X Controller Calibration Troubles

I recently tried my Xcontroller with one of my OpenBuilds Cbeam machines (8mm lead screw). I have my x controller set to 1/16 microsteps. Here are the motors are i am using http://openbuildspartstore.com/nema-23-stepper-motor-high-torque-series/. I have been just concentrating on setting the X Axis. $100=398.892. At this setting the machine is very accurate at going 1 inch at a time. If I jog to 20 inches I end up about 1/8 of inch too far (20.125) So, I’ve done the math over and over again and have recalibrated to $100=396.100. Here I am very accurate at jogging 20 inches, but when I jog 1inch, I come up short, around .980. What am I missing here? Are there motor settings that are not configured right to cause this? Thanks an advance for any input and help
Here are some of my other settings:


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What is your belt tension?

It’s not belt drive it’s 8mm lead screw drive

With a lead screw the discrepancy may be augmented by the precence of backlash.

Yes, granted.
Just thinking out loud - with microstepping how precise is the stepper rotor position really?

Backlash / uncalibrated steps per distance:
If the discrepancy is predictable, say 0.020" off per inch commanded and a 20" command yield 0.4" deviation (20x 0.020") then the steps need calibration. If for a 20" command a single 0.020" deviated is measured (same as for a 1") then it is most likely due to mechanical issues?

Numbers are not actual, only intent was to illustrate my point related to backlash or miscalibration of steps.

To be fair, after recalibration he is measuring a 0.020" error when jogging 1".
Yet when doing a full 20" jog he is “very accurate”. Real world :slight_smile:

If his calibration gave him .98" for each 1" jog (5" jog would measure say 4,9") then the calibration is off (software).
If his calibration gave him 0.98" for one inch, and also 0.020" for a full 20" travel then there is a mechanical issue at play (structural)

My point is, if there is a miscalibration (steps/inch issue) the deviation will accumulate. (He report 1/8" off before recalibration)
If there is backlash/mechanical slop the deviation will remain fairly constant.

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After using that excel calculator I’ve been able to get a lot closer on accuracy. Thank you for this tool. and yes now on my x axis I am with in .0007-.0009 when going 1"-6". As far as 20 inches I can only use a tape measure and can see that I am right on the mark with a .90mm bit. I will be making some cuts today to further test. Thank you for help. It seems to be operator failure of calibrating the machine correctly. I don’t think this was a backlash issue

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…yet… :stuck_out_tongue_winking_eye:

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Looks like @PhilJohnson is slacking a bit. I haven’t seen tears in a couple weeks.


Can I ask why you are converting to inches in the first place?

I find it bewildering that you would go through such a process, when mm is accurate and native.

Am I missing something?

5% of the world uses inches, 95% uses mm.

Accuracy is dependent on many things, it I think you understand what I meant.

If imperial measurement is the way to go, why does the manufacturer paying for this forum and web service sell their products in mm, but the software is only usable in imperial?

Surely, as I suspect well over 50% of their products are sold in the US, their machines and components should be sized in imperial?

Even US car manufacturers make in metric, nowadays.

The work needed to develop software to use imperial is significantly greater than that needed to develop in metric.

Anyway, I’m done. Not using this limited, jingoistic app. I’ll use something closer aligned to the twenty-first century.

Can you spell, “Troll?”

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