[mikey4646]

Hi, I am new to the CNC hobby. I want to build a CNC Router and maybe a CNC lathe. I have seen lots of plans on how to build one but need help with the stepper motors and the controllers.

I found several Nema 17 motors with different specs. Different voltages and amperages, 0.9 degree step, 1.8 degree step. Torque? Oz?

If someone could explain the differences?

Thank you.

[awerby]

NEMA 17 motors are too small to be useful in any but the lightest and smallest CNC machines. The smallest ones you'll want to get are NEMA 23, and for a larger router or lathe the NEMA 34 might be better. It's hard to say what you'll need for your unspecified machines, but it's usually best to build the machine first and then start shopping for motors, when you have a more realistic idea of the forces involved in moving the axes,

[mikey4646]

Thanks for the reply. I think I understand the need for a better or stronger motor to drive what I am wanting to build. So am I right that a 70 oz-in motor is not as strong as a 240 oz-in motor? What is the degree step? I see some that are 0.9 or 1.8 degree step?

I purchased a 5 Axis MACH3 Interface Board CNC with Optocoupler Adapter Stepper Motor Driver for real cheap on Ebay. I know I need the software to control the board thru a parallel cable. Do I need a power supply or will the built in usb port provide this?

[James Newton]

Yes, 240 is more than 70. For more on torque, see this page:
techref.massmind.org/techref/torque.htm

The degree step is just the number of degrees (out of a 360' circle) that the motor will move with each step. 1.8 is the standard for larger motors. Microsteps are movements /between/ those full step positions. e.g. half step on a 1.8 degree motor would be 0.9 degrees per /half/ step. 1/8th microstepping would divide the full 1.8 degree step into 8 microsteps, each being 0.225 degrees. For more on microstepping, see:
techref.massmind.org/techref/io/stepper/microstepping.htm

Anything purchased cheap on ebay is suspect. For pity sake, what ever you do, do NOT buy a TB6560 driver! :shudder:

MACH3 is the name of the software. See:
Mach3 - Newfangled Solutions

You need a power supply. USB doesn't even come close:
techref.massmind.org/techref/io/stepper/power.htm

You are doing this the wrong way around.
1. FIRST: Build the physical router.
2. Measure the torque needed to move each axis and measure the weight being moved.
techref.massmind.org/techref/io/stepper/measure-torque-rb.htm
3. Calculate the power (watts) needed to move that weight at the desired speed, and ensure your motors have the necessary /detent/ (not holding) torque.
techref.massmind.org/techref/io/stepper/estimate.htm
4. Find motors and drivers that match this requirement. Some larger motors can be found in discarded office equipment:
techref.massmind.org/techref/io/stepper/linistep/motors.htm
5. Select software that matches your interest and will run on your PC
6. Buy an interface board that works with those drivers and the software for your PC

[mikey4646]

Greatly appreciate the advise and info. Thank you.

[Al_The_Man]

Incidentally NEMA is not an definite indication of power (torque) NEMA refers to a frame size, I can have two motors with completely different characteristics, both with the same NEMA size.
Al.

[mikey4646]

Thanks for the input. I have a better understanding of the motors now.