X direction not changing consistently

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18 Dec 2021 21:58 - 18 Dec 2021 21:59 #229436 by robertjenkins
Hi
I've been retrofitting new stepper drivers to my Denford Micromill, and thought all was going well but now realise there is a problem with the X axis (and only that axis). It sometimes doesn't change direction when it should. Everything is OK with the HAL meter signals, and everything is OK with the signal as measured at the driver board (i.e. when I want it to be going in one direction, the signal the driver is getting is correct for that direction, but the actual direction the motor is going in sometimes isn't.) These are the drivers
www.cnc4you.co.uk/Stepper-Motor-Driver-4...Microstepping-CW5045
I attach the ini file 

File Attachment:

File Name: my-mill-ini.txt
File Size:2 KB
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Last edit: 18 Dec 2021 21:59 by robertjenkins. Reason: typo

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18 Dec 2021 22:21 #229439 by BigJohnT
Try increasing the Direction times for that axis.

JT

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18 Dec 2021 22:25 #229440 by tommylight
Does the X motor vibrate more than the others when running ? If yes, wrong motor wiring, power off everything and check the motor wiring.
Change the drive INPUTS fro Y to X, test again.
If that works ok, find something with "reset time" at the beginning of the .HAL file and change the value from 5000 to 10000, save, restart LinuxCNC and test after wiring stuff back.

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18 Dec 2021 22:25 #229441 by oldtech
I recently had the same issue. This may not be your solution, but I recommend that you double check your wiring, and in particular all connections, to your driver and from your driver to your stepper. In my case, I discovered that I was using bad connectors along with not being careful enough when using the screw connectors even though I had carefully checked for continuity and signal on all the lines. Being more careful with the screw connectors and replacing the connectors with Molex connectors fixed it.

Another possibility is EMI. Are you using shielded lines properly terminated?
The following user(s) said Thank You: tommylight, ikkuh

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19 Dec 2021 13:04 #229484 by robertjenkins
Thanks, that seems to have fixed it (although you have to change the time for all axes)

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20 Dec 2021 16:23 #229558 by robertjenkins
I spoke too soon. I had tested the axis from Stepconf, and it ran back and forward for a few hours without changing position.

But now it's doing the same as before, i.e. not consistently going in the right direction.

It also doesn't always respond to changes of direction from the keyboard

The same thing happens if I connect the stepper to a different driver. And the other steppers connected to the X driver run fine. So there is no problem with the driver, or the BOB. The only thing I can think of is that there is something wrong with the motor, or the wiring from the motor to the drivers. But I have checked and rechecked the wiring.

I know which the pairs are, and if I switch the polarity of one pair, the motor goes in the other direction. (If I switch the polarity of both pairs, it goes in the original direction)

The motor moves with no abormal sound or vibration, and at the right speed. It just doesn't always go in the right direction.

The cables from the drivers to the motor are shielded (and connected to ground at the motor end).

I am stumped.

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20 Dec 2021 21:44 #229576 by rodw
Your joints are missing these setting (don't use mine as they are too short, use 5000)

# these are in nanoseconds
DIRSETUP   = 500
DIRHOLD    = 500
STEPLEN    = 1000
STEPSPACE  = 1000
STEP_SCALE = 1000

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21 Dec 2021 18:24 #229639 by ikkuh

I recently had the same issue. This may not be your solution, but I recommend that you double check your wiring, and in particular all connections, to your driver and from your driver to your stepper. In my case, I discovered that I was using bad connectors along with not being careful enough when using the screw connectors even though I had carefully checked for continuity and signal on all the lines. Being more careful with the screw connectors and replacing the connectors with Molex connectors fixed it.

Another possibility is EMI. Are you using shielded lines properly terminated?

Exactly the same thing happened here last weekend. Took me a while to figure out but it was a bad connector on the z-axis. Seems to happen a lot.
 

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28 Dec 2021 18:27 #230157 by robertjenkins
Days later, and after changing both the stepper motor and the BOB, I tracked down the culprit. The wire carrying the +5V to the stepper driver had a hidden intermittent fracture inside it. Because it was intermittent, and because I was measuring the voltage on the step/dir terminals wrt 0V, it took me 10 days to discover it.

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