[steveo290]

Sorry about the poor title. I am not sure how to exactly describe my problem in one line.

I have recently converted a G0704 to CNC and am going through the alignment/calibration phase and doing motor tuning now. I am using the standard Nema 23 570oz 5A 3/8" shaft stepper motors for X and Y. I am using the MX3660 stepper driver and have both X and Y set to 1600 steps per rev. I am also using C7 grade ball screws with 5mm pitch (.508 TPI). Through my research I have found that I should be using 8128 steps per, which I am. I left the velocity at 120 and acceleration at 4, which were default.

Here is my problem. When moving a small distance in step mode, such as .001, the dial indicator will read .0015. Stepping again in the same direction the same amount will add another .002 for a total of .0035 when I only asked to move .002. I have tried this a number of times and keep getting non-uniform increments. But when I scale up to moving an inch or two it seems to work perfectly, using a tape measure taped to the bed for this part I know is not the best but I have compared the tape with a caliper too.

I have tried using the Mach3 wizard to determine my steps per as well. Having the wizard move .001 and reporting back that it moved .0015 the wizard suggest using something like 6600~. Using that number my axis will move .001 correctly but when I try to move an inch or so it will only move 3/4".

My ideas for why this is happening:
1. Dial indicator could be broke from me being a new guy and trying to push it farther than it wants to move. No specific instance in mind where this happened but it could have without me realizing it.
2. Acceleration or velocity values don't work at such low resolution.
3. I should not expect to get .001 resolution from my setup. I did not think this was the case though.

Any help would be much appreciated, thank you.
Steve

[jalessi]

Steve,

Calibrating across or between at least a six inch span will be much more accurate.

Hoss's calibration utility video will help explain the procedure in detail:

https://www.youtube.com/watch?v=ZAQHNYSYR2I


Jeff...