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need help with pitch calibration

04 May 2016 02:37 #74208 by Bradmillikan
Hi all,
Im new here and have searched for an answer but cant seem to figure this one out. So here goes. When I setup my machine in stepconf I can't get the axis to travel the right distance. I have nema 23 motors with 1.8 dgrees 200 steps. Im using st-m5045 drivers. The driver is set to move in half steps which gives me 400 pulses. Im also using a 1/4" by 20 lead screw at .05 pitch. The following is my setup.

Motor steps per revolution 400 ( I have used 200 )
Driver Microstepping 2
Pulley teeth 1:1 ( no pulley)
Lead screw pitch .05 (1/4"-20 rod)

Everything runs smooth I just cant get it calibrated properly . I can change the pitch and gear ratio around and can get close to moving the actual measured distance but I should be able to get it work by just putting in the numbers. Any help would be greatly appreciated.

04 May 2016 10:46 #74214 by andypugh
It should work with 200 steps / x2 microstepping and 0.05 pitch.

If you are not a simple factor of 2 out then something else is going on.

Are you 100% sure that your screw is not M6 x 1 ? (ie 25.4 tpi, 0.03937" pitch)

Does the error change if you halve the speed and accel numbers? Is it possible that a coupling is slipping?
04 May 2016 19:51 #74243 by Bradmillikan
So my lead screw is for sure 1/4"-20. Pitch should be .05. I did some research after posting on forum. I know for sure that these settings are right and even tried them on Mach 3. The total steps should be 8000 per inch. What's happening now though, I test it to move .5 inch it's actually 1 inch. Spot on. So I changed microstep to 1. Now it's exact but my total is half at 4000 per in. It should t be this way. The math works out to 8000. I added a snapshot of the stepconf from Linuxcnc manual. My setup is exact. Like I said though I have to change microstep to one to make it work.
04 May 2016 21:17 #74245 by andypugh
What number do you end up with in the INI file when it is working properly?
05 May 2016 00:50 #74250 by Bradmillikan
I am using 1 for micro step so 4000 is what it shows. If I change that to two it goes to 8000.
05 May 2016 09:24 #74258 by cncbasher
you dont mention what stepper drivers you are using ? some default to Half step as minium
the figure that matters is the final scale value in each axis in your ini file , not what you enter into stepconfig
i'll guess it's more to do with your drivers , just leave them at half step and enter the scale value in your ini file by hand
so long as it moves the correct distance your fine .
05 May 2016 16:30 #74280 by Bradmillikan
st-m5045 Driver by sainsmart
Set at 2 microsteps=1/2 steps at 400 pulses

All settings in ini file are same as stepconf.

The thing I'm stumped about is that these same settings work in mach3.
10 May 2016 03:33 #74430 by Bradmillikan
So I finally have this one figured out. I thought I would post it so I can maybe help someone else in the future. So when I put all my settings in stepconf and test in stepconf the actual scale is doubled when I measure it. The ini file is exact settings. So I finally gave it a whirl in linuxcnc and what do you know it all works out right with the scale. So the problem is with stepconf , it doubles when it runs. It sets it up fine in ini file . So you have to actual test your results in Linux Cnc , the stepconf file is useless for testing for acurracy.

Thanks for your posts and help, I hope someone finds this usefull
11 Nov 2016 19:56 #82706 by SenorAguas
I noticed this, as well, just yesterday, when I hooked up a dial indicator/mag base and tried to verify my calibration in stepconf.
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