I’ve got some proofgrade maple, and I’m not sure if you can see it well from the photo, but it’s a little warped. I don’t blame GF, because wood is a natural material, and a little humidity difference can easily cause this. The issues it will create in the laser with the changes in focus are clear to all of us I’m sure.
So to fix it for this piece of proofgrade, and also to add some weight to lighter stock like cardboard to prevent the air assist from moving it, I decided I needed some weight.
The 5lb bag of lead ball bearings is actually designed as a diver’s weight, but I had hoped it would clear the gantry. It very nearly did, but alas, it was probably 1/16th too tall. I ended up taking the contents and creating a flatter version in a food storage bag. It works well for smaller designs (so you can ensure the weight is out of the path of the cutting head), and I thought it might help someone, so here’s a few photos to illustrate.
If you search the forum people have given tons of links to good magnets. I have some that are bars and some that are discs. They each have good uses. I actually stack two up on each other, then wrap them in duct tape to make a little tab to pick them up with.
They’ll hold 1/8” stuff really strongly (will flatten warped plywood easily), 1/4” stuff much more weakly, but still enough to hold things down. The bars work well as “chucks” to seat firmly against straight edges of material if it’s already flat.
I use a steel bar attached to my workbench to keep them handy and prevent them from all coalescing into a giant megamagnetball.