Engraving from a greater distance than the focal depth


Does anyone have a way to engrave wood from 0.5 inches above the normal focal height?
I have made some wooden heart jewelry trays with a router and template, the hearts are about 3.4 inches wide. I am trying to engrave the inside of the heart. However, the depth of the tray is about 0.5 inches, so when I adjust the height of my laser to the standard focal distance the laser head is below the sides of the of the tray. This only allows me to engrave a very small area in side the heart before the laser will bump in to the sides of the tray. I tried engraving from 0.5 inches above the normal focal height and the results were okay but a little fuzzy, and not a consistent burn.


Your only option is a longer focal length lens… For the hobby co2 and fiber, you can get different lenses…

I think you would have to ask laser modules manufacturer if longer lenses are available for your machine.


Have you tried to remove the plastic guard and air nozzle from the bottom of your module?

That will get you a large percentage of the way to your goal

No I haven’t. I was concerned that if I removed the red plastic guard it my be a safety issue because of the light, is that true?

*my should be might

Every bit of emitted laser light is a risk to your eyes. For a diode laser, you need safety glasses that block out 445-460 nanometer wavelength.

Wear your red/orange glasses ALL THE TIME, EVERY TIME you energize your laser. Be aware of pets and children and keep them out of the room where the laser is running.

So, I used the laser without the plastic guard and that did solve my problem. However, now I am losing space that I could be engraving because I have to allow for overscan. Is their any way to keep the edges of the text from being darker without using much/if any overscan?

I always wear the provided laser safety glasses, and I keep my laser in an enclosure.

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Run the text as OFFSET FILL rather than FILL, or turn off bi directional engrave

The only way is to slow down the engraving speed so it can slow to a stop and change directions in less area.

I’m afraid you can’t beat physics.

Any chance of a longer lens available?


I am afraid not, on a 5 W diode laser… :slightly_smiling_face: Even if it is a Longer, precisely!

Tammy, why do you lose space? Overscan can happen over the raised parts, no? If you no longer have the issue of bumping on the sides. Or do I miss something?

The bottom of the laser head is still below the sides of the dish. However, since the plastic guard is removed the laser head is small enough at the bottom to engrave relatively close to the sides of the dish without bumping it, while being at the proper focal depth. Overscan must take place within the sides of the jewelry dish or it will move the jewelry dish and misalign the text.

Would it be possible to add a setting to Lightburn that would decrease the power of the laser as the laser slows down at the end of travel? From my thinking this would leave an even burn and get rid of the time spent in overscan. Any thoughts?

If you have a modern GRBL device and are using M4 (ie not using Constant Power Mode) for laser control then the laser is capable of using variable power as you describe. It will reduce power during acceleration/deceleration.

You must be using the correct device profile (GRBL) and not using Constant Power Mode for that to work.

Offset fill does not have overscan. It fills from the inside to outside.

Try that

I changed my setting from GRBL-M3 to GRBL. This is the result with zero overscan and normal fill. See the attached screenshot for the exact settings I used.

P.S. The wood is hickory. (Just another variable)

Thanks to all those who answered my questions!