Ballscrew Comp 2nd & 3rd Attempts

[cnckeith]

you got to get steps per rev, overall turns ratio correct before doing any ballscrew mapping. mapping is the last thing you do.

.62625 is not the overall turns ratio of this machine.

some simple math show that you have the Clearpath MSP software set to 800 and by the report.zip i see you have CNC12 set to 6400(good)

the pitch of the screw is 5 turns per inch.

.62625 * (6400/800) = 5

so set things right by going to the MSP software and setting the clearpath motors to 6400

and then go change the Wizard Overall Turns ratio to 5 and perform the fine tuning axis calibration. (with screw table OFF!)

[cnckeith]

i found an old post from 2017 with some explanation and copied the text here it is

Centroid screw comp is taking care of two things, #1 is pitch errors of the screw in BOTH directions! as the pitch on each side of the screw can be and most likely is different (going one way the nut presses on one side of the threads and going the other way the nut press on the other side of the threads, which are different) and also backlash in the system on the turn-around. Moving .5" between measurement point gives a good reading of the pitch error. Also, backlash can come from several locations, most common are the screw nut to screw connection and more often and often more pronounced is the screw to machine tool connection made by the support bearings. For best screw comp results, its always a good idea to reduce backlash mechanically as much as possible from all sources starting with the screw support bearings (without adding drag!) and if your machine tool has an adjustable tension nut to minimize it there as well before running the screw comp measurements.

[adrewfis1980]

you got to get steps per rev, overall turns ratio correct before doing any ballscrew mapping. mapping is the last thing you do.

.62625 is not the overall turns ratio of this machine.

some simple math show that you have the Clearpath MSP software set to 800 and by the report.zip i see you have CNC12 set to 6400(good)

the pitch of the screw is 5 turns per inch.

.62625 * (6400/800) = 5

so set things right by going to the MSP software and setting the clearpath motors to 6400

and then go change the Wizard Overall Turns ratio to 5 and perform the fine tuning axis calibration. (with screw table OFF!)

Yes, I went back and changed the setting in the Clearpath MSP to 6400 after I saw it had been set to 800. I was able to get the overall turns ratio nailed down to .0000" at 1 inch and plan to do the ballscrew comp for at least the X & Y motor over the next day or two.

post a screen shot of your Clearpath MSP software settings.

See attached. I took this pic after I changed from 800 to 6400 so now the MSP and CNC12 matched at 6400.

[cnckeith]

ok progress.
prerequisites for screw comp is everything else must be perfect first!