How to flatten ss 304 sheet after perforation or punching?

[Tarun Tanwar]

I had a stainless steel of Diameter 1000mm with a sheet thickness of 1mm. I have perforated that whole sheet through punching machine and there is 25mm margins (border) along the circumference. Now, that sheet is not flat now due to the expansion , I guess. I made a single cut equal to the radius of that round sheet and found that cut now overlaps about 5mm and the sheet becomes flat after cut. So could you help me making the perforated sheet levelled without cutting.

Thanks

 

[EdStainless]

This is why people use a process called Fine Blanking.
With enough counter pressure you can keep the parts flat.
How many holes are you punching at once?
Often you punch a stager pattern (not adjacent holes) and then keep repeating.

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P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

Tarun
An old tip I learned 4 decades ago was to use cheap cold roll sheet steel thin enough to be sheared or punched. Prevents the typical deformation. I suggest you do a test.

 

[dvd]

I wonder if this was a cold rolled sheet and the rolling direction is what we are looking at when we see the warp. All of the perforators that I have worked with over the years have used hot-rolled, pickled and oiled sheet. See the attached Perforator's Handbook for some discussion on perforating.

 

[mfgenggear]

i left out an important detail the above recommended sheet is for backing during shearing or punching.
the deformation of sheet as we know the mechanics half shears and half breaks causing a deformation,
the warping (distortion) of sheet is caused by work hardening. the work material should be annealed if possible.
if the material has to be harden like 1/4, half or full , then a better process like laser should be used.

 

[Tarun Tanwar]

Reply to EdStainless, For this sheet, I punched only one hole at once.

Thanks everyone for your inputs.

I wanted to ask you if I go for full hard sheet, then would there be less expansion in the material due to hardness?

 

[EdStainless]

I am not sure that you would like way that full hard punches, but maybe 1/2 hard would help.
There will be less deformation.
But the real trick is very high clamping force between the platens before the punch strikes.
I presume that you are using a light lubricant.
And I presume that your punch speed is high.

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P.E. Metallurgy, consulting work welcomed