# Meaning of "mm per revolution" Atomstack X7 with rotary

I have an Atomstack X7 with their roller rotary attachment. The rollers are .625" in diameter. Then I set the work piece diameter. The only way I’ve gotten the “mm per revolution” to produce the output I want is to frame my job as close to the work as possible. Then I set “mm per revolution” to the width of the frame (left to right). Is this correct? Cause it looks correct. If this is correct it might be better to call “mm per revolution” “Width of Job”.

I noticed that you put your post at the end of a two month old thread that was about a different engraver. I moved it to your own thread so we can avoid confusion and get your questions answered.

Thanks. I realized how old the thread was after I posted. But I figured even if the machine was different, Lightburn handled the “mm per revolution” the same. Mostly I was trying to see if I am interpreting the meaning of “mm per revolution” incorrectly. Gotta be a way of wording it, so it’s a bit more intuitive. Or a little “mouse over” diagram showing what it’s looking for. Everything else there makes perfect sense.

Ok, someone tell me if this sounds right. I had a cylindrical object and I measured it’s circumference. I made a rectangle 5mm high by the circumference long. I burned that rectangle into the cylindrical object and adjusted the “mm per revolution” until the ends of the rectangle were “Line on Line” . Once this adjustment is made and your roller diameter is entered. The rotary seems to be spot on regardless of work diameter.

Perfect.

Almost - and super close…

The arc length of part of the workpiece is the same length as the arc around the roller because they roll on each other. It doesn’t matter which wheel you wrap the measuring tape around - the workpiece error makes the same distance on the roller.

The mm per rotation correction gets applied to the belly of the workpiece so the ends of the belt become line-on-line - the clever part is that mm per rotation is applied to the axis length calibration in LightBurn to make everything work.

You probably should test new workpieces and adjust the circumference on your layer/drawing in LightBurn. It’s possible that the axis calibration will be ‘close enough’ with other workpiece diameters and each new layout in LightBurn to the point where no one would notice. Sometimes different objects will slip on the rollers as they move (heavier objects tend to slip more) so it’s always a good to check that the calibration is solid.