Motorsizes?

[Chris600]

Hello!

I am completely new to this world. I have a mill like BF20 ( I think its called). I have read a lot online of converting this mill to CNC. So I will now start to order parts for this build. The plan is to use Nema Steppermotors with "directdrive" for the X and Y axis. And mayby a bigger steppermotor with gear/belt for the Z axis. I will also change to ballscrews on all axis.

So now to my first questions. I have found kits on ebay with 3pcs of Nema 23 ( 3.0 Nm) inkl. powersuplly and drivers to a good price.

Does these Nema 23 motors fits for the job on all axis?
Is it better to have a directdrive also on Z axis with a bigger motor or use the same Nema 23 with gears/belt?

All other inputs are also welcome. I plan to use Mach3 on my old desktop computer to run this. I am using autocad already for drawings so I will use that and then lazymill to convert to G-code.

[Fastest1]

In my experiences 23's work fine direct drive. I do run a 34 on the Z. What kit on Ebay?

[Chris600]

These kits I have looked at

3 Axis CNC Kit 425oz.in Nema 23 Stepper Motor & Driver CNC Mill Router Lathe | eBay

【UK Stock】USB 3 Axis Nema23 Stepper Motor 425 oz-in 3A Dual Shaft+Driver CNC Kit | eBay

[abfa9358]

Hi
I have converted two mills, a minimill X2 and an Optimum BF30.

Using stepper motors is balancing act that really requires an idea of what feed rates you need on each axis.

My experience (hobby use) - using HSS tooling for steel / Ali / brass most cuts performed at 2" - 10" ipm. Rapid movements limited to 20ipm for safety.
I have always used direct drive to ball screws. The X2 used nema 23 motors to BF30 uses nema34 motors.

I suspect that the nema23 setup will be ok as long as you don't want very high feed rates. Remember that using belt reduction for more torque means that the stepper is turning faster for the same feed rate - the stepper motor looses torque at high rpm so you can chase your tail.

I used md542 drives but upgraded to Gecko drives - much smoother operation + ability to handle up to 80V. My motors run at 50v.

Personally, I would recommend LinuxCnc as the machine controller rather than Mach3. I won't go in to the pros / cons but I found it interesting to see that Tormach have moved to LinuxCnc as their machine controller.

Here's a link to my BF30 conversion...
http://www.cnczone.com/forums/benchtop-machines/107594-cnc-cad.html

[Chris600]

Hi
I have converted two mills, a minimill X2 and an Optimum BF30.

Using stepper motors is balancing act that really requires an idea of what feed rates you need on each axis.

My experience (hobby use) - using HSS tooling for steel / Ali / brass most cuts performed at 2" - 10" ipm. Rapid movements limited to 20ipm for safety.
I have always used direct drive to ball screws. The X2 used nema 23 motors to BF30 uses nema34 motors.

I suspect that the nema23 setup will be ok as long as you don't want very high feed rates. Remember that using belt reduction for more torque means that the stepper is turning faster for the same feed rate - the stepper motor looses torque at high rpm so you can chase your tail.

I used md542 drives but upgraded to Gecko drives - much smoother operation + ability to handle up to 80V. My motors run at 50v.

Personally, I would recommend LinuxCnc as the machine controller rather than Mach3. I won't go in to the pros / cons but I found it interesting to see that Tormach have moved to LinuxCnc as their machine controller.

Here's a link to my BF30 conversion...
http://www.cnczone.com/forums/bencht...4-cnc-cad.html

Thanks for your input. I have to check out the LinuxCnc

[SCzEngrgGroup]

I suspect that the nema23 setup will be ok as long as you don't want very high feed rates.

Nonsense. Many years ago, I converted an X2 using 495 oz-in NEMA 23s. Rapids were 270 IPM on X/Y, and 150 IPM on Z, with no springs or counterweights, with zero reliability problems.

Proper motor selection is a matter of knowing how much torque your machine actually requires, and what performance targets you want to achieve. You have to do the measurements and calculations, rather than just picking components based on price or easy availability. Many of the "kits" on E-Bay and nothing but cr@p. The machine, motors and drivers all need to be selected and setup properly to get the best result. You need good, low-inductance motors, and good high-voltage drivers, with the supply voltage chosen based on the motor inductance, and the supply current chosen based on the motors needs. Too little voltage (or current), and you'll get reduced torque. Too much, and you'll do nothing but generate a lot of excess heat in the motors and drivers. Choosing larger motors on the theory that "more is always better" will, more often than not, yield a worse outcome, due to greater mass, inertia and inductance.

Regards,
Ray L.