Laser bed clamps / Warped wood!!!!!

[Callum Angus]

Good morning all.

I'm having a little difficultly and I thought I would ask you guys so some best practices if you wouldn't mind.

I have been cutting jigsaw pieces out of 4mm oak faced plywood for a while now but the new batch of plywood I have received is slightly warped and bows in the middle by about 4mm which is more than enough to make the laser not be in focus at that part of the piece.

Im looking for anyone's blight ideas or previous experience of dealing with this.. I have placed all of the pieces on top of a flat surface with heavy weights on the top of them to try to straighten them out but in the mean time I need to get on cutting and etching..

Has anyone dealt with something like this before with any success? I'm currently looking for some heavy flat weights to hold the material down when it is on the bed being cut or some kind of clamps to hold to piece down to my cross bars in the laser bed as I do not have a honeycomb bed just yet.

All help is very much appreciated!!!!

[Al Launier]

Double back tape?

[Bert Kemp]

If you have a steel honeycomb Rare earth magnet work well. You need some with good pull, mine are 1"sq 1/8 thick and hold down some pretty warped stuff. Some people use heavy steel bars laid flat on the material. I've seen people drill little holes in blank spaces and zip tie it down..

[David Somers]

Like Bert, I use rare earth magnets. N52 grade specifically. I am using a 1/2" x 1/2" x 1" magnet (I have 6 on hand) that I got from KJMagnetics.com. That gives you 38lbs of force. On a steel honeycomb it is very effective. The 1/2" height easily clears the tube of my 2" lens tube.
If you needed something stronger, check the distance between your lens tube and your material (just measure the height of your focusing gauge) and keep the profile of a magnet less than that. 1"x1"x1/2" would clear the lens and give you 67lbs of pull. That is a lot. 4 of those and you would be in good shape. Assuming your honeycomb is steel of course. Otherwise Berts suggests of steel or lead bars is good. You could be sneaky and coat them with rubber tool handle coating to protect your surfaces. Or, apply tape to the bar for the same reason. Just make sure whatever you use clears your lens tube to material clearance.

One word on N52 magnets. They can be dangerous. Magnets like Bert and I use will slam together HARD if you permit them. They will often shatter when that happens and the pieces fly far and fast. An eye damage hazard to be sure.
The other hazard is swallowing them or pinching skin between two magnets. Especially if you have kids or pets. 2 magnets, swallowed separately, can end up close enough in the gut to pull the two magnets together with tissue between them. That can cause death due to gangrene or intestinal blockage. And Doctors and Vets generally dont encounter magnets and may not know to look for them as a source of a stomach problem. So you HAVE to keep tight control of your magnets if you have kids and pets about. Having said that though, N52 magnets are wonderfully useful. I use various sizes all the time.

[John Blazy]

I couldnt agree more with Bert and David. David turned me on to the 1/2 x 1/2 N52's from KJmagnetics, and they are awesome for holding down warped material. AND I couldnt agree more with the warnings. I made a holder for my magnets that space them 3" apart - not enough. I call them my teenage boys because they hate being anywhere near each other. Unfortunately all five of my 2" long magnets are broken because it took a long time to program my brain to pick each one up separately and put them away separately. Picture a laminate on my laser bed with several N52's on them. When done cutting, I grab one, and with the same hand I grab another to be efficient, then CRACK - they slam into each other right in my hand. Got a few pinches too. Simply sliding them across the laminate to another space and they fly right at another one eight inches away.

So now I have ten N52's, but smaller. Oh, and don't grind the sharp edges of a broken N52 in a way that creates much heat - reduces its magnetism significantly.

[David Somers]

I know that KJMagnetics does have rubber coated N52 magnets in various sizes. I have not used them but they may help some with impact. Or you could try coating them with paint on tool handle rubber that you get in a hardware store.

I keep 6 on my table at any time. I used some Sugru (sugru.com) to make little bays for them so they cant get moving too fast when they slide to each other. (the bays are on the frame of the honeycomb, not on the comb itself.) That has helped, especially if I slide one to a bay. Then another. Then another. Always working seperately. They are wicked strong little puppies.