Laser Engraved Acacia Wood

[Grant Carson]

Good Morning All,

I was wondering if any of you have any tips for getting a more consistent engraving on acacia wood (or any wood with color variance). I'm having some difficulties getting the results I want on acacia wood. The products we received have a light stain and some sort of clear varnish on them. They were not supposed to be stained, but they're here and now we have to work with them. Also, the wood is much more inconsistent than the samples we successfully engraved. The issue I'm having is that the contrast I can achieve on the lighter streaks in the wood now match the stain, so the letters don't show up well (see attached images). The first images shows half of the wood with the stain, and the other half with the stain sanded off. We can't just sand all of these because this is just a piece to a larger product. Sanding everything would not be a viable option. The second image shows how the letters are blending in with the stain. I'm running an 80w Trotec Speedy 300 with a 2" lens (we have a 4" also). We're currently doing these in two passes at 333dpi. The first to get some depth, and the second to get the contrast. The first pass is at 100 power, 100 speed, and 0" offset. The second pass is at 100 power, 40 speed, and 0.5" offset.

We can't totally change the look of the product (i.e. we can't paint it black and show a light engraving). We've tried switching to 500dpi, and even 1000dpi. The differences are barely noticeable. One idea we're going to try is to apply a coat of wax before engraving. Then, after engraving, quickly wipe on and off a dark stain. The thought is that the stain will soak into the engraving and help provide a darker contrast, while the wax will keep the stain from penetrating non-engraved areas. It's a long shot, but we're getting desperate. Any other ideas out there for how we might achieve a more consistent engraving across the darker and lighter sections of the wood? I appreciate the help.

Regards,
Grant

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[Gary Hair]

Paint fill is really the only way to get 100% consistent results. Since they are finished already you can use acrylic and apply with a stencil brush then wipe away with a squeegee and then a paper towel on a very flat piece of wood. Another option is to mask and laser through it, but that can be a pain to remove when you are done. If the letters are large enough you can spray with a clear coat and then wipe in stain or acrylic, the clear coat eliminates wicking.

[Mike Null]

In my opinion, your first pass at 100 speed is a waste of time. I don't know what you mean by offset.

Light and dark wood will not engrave the same no matter your settings.

Since there is a clear coat follow Gary's advice and paint fill.

I would not use a stain--it's likely to bleed. Use paint or shoe polish. Test the clear coat to be sure it isn't acrylic. If it is do not use DNA to remove your paint fill.

[Glen Monaghan]

We're currently doing these in two passes at 333dpi. The first to get some depth, and the second to get the contrast. The first pass is at 100 power, 100 speed, and 0" offset. The second pass is at 100 power, 40 speed, and 0.5" offset.

Did you report your power and speed settings correctly? You say your first pass is full speed and second pass only 40 speed. With both at 100 power, you'd be getting most of the final depth from the 2nd pass, and that pass would probably be vaporizing wood instead of making maximum contrast. With only 40 watts available, I typically run the 1st pass full power and dial the speed up as high as possible while still getting the desired depth. Then the 2nd pass is at a lower power and (usually) lower speed, sometimes slightly out of focus, so that the beam has longer "dwell" time causing the wood fibers to "toast" or caramelize, without applying so much power that the wood vaporizes. If your second pass is removing material and increasing the depth, then you are not getting maximum contrast.

***edit*** I missed the offset part. Assuming that offset in the second pass puts the beam out of focus, then your settings might make more sense, but I'm guessing you are still applying too much power on the second pass and removing material.

[John Lifer]

Yep, color fill is the ONLY way to get consistency with that much of a difference in color. Mike and Gary gave you the correct advice. Either accept the results or color fill

[Bruce Clumpner]

I'd mask and paint fill, but also shoot a clear-coat before your color so there is no chance of the color bleeding into the grain. Should be a fairly easy process for you, get some 18" high-tack transfer tape and laser through it...

[Grant Carson]

Gary Hair

Paint fill is really the only way to get 100% consistent results.

Thanks Gary, I'll give that a try.

Mike Null

In my opinion, your first pass at 100 speed is a waste of time. I don't know what you mean by offset.

Thank for the reply Mike. The reason for the first pass is to get some depth to the engraving. This helps give some definition to the text. Since the second pass is so far out of focus (what I'm calling offset), it doesn't really achieve any depth. It only "burns" to give a darker appearance. I believe Trotec refers to this "offset" as z-offset.

I missed the offset part. Assuming that offset in the second pass puts the beam out of focus, then your settings might make more sense, but I'm guessing you are still applying too much power on the second pass and removing material.

Thanks for chiming in Glen. You are correct, the offset prevents it from going deeper into the wood. I don't really notice any extra depth from the second pass, but I'll try dialing back the power a little bit to see if I can get more contrast.

Bruce Clumpner

I'd mask and paint fill, but also shoot a clear-coat before your color so there is no chance of the color bleeding into the grain. Should be a fairly easy process for you, get some 18" high-tack transfer tape and laser through it...

Bruce, thanks for the tip. I never thought to clear coat before paint fill to prevent bleeding. I've never really paint filled before, but this is a nice trick to know when I try it.

[Kev Williams]

I made some personal rules after a 'wood deal' with some guy and his wife, he who insisted on the largest walnut plaque I could find in a hurry, which I got from Marco (5 minutes from me), a 16" x 20" dark-light mix, which should've NEVER been sold as an award plaque-- I told this guy from the getgo that ALDER would be the best choice for what he wanted, but no, he thought Alder was 'cheap', and the biggest I could get within 2 hours was like 12x18". Sent my BIL to pick up the walnut, and uh oh...a patch job, right in the middle, and I swear the one half looked like pine and the other half was nearly black.. I called the guy and told him he wouldn't like it. No, sounds unique, it'll be fine, run it...

I ran it, and those Acacia samples above look fantastically stellar compared to this walnut. Neither side changed color, just cleanly vaporized. I ran 4 passes trying to get it to darken up the light side at least, but didn't matter, you could barely see the engraving! Guy picked it up, and -- well, was less than thrilled. I told him he might want to try staining the engraving... I also explained that what he sees is why I suggested Alder...

About an hour later the doorbell rings, and his wife is at the door, beside herself wondering what she was supposed to do with a plaque that she, nor who she was presenting it to in a few minutes, could read!? Not going to pay for this, want my money back!! What am I supposed to do!!??

Well, I explained to your husband that I thought that a different wood would be better for this--

Hell hath'd no fury is the best explanation for her new expression... "Oh. You did. I see. I'm sorry..."

I'm glad I wasn't the one in the car with her after that...

So yeah, after that fiasco, ever since then: (a) since Murphy's law works, I will always assume wood engraving will turn out like crap, and (b) I make sure to tell anyone who wants wood engraved the same thing, and they are proceeding at their own risk

And for the record, speaking of wood: NEVER EVER offer to laser engrave a violin that someone other than the actual owner brings you...

[Grant Carson]

I made some personal rules after a 'wood deal' with some guy and his wife, he who insisted on the largest walnut plaque I could find in a hurry, which I got from Marco (5 minutes from me), a 16" x 20" dark-light mix, which should've NEVER been sold as an award plaque-- I told this guy from the getgo that ALDER would be the best choice for what he wanted, but no, he thought Alder was 'cheap', and the biggest I could get within 2 hours was like 12x18". Sent my BIL to pick up the walnut, and uh oh...a patch job, right in the middle, and I swear the one half looked like pine and the other half was nearly black.. I called the guy and told him he wouldn't like it. No, sounds unique, it'll be fine, run it...

I ran it, and those Acacia samples above look fantastically stellar compared to this walnut. Neither side changed color, just cleanly vaporized. I ran 4 passes trying to get it to darken up the light side at least, but didn't matter, you could barely see the engraving! Guy picked it up, and -- well, was less than thrilled. I told him he might want to try staining the engraving... I also explained that what he sees is why I suggested Alder...

About an hour later the doorbell rings, and his wife is at the door, beside herself wondering what she was supposed to do with a plaque that she, nor who she was presenting it to in a few minutes, could read!? Not going to pay for this, want my money back!! What am I supposed to do!!??

Well, I explained to your husband that I thought that a different wood would be better for this--

Hell hath'd no fury is the best explanation for her new expression... "Oh. You did. I see. I'm sorry..."

I'm glad I wasn't the one in the car with her after that...

So yeah, after that fiasco, ever since then: (a) since Murphy's law works, I will always assume wood engraving will turn out like crap, and (b) I make sure to tell anyone who wants wood engraved the same thing, and they are proceeding at their own risk

And for the record, speaking of wood: NEVER EVER offer to laser engrave a violin that someone other than the actual owner brings you...

Well at least now you have a good story to tell. Thanks for sharing. We're constantly battling with Walnut as well. It's a beautiful wood, but can be a challenge to engrave with the blonde strips that run through it.

[Glen Monaghan]

Thanks for chiming in Glen. You are correct, the offset prevents it from going deeper into the wood. I don't really notice any extra depth from the second pass, but I'll try dialing back the power a little bit to see if I can get more contrast.

It won't help to simply reduce the power on the second pass. You have to get a combination of speed and power (at a given focus) that adds enough heat (power setting and focus which changes energy density) for long enough (speed setting) to "toast" the wood without vaporizing it.

My experience is that I have to go much slower to accomplish this than I find economical for anything more than a line or two of text and, at best, it is a hit-or-miss process because each piece of wood reacts differently. I found a setting that generally worked for rosewood, as an example, but about 1 out of 5 or 6 pieces simply wouldn't darken. Much faster and more consistent to fill. I use the same process others have mentioned... Mask, engrave, quick burnish to make sure the edges are tight, shoot a clear coat to prevent fill from wicking into the grain, wait just long enough for the clear to dry, shoot high contrast fill, wait until dry to touch, and remove the mask. When doing multiples, it's faster and produces far more consistent results than trying to tweak multiple slow passes.