Acorn + Clearpath = Step input timing error

Hi,

Completely unsure where to put this as I am not sure exactly where the issue lays.... I have built a DIY cnc machine that somewhere along the way became much larger and more expensive than a first time builder should have done.
The unit is about 1.8m x 2m using clearpath SDSK motors and running an Centroid Acorn control board.

My issue is the Z axis constantly reporting motor trouble and faulting out, the cable is 6m long shielded and designed for servo systems. The motor reports [error 73: Step Input Timing Error]
I have checked the cable at both ends and replaced the connectors, I have had an earth rod installed at the shed and run new ground wire with a star point ground in the machine. I only receive this error on this cable, none of the others.
I get the error when acorn is running at 100k, 200k and 400k pulses a second.
The motor has been disconnected from any load, no change in error.
The error happens randomly, BUT if I connect the cable shielding to the ground plate the fault happens within a few seconds. I have checked the cable lines and the shield, there are no shorts on any of them.

The VFD is not even powered on, so no noise from that.

I realize that I am rambling and much of this probably won't help, I am just clutching at straws as I have been trying to fix this issue for a month now by myself and had very little luck.

I appreciate any and all help or insights that are provided.

Daniel.

Try to run the motor with the Y axis cable to see if the motor faults out. Also, take a look at the motor setup again. Can you run the motor from the setup program with the USB cable?

If you made the signal cable, is it possible that the step and direction inputs are inverted? Input A is direction and input B is step as I recall.

Are the returns on both of the inputs properly connected?

You should probably post your question over at the Acorn help forum over at Centroid. They have knowledgeable people there ready to help. You will likely get an answer fast there. Make sure you read the post on how to ask for help. They will want some specific information in your first post.

My guess is the Z motor is overloaded.

https://centroidcncforum.com/viewfor...9fe6e4e1248a17

Quote:

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Originally Posted by De-Evolution

Hi,

Completely unsure where to put this as I am not sure exactly where the issue lays.... I have built a DIY cnc machine that somewhere along the way became much larger and more expensive than a first time builder should have done.
The unit is about 1.8m x 2m using clearpath SDSK motors and running an Centroid Acorn control board.

My issue is the Z axis constantly reporting motor trouble and faulting out, the cable is 6m long shielded and designed for servo systems. The motor reports [error 73: Step Input Timing Error]
I have checked the cable at both ends and replaced the connectors, I have had an earth rod installed at the shed and run new ground wire with a star point ground in the machine. I only receive this error on this cable, none of the others.
I get the error when acorn is running at 100k, 200k and 400k pulses a second.
The motor has been disconnected from any load, no change in error.
The error happens randomly, BUT if I connect the cable shielding to the ground plate the fault happens within a few seconds. I have checked the cable lines and the shield, there are no shorts on any of them.

The VFD is not even powered on, so no noise from that.

I realize that I am rambling and much of this probably won't help, I am just clutching at straws as I have been trying to fix this issue for a month now by myself and had very little luck.

I appreciate any and all help or insights that are provided.

Daniel.

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Hi Daniel,

I'm sorry to hear that there are some issues with one of your machine axes. Hopefully I can provide some helpful information for troubleshooting further.

I believe that you may have sent in a contact request and had another Teknic engineer reach out to you, but I figured it'd be helpful to respond to your post here as well (in case others are experiencing something similar).

The ClearPath motor inputs are optically isolated inputs and we have many customers who regularly use ClearPath in noisy applications such as plasma machines and laser cutting applications.

A step input timing error in a ClearPath motor is caused when the motor detects electrical noise on the step input. Generally this error is caused by one of the following:

-The controller is outputting less than 4VDC and is unable to reliably turn on the ClearPath motor's optically isolated input.

-The controller uses open collector outputs and the resistor specified in the ClearPath manual (link) is not installed correctly. Generally this will only affect machines with cable runs longer than 10ft, however, in applications with a large amount of electrical noise (such as plasma cutting applications), the resistors may be needed on shorter cable runs. The Acorn uses 24VDC open collector outputs, so 10Kohm resistors across the Step outputs and Direction outputs would be appropriate.

-The Controller's maximum step pulse frequency is higher than 700kHz or the minimum step pulse time is less than 715 nS (link). These settings are typically configurable in the controller.

-The wiring to the ClearPath inputs does not maintain a separate signal pair for the step and direction signals between the motor and controller. Sometimes this can happen when a controller doesn't have enough connections for V+ and GND.

I hope that this information (along with any information as a result of your contact request) is helpful for finding the source of the error. If you have any other questions, please feel free to use the "Contact Us' form again (https://www.teknic.com/contact) or give us a call at 585-784-7454.

Best,
Bridgette G. - Teknic Servo Systems Engineer

Thank you for all the feedback.

Problem solved with the bigger pull up resistor mentioned above, the unit performed a twelve hour test cycle last night without faulting.... I could seriously hug you!
Now I need to put everything back together after tearing the machine apart trying to fix it, and obviously post it on the forums.

Stay safe and thank you.

Daniel.

I’m having the same issue, although I used 1k resistors as shown in the SDSK manual. Would changing to 10k as Bridgette suggested make a difference? OP mentioned a “bigger pull up resistor” which tells me he may have already tried the 1k.

Glad to hear and see that the setup worked for you and the support here from Teknic.

I had an issue with teknic motors that were setup a little like clearpaths, in that the drives were on the machine but not right at the motor....and I had a 3 year nightmare of tracing a phantom step generator. (it was the power cable for the hsd cooling fan with an intermittent short). So, suffice to say I am not a fan of a clearpath type motor.

I'm still not, but glad to hear the shielding and brains are designed for such issues.