Pacific Scientific Driver/New Motor Issues

I'm fixing up a homebrew CNC router that was donated to me after it was dropped off of a forklift. One of the steppers was ruined and I replaced it with one that had slightly different ratings. As of right now, I have it working just enough that the axis can move at 90ipm, so I know that it's possible for this stepper/driver combination to work.

But it buzzes when you try to jog it, like it's having trouble getting started. Sometimes it will move in the direction specified, other times it will move in the opposite direction. When switching directions while in motion, sometimes it will switch, other times it will stop and keep going in the same direction. I've increased the Step Time, Step Space, Direction Hold, and Direction Setup settings in linuxCNC and this didn't help much at all. I wasn't really sure what I was doing there though, so was I missing something?

The only other thing I can think of is that the new stepper has four wires and I'm not sure if we put the coils in series or parallel. The old, damaged stepper motor specifically says bipolar parallel. Could the driver be choking because I accidentally wired the new stepper in series? The drivers are rated for 5.1a but the new stepper is rated for 5.5a per phase.

Here's a video if my explanation is a little confusing:


Your help is appreciated!

sounds more a config issue and missing steps

check the ballscrew for mechanical issues binding , stiffness etc . as you know the machine has been dropped
you should be able to move the axis with resonable ease the full length etc
just in case the screw is banana shaped . or displaced bearings or mounting plate

the rating of the motor is not a problem
but the wiring of the stepper may be , perhaps a coil is in the wrong phase in respect to the other
the timings should be the same if your using the origional drivers

intermittent turning the wrong way , could indicate a broken or damaged direction wire to the drives or poor connection
you may find using the motor with parallel windings is better , but beware of wiring them in the correct phase

the velocity and speed values may need to be different


hope this helps pin it down

I'm not sure why I wrote 4 wires... the stepper has 8 so i'll try a different wiring config on Friday and report back. The only way I've gotten it to move as "well" as it does now is by reducing the acceleration to a creep, and it'd be too slow to use even if it moved reliably.

I'm 99% sure the ballscrew is fine because it's easy to turn by hand when the stepper is powered off. There is a splice in the wires and they're only twisted together with tape for now so i'll bring wire nuts on Friday and see if those help

That makes sense. I think I have the wiring diagram for the motor on the datasheet so if i'm lucky it will be correct and I can skip to trying series wiring. I'm super excited since I haven't tried this before and if it works... oh man

Argh! I didn't get a chance to work on it on friday but I did today. And i wired the stepper coils in series - no change for the better! It spun slower but still have trouble starting up and didn't change directions reliable. I changed the base jitter period, and the other four timing variables to no avail. I even took the motor off of the machine and it still jiggles so I know it's an electronics issue. I set the stepper driver to full steps and it still would not turn right. I'm out of ideas.