Laser rotary with a cheap rotary attachment

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Hey all, I’ve been messing around with a little rotary axis I picked up for doing laser work:

I picked up one of these:

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I wired it into one of my stepper machines as an A axis. I had to drop the amperage on the driver down to the minimum as this rotary has a puny little 2amp stepper on it.

I had to work out the motor tuning settings by doing some napkin math and some tuning in CNC12. Once I got that all sorted it out it works just like our “big” rotary.

The thing doesn’t have any power for cutting, but it works great for laser stuff.

I had been doing tumblers and things on the Avid rotary, but this one is more fun for “little” stuff… mostly because of the bearing rollers and the fact that you can easily angle the rotary so that you can do beer glasses and things like that.

Once I do a project that doesn’t have some personal information on it (like names and phone numbers!) I’ll post some results.

I had to do a little testing to figure out the power levels to burn the paint off of those Yeti tumblers, but once I got it it was easy to do.

For those wondering: On a 45 watt laser I was doing 30% power, 150 IPM and one pass.

PS: This is not an official Avid project, this is just some personal hacking around I did!

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That’s a cool idea Eric I kind of thought it could be used with avids rotary system was it difficult to hook up?

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Nice! I have often considered buying a cheap bench top lathe off facebook and converting it to a stepper motor as a way to get a rotary axis.

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You can totally use it with our rotary system. I do that a lot.

I wanted something I could use on my smaller machine, and I want something I could tilt on an angle.

The tilting means I don’t have to make complex rotary tool paths in fusion, I can just treat them like flat simple tool paths and use vectric.

This all started because I wanted to rubber covers for the rotary like this one has… I ended up just getting the whole rotary :slight_smile:

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This is exactly what I’ve been looking for! Any chance you could share the settings you figured out for setting it up to get me close in CNC12?

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The settings really depend on which rotary you get (There are a lot of them)

What I did was this:

I ordered the rotary and then immediately too it apart to see what amperage the motor was. The two specs that I needed were stamped on the motor: 1.7 amps and 1.8 degrees per step.

Those are both pretty standard figures.

Our stepper motors run at much higher amperage, but our stepper drives have adjustable amperage:

If you look on the side of a stepper driver there are dip switches that you can configure. One set of them is for the amperage. Stock I believe we max them out at 7 amps, with the flipping of a few switches I was able to drop it to the lower amperage I needed so I didn’t cook the stepper motor in the rotary.

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Our stepper motors are 4 wire (two wires per coil) and so was the stepper on this rotary. To find which wires go to which coils you can use a multi meter, or just pinch two wires together and see if the stepper gets a lot more resistance when you spin it. I did this method and I was easily able to find out which wires went to which coils on the new rotary.

Then it just a simple matter of running those four wires into the stepper driver plugs in the control box.

You’ll see on the side of the stepper there’s A+ A- and B+ B-. Depending on which pair you put into which, this can make the motor spin clockwise or counterclockwise.

You can decide if you want to hardwire it “correctly” or just do whatever and fix it in software.

Now the motor tuning part…

There are a couple of ways you can go about this… You can do the math ahead of time, or you can guess and dial it in…

There’s a great article here:

Without repeating that entire article, basically there are two things you need to get right in the wizard:

Steps per rev, and distance traveled per degree (Turns ratio)

Steps per rev is fixed… 2000 steps will spin the STEPPER motor 360 degrees. The second thing you need to figure out is how many degrees the motor spins given a particular command..

This can change depending on the geartrain that you have on your rotary. The Avid rotary is 10:1 reduction. This little guy I got is 4:1. I’ve seen a lot of 6:1 ones out there.

That article I linked should help you math it out.

Another method you can do is to navigate to CNCM/system/axis calibration (you load a G code job in there called "Axis calibration)

This will guide you through calibrating your axes. You can do a rotary this way. I ran the utility, made a mark on the rotary and then spun it 360 by hand jogging. I lined it back up with my mark and this utility told me the turns ratio and set it for me.

This is an effective way to do it, BUT if you’re off EVEN A LITTLE your errors can compound. I used this to get me “close enough” which helped me verify my math. I ultimately used the math formula for my final settings.

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Thanks for the deep dive Eric :wink: :+1:

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Thanks for that. I actually hit buy on the same one you have so I’d love to get the numbers you came up with for it :slight_smile:

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I would go through these steps so that you know how to setup and tune it.

Even with this particular model there three variations of it that may have different settings. You’d be best served by learning how to tune it on your own, so that you can troubleshoot.

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I’m pretty familiar with tuning from my current custom machine. I’ll give it a shot :slight_smile:

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Nice! Let us know how you make out!