Laser Cutting Perforated Sheets - Problem with Warpage 1

[Justin Langley]

For quite some time now, our company has been manufacturing laser-cut perforated sheets with a fiber laser, run with nitrogen for our perf. While we do occasionally purchase punch-cut perforated sheets, we found that our laser gave us the ability to make completely custom designed perforated parts. But at this point, we’re beginning to run up against a wall as to what may be possible. A customer requested the fabrication (laser cutting and forming) of a number of perforated sheets, two of which had 0.1875 holes and 0.15625” holes, smaller than anything we’ve ever cut. The first sheet was 65” x 36”, with a gap between each 0.1875” hole edge of 0.06” - yikes. (We later tried 0.09”). We tried two different programs, the first one skipping four holes at a time, while the second one only one row. We first tried using 14GA hot rolled steel and then 18GA cold rolled steel. With both attempts, the resulting warpage was tremendous and with such a very small margin of error, towards the end of the CNC program, the rows of holes would inevitably run into each other, caused by the fact that the sheet was contracting on the X and the Y axis. We had one side clamped, both times. One idea that we came up with was using clamps to secure all sides of the sheet to the table, but we’ve put off that idea for now because we’re worried that it’ll potentially make the problem worse with the middle bunching up and swelling. We never attempted the 0.15625” sheet, for obvious reasons, and were forced to subcontract with a company that could punch the desired sheet for us.
Does anyone have any experience with such a specific application? I understand that, in laser cutting, very few companies attempt to do perforated parts, due to the cost (excessive use of nitrogen + time + wear and tear), so I’m skeptical there will be anyone else who has experience with this. Any thoughts or comments would be appreciated!

 

[3DDave]

It seems like you need stress relieved material. Cold rolling leaves metal with significant internal stresses. i have seen thick plate pop up like a potato chip following metal removal.

As a shot, try cutting from the middle and spiraling out with some random cuts to even up the shrinkage, but stress relief is probably the best way.

 

[ZixmiX]

Im unsure what equipment you're running, but if available try cutting while utilizing heat avoidance. This will randomize the tooling path so you never cut a hole next to one that was just cut. We had this same issue on our fiber laser when we first started cutting panels with 100's of small holes.