Grayscale engravings very light

Hey there!

I am hoping to get some help understanding a few aspects of the gray scale engraving process. Specifically I continue to have issues regulating the darkness of the engraving. They typically come out much lighter than expected. I am using a Jtech 7W laser attached to a Shapeoko XXL.

A couple questions if you wouldn’t mind.

  1. When using gray scale does my min/max power setting actually effect the outcome of the engraving or does the software adjust itself accordingly based on the picture provided?
  2. If the above is true, should I just leave my min/max power settings at 0/100 during any gray scale operation?
  3. Is gray scale always the best option for a photo? If not is there a general rule of thumb for making this decision? I know there are provided thumbnails when selecting an engraving method, but I’m not quite sure I understand the benefits to either one.
  4. Is speed the best way to regulate the final darkness of a gray scale engraving? Will 100ipm be darker than 150ipm with the same min/max power settings on a gray scale engraving?

Here is a recent example of an engraving I did. The picture is older and in black and white but I cant seem to make the engraving darker regardless of power settings.

This example is the same photo but done on canvas with the same settings. The only difference is that this engraving was done multiple times in an attempt to darken it, however after slowing it down and increasing the max power, the engraving still came out very light.

Here were my settings for the above images. I am currently running another pass on birch ply with 5/100 min/max power settings and its still coming out very light.

Thank you for any help or tips you can provide!


Settings -3

Here is the most recent attempt that I mentioned earlier.

As you can see… well you cant really see…

Min & Max power, in grayscale mode, are used for the white parts and black parts of the image, respectively, and everything in between those two brightness values will fall somewhere in between.

Going slower or faster will darken or lighten the image, because you’re putting more or less power down on the material in a given period of time. Using a higher DPI can help too - too large and you’ll get gaps between scanning rows, and your LED should be able to give pretty good detail. Make sure it’s properly focused, as that’s pretty important.

Your other settings are reasonable, but check the $30 setting in your firmware (type $$ in the console and look at what it spits back out). Your S-value max is set to 255, and should match whatever the controller is set to - if it’s 255 you’re good, but if it’s 1000 (a common default) you should set the S-value max to match it, and that would help too.

Check that and post back.

Sorry was at work, here is a screenshot of my $$ settings as well as a photo of a power scale I did a few weeks back using threshold.

Would increasing my min power setting just bring the light and dark spots of the image closer together or will the dark portions of the image increase proportionally? Does that make sense?

Increasing Min power will bring up the lighter parts. It would be like starting your graph one line lower.

Alright so increasing min power would eventually lead to the white parts matching the dark parts. But in my particular case the dark parts are barely noticeable. In this example

the engraving was done at 150 speed, 5/100 min/max power. Is that just way to fast…? According to my power scale I had kind of assumed that with a 150 speed, even if the blackest parts of the image were engraved at only 60% they would be quite a bit darker. I assumed that using a black and white image, the power output for a grayscale image would be pretty high? Is this just the wrong way to think about it?

Thanks for your help by the way, definitely hoping to understand this better.

I don’t think it was too fast, but it might’ve been too large on the line interval. When you did the power grid, what was your line interval there? Did you use the same number (lines per inch) as you did for DPI on the image? If you used a higher lines per inch number with the power grid, that means you were putting more energy down into the same area, and that would explain why it’s darker.

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