Good morning
My specific task is PCB.
I am using a Gerber file converted as PDF.
I try to engrave (remove the paint) in both positive and negative,
The result are not consistent. In the positive version, the one I need some lines
simply become invisible.
The dimensions of the global printout are correct, there is no way to use the axis calibration. I attach both versions and they are clearly different. The negative version have lines much fatter than the precise picture, which in the positive disappear,
It is my first post I hope the images are correctly visible
Those look like extremely low resolution lines, with visible pixellation: if those are RF microstrip butterfly stubs, their gritty edges will wreck the impedance.
The whole process would (probably) work better by converting from Gerber to SVG, because that should eliminate a vast amount of PDF cruft. You can then import the SVG files as LightBurn vectors and use Fill to get the proper line widths.
Good morning
Thank You for coming to me. I could not process the answer during week end.
I see a range of video and everyone is getting better results. I don t understand
why I am so far from there.
I am preparing another surface with the painting to collect the experience.
I have converted the gerber in different formats but the only hi resolution conversion is the PDF.
I used as is and I also converted in place to bitmap with 1200 DPI than tracing to get a vectorized version. And the result is the same.
I tried to convert to SVG but the conversion is totally inconsistent. In one way the dimension are wrong (using ViewMate) and I did not get a way to scale, in another way I got only the external lines and some internal lines with no way to fill them. Anyway I was expecting with the vectorized version to have a contour follow up during the engraving but it is a normal raster process.
What it seems to me the laser is not expressing correctly.
Later I will try with a plastic surface …
Please suggest whatever to unlock the situation…
Hi
Thank You for the follow up.
I am going to engrave the project . I just scaled to have a compatible dimension.
I will also engrave the other surface.
I tested everything and the result does not improve. On a plastic surface the precision is the same.
My evaluation of what happens is, the raster begins too much ahead and it stops too late. The precision is 80 pulses per cm, while the spot is much bigger. It should compensate for the spot diameter in a way that if the line extends from x1 to x2, the effective engrave should begin from (x1 + spotDia/2) and finish in (x2-spotDia/2) …
Are parameters taking care of adjusting these compensation?
Note the open area where the left butterfly overlaps the PCB trace and the incorrect vias along the bottom. LightBurn uses a simple border-crossing count that doesn’t handle those situations correctly.
Importing the same SVG into Inkscape shows a similar problem, although with different results:
Inkscape has an option controlling how overlapping shapes interact. In this case, it simply fills the overlaps, which isn’t correct for the vias along the bottom.
However, the key point is that the SVG files maintain the original vectors from the Gerber file and do not suffer from the poor resolution of the image you originally showed.
The method I suggested earlier does not work, because the Gerber files produce SVG images that LightBurn’s Fill method cannot handle. I think Kicad can produce correct bitmap images of the copper layers, but I have not explored that.
If that is the stepper motor step/mm setting, it is much too low.
If that is the image pixel resolution, then you must find a different way to convert the Gerber / SVG images to bitmaps, perhaps using variations of the sequences @JohnJohn and I have explored.
Thank You
for the follow up. I am testing everything. I am aware of the artifacts the conversion places, I was just selecting each part and using union in LightBurn. The result seems qualified.
I will test your solution. I think the problem is much bigger than this.
The 80 is the pulses per mm. it should produce a precision 0,0125mm. it is just competing with the dimension of the spot. It is better to have a resolution of the positioning much better than the spot but that’s it.
The laser is not a basic product, I made the choice as maximalistic. If it is not enough for a qualified engraving I have been fooled.
Which precision do other device offer?
The spot size for a diode laser will be on the order of 0.1 mm, ten times larger than the motor step size, which is entirely adequate for your purposes. Changing the step size on your Creality or using a different laser machine with smaller step size will not change the results, because the motor step size is not the problem.
GRBL maintains the commanded position internally as a floating point number and picks the closest motor step to that position on each command; there is no coordinate rounding or loss of accuracy due to the motor step size.
The motor step size has no relation to the poor resolution of the images you showed, which seem caused by the conversion process from the Gerber file to the bitmap image. The laser will reproduce those terrible images very exactly: there is no way to compensate for poor input images by adjusting any laser or LightBurn settings.
Ideally, you would be able to convert the Gerber files to a vector format compatible with LightBurn’s Fill algorithm, because that would eliminate problems with converting the vectors to bitmap images. I do not know how to do that, but there is a great deal I do not know.
If you can create a bitmap image from the Gerber files with a resolution around 10 pixel / mm (about 254 DPI), then LightBurn would be able to trace it back into vector format with the correct fill results. I do not know if the accuracy of that trace would be good enough for RF layout work.
