Cutting Plywood?

[Michael James Smith]

I am trying to cut 1/8 in 3-ply baltic birch with a 30watt system. Not really having a problem cutting it, but does any one have any tips to help reduce the charring? I am aware that solid wood works better but its not available in the sizes I need to use. I know that the glue in the wood is causing the black edges, but it would be nice if I could reduce it to a dark brown. I've lowered the ppi and adjusted speed so it just cuts through but no change in the coloring of the edges. I guess my real question is am I trying to achieve the impossible or can only the higher wattage lasers cut through ply with less charring?

[Mike Hood]

Lots of air pressure, and a PPI that's as low as possible. Also.. I've found that a very close watch on focus helps.

[Todd Schwartz]

I agree with Mike. When all is going right, and the moon, planets and stars are all aligned, I can get my vector cuts to the point where they will be dark brown, with little to no charring.

I have found that there are different grades of Baltic Birch, ran into a batch a while back that I thought I was getting a great price on to realize that it was full of voids and glue pockets. Gave me fits.

My settings for my 50watt ULS is 2% speed, 50% power and 200 PPI.

Todd

[Richard Rumancik]

When you say charring I assume you mean that there is loose carbon deposits on the edges that will transfer to your hands etc when touched. You should be able to cut 1/8 baltic birch with a 30 watt easily without charring, but I expect you will get a very dark brown. At least I do. But I have nothing on the edges that rubs off.

I am looking a a piece right now - I do notice that the color depends on whether you cut with the grain or across the grain. I have 3 ply here - when cut "with the grain" (outer layers) the core (endgrain) layer is blacker. When cut "across the grain" (outer layers) the two outerlayers (endgrain) are blacker.

To reduce it to a lighter brown it might be possible to use nitrogen assist but that could be an expensive solution.

Offhand I can't suggest a speed/ppi setting for you. But I use a 2" lens when cutting birch plywood.

However, when I cut very thin birch plywood (1/32" or 1/64") I do get charring on the edges - not sure why that is. Perhaps the ratio of glue to wood is higher.

[Michael James Smith]

I am also noticing more black on the endgrain, and I am refering to the charring as the black rubbing of on my hands. I am also using air assist, with my power set at 90 and speed at 1.2 and 175ppi. A dark brown would be very acceptable to me if I could get it. The projects I have in mind would take alot of detailed sanding to clean up. I just don't want the black to be rubbing off and making a mess. The plywood was ordered from Cherry Tree I am cutting through 1/8 inch solid alder, with only a very light brown on the edges, but I just can't seem to get dialed in and still cut through the ply with faster speed.

[Bill Cunningham]

The amount of moisture in the plywood will also affect the cut.. I salvaged some 3/8 plywood from a old chest of drawers I bought almost forty years ago.. The wood was dryyyy, and it cut like butter on a 35watt machine, and only had a brown edge to it.. I wish the heck I had a full sheet of the stuff...

[Michael Kowalczyk]

Hey Michael,
Different glues will effect the edge as will quality of material. Beware of Chinese birch being substituted for Real Baltic Birch. If yours does not look like the ones in this link (scroll down to #5) that I make then it could be your ply.

http://www.sawmillcreek.org/showthread.php?t=61809

PM me if you want to get the right stuff or maybe one of the many user's here on the Creek will chime in and tell you how they like mine.