Trouble with gray scale

Basic machine info: K40, Cohesion Mini, Cluster Firmware, Lightburn

I just upgraded to cluster firmware and lightburn (was using laserweb before) I succeeded at doing some basic laser cuts, now I am trying to get grayscale to work. I am having trouble finding much information on grayscale settings. I tried a several different settings so far with much luck, Its like its burning the white pixels and well as the black.

I have the min and 0 and tried the max at several different levels. One thing that occurred to me as I am writing this is maybe I need a value in min to actually get white? I will try that tonight when I get a chance to play again.

Here is an image from on the left I cut this a while back with the old firmware and laserweb, to the right is the best I was able to get with the new setup so far. Thanks for your advice!

(edit: Sorry at work and forgot to grab the source image, if anyone is interested I will post it when I get home its a 3d grayscale lion bust)


You mentioned you had a Mini… please show me pictures of your machine, panel, and how it is wired. Do you still have a panel with a potentiometer in play?

I will get the pictures tonight. I do have the pot in play still, maybe there is a wiring revision I missed that recommended to remove it.

I believe I tried it it the pot at full if that makes any difference. If I remove the pot how do you control the power of the beam when you are test firing during calibration?

I think this is basically all the angles, let me know if there is anything else you would like to see.

Here is the image I am trying to burn


Follow this and heed the advice in it such as keeping the pot at 10mA, not ever full power.

Interesting, I never typically go to full power I figure (maybe wrongly) that the closer you get to full power it will disproportionately eat away the life of the tube. Only had tried it after several attempts at lower power to get gray scale to work. That said the setting I have was arbitrary I had not been watching the mA gauge it’s nice to have a real target.

Either way thanks for the info! I will definitely try this tonight :slight_smile:

Success! The advice in that thread was perfect :slight_smile:

Here are a couple photos so my playing around last night. I am going to do my own research of coarse, probably a little photo manipulation to get better contrast and play with feed rates and stuff. But do you know a thread that talks about optimizing and cleaning up the engraving (only if you know one off hand, if not I will figure it out). In the second photo I am including, I can clearly see that lines from each pass especially in the area I boxed off. Its almost like I am too focused, or maybe passes are too far apart.

Look at the ‘Line Interval’ setting in the engrave layer properties. This can be set to a lower number to decrease a bit of what you’re seeing. But really, there’s only so much you can do: honestly, chalk it up to wood being an inconsistent medium. Side note: I’d definitely go for as focused as possible.

Thanks! I will check out line interval on my next series of tests. I found that I can get a smoother engraving but upping the DPI, I haven’t run enough test to have anything definitive, but is seems to me so far that 300 is definitely better then the 254, I have a test at 400 that looks great too but I haven’t done enough to really see where the sweet spot is for my laser I have a feeling will depend a lot on your optics

I understand that while the laser dot might be larger then what you get with 300 or 400 dpi it does seem to minimizes the peaks and valleys between each pass. Its kind of like the difference between a high def and 4k screen, sure if you back up enough you cant see pixels in either but you can still tell that the picture seems sharper on the 4k.

I assume Line interval will mess with the spacing in a similar way. the odd/interesting part is I think the laser was actually traveling perpendicular to the lines rather then with the lines believe it or not…

More testing is needed, I am working at a Z axis right now so testing is on pause for another week will I finish it, I have it about 80% designed and printed and test fit mostly just need to figure out the Stepper mount.

I am pretty sure that line interval and DPI are directly related. You either set one or the other. When you change the DPI, the line interval will automatically change. It’s better to use line interval if you understand it since it is directly correlatable to your beam width at what ever focus you are at. I have heard that if you line interval is too tight, you can cause grooves do to the overlap of the beam width from pass to pass. Also, the C3D board can only process info at a certain rate. If you are running smoothie with the older firmware that rate maxes out at 100mm/sec with a .1mm line interval. Any more and you will start to see anomalies in the image. With the newer firmware and the appropriate settings in light burn, this rate has been increased by 300- 400%. Make sure you are updated if you are running smoothieware