As laser cutters don’t bring any mechanical force to the object that has to be cut or engraved they often don’t have any fixing for the material. It simply lies freely in the machine.
When you want to cut some plywood with a laser cutter the problem that occurs most of the time is that the plywood doesn’t stay in a flat state. It either can be already waved when you buy it or store it at your site and the laser can do the same while cutting because of the laser’s heat. You can see this also when cutting acrylic heavily. This effect will always make you a problem because the laser needs a flat object to work on. Otherwise there is no proper focussing in every region of the cutting area. For good results your plywood has to be flat before and during the cutting process. So you have to make it flat by fixing it on the machine.
I made some experience on a Epilog Zing 4030 and I thought about different ways to fix the plywood. This laser has a grating where the material lies on top. After thinking about clamps, magnets, weights and so on I decided to make something that can be produced completely with the laser. So I took the plywood and the laser to save the problem the laser has with the plywood ;-). With my idea you can fix every material with a thickness of 3mm or 4mm.
Attached are the PDF files you can directly send to your laser. You will need plywood with a thickness of 3mm and 4mm. Everything is cut out of the 3mm plywood except the layers for 4mm material. You need them only when you want to cut 4mm.
The fixing consists of three parts: The one with “noses”, the slider and a layer of material with the same thickness as the material you want to cut, here 3mm or 4mm. The biggest one with the “noses” is in upright direction. The noses go between the grater and then can be hooked from downside to the grater. But before that you have to put the sliding part onto the noses. On one side of the upright part lies the material you want to cut. On the other side you need a layer of the same thickness. Then move the slider back and forth to lock and unlock your material.