[hpoon]

Hi all,

I've got a slight issue with one of my axes and I was hoping to see if I could get some help here. Any advice would be greatly appreciated. I've got a problem where my stepper motor stalls. Current spikes up to about 1.5A and I hear a loud rattling, but the ball nut goes nowhere.

A pic of my setup:

http://www.cnczone.com/forums/attach...d=359902&stc=1

http://www.cnczone.com/forums/attach...d=359904&stc=1

Stepper motor info:
Rated current: 1.7A
Winding inductance: 3mH
Rotor inertia: 51gcm^2
Bench supply voltage: 24V

Ball screw info:
Diameter: 16mm
Pitch: 5mm

Software:
Arduino + gShield running grbl 0.9

From what I understand, a stepper motor with these specs should be able to drive this ball screw with no load rather easily.

Things I've tried
- Replacing the ball screw
- Checking sections of the ball screw to see if there are sections with more friction (letting it stall and then manually rotating the screw to see if there are rough patches) - but there seems to be no consistent position where the ball nut gets stuck
- Reducing feed speed (tried speeds ranging from 250mm/min to 500mm/min)
- Loosening up the assembly (to give room for components to move around slightly in case of some over constraints)

Not quite sure what to do here at this point.


PS: please move if this is in the wrong sub.

[1stPrototype]

Hi all,

I've got a slight issue with one of my axes and I was hoping to see if I could get some help here. Any advice would be greatly appreciated. I've got a problem where my stepper motor stalls. Current spikes up to about 1.5A and I hear a loud rattling, but the ball nut goes nowhere.

A pic of my setup:

http://www.cnczone.com/forums/attach...d=359902&stc=1

http://www.cnczone.com/forums/attach...d=359904&stc=1

Stepper motor info:
Rated current: 1.7A
Winding inductance: 3mH
Rotor inertia: 51gcm^2
Bench supply voltage: 24V

Ball screw info:
Diameter: 16mm
Pitch: 5mm

Software:
Arduino + gShield running grbl 0.9

From what I understand, a stepper motor with these specs should be able to drive this ball screw with no load rather easily.

Things I've tried
- Replacing the ball screw
- Checking sections of the ball screw to see if there are sections with more friction (letting it stall and then manually rotating the screw to see if there are rough patches) - but there seems to be no consistent position where the ball nut gets stuck
- Reducing feed speed (tried speeds ranging from 250mm/min to 500mm/min)
- Loosening up the assembly (to give room for components to move around slightly in case of some over constraints)

Not quite sure what to do here at this point.


PS: please move if this is in the wrong sub.

You probably need to adjust motor driver timings for parameters of step length, step space, direction hold and direction setup.

Sent from my SM-G900V using Tapatalk

[hpoon]

Since I'm using grbl, the only configuration values (https://github.com/grbl/grbl/wiki/Co...#grbl-settings) that I see are relevant are:
- Step pulse, microseconds (10 microsec) - I played with this (tried like 100 microsec), but I'm not sure what to set it to for my driver (DRV8818)
- Step idle delay, msec (25 millis) - Seems like a long time - I didn't mess with this
- [X,Y,Z] steps/mm - 200 steps per rev * 2x microstepping / 5mm pitch = 80 - this setting I had already set and thought was all I needed
- [X,Y,Z] Acceleration, mm/sec^2 (10 mm/s^2) - I tried setting this to 2.5 mm/s^2, which didn't help

Thoughts?

[Biggs427]

Have you tried with the stepper unattached to the ballscrew?

[hpoon]

Ahh good catch. I just tried it and it stalled the same way. I think you nailed the problem on the head. I tried running that stepper motor with nothing attached to it, and it makes a super loud noise as it runs and then stalls sometimes. I tried out a different motor and it ran smoothly and much quieter. I guess that stepper motor may as well be trash right now

Thanks a lot!

[1stPrototype]

Page 6 of the driver guide has the timings you need to translate.

DRV8818 2.5A Bipolar Stepper Motor Driver with On-Chip 1/8 Microstepping Indexer (Step/Dir Ctrl) | TI.com

For instance, your step pulse duration appears to be 1 microsecond.

Sent from my SM-G900V using Tapatalk

[KH0UJ]

The stepper motor on your picture is huge, if you want to use that kind of motor in an arduino shield, you need another driver on that motor with a separate power supply.