Oh, those are fantastic! (Especially love the little dimensional windmill.) 
You have been busy. Those are great.
Engraved some business gifts for a friend
I had to craft a jig for the fan to not knock into the material (bamboo)
engraving bamboo gets nice contrast. But the grain will interfere for a uniform look. I decided upon these settings : 1000/80/1 with a 2x focal depth. I had to use the -0.5" riser for this.
And I quickly crafted a makercase cardboard box (it’s not perfect)
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Before pulling off the masking (mask before engraving) give it a spray of Minwax Mission Oak poly. That will give you a nice even dark shade.
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I don’t know what that is but we’re sure to have some equivalent product in Europe. I don’t think it needs it though.
It’s a polyurethane & stain mix so it’s one-step. It matches the color of lasered bamboo so if you have uneven results due to the grain of the bamboo you can make it uniformly dark.
Here’s what it looks like, it’s available as a brush/wipe-on and in a spray can in both satin and gloss finish.
Similar to a Danish Oil finish - not sure who manufactures those in Europe or what colors you might find that can match the bamboo engrave color.
Is it food safe? If you put that on a cutting board for example, will I have to worry about toxity when dried and cured?
Don’t know. I use a butcher block oil treatment for cutting boards & wooden spoons. Danish oil & Minwax for other non-food projects.
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I’m trying to figure out how to even out the color on bamboo for cutting boards. Hmmm.
Usually I figure the engraved side of a cutting board is just for show so I’d use it.
I did look and Minwax says it’s food safe when fully cured. The FDA says hard film finishes including polyurethane are considered food safe as well.
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That’s what I’ve been doing. I label one side for food and one not, but if poly is non-toxic when cured then BONUS!
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I just did a search of “defocus” and, honestly, am still confused. Can you tell us more about this?
What specifically are you confused about? Might help to fosrmulaate an answer. The basic idea is you enter the “wrong” height, focusing the laser either too high or too low, which makes the beam wider and weaker at any given point where it hits the surface. It has its uses, which I won’t get fully into yet.
Just let us know specifically what you want to know and someone can flesh the concept out for you.
Thanks for the reply. Specifically, I’d like to know when it makes sense to defocus and how to do it correctly. Assuming it means adjusting the setting for the thickness your material, do you move the lens closer or farther away from the workpiece?
Yup!
I’m not sure it matters too much physics-wise. Think of the beam as an hourglass or X shape (it’s really 2 cones that are tip-to-tip), where the focus point is the narrowest part. If you move up or down from there, it should widen by the same amount, so I think all that matters is how “wrong” you are. As in, if you move it 1/8" too high or too low it should be the same result.
This is all theoretical, I haven’t done it, so someone with more empirical evidence might disagree. The physics check out, though.
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Oh sorry I didn’t tackle this part.
Basically you defocus when you want a wider beam. That can be handy for making wider score lines (they get a little hazy around the edges if you defocus a lot), or if you want to smooth out the texture of an engrave. This works really well on acrylic, check it out:
The tradeoff is that you lose some sharpness. There are ways to mitigate that with a quick edge score, but it’ll be up to you to decide when to use the technique.
As for when it makes sense: it’s up to you! This sort of thing is a “feel” kind of situation. I’ve said it elsewhere before, engraving is as complicated a thing as we can do with the GF, and it’s where artistry plays the biggest hand. You can make relatively small tweaks to settings and get really different results for the same piece. It all comes down to what you’re trying to do and your preferences.
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Thanks for the explanation. This is very helpful.
Excuse my ignorance, what is meant by 2 x focal depth?
If your material is 3mm. I defocus the laser to 2x3mm = 6mm.
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Thank you, makes perfect sense now.