Gear Motor for 4th axis

[jdk3d]

Hello,

I’m acquiring the parts needed to make a tabletop micro CNC milling machine that will utilize a 4th axis rotary table. I happened to find this site/forum in my quest. I don’t know much about robots, but I guess my project could be classified as a robotic carving machine.

I’ve seen some cnc mill builders use harmonic drives as a 4th axis motor. They’re very accurate, but priced out of my overall budget, so I’m looking at this unit as an alternative mainly because the description says it has low backlash, but I’m not sure if the other specs fit my needs-

Cytron 12V, 60rpm, 93oz-in Gear Motor w / EncoderProduct code : RB-Cyt-92

I need a motor that can be precisely moved by micro steps to index-able positions by a CNC controller running Mach3. The micro mill I’m making will be moving very light loads, cutting wax and perhaps some plastic.

Would this unit be at all suitable?

Thanks,

jdk3d

[jdk3d]

Thanks for your reply… I Googled “DC Gear Motor encoder in Mach3” and there does seem to be some documentation that Mach3 supports servo motors but I would have no idea how to set something like that up or whether it would work with that particular gear motor. That’s what I was hoping you could tell me.

I knew I was was mixing terminology when I referred to micro-stepping in regards to the gear motor. With the rotary table I’m using on my current machine, I’m using a stepper motor with a Sherline rotary table moving in degree increments rather than steps that translate into a linear distance. I believe the Sherline has a 72:1 reduction worm gear. I would like a lighter, more compact 4th axis unit for the mill I’m planning, hence my inquiry about the gear motor. I will check out the geared stepper motors that you mentioned. I noticed that you sell a Sherline Rotary table that runs independently of other CNC controllers. Do you have a stepper or gearhead motor that could be rigged up as part of a 4th axis system to accomplish the same results as the Sherline rotary table, meaning it can do a Rotation Speed of 1°/ sec to 50°/sec (programmable) and a resolution of: 28,800 steps per revolution (±.006° per step) or perhaps something close in functionality?

Thanks,
jdk3d

[jdk3d]

OK, thanks… if nothing else, I learned a bit more about gears and motors.

[cbenson]

The motor has a 100:1 gear reduction, and the encoder is at the rear, which gives you the accuracy. Many CNC controllers are made specifically for stepper motors, so you’ll need to be certain you can run a DC gear motor with encoder. Note that most when you use the term “steps” you are most often referring to a stepper motor (we have geared stepper motors as well, which can be very accurate).

[cbenson]

Do you have a stepper or gearhead motor that could be rigged up as part of a 4th axis system to accomplish the same results as the Sherline rotary table, meaning it can do a Rotation Speed of 1°/ sec to 50°/sec (programmable) and a resolution of: 28,800 steps per revolution (±.006° per step) or perhaps something close in functionality?

Geared stepper motors only, and you may need to sacrifice 50 degrees per second if it’s heavily geared down. We don’t carry anything with 0.006 degree accuracy (even with microstepping).