Piercing option?

I have some parts to cut in acrylic that I want to be able to pierce without actually cutting. This is to mark them for subsequent drill and tap operations. Some of the threads will be M1, so I don’t want to cut a hole less than 1mm in diameter as I can’t see my machine being accurate enough for that. But if I can move to the correct location and just pierce, or even mark enough to locate a drill point, that would make things a lot easier. As it stands at the moment I can’t see that it’s possible to get G-code generated that will fire the laser without a G1 command

My solution at the moment will be to use a macro to add the piercings before cutting the parts, or maybe manually edit the G-code. Neither idea is particularly appealing. Anyone got any bright ideas or a solution I might have overlooked? If not I’ll probably add this as a feature request.

Why not have one layer to do the cutting, then another payer to “pierce” or “mark” that is a lower power that will not cut or pierce through? Run the marking layer first, then cut out the part.

The problem is that I only want a point, and there’s no way to do just that in LightBurn that I can see. Maybe that should have been my question. Anything I put on a separate layer still has to generate G-code that will fire the laser without movement. This is the issue as I see it. I have thought of maybe a small cross-hair mark which I would put on a separate layer, but I haven’t experimented with this yet. I just found out yesterday that my laser head isn’t perpendicular to the work so I have to fix that today. While I’m out in the shop I’ll do some tests.

I did something similar to mark hole locations on a plinth.

For you, maybe draw .1mm circles and place them where you want. Then mark them with some low power as mentioned previously. .1mm is probably smaller than your beam diameter.

My holes were 6mm, so I did a 1mm circle and made a shallow hole ( I used the line and fill option ). Made a good pilot for the drill.

I guess I should do more experimenting. I was thinking line and fill on something that small would be difficult to achieve good results. 0.5mm would be sufficient I think, and if you had success with 1mm I guess it’s worth a shot.

If you use ‘Cut Through’ in Line mode, set a delay and power, but set the layer power to 0%, it will fire a dot at the start of the line, but nowhere else. Then you could just make short lines that start where you want the dots placed, or even make tiny circles (like 0.01mm diameter).

Thanks Oz. This sounds like what I need. I was testing cutting yesterday to get a feel of power and speeds needed for the thickest acrylic I’ll be cutting and got some great results. Today I’ll do some piercing/drilling tests and see what works best.

Just some clarification. If I wanted 4 holes on a 2x2 square grid and drew a square between the hole centers would LightBurn cut this with one start and one end for the complete square, or one start/end per edge? A lot of my holes will be on a rectangular pattern and I could join pairs of them with lines and set start and end cut through so that I always get the correct location regardless of which direction LightBurn ends up cutting the line, if the square option only has one start and end.

For single holes I’ll probably do the tiny circle idea - does LightBurn use a consistent start point for circles or is it dependent on the location of previous cuts to get optimal travel?

EDIT: Answered my own questions through testing. Lines between holes with start and end cut-through enabled is the way to go. Works great other than a couple of issues which are machine related and I’m working on fixing.

Not quite as elegant as having a native ‘Point’ shape, but hopefully good enough until we can get that in.

Should I add it as a feature request? I know LightBurn is many things to many people with laser machines being used for engraving as well as cutting, but for my use case which is mainly mechanical parts a piercing/point function is extremely useful. The work around is extremely easy to implement, but as you say not as elegant as a native option would be. The result is exactly as I had hoped - a nice clean tiny hole suitable for drilling out to a specific size for tapping.

No, if I can just get my damn machine to stop cutting at an angle! :roll_eyes:

Support for points is something that will happen, but it might be a bit - there’s some plumbing work to be done for them to fully happen, and they wouldn’t be supported by at least one controller.

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