Closed loop stepper driver configuration help

I'm trying to get my PnCConf configurations dialed in for a closed-loop stepper driver that doesn't have much documentation. I've attached the manual for the drivers.I have a Nema 34 Servo Motor closed-loop 86EBP181ALC and a ZDM-2HA865 stepper driver. I know my ball screws have a lead of 5mm, but that's about all the info I can get for them. The Nema 34 has a 1.8° step angle, and the drivers say they are set to '16' on P001. I'm not sure what '16' means; I think it's 16 microsteps, but I'm not sure how many revolutions that is. The manual says it can be set to these options: 2, 4, 5, 8, 10, 16, 20, 25, 32, 40, 50, 64, 100, 128, 200, 256, with the maximum 256 subdivision being 51200 pulses per revolution.So far, here are my settings. They get me into the ballpark for movement accuracy, but I'm pretty sure they could use some fine-tuning/corrections.

• PnCConf
• Step on time: 5000
• Step space: 5000
• Direction hold: 10000
• Direction Setup: 10000
• Microstep Multiplication Factor: 16
• Leadscrew Metric Pitch: 5.000
• Motor Steps per revolution: 196
• Motor steps per unit: 627.2

Motor steps per revolution should be 200, not 196.
200x16=3200/5=steps per unit, or steps per mm in this case.
Make sure the screws are actually 5mm, as there are imperial ones at 5.08mm per turn.

They are definitely metric 5mm (from China). But I'm thinking the 16 might represent something different because setting Motor Steps per revolution to 200 makes it move too far, (or not enough, I can't remember).

I'll try setting it to 200 again and see if it makes a difference this time around.   

I set the motor steps per revolution to 200 and, yes I think it's the correct setting. The issue now is can the accuracy be increased via stepper settings or other configs ?

When I do a test cut, I get about +- 0.10 mm and I'm pretty sure it can do better. I've read about ball screw mapping, is there a guide or info on how to do this in LinuxCNC?

The machine's specs say the ball screws are this type ? There's not much info out there on this.
TBI C7 grade 2005-4

thanks again

Couple suggestions before you try to chase this down inside LCNC:

• Check the drive parameter P111
  • See if this is set to "1" as this sets the drive's internal positioning accuracy.  If it's not a "1", the drive will consider 'close enough' as acceptable.
• Check your ballscrew fixed bearings for end-play.  If you have C7 ballscrews it's possible (likley) the bearings have some slop or compliance.
  • Disconnect the motor and put an indicator on the free end of the ball screw.
  • Push the ballscrew back and forth and see if you've got some play.
• Same thing for ball-nut.  There may be some internal backlash in the ballnut.
• Same thing for ballscrew coupler.  See if it's rotationally stiff or if there's some spring/slop

A bit of play in the bearings, plus a bit in the nut, plus a bit in the coupler, plus some compliance in the whole machine, plus maybe a bit in the drive...

could all add up to 0.1mm of repeatability error.

Thanks, I'll give this a shot. if I do find that things are loose, what is the corrective action ? just tighten the screws or is there anything else that can be done ?

The driver's P111 setting is set to 1.