I am trying to etch a rectangle .50mm x 63.5mm along the axis of a cylinder that is Ø29.98mm. Now the catch, I need to etch 12 of them 30° apart. We have an Aurora 8 and a Roto Boss Low Roller Rotary.
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Not an engineer, but here is how I would do it:
- Draw a Tool Layer, height= oops, I see an issue…
65.3mm along a cylinder 29.98mm long. I need an interpreter here. Is “Ø29.98mm“ the circumfrence of the cylinder? Said I was not an engineer, right?
Continuing…
- Draw a Tool Layer, height= height of design, width= circunfrence of the cylinder.
- Imagine you are laying out the design on a flat surface that will wrap around the cylinder.
- Draw one rectangle with the desired dimensions.
- Use the Array tool to create 1 X column and the number of Y rows to give you the desired spacing. I expect you should already know how many rectangle strips you can get on the surface of the cylinder. If not, have fun playing What-If.
The array tool will not give the desired results. After step 3…
4. Draw a line across the rectangle the same length as the rectangle. Make this a tool path as well.
5. Select the rectangle shape and align it to the left end of the large tool path.
6. With the small rectangle still selected, shift select the line,
7. Go to Arrangement Menu> Copy along Path. Input 31 copies.
8. Delete the first or last small rectangle and you now have 30 evenly spaced small rectangles that fit on your cylinder.
That is what I get for not trying it first! 
Actually, you can get there with the array tool, but it requires math to define the proper spacing or a lot of experimentation. The copy along path tool does the math.
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But he is an engineer. Don’t they live for math? 
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Here is what I came up with, assuming a 29.98 circumference.
CYL Strips.lbrn2 (42.7 KB)
I misread the original request. I designed for 30 lines, not 12.
Spacing from center to center (of the .5mm) would be 1.8836mm.
Wait, no. 22.8483mm.
Maybe. Got up to early to be thinking now.
7.8483 is my final answer.
Wouldn’t repeat marking set for 30 degrees and a single rectangle be the most accurate or doesn’t that work so well on rollers? It would be the most accurate way with a chuck rotary.
I should have mentioned that I had tried that and found that it did not work.
That is okay, not all of my good ideas are brilliant ones. 
Where in Light burn can I do what you mention?
I didn’t notice you had a roller rotary. This is a really precise way to do it with a chuck rotary, should work with a roller but I have never tried one. With a chuck you are working with degrees so a little taper or out of round doesn’t hurt. Rollers you will have to assure your size is as accurate as possible, but that would be true with the other methods mentioned above. Same with acceleration, go slow so it doesn’t slip.
That is a lot of help. The issue I am having now is after the first line etch, that rotation to the second is less of a rotation than the next 11. The next 11 all measure the same distance between them, but the first move/rotate is less. I have been doing this testing on a Ø2.00 piece of steel, SPR is 5150 with a roller diameter of 1.58.
See the attached photo, I need to etch these lines on the smaller diameter section of the part that is inserted into the Ø2.00 holder. I have 6 different part diameters I need to etch on ranging from Ø.866 down to Ø.484.
Looks like a heavy workpiece and a light rotary. Might be just a little backlash in the rotary so first thing I would try is to rotate the the workpiece one way or the other so rollers pre-loaded. Slow down the acceleration some more. (Bigger number) Maybe turn off “Return to start” and run it once with 0 power, or could probably do it by hand, just take up any slack. That MIGHT be the problem. Like I said I’m not a roller rotary guy. Have a big rotary table, 2 different chuck type rotaries, and a linear table but no rollers. On the big rotary table I have ran into backlash issues due to a lot of rotating mass working the setscrew loose.
I need to etch on ranging from Ø.866 down to Ø.484.
You might be better off getting a chuck rotary. Repeat marking is not measurement dependent, only have to mess with focus.
Thank you everyone for your help. I got my parts done and learned about some features in Lightburn that I did not know about. I ended up using Albroswift’s idea.
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Nice to know it works on a roller.
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