Does LightBurn take into account the taper of a tumber when calculating gcode

Most tumblers have a taper as part of their design.
Using a rotary like Randy Smith’s HM rotary, and perhaps most other rotaries,
with circle (tumbler) diameter and circumference provided at widest part,
a designed circle comes out in the shape of an oval, not round,
The more the taper, the more oval the shape outputted.
Does the gcode produced for burning take into consideration the taper?
I personally don’t see how it could as the circumference at the bottom of the tumbler or the tumbler taper is not provided.
The desire is to design a circle, lase a circle and have both come out round on a tapered tumbler.

It doesn’t, no. It would be fairly tricky to make it do that.

I came across this issue in the summer, my fix was get a piece of flexible foam and use your laser to cut out a circle with a hole in it. The outside of the foam has to be the same diameter as the outside of the larger end of the cup. And then cut the inside accordingly to the smaller diameter side. Slide it on, I had to make some minor adjustments with image but it worked. Nice part is the laser makes a perfect foam sleeve, give it a shot and good luck


I firgot to say you might need a small piece of tape to hold it on. I had one spin out

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put a levelling wedge under your rotary device , or use one that has the adjustable rollers at one end to level the taper out.

the aim is to physically hold the item so the laser surface is as level as possible.

that way the laser focus is sustained too.

notice this image from trotec , showing the rotary device tilted to present the glass as flat as possible to the laser


I like this one - that’s something I hadn’t thought of. Clever bastards. :slight_smile:


here’s a link to a video that explains it nicely.

Not as fancy as the Trotec solution but this fully manual $1.80 solution from the hardware store has worked well for me for a couple of years :wink: You do want four of them to create a really stable situation that will not rock during motor spinning.



and at a great price too

I drilled & tapped mine for leveling screws.


Great thinking, Hank.

Are those wood/wood-like slats actually adjustable end supports so you don’t have to deal with mounting open-ended tumblers to the rotating center spike? Please show more pictures from different angles.

Yes, it’s just a bit of 1/4" plywood with a roller bearing on one end and a bolt/wing nut on the other so they can be pivoted around for adjustment. The center spike is not always convenient and one day I had a long bottom heavy glass that just would not stay straight in the chuck so I tossed those together in a hurry to get a job done.

The extra set of holes gives me additional adjustment possibilities. It’s simple and was thrown together quickly from hardware that was laying around, but it works pretty well.


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One more with a glass in place.

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Nice problem solving and execution. Thanks for posting the pictures. I wasn’t able to tell those were bearings before.

I usually have to use my rotary on its side due to height clearance issues so your setup would require some more mounting points. I have made a set of “caps” incoporating center holes for my most used item diameters, plus one universal cap for the rest.

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Wow, these are much nicer solutions than just finding whatever materials I have laying around to prop up the rotary. I might even invest in a set of doorstops!

I did the same with mine works a treat!

I have caps for each size of glass too, I also had a bottom cap with a hold in the center to align the pin side.
I used plywood but now I have a 3D printer I’ll make flexible “cups” to hold each end of the glass while engraving.

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A buddy of mine printed both shapes shown in the
Trotec adapter picture at the start of this thread (both covex and concave shaped) with an added installation shaft. He can fit either into the jaws of the chuck and then be able to quickly center most cylinder/round shapes.

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Here is mine for a hot dog roller. Screen door rollers on acrylic frame. Takes about 5 minutes to draw and cut.

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You forgot to list the rubber band and duct tape. :slight_smile: Great hack!