How to deal with incomplete burn through

Hi Everyone,

I have a file and settings that usually burns through my 3/8th inch Baltic Birch projects. However, about 20% of the time it does not cut completely through, leaving one or two small places on the back intact. I have tried using a knife to complete the cut, but does not work all of the time. What is the best way to salvage these pieces? Do I run the file again? Seems that I would need to lower the power and just run the cut layer, but that does not sound very convenient.

Any help will be greatly appreciated.

Thank you,

Jim

Plywoods like baltic birch can contain knots, especially in the middle layer/layers. You never really know whats inside a ply, its where they put the less attractive wood, as ply is sold by grade of face generally so you might have tough knotty bits inside.

Do I run the file again?

Yes I would. Obviously you’ll be keen to ensure the work piece hasn’t moved. Better still, you should anticipate that your material is subject to such problems, it is “natural” material after all, you shouldn’t treat it like a predictable synthetic. Set all your cuts to do multiple passes or slow down your cuts to find the “guaranteed” settings for a cut. Also be sure to regularly check the focus of your laser. I could offer more suggestions, but I do not know what sort of laser engraver or cutter you are working with.

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Hi Dominic,

Thanks for the response. Just want to make sure I understand you here. Are you saying that it is a good practice to create the file with two cuts right from the start, instead of trying to cut it with one? My machine is a Thunder Laser, 100 watt version.

One more question if I may. When I am engraving pieces, I get, for lack of a better term " over burn" on the right side go the piece. Left side is no problem. This is when engraving from left to right. Takes a little time to clean up by hand. Is this a speed issue, power issue or both? Can I expect to get a piece done without having to clean this up at all?

Jim

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No I’d not say that was good practice for a CO2 100W laser, at the time of answering I rather assumed you had a diode based laser. Slow it down would be my advise. Also you need to make sure you have a good understanding of focal height across your work bed and keep on top of alignment. If you’re alignment is poor and your mirrors and optics are dirty, you will get variance in the cut. Also if you have poor extraction, this can have a big effect on efficiency as well as the other things I mentioned above.

I get, for lack of a better term " over burn" on the right side go the piece. Left side is no problem.

This sounds like your machine is poorly aligned or your bed or work piece isn’t level. i.e. when you get over-burn it is well focused and when you get poor burn it is badly focused.

I have made 2 videos on this topic that might help you (sorry they’re a little old now I need to re-do them).

Simple Alignment Test:

and

Downward Alignment Test

Dominic,

I will take a look at the videos. I am pretty sure my machine is level, I will check again and also see what the bed looks like, as far as level.

Jim

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…and the alignment. If you have differences from one side of the bed to the other, its not about your settings in LightBurn.

Dominic,

Checked both my machine and honeycomb bed for level and they are pretty much spot on. Cleaned my lenses and mirrors. Ran same file on a flat piece of MDF and still had that “overturn”. So I started to go through the alignment process. I think I am pretty good from laser tube to laser head. Tape on bottom of laser head cone is pretty much on center with the indentation of the cone orifice. Still getting overturn. May be the verticality but not sure how to proceed, adjusted it a number of ways but no solution. There must be a more accurate and more foolproof way to do this. Anyone have some suggestions?

Thank you,

Jim

Spell check keeps putting overturn in when I mean overburn.

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