Engraving into curved surfaces

Estlcam is the software that I have and have been using, so it’s the preferred solution, but if there’s another way, I’m game.

So I want to do some engraving into the bamboo “swords” that we use for Kendo, called shinai.

These are basically 4 staves of bamboo pressed together and secured with leather, and held with a line down one edge. Each of the bamboo pieces is curved on the outside, and it’s carved into a circular or oval shape for where the handle comes over.

I wanted to put a little engraving into the side.

  1. The engraving can’t be too deep. These are used in a full contact martial art, after all, and I don’t want to weaken the bamboo any more than necessary
  2. For the same reason, I don’t want to actually carve any extra surface material away. Also, the skin of the bamboo is deliberately left on the staves. I can model the shape of what I want, but I don’t want to carve it out.
  3. Because reasons, I won’t be using a Roman alphabet font. Assume that I’ll be starting with an outline picture.
  4. For simplicity sake, over the size of what I’m carving, I could assume that the surface is a cylinder.

I want to engrave into the curved surface something about 0.5mm deep. I would be willing to do it as line art, but would prefer to get pocketed areas in it.

Of course, this would be 1000% easier with a laser, and I might just go that way at some point…

Some solutions that immediately come to mind:

  1. A 4th axis or some other way that you would rotate the sword nearly exactly on its axis instead of one of the linear axis. A pattern in 2D would just follow the surface of the sword instead. You could make a very light engraving that way.

  2. Cut out a sticker and use some kind of burning or etching. I don’t know what would etch bamboo. But it might be cool to do india ink or just paint with a custom vinyl mask.

  3. You could cut something very tiny without the machine knowing it is cutting on a round surface. It would have to be tiny to keep it from cutting too deep

  4. Make a 3D model of the part and try to use fusion to etch while following the height. I have no idea if that is possible. I am 90% sure it isn’t possible for estlcam

  5. Make a post script that would read in the gcode from estlcam and add Z moves to adjust it to follow the curvature.

  6. Make a design in 2D in something like a flexible cutting board and use it as a template to carve it by hand.

This is really a brain dump. I am not sure how each of those would work. But maybe aomething in there would make you happy.

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a laser would easily etch bamboo.

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Thanks for suggestions.

The geometry is difficult, because the surfaces have a radius of maybe 3" or so, but the whole piece is maybe 1.5" diameter. A 4th axis would just change the difficulty from one way to another, though I suppose that I could space the pieces back to their original radius. I might look at something to do that.

A post script as a programming solution might actually work for me.

Doing any of this by hand… Not gonna happen. I am hoping to just have something that I can run periodically. A shinai has a service lifespan of anywhere from a couple weeks to a few months. They’re consumables, basically. I wanted to do a number of them, and I wanted uniformity, plus I will want to do more of them when I order them next. I’ve been doing some marking with ink, but wanted something a little different.

At this point, the likelihood seems high that I will just wait until I have a laser going, since I’ve got it about 80% designed, and about 20% built. I suppose too that it’s not like I couldn’t just pretend that it’s a 2D carving, keeping the width to maybe 5/8" or so.

I was hoping there would be a way to do this, but I’m getting close to being 100% sure that there isn’t a way to do this in Estlcam.

While true, that wasn’t my question.

Due to the way that the shinai is used and other factors, I’d keep away from chemical etching. I might have access to a sand blaster, though I don’t think the media tank is quite long enough. The staves are ~4’ long. It might be doable if I don’t mind losing the media.

Well, my “5.5W” LED laser should be here Friday… Then I’ll need to figure out where I can get 5V PWM from, lol.

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I know your question is about EstlCAM, but I believe this is doable in Fusion 360. It would be easiest to use a V-bit and trace vectors…either as stick figures or as an outline. If you provide some geometry/measurements for your shinai, and art you want placed on it, I’d be glad to give you back both a sample Fusion 360 file and a g-code file that you could run.


Robert is right. The functionality you want to look for is project, and relatively new. You can model the 3d surface as a solid, create a sketch with the art you want, and project it into or onto the surface.
The challenge, i think, is going to be hitting the steeper parts with the mill, but that’s me not fully understanding the shape.
I do like the laser idea best, but since you brought up the sandblaster, you could drape a plastic sheet over the door and fix it to the inside of the cabinet with magnets. That would save enough media to make it practical.

A shinai isn’t huge…

The handle is about 30mm diameter, and at its thickest, (Where I want to engrave) it might be 50mm. It’s cut from 4 slats of bamboo, which might be 120-150mm diameter to start. Those slats are shaped to be a double taper maybe 35mm at its thickest, and down to 10mm at the tip. The overall length is nominally measured in “shaku” (3.9) which is a traditional Japanese measurement, but call it 47.75" and that works.

The photo is a little difficult to get the total shape from, but that’s the area I want to engrave. (Not on the bamboo segment bump though.)

I’ve got tons of broken ones, so maybe I’ll experiment a little on ones where it doesn’t matter if I screw it up. It’s a real pain to take my Makita router out of my Primo, or I’d try the laser in it. Maybe I can make it work in my 3018. That seems to be what it was made for anyway…

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There are logic level converters for like $5. Then you can use a fan port at 12V without recompiling. But I know you will want to configure and compile it yourself. So there should be several 5V pwm pins. I forgot which board you are running.

This is a very nice thing to volunteer, Robert. :clap:

I saw a laser mount that built into a cylinder that had the same diameter as the router. The user would just loosen the two screws on the router mount, slide the router out, slide the laser in, and tighten the screws. A quick search of Thingiverse did not yield the one I ran across earlier (which was for either the Dewalt or Makita, but I did find this conceptually similar one. If/when I do a laser, this was my plan since I hate taking my router mounts off the Primo.

Is the issue that the ink is not permanent enough, or that it is too time-consuming to ink by hand? I think Jeff mentioned cutting out a vinyl mask which would make inking very quick. You could even mirror it, and make a stamp out of rubber. ESTLCam should be able to do that easily.

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I like the 4th rotating axis idea. Also, if you use bCNC you can wrap the sword with tin foil, probe it, and use bCNC leveling to engrave from a 2d gcode. The latter would be limited with the bit angle though.


There was a stamp project a few years ago by @vicious1 himself. I think he stamped the boxes with it for a really long time.

I have my tiny laser (which I haven’t really played mich with) attached to the side of the 611 plate. I take out the router and I cut the cord to install a small pigtail to make unplugging it easier.

Do you need a 4th axis? Couldn’t you just plug a rotary axis in in place of the x or y axis?

I got a stamped box today… must still have that thing.


Actually in this case probably yes, and that would make the gcode even easier to create.

FWIW, this is what I was suggesting. It has been done a few times and I love the idea that steps /mm becomes steps / mm at a certain radius and shapes still look like shapes.