I was attempting to follow others I have seen on here and Facebook with a Grayscale photo etching. The settings I had were 130 in/min @ 25% power and 300DPI. The preview looked great and showed an estimated time of around 12-13 mins. My photo was only 2” x 2.5”. I started the job and it ran super slow but I let it go to see what was going to happen. 10 mins later it was only at 3% completed and it was basically burning everything it etched. Does anyone know the reason the preview would look so great but the results sucked so bad?
Can you post a pic of the settings used, the picture you were attempting, and the output? A picture is worth a thousand words, and all that - it helps to see what you’re working with.
130IPM at is about 55 mm/sec. 300DPI grayscale is about 12 dots per mm. At 55 mm/sec you’d have about 650 gcode instructions to process per second, and your 8-bit controller is capable of roughly half that, possibly a little less (I think 8-bit GRBL caps at about 250 to 300 gcode instructions per second). So, that could explain the performance hit.
GRBL will lower the power to compensate for the fact that it can’t hit the speed you asked for, and if the controller is set to use 0 to 255 as your spindle range, you were starting with 25% of that, meaning 0 to 63 possible shading values. If you’re only going half the requested speed, your number of unique shades is now down to 0 to 31.
Increasing the S-value range on the controller might help, as it would give a higher range of numbers, though I’m not sure if that controller can use them. The chip is capable of up to 16 bit PWM resolution, but it depends on which of the outputs they used and how it’s configured.
Increasing the speed would actually reduce your power at the DPI you’ve chosen - the controller simply isn’t capable of going that fast with the amount of data you’re throwing at it. Reducing the DPI will reduce the number of gcodes it has to process, which will let it go faster.
Because it has no idea what type of laser beam your system makes, what material it’s on, how that material responds to laser energy at your wavelength, how it’s responding to commands, what your beam diameter is, etc, etc… It’s showing the commands that will be sent, not how they affect the output. That would be a very difficult preview to create.