# Rotary Engraving Add-On Idea

Just need a couple of 8 pole double throw toggle switches and some easy driver stepper motor controllers if you were to build it yourself.

I’d really love to hear any constructive criticism of the idea / design.

For the steps/mm you only have to do the calculation one time, once you know what steppers and gearing between the stepper degrees per step and pulley ratios. Once that is done, you just scale your Y axis by that ratio of current steps/mm to new steps/mm and you have your scale to make it come out correctly proportioned. A simple Excel calculation with the diameter of the round object as the input should give you the correct scale factor, and you are set…

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It would be nice to do — I’ve long had an idea for a far simpler mechanical solution which would put racks on the wasteboard, and have matching gears/pinions attached to the gantry so that movement along the Y-axis would be translated into rotation — hopefully I’ll get some time to finish that up once I finish the designs for my Kickstarter book.

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Like this?

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Yes, pretty much that, just slightly adjusted to be a bit more flexible and to fit on the SO3 gantry.

Neat idea. Just curious, why would you need two stepper motors for R1+R2 for handling a single additional rotation axis ? Something torque-related for really long pieces that you would rather drive from the two ends?

I think I was just trying to duplicate the two Y-axis stepper motors. No other reason.

One rotating stepper motor is probably all that’s needed.

I’m curious as to how you direct the CAM software to translate the 4th axis commands into Y movements.

You don’t have to. The y-axis becomes the rotating axis. If you are using a lathe chuck, then all you have to do is the calculation to go from steps per millimeter to steps per Revolution.

You set up your workspace so that your Y length is that value and then you vary your X depending on how long the cylinder is you are Engraving.

Go check out a video on how to make a design in Inkscape for an EggBot to see what I am talking about.

I’m in my car using a combination of voice to text and typing on my phone, so it’s kind of difficult to get to in-depth on it. But come Monday when I get back, I’d be more than happy to go into it a little more. I’m still kind of winging it myself anyway.

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There’s a utility from Scorchworks (the guy who does F-Engrave) which will wrap a design around a cylinder which may be useful.

Well, it appears that VCarve Pro has the ability to use the X or Y to wrap a design across a cylinder. Since I have VCarve Pro, all I need is an accessory like the one you showed. Too many possibilities and too little time!

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