More tests with the new 30w diode laser

Been doing a lot of messing about this afternoon, again. This time basically trying to see if I can get good results at much faster speeds than I have been using. Most of this is on slate coasters, ignore the four dots, that is where I removed the rubber feet so I could use the back sides.

I find it incredibly frustrating that images with very similar grayscale ranges and contrast on the same material can have vastly different quality output given the same settings.

These are all grayscale images engraved using grayscale mode.

First pic is a bass with the image negated and then not negated.

Second pic is the same bass closer up.

Third pic is same bass this time on black acrylic. One on the left was done with transfer tape in place, on the right was without the transfer tape. Don’t be fooled by this picture, it looks good here, but in person you can barely see the fish. The camera in my phone just enhance the light bouncing/reflecting off the grooves in the plastic.

Fourth pic back to slate doing some mountains with slightly different settings.

Fifth pic is a doggo. That weird area on his lower jaw is the laser starting to engrave the bass over the top of the dog.

except for the mountains these are the settings used

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Two things to add here:

  1. slate is a natural material, and as wood, no piece will be exactly the same as the next. Results will only be the same on artificial materials like acrylic and anodized aluminum, for example.
  2. what’s the baud rate you use to connect to your laser? Be aware, that if it’s 115,200 (very common) you can’t reach 17,000mm/min at grayscale, because the data can’t be transmitted fast enough. The bandwidth limit is about 7000 mm/min. Going higher creates unpredictable results, since the speeds change with the image contents (higher contrast areas will run slower than low contrast areas). 400 DPI also sounds very high for a 30W laser, it’s more likely to be half of that.
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From my understanding of grbl, the overscan should be enough to reach speed before the image.

You’re overscan is only 1.4mm, not knowing your acceleration value ($121), I’ll be using an acceleration rate of 1000mm/s^2 it takes almost 40mm to reach the specified speed of 17,000mm/m (283.33mm/s). Even increasing the acceleration to 5000mm/s^2, it takes about 8mm to reach that same speed…

I don’t know grbl well enough, but my dsp ignores a minimum power value if you are scanning. Because a dsp computes it before the job runs, it assumes the head is up to speed by the time it needs to lase. Minimum power is only used in vector engraving/cutting. I think @misken will correct me if I make an error here.

As a general rule, if the material is dark or black and the laser leaves a white mark, you need to use the invert option. Some types of slate mark white, some dark. Both of these are different types of slate.

As @misken pointed out, all of these materials, so far, are natural and every one varies from the other, just like anything that nature is growing or creating. Rocks are included with this.


I wonder about using grayscale. It is the most difficult to use. Different materials (sometimes the same material) vary in how they react. Usually it’s used to produce a range of depths.

If you want a grayscale, then the material has to be able to have the type of destructive machining to reflect the complete range of your photo. Most materials don’t. If your wood starts to change color at 42% power and it burnt at 60% power, then you only have a possible grayscale existing between about 40 and 60%… to exacerbate it even more, it’s very unlikely to be linear from that 40 to 60%.

Even varying depths sometimes don’t show up well. I’d suggest you use a dither of some sort instead of the grayscale.

What resolution you can attain is really the relationship between the tool size (laser) and the size of mark left. If you have a beam 1 inch in diameter and when it strikes the material, it leaves a 2 inch mark… your best resolution is 1/2 dpi, even though the beam or tool is smaller..

Make sense?

Nevertheless, love the puppy and the inverted fish :tada:

:smiley_cat:

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Minimum power setting is 9nly available to me when in grayscale mode on an image layer.