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We created a 10" X 10" puzzle in inkscape and saved it to a DXF format. We then imported the file into KeyCreator to generate the gcode for cutting it with our 6W laser diode.
We first TTL laser engraved (pulsed on/off) a B&W image on 1/8" Birch Ply the same size as the puzzle pattern we created, then cut through the Birch Ply afterwards.
We just did a feedrate test engraving a Dithered image with just S0 (white) S255 (Black) commands to pulse the laser on/off. The Feedrate was set at 200IPM in the gcode file and it took 47:29 (2849 sec) in time to engrave. The engraving is 10" X 8.34", but we used Skip White in PicEngrave Pro 5 to cut down on the overall engraving time.
We reversed engineered the gcode and it has a 9417.644408 inch perimeter (travel distance). To confirm the actual feedrate it engraved at, we did a simple calculation.
This test confirms that the S commands for laser control are executed close enough in real time when using the J-Tech PWM grbl. To achieve these kind of accurate feedrates, some settings need to be changed in grbl to increase the overall performance.
200IPM, 30% Feed Rate Change, .007" Pixel Resolution, Min 20/Max 255 (full) laser power, 10"X10" engraved size and 2,053,505 lines of gcode streamed with PicSender. 2:14:00 total time to engrave on Birch Ply with our 6W LD.
Original image that was resized, edited and cropped in PEP5.
We have been testing the new PicConvert DAC from J-Tech Photonics and our results have been very successful. The DAC takes the Z,A,B or C axis step & direction signals and outputs Analog Modulation or PWM to a Laser driver for engraving photos. For those that use Mach3 or TinyG CNC controllers with there X-Carve that want Varied Intensity laser control for 2D or 3D Laser engraving, this will give you that option.
We did this one with Mach3 using an Analog Modulated M140 2W Laser Diode on Birch Ply with the new PicConvert DAC.
These were done on our 3W EmBlaser. 130IPM, 25% Feed Rate Change .006" Pixel Resolution, Min 0/Max 255 and engraved at a 45D angle. The same gcode file was used for both of them.
It took me forever to get mine working but with Jeff and Jay’s help I am now getting good results. Jeff can chime in as he knows loads more than I do but from what I have learned I have a few guesses. First I found pine is horrible for burning on as it has very loose grain. That could be one reason for the lines. Try using a tighter grained wood like poplar, or burn in the same direction as the grain. Another is the J tech lense makes an oval shape beam, not a round one so it helps to burn in the same direction the oval is facing. With my unit I run a .006 pixel resolution. With the 3.8 you may be running a bit slow. I have the 2.8 and find around 70 ipm to work well. I also find I get the best results running a 45 degree engrave regardless of whether I am doing an image or text. That solid white line all the way across looks like a missed step. As I said there are many other users with much more experience than myself but this is what I learned since I started attempting to engrave images last October.
There are ways for improvements as Rick mentions. Pine is will engrave black & white without issue, but the image must be Dithered in the PEP5 image editor first. We always sand across the grains with fine sandpaper with any wood we laser engrave images on. Grayscale engraving is better achieved on less prominent grain woods such as Poplar so the burn/shades is more linear.
Looking at the original text, I can see some grayscale, but it may be because it was attached as an image here on the forum. The Threshold Dithering Algorithm works best for B&W logos or text providing the DPI of the image is not too low. A minimum of 100DPI is recommended and the PEP5 image editor will save at 100DPI. But, any image needs to be edited & resized and saved first before reopening it to Dither the image. If there is not just pure black & white in the image, there will be ramping of laser power on the edges which looks like what could be happening. Look in your gcode file and see if there is any S PWM values other then S0 & S255. If there are, the image is not pure 1bit B&W.
The focal point size (.006"-.007"), focusing height (3"), beam orientation (parallel with the engraving angle) and the engraving angle itself is important. As Rick stated, a 45D angle works best for motion smoothness when raster engraving running in grbl and because 45D brings the burn lines slightly closer together. On post 85? in this thread, I have some recommended grbl settings changes.
The Un’-burnt line almost looks like a PWM connection was lost on that pass, but it’s hard to really tell what actually happened there.
When raster laser engraving with grbl , the Analog/PWM engraving profile is recommended as it has the most features. Select Skip White when using B&W Dithered Logos or text as it will cut down on engraving time. Also the Feed Rate Change feature will speed up the feedrate in white areas and slow to burn in the black areas. You can start out with a feedrate at 150IPM? and use a FRC of 40%?. You can experiment with these values to get the best engraving results and cut down on your engraving time too.
To supplement what Jeff posted above about the minimum recommended DPI:
Looking at the original image, I am pretty sure that the “jagged” edges of the letters are being reflected in the laser engraved image’s “jagged” edges. This can also be caused by excessively enlarging a small image into a larger size for engraving. I often redraw (trace) a smaller image to a larger size using an image editor such as Inkscape to eliminate the jagged edges.
John www.picengrave.com
I posted this in another topic, but hasn’t gotten any traction (and I’m not the most patient ).
Just got the JTech 2.8w laser, and trying to figure out good starting points in terms of feed rate and number of passes to cut various materials. Any references for this sort of thing? Know it’s going to differ per person, but need a starting point otherwise I’ll waste a bunch of material guessing.
Thanks @RickPeterson@picengravertoo@JohnChamplain for the quick help. I have some poplar so I’ll give it another try this weekend and see the difference. I will try some of the settings you mentioned and 45 deg also for direction. The missing line is a separate issue I am already resolving. My lens is quite wobbly relative to the laser body so as the machine starts and stops it can shift enough to miss a line. The recommendation I got from the JTech crew was to use teflon tape on the threads. I am going to look at that as well as find a little stiffer spring.
The image I used for this was actually mostly grayscale (it’s an ultrasound). The text however was black.
@picengravertoo I had already updated the settings to your #86 post. I had also had the laser focused at only 1" which is what the Jtech stuff said. I will change to 3" when I redo as well. @JohnChamplain I actually made this in Inkscape. What format do you find to export gives the best results?
Here is a full picture. From further away it doesn’t look terrible but I know it can be much better.
I was not aware there was an image with your text. The Atkinson dithering algorithm should work better then Threshold when lasering on Pine. It’s adjustable.
Ok so to start I didn’t flash my Arduino because i’m not excellent with computers and don’t wanna tamper too much. Easel suits me very well.
So far i like Inkscape and mainly want to do logo’s mainly. To start my laser I press M03S1200 but as soon as I sent a file to Gcode it moves but doesn’t turn the laser on. If i enter M03S1200 it only flashes the laser on for a second so I end up turning it on Manually. NOT ideal. Any help is greatly appreciated. Do I have to flash. Will that mess up Easel?