For me trail and error on a test piece is the way to go.
Did the pre-preset of Luban work?
I would try a step-down of 2mm with 4 passes and a speed of 200mm/min (like 3mm basswood, if I remember correctly).
Stepdown height is maybe not possible because of the tiny focus point, you have to check for collision before starting!
I frequently cut 6mm Basswood with 40W laser using half diode, 100% power, speed 250 mm/min, one pass. I recently cut 60 pieces of basswood using these settings. There is no avoiding the burning nor the tar left by the residue of basswood glue, unfortunately. I have cut larger pieces of pinewood up to 18mm with a single pass - just lower the cutting speed. I also regularly cut 6mm poplar using 100% power, speed 450 mm/min, one pass. Using a 10W laser I cut 6mm basswood using 100% power, speed 250-300 mm/min, and two passes. I found that the z step does not make much difference in the cutting efficiency or charring. I suspect the settings for 8mm basewood would be approximately 150 to 250 mm/min with two passes.
Hi,
Thank you - this is very useful information and much appreciated.
May I just ask what (for my 10 Watt laser) would you consider to be a sensible Z step to use?
I am always confused by this.
Should it be 0.2mm, 0.5mm, 1mm… etc?
As regards the charring on basswood, noted. I can confirm that its less evident with masking tape, but then you have to patiently peel it off afterwards. It also leaves some stickiness from the tape glue. I have tried spraying with isopropanol and even applying some hand soap then drying it with a small hairdryer. The stickiness is not much reduced but the burnt wood smell is covered up well.
Side note: I was using the yellow (basic) masking tape. I need to experiment now with the blue painters tape. I also have a spray that dissolves label adhesive so I will try that too.
Beware the adhesive remover spray. Many contain petroleum based solvent and will leave oil soaked into the raw wood.
Always test before a production run.
I find that the z step is very useful when using cnc cutting but of very little difference in laser cutting. Ive done many test cuts on 6mm basewood adjusting z step increments from 0 to 3 mm, number of passes from 0 to 4 passes, laser power from 50 to 100 % and speed. I found that adjusti g step made very little differnce in comparison to other parameters. I susgest that you sacrifice a piece of 8mm basewood and run several test cuts varying the speed and number of passes. These being the most significant parameters. Selecting the best speed and number of passes from the first run then run a series of cuts adjusting the z step to fine tune for your material. Ive used painters tape too but because i mske msny wooden toys from same templates i find it impractical and too time consuming. Im resigned to using a finishing sander to remove charring and tar stains. I also find that elevating the material by one millimeter above the plate helps a little with the tar stains. I do this by taping a littke bit of materual on each corner before putting it on the plate. Best wishes and good luck
In theory, for cutting, the Z step should be equal to the depth of cut achieved with one pass.
Think about it; at first your laser is accurately focused on the top surface of the material. So, after one pass, for maximum efficiency, it now needs to focus on the bottom of the previous cut, therefore on the top of the remaining material that’s inside the cut. The limitations of this are of course that, after many passes, the laser head could eventually contact the top surface, and that you must keep in mind that the beam is conical and the sides of the beam will touch the edges of the first cut and not fully penetrate to the bottom of the cut.
Other than guessing from experience, I can think of two methods to determine the Z step for efficient repeatability: after one test pass on a sample, break it apart and try to measure the cut depth; or test for the minimum passes necessary to cut through and then divide the thickness by the number of passes.
If you change the speed or power then you will have to repeat the above or compensate by estimation.
