For whatever reason, I decided to run our “shades_of_grey” JPG through Image2Gcode… the other one, the MPCNC-customized one from a much earlier thread. Interestingly, it DOES NOT have the darkened edges we’ve been looking at, though it seems to have other problems less interesting (probably user error)…
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Here’s the gcode file it created… this file scans top-down vs. bottom-up
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– David
shades_of_gray.gcode.zip (509 KB)
David, can you share the settings you used for ImageToGcode or Image2Gcode or whichever you used to make the Garfield gcode? I scanned through the thread and couldn’t find them, but I may be overlooking them.
Here’s the ImageToGcode screenshot showing the parameters for the Garfield gcode we’ve been running… this is running under Wine, which explains the slight misplacement of field labeling…
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– David
I would say 0.2mm resolution is probably unnoticeable and less buffer work.
I’ve started playing with LightBurn. Very nice software. But my first attempt to use it with a new image on a new material didn’t go so well. Too many changes at once. I wanted to take a step back and set a baseline with the same settings in the same software that made the Garfield gcode but a new image and then transition that to LightBurn.
Not unnoticeable, I printed Garfield at three different resolutions using Viktor’s ImageToGcode… our original 0.1mm, 0.2mm, and 0.3mm. I left all other parameters the same… travel and burns rates were both 50 mm/s. File sizes went down accordingly. print times got quicker, and putting fewer burns down on the material lightened it considerably. The 0.2mm resolution did indeed seem to work well for my laser, spot size, and the cereal box cardboard I was printing on…
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– David
I saw that on my tests as well. I believe it is not as dark because it is not moving as slow, because the buffer is not as starved. So I think we kept trying to overcompensate the speed for the buffer issue. Using the right sized resolution and the right speed (30-35?) Might get us better results. Or even trying to limit the power output of the laser and find the speed that works without starving the buffer. I might get a chance to play with it some more, but, exciting…I am moving to a spot with a larger work area for me. I have to Pack and I kinda need to try and get all of my prep done so when I do move my shop I won’t miss shipping for more than a day.
Ryan, I think you guys talking about buffer issues, have nailed it. I’m convinced.
Shades of gray… opened ImageToGcode and created 3 quick files… changing only the travel and burn rates. I used 0.2mm resolution for all files… and 50mm/s, 25mm/s, and 20mm/s for the rates. Slowing the rates definitely darkened the image and did away with the “acceleration effects” we’ve been seeing.
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Well done!
– David
Am I understanding it correctly that “Feed Rate” is the speed when the laser is on and “Travel Speed” is when the laser is off?
That’s my understanding. I’ve only set them both to the same rate in tests so far.
Nice, thank you David. So it looks like 20mm/s is primo right now. I do suggest keeping both numbers the same for now until we get things sorted out more clearly.
We do have the option to increase the buffer, but I do not know what consequences might come of it or if it will actually help.
Hello, guys! You, this forum and this thread are awesome! :)At the beginning, as I wrote my app, I had a cheap 1W UV laser (but it was actually less than 0.5W). I made really good results with it. But with max engraving speed of 250 mm/min. I unfortunately broken this tiny laser (it was really small) and bought a real (I think) 0.5W EleksMaker laser module and with it I got the same good results but with speed of 1000 mm/min. Then I bought a new 2.5W EleksMaker laser module in hope I can engrave much faster, but if I go faster then ~25 mm/sec my X-axis begins to stutter. I engrave with 0.07mm resolution. If I change the resolution to 0.3mm I can engrave with faster speeds without stuttering. So it seems (like Jeffeb3 said) to be a buffer and planner issues. I am not frendly to Marlin firmware to fix this issue, but I can change the Gcode 
So my idea is to adjust X- and Y-axis resolution separately. I will make some tests and post the results.
Hi, Ryan!
I have done two pics, one with 200mm/s travel speed, another with 25mm/s. The feedrate was 25mm/s for both pics. Engraving time was 5:01 and 22:40. Can you see the difference?
Victor you are using Marlin? With the tweak we are doing pretty good with M106/7 now.
yes, I am using Marlin 1.1.9
but in this version marlin.cpp does not exist, so I am not able to try it out.
If I understand it right, you can go over 25 mm/s without stuttering? Which resolution do you use?
Ok. Here are a few tests I have done with the same images. The far left image, where it looks like something was started was done at .2 resolution at a FR of 20mm and TS of 20mm. I seriously cannot get a usable image at all at .2 resolution. Maybe I’m misunderstanding something. The .12 resolution looks ok. The bottom 2 tests are run at the same settings. The wood I’m using is birch I believe. I got them from Hobby Lobby.
The .12 looks pretty good to me but I’m not 100% sure what I should be looking at/for. It could just be the wood. Did you try on cereal box cardboard? Did you sand the wood before burning?
Really I’m wondering if I’m misunderstanding something. At .2 resolution I can’t even make out a picture at all, it just looks like some random burn mark’s. Are you guys bumping .02 resolution at a time, from .1, or actually going .1 to .2 to .3 resolution? ?
I was only ever using the gcode files that were posted in this thread so as to eliminate variables. I’m not sure what resolution they were set up at off hand. Are you using those files?
I did use the gcode files that David posted, and they were fine. I was just experimenting with the settings others were using.
Hi, Kelly D
I had the same problems with a piece plywood. On the same sheet, but on different places the results were very different. Now I get the best results on hardwood and cardboard. And on cardboard I can get an interesting effect if I engrave with smaller laser power. The surface becomes lighter 
