2.8 Diode / Photograph on MDF

I have a Shapeoko 3 with a JTech 2.8W Diode – I’ve successfully burned text / graphics but this is my first run in with photographs.

I created a file with some test faces and have been playing with different grayscale burn settings but not having any success getting an acceptable burn on MDF (results are even worse with Birch plywood).

The image is .8661" x .9449", at 145 DPI which is about a 0.007 line interval. The source is exactly the same size and DPI converted to grayscale in Photoshop. Output is also the same size, it is not being resized in Lightburn.

I’m using Grayscale mode now… not opposed to one of the other options, it just seemed that my PNG is made up of gray dots and the laser should be able to reproduce that… maybe I’m wrong on how it works.

Settings have been in the 20% min-100% max around 40-60IPM… so I could be way off there also.

I’ve attached the source picture as well as a photograph of my poor results. Any tips or assistance would be appreciated!



Have you ever done a test to see if your focus is optimal? Those look a bit blurry to me. Look up ‘ramp test’ for an idea, though with a diode usually you just focus the lens itself with the beam on very low power.

Thanks, I did focus the laser. It appears more that it is missing some of the in between grays. I will look into a ramp test but yes, this model you set to 3" and then focus it to a small dot at 2% power.

Grayscale is a pain in the butt, and the material plays a role, especially with a visible light laser. Light surfaces will reflect most of the beam power until it starts to heat up and char, and then as it darkens, it absorbs more power, and so the darkening accelerates, which makes some things really hard to tune. Dithering doesn’t have this power curve response problem because it’s just on/off.

Don’t worry about sizing the image to the output - LightBurn internally resizes the output to match the DPI and scale used, and the resizing code is decent. If you start with higher res than you need it gives the software a little extra detail to work with, and means you can play with DPI settings more easily.

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.