Quick question. Are 2 passes at 20% power close to 1 pass at 40%?
Thanks!
Dale
I don’t know about diode lasers, but with CO2 lasers the equation doesn’t quite fit. The power curve is not linear, that’s where the “problem” lies. But of course you can find a setting that corresponds to 2 passes for your single pass, it’s just not equal/proportional.
Thanks. I have a CO2. Allowing for glue, and internal knots/grain, I need speed of 12, power 28 for 3mm. I got some supposed 1/8inch material that is close to 3.5mm. I tried 2 passes at, 25 power, still a few cutouts that I have to carve out. But, a lot of scorching that requires sanding. Would you recommend lower power with more passes?
Dale
What power is your laser? Bern and I have the same 60W CO2 unit.
I never do more than one pass when cutting except for very unusual instances.
Buy some maple or birch veneered MDF. No knots, glue globs.
Your laser is probably different than anyone else. Seems these beasts have niches of their own.
Slope test is your best friend.
I cut 3mm of above material with speed between 7 and 10 and power from 35 to 50.
My 2 cents here
a) the laser module response is far from linear.
0 to 20% there is a non linear response… 20 to 80% is roughly linear, then the last 20% are… far from linear. many times a flat ish curve
This is a rule of thumb on most diodes and CO2 (unsure on fibers)
b) The way the material responds to power is also not linear, special with carbon based materials (woods, leathers etc)
c) speed and power are really not linear
1000mm/min 50% power is NOT the same as 2000mm/min 1000% power
It might be like 1720mm/min 100% power.
d) the LIGHTER (in tone/colour) the material is, the less linear the power response is
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Thank you!
Can you please update your profile here is that you are on a diode laser …
Another thing so we all speak the same language please use measurements for speed and power (LB% or mA for CO2)
I think you should do some tests with all the materials you want to work with. As a starting point (as I see and practice it) I try to find the fastest speed with the smallest power. Do you have enough Power avoid more passes. If your plywood is very difficult to cut and turns black, find something else, better, interior glued plywood. Working to clean this material takes a lot of time and the result is rarely good …
I also have a 60 watt. I was running speed of 12 and 28 power, 1 pass and did pretty good with 3mm material. I just got a bunch of 1/8" Baltic birch that actually measures about 3.4. I have [problems at the 3mm settings and when I boost power to 30, I get too much scorching from the oil in the wood. I’m now trying speed 10, power 20, 3 passes and I get a lot less scorching. Since I’m not in this for the money, I can spend the time for a better result.
Dale
Yes, I was trying to find where to make the changes but got sidetracked. Where do you update profile?
Are you running any kind of air assist? This helps a lot, reducing the scorching.
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KV, Km/h, mA, potatoes…???
Please adhere to the “technical conversation rules”, otherwise it is guesswork with all the possibilities for error it entails.
In this case, it has nothing to do with surplus time. I also run my machine relatively “conservatively”, i.e. for the speed/power curve I often choose the second best result, thus I also take into account some unevenness/impurities in the material.
Some materials require the highest possible speed in relation to power.
For “normal” 3-4mm plywood I use 30-40% power at 20-25mm/s in speed.
Besides the possibility that it is “unsuitable” material you are trying to cut, it is also possible that your focus is not ok or you are not using enough air to blow the dirt out with.
I have a batch of 3mm in stock with a label “bad for laser”, this material is very likely glued with special glue that our CO2 laser with their wavelength cannot cut (clean). I have tested this material twice and now I use it for cabinet bases and saw it on the circular saw.
Just click on your avatar 
Yes, I have a 60 watt Omtech. I just changed my profile.
Somewhere along the way, I read in this forum That instead of boosting laser power to cut through, use lower power with more passes. Maybe, I need to increase the speed at the same time? Also, there is the strong possibility that the Baltic birch I just got is queer. I’ve been buying this stuff for 50 years for cabinets but pretty new to lasers.
I got some 1/4" from the same source, and it just won’t cut. It may be the glue.
Dale
Profile has been updated. CO2 cis pretty new. Sorry!
Yes, you’re right. I’m relatively new to lasers. But kV, really? I sold substations up to 500kV. And I don’t think you are talking about power transformers, breakers or instrument transformers.
No need to apologize, thanks for the update.
20-35 kV is the ignition voltage range for consumer CO2 tubes
Where would that be relevant to a discussion of power and speed settings concerning scorching wood?
It’s a pet peeve among regulars that those seeking help (or even giving it) omit important information such as units of measure. It’s not infrequent that somebody’s problem is caused by not understanding units play a vital role. “The man in the YouTube video said it would work at 250 speed.”. 250 what? What machine? 250mm/s with a 150W CO2 is not even in the same universe as 250mm/min with a 5W diode.
Yes, I agree!
Some of the commercial machines, require both speed and power to be entered as a percentage.
Then there is this little faux pas …