Need some help from the pros… I have a couple of questions. First, I have been trying to engrave a dithered image on a slate tile. With that said, there are only 2 colors in the image. When I create the gcode in LW4 and view gcode, there are actually many variations in power levels when I view the gcode file. How do I get it to use one power across the whole image for blacks and whites? Is it possible? I need the constant power because very low power levels will not look right on the slate when engraved. Second, I am not sure if this is an issue or not, but I could not find a solid answer when I searched regarding the stuttering of the smoothie/C3D board and k40 during a raster operation. I found a pretty lengthy thread and link to a github issue, but I cannot tell if there is a workaround for this or not. But it sounds like it is due to smoothie varying power/intensity? For this case, I really don’t want anything but the laser to turn on and off with one constant power. I had overscan set to 10mm on this engraving. Thank you for any help you all can provide!
Regarding stutter, 2 things.
First, try putting the gCode file onto the MicroSD card in the Mini and running from there. You can run via the GLCD menus or using the “play /sd/filename.extension” syntax from LW terminal.
Second, have you updated to the latest version of LW?
There is a Laser Power Range in the Laser Raster which allows you to set Min (white on image, black on the slate) and max (black on the image and white-ish on the slate) power levels for the image.
Since it very likely will be averaging pixels (unless the dithering after scaling is coarser than the laser’s resolution), there will be some grayscale variation, so it wants to adjust power.
How much it adjusts will be controlled by the Min and Max fields.
(Also play with the ‘Join Pixels’ and ‘Burn White’ options to see what works best!)
The latest versions of LW4 even have Raster Filters for smoothing, brightness, contrast, grayscale, invert color (for things like working on slate ) and dithering!..
@raykholo I’ll try the gcode on sd card route. Yes,. I have the most latest version of LW. Thanks. @CescoAiel ok I’ll try changing the min/max power levels. I was under the impression that the filters you mentioned are for images that you have not edited, kind of a last resort thing? I’ll try using them now! Thank you.
Yes, pre-editing images is better IMHO.
However, although I haven’t had a change to test dithering yet, I am interested in testing that option.
The filters do allow however for adjustments after the fact… It just takes a while to do the raster gcode generation!..
First of all, make sure you are not scaling the dithered pictue the wrong way. The dithering pixel size should exactly match the configured laser diameter. To reach that, first select the wished “Beam Diameter” in machine settings. Then insert the dithered picture and click the orange “Raster Opt.” button on the positioning dialog. This makes sure that the picture is scaled to a pixel size of the beam diameter.
And just to clarify: my response and Claudio’s are not opposed… Mine was assuming you need a fixed size, and if that happens not to be 1:1 (dither optimized), it will merge and average pixels.
Claudio’s response assumes you can scale the image to dither optimized scale…
Thank you for the info. When I edited the photo and dithered it, I used formula 25.4/240, which was the image resolution to give me a scan gap of .1058 to match the image. Watched a few tutorials on that so I hope I am doing that right. I have not used the raster opt. button. I’ll try that process as well. I did have join pixels on. I was using 300mm/s but the actual speed was no where near that. @cprezzi 20-40mm/s seems slow compared to what I have been using. I’ll give it a try! Thank you all again for your input!
The thing with dithering is, that the laser tube has to switch on and off for each pixel, an the tube needs some time to start lasing (probably something around 1ms).
SO, we have a max of 1000 pixel/s, that’s 100mm/s with 0.1mm/pixel.
With grayscale, we can theoretically overcome that pixel/s limitation, if we set a minimum power that holds the laser on (whith low power) and activate “Join Pixels”.
This has nothing to do with the stuttering, which is a limitation of the gcode transfer and queueing (especially with smoothie). That’s why Ray asked to run from the SD card.
@raykholo I cannot get the command “play /sd/filename.extension” to work… My file name is just gcode.gcode, so I put that in place of filename.extension as I should. LW says it cannot find the file. my file is in the sd root directory along with the config file.
Some testing from today. Bottom left seems the best so far. Pot set at 4mA power 1-40% 40mm/s. The pot is extremely touchy and hard to set right… I am wondering if I am doing that wrong. Set pot to say 15mA andadjust power in LW way down or adjust pot to max mA you want (ex. 4mA) and adjust LW power to a higher value? Thoughts?
I would always set the power (if possible) with the pot and use the software settings only for the range. If you set the pot to max and do the whole reduction in software, you loose grayscale graduation.
