DISCLAIMER: All images are from the web. None are mine.
After a long hiatus I’m back playing with my K40.
Any idea why I can’t get the clean engrave look like the ones on the photos (dough roller, your logo, tiger, coffee house)? All my engraving end up with a black burnt finish like the watch and the gray scale. The stock m2 nano gives me the clean/no burnt look but I can’t get that with a different controller. So far I have tested an arduino/mks_sbase/cohesion with both grbl-lpc and smoothie. I always end up with a black engraving. I understand that is what most people are aiming for but its not my case. I want a somewhat deep engrave but not black/burnt.
Have you been able to acchieve the clean look I’m looking for? If so, how? what did you do?
@Jeff_Lamb What you consider a fast speed? I’m using 350/20% (3ma) and still get the black engraving. On the smoothie I have tried 100 / 150 /200 us. On the grbl side I have tried from 2KHz to 10KHz. All ended up with a black engraving. I think I covered all variables but clearly I’m failing somewhere.
Is the question about the amount of grayscale contrast? Your top row of the grid looks fairly decent. On smoothie you should try 200 (C3D default) or 400 as the pwm period in config.txt
For grbl-lpc it is the frequency which is 1/period value. *1000 I guess.
Sounds like you’ve tried a bunch of these. Some K40’s respond less to pwm than others.
Jeff is correct that grayscale is more vivid at lower speeds. For example, 300+ is definitely on the faster end. Try 100mm/s.
I don’t know if I’m getting it. What you call vivid? dark? blackish? That’s what I don’t want. I want a deep engrave but not black. Look at the tiger. It is almost like it was carved. That’s what I’m looking for.
To reach deep engrave with less darkening you should use shorter PWM periods like 50-100us on smoothieware (higher PWM frequencies like 10’000-20’000 Hz on grbl-LPC) with fast feedrate, max. 50% power on gcode and high power on the pot. Don’t go lower than 50us (or higher than 20kHz on grbl-LPC) because that’s about the limit of the laser power supply.
Material has a big impact on the final outcome. If you use ply material, once you hit a glue layer line, it turns dark. The pitch from pine boards also burns. Clear pine lasers nice. Cherry will laser dark at even low power.
You can also probably clean the engraving with a toothbrush and a cleaner. I think I recall people mentioning something like using GoJo hand cleaner perhaps.
@Bruno_Ferrarese Fastest I normally run is about 300mm/s, slowest for engraving tends to be about 95mm/s. pwm period is set to 400 (I run lpc-grbl but cant remember the converted figure). Hope that helps.
@cprezzi I tried what you said. At 10KHz my laser wont fire. At 9KHz it gives me a better engraving but still very dark.
@Jim_Fong Thanks for the pictures. I can’t get those results. Not close to that. Same speeds/power.
@Nedman That’s a help in having a better final product. Thanks.
What drives me crazy the most is the fact that have I tried whisperer from @Scorch with the original m2 mano and voila I get the clean deep engrave I’m looking for.
@Bruno_Ferrarese I’m using the stock grbl-lpc pwm frequency settings. Not sure what it is. I can look it up when I get home from work. The potentiometer is set at 10ma for 100% power. Although I’m using Lightburn laser software, it would be the same with Laserweb4.
If the stock M2nano works, that would lead me to believe the other controllers are not correctly varying the power somehow. @raykholo would have to look at your wiring to the Cohesion3d board. Same board I am using.
