Burn Edge with Birch Plywood 6mm

[Dimitris Bazinga]

Hi, i run a lot of test with Birch Plywood 3mm & 6mm, Okoume Plywood 8mm to find the cut without burn edge

Settings are optimal to take a cut.

Birch Plywood 3mm, perfect edge with 35mm/sec - Power 25%
Birch Plywood 6mm, bad burn edge with 10mm/sec - Power 45% if i increase speed there is not cut
Okoume Plywood 8mm, acceptable burn edge with 15mm/sec - Power 35%

I use 2,5" lense, focus is ok, air assist is ok
I changed Laser frequency to 500Hz but the result was the same.

Birch 6mm has 5 layers so Okoume 8mm. Any ideas why is so difficult to cut 6mm?

[Jeffrey Aley]

Could the charring be caused by the glue in that particular plywood?

Russ had a video on reducing charring. I think it might be this one (episode 87 - Maximizing air assist efficiency): https://www.youtube.com/watch?v=OCVsMXw6yh4 .

[Tim Mellor]

It is also possible your 6mm Birch is just faced with Birch while the centre cores are Pine or some sort of softwood to keep manufacturing costs down. Grab a bit of scrap and remove the outside faces with a chisel or knife carefully and have a look at the timber. This is more common with thicker Ply but might also be happening with your 6mm.

I did some cutting of off the shelf bulk store Ply a while ago but I have now found a source of Ply with a more suitable adhesive for Laser use. The Glue residue is far less and a much cleaner cut results. So maybe have a look around locally and see what is available. I am 4 hours away from the links below so I have sheets freighted as needed. Notice the change in bond types.

Non Laser Grade Birch https://plyco.com.au/collections/all/pr ... 6895701456

Laser Grade https://plyco.com.au/collections/laserp ... 0672839696

[sebastien laforet]

my guess is that the glue is different. depending on the glue quality, you can get very different cutting success.

i've had a batch of ply where the glue would smoke so much (black and thick, greasy smoke) that i had to stop using it. even when cutting, i could never have an edge that was not carbon-black and sooty.

[Gene Uselman]

I only use cabinet grade plywood which uses mdf core, much more uniform and does not warp as bad as 'real' plywood.

[Willy Ivy]

Just a thought.
I see that you use 3 different power settings for the 3 different materials.
Have you tried your highest power allowable by your tube and more speed.
For all three of these, and 99% of EVERYTHING ELSE I cut is done at 67.5% power (max. -1 ma. allowable for my tube). I adjust the speed to the material with favorable results on most everything I cut.

[Dimitris Bazinga]

Thank you every one for your answers.
Here in Greece you can't find easy plywood for laser cut, οnly the common plywood.
I examing Birch 3mm & 6mm and center core is from different wood material. Okoume 4mm & 8mm has the same central core and of course the same cutting result but Okoume 6mm has different central core and gives black edge.

[Tim Mellor]

If you are having trouble finding a more Laser suitable Ply also look at the Marine grade plywoods if you have them available. Generally the faces are higher quality (Hardwood in a lot of cases) and the internal cores can not have voids found in cheaper ply as holes in boats are a bad thing

[Bryan Kelly]

I use Baltic Birch, used for draws etc by (quality)cabinet makers etc.. I use for cabinets myself, stiffer and less warp etc to basic standard plywoods, and not that expensive unless getting 1/2" and up in my area at least.. basicly zero air pockets, knots or sub grade center layers..in 3 and 6mm, no idea what other areas of the world have access to, but in north America we can get Baltic Birch, I'd assume Europe etc would be closer to origin of the plywood and even easier to find ?? but no idea other than where I live..but if can get it, try it?