Cutting and 3D engraving copper (all turns black) and it will literally take ages?

Community Laser Talk
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Hi guys!

I am working with thin copper sheet (16 gauge) and I am trying to engrave it with my Gweike G2 50W fiber laser. I am a complete noob, and I realize it more and more every time I work with my machine.

I am working with depth maps (grayscale PNG), and I am a bit unsure, some say that the 3D slice mode with 256 passes works the best, and some says that the Grayscale mode with an unknown amount of passes works. The first issue I run into is that Lightburn estimates my worktime at around 200 hours or even more. And I might mention that I use fairly reasonable settings, not like 12000 DPI or something like that, rather 800-1000, which I suppose is needed to get something like a clear embossing, without a linear pattern side-effect in the design. With the grayscale mode and about 15-30 passes, the worktime seems a bit more reasonable at a few hours. But I have seen people on YouTube doing designs in about 45 min - 1 hour.

Next issue is that the design gets very rough, gritty and almost black. I suppose the cleaning passes are meant to take care of this?

Brad

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Could you share some pictures of the model and latest results?

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But it is an grayscale as a PNG, all set up properly. I had a run now at three hours almost, with a cleaning pass. The only effect I get that the copper gets charred, design is not visible and not deep, however it seems like the charred copper swelling out of the sheet. Its just a disaster.

Did anyone try copper or brass in this type of machine, and have some ideas about the settings? Some settings that would do a clean and deep cut.

Brad

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Using grayscale with an led is it’s original design to produce a grayscale, for a co2 machine grayscale creates 3d type engravings that have depth.

How an LED and a co2 operate, compared to a fiber (pulse) 3dslice was created to make use of the way a fiber operates.

This is 3dslice operation as stated by Oz in the beta area.

With 3D Slice, each pass is thresholded to the current threshold value, and the result is run as a 1-bit image. If you use 256 passes you get exactly one pass per gray-level in the image. Every pixel at or below brightness 255 for the first pass, every pixel at or below 254, then 253, and so on.

If you choose 128 passes, you get every pixel at or below 254 for the first pass, then 252, then …

It “clusters” the layers together into batches if you use fewer than 256 passes, and will duplicate some layers (with even spacing) if you use more than 256. 384 passes would duplicate every 2nd layer. 512 passes would duplicate every layer.

Someone asked about using 3dslice with a visible laser (led), the response from Oz was

Diodes have extremely good power linearity, and you’re generally just engraving wood or plastic, so use ‘Grayscale’ mode - that’s what it’s for.

Grayscale mode does not work well for deep, consistent metal removal for galvos, so 3D slice was added for those machines. It was not “removed” for diodes and CO2 systems, as they already have the grayscale mode to accomplish this.

Maybe this helps clarify…

I’d expect better results in a 3d design with 3dslice on a fiber.

Good luck

:smiley_cat:

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I tried the 3D sliced mode too, it was considerably better results, in the question of depth, but the result is still kind of low res and charred, the work area is very rough and would be hard to clean without destroying detail. I also prematurely shut the machine off, since it was with those settings something similarily stupid like 80 hours or similar.

Not to mention a 256 pass is calculated in Lightburn to take 880 hours to complete. It just sounds crazy. Seeing people getting it done in 45 minutes with considerable depth. I am not sure what I am doing wrong really. The deepest I got this far was maybe 0.1 mm in the material.

Here are my settings for an 20 x 20 mm artwork. Which according to Lightburn will take 880 hours to complete.

Speed: 2300 mm/min
Power: 60-70 (tested different settings here)
Hz: 30
Passes: 256
Line interval: 0.0254 (1000 dpi)
Dot width: 0.080 mm

Brad

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what does a simple material test look like? charred on all settings?

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Its just copper and brass sheet, shiny metal. I however think I know the issue. Speed 2300 mm/min, not per second! I got it down from 880 hours to about 10 hours. Which I saw other people had too when doing a preview on the 3D sliced mode. So I suppose it will be done in much less. I will do another run now!

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yes and no; you should optimise for material removal rate first; sounds like you are running to hot. Intermittent cleaning passes help, and they tend do be of a higher frequency and lower pulse width, but it’s very material dependant. What speed/power/pulse/frequency/interval are you using? how did you come to chose those settings? Try a material test with varying the number of passes on one axis, and $whatever setting you think might improve the rate of removal/surface finish.

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When I changed the mm/minute to mm/second the output was damn outstanding. Perfect almost at the first try. The only issue now is that the surface is a bit pitted when looking up close.

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