[Big_Al]

As a treat for #3 (CNC not wife!), I recently bought her a set of leadscrews and precision nuts from Lead Screws, Ball Screws, Shaft Couplings : ABSSAC Power Transmission from a very helpful guy called Phil who gave an excellent service and a bloody good price.

The lead screws were to replace the M8 all-thread rod on my latest hobby CNC router that I use for cutting ply and MDF. I drive this beastie from a fast PC using EMC2 on Ubuntu.



However my Z-axis is now stalling at all but the slowest speeds due to my hasty purchase. This will teach me (again) not to impulse buy, but of course it probably will not. Sigh!

So what should I do now? Upgrade the motors/drivers and PSU?

Forget all about CNC and take up crochet?

I have been looking forward to a much improved and faster #3 CNC router, but alas I made an ar$e of it, and not for the first time.

Instead of impulse buying yet again, I thought I would reach out for some advice from you generous guys.

I have learned from reading other posts that you like numbers:

Weight of Z-axis and spindle = 4.5kg

Existing Power supply = 30V at 2A

Current Motor Stats
Weedy Astrosyn Nema 23, MY103H702, wired Bi-Polar Parallel


Current Routout Driver Stats
2.5A Routout Driver Card set to quarter step

New Z axis, Lead Screw Stats
Thread = 5/16-8-4
Thread Diameter (inch) = 0.313 (7.95mm)
Threads per Inch = 8 (3.1mm Pitch)
Thread Starts = 4
Thread Type = stub acme
Thread Lead (inch) = 0.5000

I was thinking that I would need to replace the motors, drivers and PSU, and i was thinking of this kit from ZappAutomation;

"This CNC Driver kit is designed for 3 axis of stepper control (X, Y & Z)

This kit consists of the following:

1 X ZP5A-INT Breakout board

3 X 4.2A PM542 Microstepping Drivers

3 X 3 Nm SY60 Stepper motors

1 X EP002 - 43V, 500W regulated power supply"

Is that motor/driver/psu setup going to be up to the job?

I have about £250 to spend and would prefer to continue to use EMC2.

What would you propose I replace or reconfigure?

Thanks in advance, BigAl.
The Crapworks

[ger21]

How fast is it going now?

I believe that your Routout card is similar to the Xylotex that I use. I would expect you to be able to get pretty decent performance.
First thing I'd try is to change microstepping to 1/8. Then play with your acceleration settings and see if it makes any difference. You could be seeing resonance. If you have a double shaft stepper, a damper may help.

It's also very important that there's absolutely no binding anywhere. With power off you should be able to easily turn the screw with 2 fingers.

I think the simplest thing to do is try a new, slightly bigger motor, (1.75-2Nm). You'll also probably want to get at least a 5amp power supply.

[Big_Al]

Hi Gerry, Thanks for your reply. I changed to 1/8th step and slowed the Z down to 0.1 inch/sec.

I also changed a setting in EMC2, 'Driver Microstepping' was set at 2.0 for the previous configuration of half-stepping, but the only setting for this that would drive the motor when the jumpers on the driver card were set to 1/8th step was 1.0. To be completely honest, I don't know why this EMC2 setting would make a difference.

I have still to do some callibrating but so far it seems much better, but at any greater speed on the Z axis the motor stalls intermittently.

The x-axis is running at 0.5 inch/second with no apparent problems.

Do you think changing from Bi-polar Parallel to Bi-polar Series would make a difference here?

[RomanLini]

...
Do you think changing from Bi-polar Parallel to Bi-polar Series would make a difference here?

(That was directed at Ger21 but I will try to answer) - Changing from bipolar parallel to series won't help you, that change will only reduce the motors torque at high speed.

One thing that should help would be to switch to finer microstep setting, as quarter microsteps is pretty coarse and you are losing power in resonance.

Overall probably the best change would be to put some big motors on it and microstep at 16th usteps. Motors of about 300 to 400 oz-in are ideal, (much more overall torque) and with less inductance than your motors now (so more torque at higher speeds).

I didn't check the link you provided for the new motor kit but most of the suppliers offer a good choice of motors and drivers in the long Nema23 motors, torque 300-400 oz-in, low inductance and microstepping.