Need Help!- "motor steps per resolution" and "driver microstepping" settings

[margni74]

Hi Again folks,

background: I'm running small servo motors with US digital E2-250-250 encoders
250 CPR/ 1000 PPR driven by gecko 320/340 drives.

1) Thus far I've set the microstepping to 1.0 on all axis, but this was just a guess on my part. What should the true setting be? Isn't this more of a stepper specific setting?

2) "Motor steps per Revolution" I currently have it set to 1000.0 (I guessed that I should be using the PPR of 4xCPR). Im not sure if i should be using the CPR or PPR number?

things have been working pretty decently on the machine, however I havent brought out the calipers yet to really check my accuracy. I just know the machine seems to move the right distance and things arent totally out of proportion


thanks again.

[Zig]

Servo motors ..no microstepping set it to one ( 1)
If Your shaft encoder generates 1000 pulses per revolution and it outputs a quadrature signal then Your driver ought to be able to resolve 4000 distinct points around the circle.
I guess You are using step/direction to drive the servo then it is equivalent to a stepper with 4000 steps per rev. I think You are using an encoder with 250 pulses in quadrature, treat it like a stepper with 1000 steps per rev.

[margni74]

Originally Posted by Zig Servo motors ..no microstepping set it to one ( 1) If Your shaft encoder generates 1000 pulses per revolution and it outputs a quadrature signal then Your driver ought to be able to resolve 4000 distinct points around the circle. I guess You are using step/direction to drive the servo then it is equivalent to a stepper with 4000 steps per rev. I think You are using an encoder with 250 pulses in quadrature, treat it like a stepper with 1000 steps per rev.

It's a gecko 320 that sends direction and step outputs... so is it 4000 steps/rev or 1000 steps per rev? It is an encoder with 250 pulses in quadrature, that's what the us digital specification says.

I guess if all other things are correct I could always try both settings and see which one drives the axis the correct distance.

[Zig]

Encoder produces 250 steps in quadrature this implies 1000 resolvable points per turn. So set it to 1000 pulses per turn.

Quadrature is a term which in general refers to a phase relationship between two signals meaning they are 90 degrees or a quadrant of a full period of the wave form apart ( either leading or lagging).

As a result of this relationship You can identify 4 distinct statesof the two signals.

[cwaugs]

I thought the setting is in counts/inch of actual cutting tool movement for servo motors? What good would counts per turn do as the software has no clue whatsoever as to the gear reduction of the motor to the ballscrew, or if direct drive it has no clue as to the turns/inch of the screw itself. My Mill comes out to approx 35000 encoder pulses/inch using 1000 line/turn encoders times 4 times the 1.5 reduction of the drive X the ballscrew turns/inch. HTH Wayne

[Zig]

We are talking EMC2 as the control software are we not?

[chester88]

cwaugs

Stepconf (for EMC2) asks you for the information separately.
motor steps per rev
micro steps multiplication
gear reduction
and thread lead.
Then it calculates steps per inch or per mm

BTW setting the microstepping setting to 1 means there is no microstepping.

[Zig]

Chester,

Thanks for the post. The purpose of asking whether we are talking EMC was to point out the components as You have done so aptly.

[cwaugs]

My bad, I was just tryin to help, and have never used EMC2. I back out quietly with my size 11 shoe in my mouth Note to self. Always look what forum you are in before opening your mouth. (I was using the search engine to locate information and stumbled in on this post)

[Zig]

Size 11? You are lucky.. Mine are 9 1/2 double E ( extra wide) go off like a champaigne bottle when extracted.