I have and ACMER P2 33 watt Diode laser; Lightburn 2.0.04; cutting Baltic Birch 3mm. Exhaust is xTool AP2 Safety Pro w/ Cyclone
I have tried many different cut settings in Lightburn and seemed to have settled on 1500/100/3 (speed/power/passes). Less than three passes does not cut through the Baltic Birch. I started with 500/100/1 and it cut but the residual burn to the edges was too much for me. I still get some flashing/burning (not sure the correct term) on both the front of the wood sheet and the back. The result is a fair bit of sanding to resolve it.
I am relatively new to laser cutting and wonder if I am missing something. I always use air assist to the cuts - not on the highest level, but about 3/4 of the way.
This photo shows the back on the left and the front of the cut on the right and the level of burn that I am getting. Am I chasing something that doesn’t exist? Will I always have to do a fair amount of sanding?
Do you have a good air assist integrated? It doesn’t really look so. The marks on the back seem to be caused by the honeycomb; you can raise the workpiece a little above it. See some tips here:
For cutting turn up your air assist. I get pretty clean cuts on 2.8mm Baltic plywood on a honeycomb with both 20w and 40w. I also installed 3 each 1-inch fans for a crossflow to help the smoke move out.
I really appreciate the responses. I am using the air assist that came from ACMER. It is the ACMER C4 which is an adjustable 30L/min airflow. The one that came with my laser from ACMER is also 30L/min but is automatic and I could never get it to work reliably. I do focus the laser prior to each cut - is there another kind of focusing that I should do?
I will try to raise the wood slightly off the honeycomb - oddly enough I purchased a new honeycomb bed because I thought that would help. Seems that there is a lot of sap or something along those lines that populates on the metal plate under the honeycomb. I get my Baltic Birch from AMAZON and haven’t really tried another source. Do you have alternate sources you all would recommend?
Seems a 33 watt should have no trouble cutting 3mm in one pass.
So either your not getting full power, your lens is dirty (highly possible with such a dirty cut), or your laser is not focused. There is a focus test in Lightburn under laser tools. Your sample looks like mine when I forget to use air assist.
LOL, I just use underlayment from Lowes and have had good results except some with voids, but I’m just cheap.
DsKall: I will try the laser focus test on Lightburn and see if that helps. Now I will just have to look up how to adjust focus for my laser as I have been under the delusion that when I use the focus arm on the laser module (to adjust to the surface of the material to cut) that was laser focusing. Must just be material focus for the laser. You can tell I am very new at this, but loving it.
Sounds a lot like Your material isn’t intended to be laser cut, the “sap” You mention is most likely melted or condensed residue from the adhesive that’s used to glue the plies together.
The fact that You have to use three passes even with a powerful laser IMO supports this, especially if it’s a 3-ply plywood since You are able to reasonably cleanly cut through one ply and one adhesive layer at a time, but the more or less molten soot prevents You to cut deeper cleanly.
When the soot solidifies, You’re able to cut through it, through the second ply and scorch the next adhesive layer, and so on.
While there should always be a protective surface (metal/slate/etc.) below the honeycomb, the honeycomb has to be raised.
More if there’s no airflow or exhaust underneath it, less if there is.
Otherwise the explosive gasses will ignite at some point, causing all sorts of nuisances and even problems.
That’s the idea, but the arm may or may not focus the laser correctly.
A prime example is the older xTool 2W IR laser, the focus set with the arm was so badly off, it was over the DOF (depth of field) range so the laser didn’t leave a visible mark on anything.
A ramp test is Your friend, fast and easy way to determine the focus and DOF of Your laser.
I raised the hex bed ever so slightly and also turned the assist up to full and then slowed the cut from 1500/100/3 to 500/100/1 and the cuts are really clean. No burn marks and what I was hoping for. The only thing I have not done yet, but plan to do is to do the ramp test to determine the true focal point.
The Baltic Birch is for laser cutting and the residual that I was getting was perhaps from over burning with 3 passes and no air space below the hex platform.
