How do I flatten Proofgrade plywood?

[thejambi]

Often I have boards that are warped a little bit. I wouldn’t really call them “warped” because they will definitely cut and engrave no problem, but they are not perfectly flat. Well, I need to cut 10" pieces out of them that need to be flat, and I’m not sure how to get them to flatten out.

Do you ever cut out large pieces that you need flat? How do you flatten large cut pieces from material that is slightly warped like that? Should I start looking for something besides ?

[Jules]

I use these for cutting:

Honeycomb bed holdown pins

the best laser results are achieved with flat (non warping materials) in order to maintain consistent focus. Also, when cutting light materials like paper, the exhaust turbulence can kick up the material and ruin your job or at worst… catch fire. (speaking of which, I hope you all keep a small fire extinguisher in easy reach, near your machine - safety FIRST) I hope you find these useful. I used to 3d print them for my other laser cutter but occasionally , they would see the wrath of the laser …

If you find something that warps less than Proofgrade, let me know what it is. PG is generally a lot better than the local stuff I can get.

[thejambi]

It will cut just fine as it is, no problem. But I’m not sure how to flatten large pieces after they’ve been cut. Maybe I just need to expect to buy 3 sheets of plywood and hope to get one good flat one? I was thinking that the thick plywood would be more flat, but I got one that makes me think otherwise…

[Jules]

Maybe keeping it under pressure for a while. Stack some other wood on top for a couple of weeks and make sure it’s well dried out.

One thing that does help is gluing it down. Once it’s glued, it holds it’s shape.

Stuff always warps here too, the humidity is just too damned high.

[jbmanning5]

It’s all about storage and a consistent environment for any wood storage. Either cut it right away when you get it before it starts acclimating, or wait a few days for it to fully acclimate, is my opinion. The other thing is a consistent environment - humidity swings will make the wood never acclimate. It’s constantly taking on water, losing water, and back and forth, causing expansion and shrinkage. I have good luck just stacking my materials horizontally but my interior humidity stays very consistent.

[thejambi]

Thanks! Well, sounds like it’s not much use trying to get it perfect if I’m just shipping it off around the world, eh? The one I’m working on now is pretty close, so hopefully that’ll do.

[rserrano7]

PG ply is pretty flexible as it has an mdf core. I normally bend it opposite the direction of the warp prior to cutting. But as mentioned by JB it’s all about right environment humidity wise. Now the fact that its core is mdf makes it more stable but the veneers will still cause warping if allowed to move. And if you’re shipping something to another climate all bets are off it might be ok or it could go pretzel on you. I believe that is why PG is also pre finished to avoid massive warping.