a difference too. Not sure exactly how they do it.

Isn't the diamond a major part of the design though?

 

[Welderpaul]

Yes, the diamond is a part of the design, but they are hapy without it

 

[Arsonista]

Paul, you must be gutted, that looked like a nice piece of work. I've been kicking this around all day. I think between all the guys on the forum you may have come up with the answer. Before galvanising, the job would have pinched or shrunk where you welded it, that would have created a 'pant' in the triangular panels and you would have got that out by dressing the welds to release the pant. All normal so far. The only thing I can think of after that is when the part was in the galvanising tank, it expanded and then they quenched it for handling. The quenching froze the material in place. Maybe they need to 'let it down' a bit more naturally to allow it all to return back into shape. Maybe. Hope it goes better tomorrow.