I have a problem where my longer vectors need significantly fewer passes than my shorter passes. Now for this one design I can simply cluster the pieces in 5 groups and just use different colours to have a different number of passes, but it would be great if I could just link the number of passes to the length in mm to the cut. Is there a way to script it or something?
Is the Min power value for the layer more than maybe 10% less than the Max power value?
The controller reduces the power when the head is moving slowly, which it will be in a series of short moves, and increases the power as the head speeds up. If the Min power is too low, then short vectors don’t get enough power.
For example, if you have Max power set to 70% and Min power set to 10%, those short vectors will starve. Set the minimum to 60% and they’ll cut as you expect.
If that doesn’t get you closer to the goal, upload your *lbrn2 file so we can all take a look at it.
Hum… Thanks for that explanation, but I use the same value for min and max. File incoming when I get to a pc.
Do you have the Spark Mini 40 W laser? The first search hit was a femtosecond pulsed fiber laser that seemed … excessive … for ⅛ inch balsa. 
But a CO₂ laser shouldn’t require more than one pass for balsa and certainly not two dozen.
On the gripping hand, your profile shows a Ruida controller, which isn’t typically found on diode lasers.
Tell us more about your laser; a link to the manufacturer would be helpful.
LOL! that spark mini 40w you linked is the one I have. I am using 3mm baltic birch ply.
I am curious about what you found. Femtosecond pulsed laser? (sounds awesome)
That’s a super interesting laser. It’s like what you would get if you told a Canadian engineering team in a blackbox what the K40 laser was supposed to be and they went off to design it their own.
And got it right!
Definitely not the right hammer for your job!
Then the search degenerates into hair removal and skin resurfacing and things I’d rather not know more about …
Now, that’s distinctly different from balsa, but still shouldn’t require more than one pass with the right settings.
My alleged 60 W laser cuts 3 mm baltic birch plywood at 20 mm/s & 60% power in a single pass.
Your layer settings of 200 mm/s & 50% moves an order of magnitude faster while applying half the power, so it’s not surprising you’re not getting any traction.
Run a material test on that wood and see what the right answer for your machine turns out to be.
I’ll have to try again. The thing is that my short cuts (the small squares at the top of my file) work just fine at 200mm/s in 4 passes and I do it to reduce scorching.
I guess I’ll go back to being slow. The small squares cut up in 1 pass at 20mm/s 30%, but the large ones still require 3-4 passes at 20mm/s 50%.
I’m out now so I’ll run another material test this evening.
That he did. Mine was unfortunately a nightmare to get going because of UPS, but Yousef makes amazing stuff. He also made my old business a custom tabletop 1m^3 enclosed 1KW fiber laser with 80cmx80cmx20cm work area.
Agreed, and it’s cool that the chiller is built-in, and the tube is in the gantry so it only loses power on 1 axis (x) instead of both x and y. I got the first unit so it had a few kinks we worked out together (little tweaks like inserts for a belt tensioner, a different placement on the lid sensor, moving the air hose behind the mirror), minor stuff. He really thought this machine through.
1 Like
More assist air flow may improve that: you want the beam to burn completely through, so the air pushes the fumes out the bottom of the cut.
Directing the cabinet’s exhaust air across the surface so there’s no accumulation of smog on top also helps.
Raising the wood off the honeycomb on spikes or knife edges helps eliminate flashback / reflection scorching on the bottom, to the extent that I cut critical pieces “good side down”.
By and large, the less time the laser spends burning the material and the faster the assist air removes the fumes, the better your results will be.
I mean, if you want to spend too much time cutting wood, get yourself a seriously underpowered diode laser. Otherwise, crank on the power you bought and get things done …
I’ve been debating turning up my compressor a bit higher psi, but it’s already pushing small pieces around 
.
My exhaust is under the table, but it really has no problem clearing everything out.
I’ll be running that material test tonight. I know for sure that my plywood being all warped has not been helping 
I’m even considering making an aluminum frame for my sheets.
The secret is to have the air flow across the material; if you have honeycomb all around, the air flow tends to leave the smog over the material: you don’t get much smell in the shop, but you do get smudges around the cut.
I arrange cardboard around the material with an opening at the rear. The air flows in through the front of the cabinet, across the material, then down-and-out at the rear.
For little pieces, I set up a couple of tabs that mostly cut through, leaving just a little material: a touch of an Xacto knife frees them. Much better than fishing little shapes out of the chip tray!
Sorry, couldn’t find the femtosecond pulsed laser… Googled it … been reading all I can about these… 
OMG, just started the material test and there is definitely something off in my settings. The material test is blindingly bright, I’ve never seen my laser that strong, nor heard the power coming from it destroying the wood like that lol. Going to let it run then I’ll play with it for sure.
1 Like
Ah! The femtosecond pulsed laser upgrade is in full effect …
Huh… Material test result run a few times, 3mm ply at 100% of 40w requires 4.5-5 passes at 40mm/s. I think my wood being warped is my biggest problem. Time to use send cut send to make an aluminium frame.
In fact, when I’m in a flat area and perfectly focused, chat gpt is spot on with its recommendation
Power: 85-95%
Speed: 10-20 mm/s
Passes: 1
Air assist: Enabled