Grayscale preview vs actual etch

Question about Grayscale:

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.

Hi OZ. I will post some pics as soon as I get home. Stuck at work today. :frowning:

Since I’m 100% green at I was taking setting from others I have seen on Facebook using the 2.8w. would increasing the speed help?

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.

Why does the preview look so good with the setting I have plugged in?

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. :slight_smile:

Understood! Thanks for that explanation! Basically the preview is what your etch could look like once you have all the other factors dialed in?

Maybe further investigation of what others have found successful for the laser that I have would help while I also continue to try and dial in the proper settings.

I see this and get really confused at the settings used…

That’s 60 in/min if I did my math correctly and 90% power. I would think that would burn as well.

He used black card, which absorbs most visible light, whereas white paper would reflect most of it. He basically burned the card while it was under the glass and caused it to stick to the glass.

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.