Tips or some type of weight for keeping warped wood flat during laser cutting?

[Jason Saul]

We are currently using heavy blocks of granite to keep warped wood flat when we are laser cutting, leaving us uneasy in case the laser were to run into or hit the granite! Are there any types of small but heavy weights that could assist in keeping the wood flat? or any tips to solve this issue?

[Doug Griffith]

Think about incorporating neodymium magnets.

[Richard Rumancik]

Jason

What kind of wood is it? How thick? If you are cutting shapes out of it, one option that could be considered: add some "stress-relief cuts" between the shapes in the file on a separate layer. This layer would be cut first before any shape cutting is done. The power can be set a bit higher than normal (because of focus range); if it does not cut really nice it should not matter as it will be part of the scrap section. Once this is cut, the sheet should relax somewhat and sit flatter on the table. For a simple example, you could cut a cross ( + ) in a square sheet missing all the parts. The "cross" does not need to go right to the very edges. It will cause the bow in the center to relax onto the table. It might sound a bit complicated but it is not that bad in practice. In some cases even one cut might help a lot; it depends on the nature of your sheets and what kind ow bowing you are seeing.

[Daniel Wolanski]

Jason,
Go on Amazon and get yourself some neo magnets like Doug suggested. Just watch your fingers if you get them too close to each other. They BITE!

Also watch out for getting them stuck into a corner that is inaccessible for removal. I have one that it lodged in the corner of a lip that I seriously cannot remove. I just gave up and bought more!

[Jason Saul]

Thanks everyone, we will experiment with both ideas!
If I use the magnets, should I have any issues with them getting magnetized to laser while i'm cutting?

[Matt Turner (physics)]

Sounds like you've got some good ideas here. If you decide to keep using weights, though, use something other than granite. Steel, copper, and lead are all multiple times denser than granite.

[Jason Saul]

Dan and Doug...could you describe or explain how you go about using the magnets while laser cutting? or if possibly send a picture showing how you use them?

[Daniel Wolanski]

Jason,
This solution assumes that you have a steel honeycomb table. The standard aluminum knife table than many lasers use won't work. Just hold your part down with the neo magnets as shown. They don't affect the beam whatsoever... unless you get it under the path of course. If you do hit the magnet it doesn't hurt a thing except create a missed portion in your job.
magnets.jpg

[Doug Griffith]

Here's something I do every now and then.

Blind rivets pressed into the honeycomb table. 1/4" rivets fit in my table with just a small amount of tension. Enough to hold material down but loose enough that I can still pull out from the top with my fingernails. I probably wouldn't do it too often as I'm sure this method puts some strain on the table. My table is well worked so I don't really care at this point. It's all about getting the job done.

rivet_1.jpgrivet_2.jpg

McMaster Carr #97387A347

http://www.mcmaster.com/#standard-rivets/=l6fjq2

[Doug Griffith]

You could use shorter rivets (3/8" long) and bond a small round neo magnet to the end. Push in from the underside of the table and use a floater magnet on the top of the material.

Here's something I do every now and then.

Blind rivets pressed into the honeycomb table. 1/4" rivets fit in my table with just a small amount of tension. Enough to hold material down but loose enough that I can still pull out from the top with my fingernails. I probably wouldn't do it too often as I'm sure this method puts some strain on the table. My table is well worked so I don't really care at this point. It's all about getting the job done.

rivet_1.jpgrivet_2.jpg

McMaster Carr #97387A347

http://www.mcmaster.com/#standard-rivets/=l6fjq2

[Mohammed Issa]

why dont you use strong double-faced tape? that stuff holds very well, and is easy to remove.

im sure it will also work on the honeycomb table too. (although many holes, but it will still hold on the ridges of the honeycombs.

hope that helps!

[Rich Harman]

I use pairs of .5"x .5" x 2" neodymium magnets. Another thing I use is "T" shaped "clamps" that are cut out of 1/4" acrylic. They are gently tapered so that I can press them into the honeycomb and then twist 45 degrees to lock in place.

[Bert Kemp]

I'm assuming the wood is fairly thin, what I have done in the past was to soak the wood in hot water then put heavy flat weights on top and let it dry . It makes the wood flat again. It also takes time. if you have a way to get air circulating around the wood it will dry faster. If its plywood you want to be careful that the laminates don't separate.

[Kevin Groenke]

We just use 1/2 x 1/2 steel bar stock cut to various lengths and place them on the edges outside a margin or where there will be no cutting. We usually use 2.5" lenses which gives us about 1/4" between the nosecone and the weights.

-kg.

[Steve Stram]

I have been cutting veneer for marquetry on a laser for couple months with mixed results. Best way at this time I have found is to use Scotch double stick permanent tape between the veneer and a substrate. I use melamine as a substrate for it being flat and able to clean easily afterward. The tape will peel off the veneer parts with a single edge razor blade to start the edge up. Then use a putty knife to scrape the off-cut and remaining tape from the melamine. The "temporary" double sided does not work, you need the permanent.

You do need to plan for the tape stripes to be under each part adequately. This can take some trial and error. Another problem that can happen is for a cut part to become airborne and float under the beam cutting another part, result is two parts with an issue.

The tip from Richard about cuts in unimportant areas is something I will try soon.

One other idea I want to work with is to put a vacuum platten in the laser to really pull down the veneer. Shop safety guru is hesitant to letting me violated the cabinet for a hose.

Steve.