So, I used Fusion 360 to create a rotary so I can laser engrave round things.
It consists of a Nema 23 Stepper Motor, 1.8-degree, 1/8 micro stepping = 200 steps per rotation. This is set up on my controller replacing the Y axis on the CnC.
The stepper motor has a GT2 Pulley with 20 teeth on it.
I have two rollers below the stepper motor (think triangle with the SM on top). These rollers are approx. 12mm in diameter. They also have GT2 Pulleys with 20 teeth on them.
I have a 180mm-2GT-6 (90 teeth) belt installed that ties all of them together.
Then, I opened up Lightburn V1.4.0 and set up my rotary. Enable it, select Y as the axis.
The object I am testing on is a tube approx 117mm in diameter.
I put in 12mm for the roller (is that right? there are two of them connected via the belt/pullys…).
I put in 24.5 for the steps per rotation. Found this by just throwing in random numbers…
When I click test, it does a 360 rotation on the tube, dead on my index. All good right?
NO!
When I jog the Y axis 117mm - the diameter of the object, it rotates like 4.5 times. I’ve gone back in the test, changed the settings, gone back out to jog 117mm and still the same.
So, what do we think is the problem here?
Much appreciated for any support. Sorta driving myself crazy here. LOL.
I have their Longmill Mk1 CnC. I ordered a replacement stepper motor for it just in case. Meanwhile, I thought about putting a rotator together. I just got around to doing this.
I am using the same controller for the stepper motors as the CnC, and nothing is different other than the gears and the belt.
In the firmware $101 = 200.000 for Y-axis travel resolution [step/mm].
I primarily use this CnC for engraving. So, changing firmware setting each time I swap from the rotator on the Y back to the Y axis steppers on the CnC, is just another step I’d like to avoid. Does that make sense?
I still would like to know what I put in for 12 mm for the roller but there are two of them driven by the belt. What should I put there?
In the steps per revolution box, enter the number of steps it takes your attachment to make one full revolution. For a chuck rotary, this will be one rotation of the chuck, and for a roller, it will be one full rotation of the roller, NOT the item.
How you accomplish this is up to you, but the basic idea is to have the driving wheel rotate one complete turn and back when you press the test button in Lightburns rotary gui.
I’d suggest getting the correct steps/rotation of the motor itself… than figure the ratio or gearing.
You can set the gui to the proper steps/rotation of just the motor… and test it using the test button…
If that is correct, figure out the drive ratio and multiply the steps/rotation of the motor by the gear ratio.
Using a ratio of 2.5:1 as an example, you would multiply steps/rotation of the motor times the gear ratio. That should give you the correct value for the gui.
