[nickjb]

I have an old Pacer CNC router that has been modified to run with with Gecko and JVL drives. I'm having an issue with low torque on the Y axis. The motor is occasionally stalling when doing a fast move, but also a slight touch on the lead screw will stall it. Really, barely a fingertip pinch. This has a hefty Sigma stepper motor (Bean can sized), gecko G201 drive and a good sized toroidal transformer giving 40v so I'd expect a lot more torque. The Y axis has a JVL drive and moves the whole gantry and that one won't stall even with a very firm grab of the screw, as much as I can manage. Runs off the same power supply so I assume that is fine

I'm sure it used to be much torquier so seems like something has changed. Its all quite old admittedly, but don't want to just start changing parts. What can I look at to try and get to the bottom of it?

Only thing I have actually changed is the 5v power supply after the last one died. Maybe this dying has hurt the drivers but could that cause low torque, rather than not working at all?

Images of drive, motor and config:

Attachment 513490

Attachment 513492

Attachment 513494

[nickjb]

A bit of an update. I see these Gecko drivers have a resistor to set the current. It was a 20k limiting it to 2A. In the interests of science I swapped it for 68k which should take it up to 4A. Did a very quick test and it was way better. I could still stall it with a firm grab, but properly firm, loads more it was stalling at before. Anyone know what it should actually be set to? Best I can read the motor is a Pacific Scientific H33NRFS-LNN-NS-02 Sigma Stepping Motor but that only comes up with one eBay hit. I'm sure this motor must be good for more than 2A (and probably more than 4A) but don't really want to cook it without knowing the actual numbers.

Secondly its be fine for 10 years, the resistor hasn't changed. I wonder why I'm having issues now. I'm sure it never used to stall so easily.

[awerby]

Have you tried adjusting your acceleration settings? Sometimes it's not the velocity that causes stalling, but how quickly it ramps up to speed. Cut them in half, and see if anything changes.