Acorn + Clearpath success stories?

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Gary Campbell
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Re: Acorn + Clearpath success stories?

Post by Gary Campbell »

When shipped, due to using <10 cables, these machines did not have the resistors, or for that matter, any issues. The error did creep in after a number of months. Resistors and an EMI filter on the VFD power seems to have solved the issue.

That said, I am curious as to the actual cause, especially as it relates to not being present during setup and testing but occuring at a later date.
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Re: Acorn + Clearpath success stories?

Post by Gary Campbell »

Is it possible that the actual outputs from acorn are being effected due to noise in the cabinet? Possibly in a way that only clearpath servos are sensitive to?
Here is the way that it goes:. The motor mfgr, the control mfgr, and the control mfgr all assume and profess that nothing is wrong with their respective product. Most likely true.

Eventually, someone with a scope will hunt the issue down and define it. Or, we already have the cure.
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Re: Acorn + Clearpath success stories?

Post by Dave_C »

Question:

At one one time were we not told to use 1K ohm resistors? [Page 47 of the Clearpath manual] Now I see they are saying 10K Ohm resistors.

Edit: I'm using the SDHP series, not the "stepper Killer" version.

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Re: Acorn + Clearpath success stories?

Post by carboncymbal »

Dave_C wrote: Fri Feb 19, 2021 2:53 pm Question:

At one one time were we not told to use 1K ohm resistors? [Page 47 of the Clearpath manual] Now I see they are saying 10K Ohm resistors.

Edit: I'm using the SDHP series, not the "stepper Killer" version.

Dave C.
Yes, that is true about the current manual. I have seen other posts by Teknic where it seemed they chose a 10k resistor based on a 24v operating voltage. I’m assuming lower resistor value was selected for a 5v system. I’m just reading between the lines here. Maybe Teknic will clarify.
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Re: Acorn + Clearpath success stories?

Post by martyscncgarage »

carboncymbal wrote: Fri Feb 19, 2021 3:51 pm
Dave_C wrote: Fri Feb 19, 2021 2:53 pm Question:

At one one time were we not told to use 1K ohm resistors? [Page 47 of the Clearpath manual] Now I see they are saying 10K Ohm resistors.

Edit: I'm using the SDHP series, not the "stepper Killer" version.

Dave C.
Yes, that is true about the current manual. I have seen other posts by Teknic where it seemed they chose a 10k resistor based on a 24v operating voltage. I’m assuming lower resistor value was selected for a 5v system. I’m just reading between the lines here. Maybe Teknic will clarify.
10K ohm resistor = 24VDC

So +24VDC to 10k ohm resistor. Other end of resistor to Step Header
They are recommending same for DIR header.

Hopefully within the next few weeks CNC4PC will have a board with terminals.
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Re: Acorn + Clearpath success stories?

Post by jpmsteadi »

Just to chime in here with a success story: I did an install of clearpath SHDK NEMA34 servos on my PM-728VT conversion and it went smooth as silk. The motors are for sure overpowered in this setup, but its nice to know there won't be any issues with them. Getting 3000 mm/min rapids on all axis and I am sure I could push it higher, but don't really want to on ways. Have yet to loose a step anywhere. If anyone has any questions on how stuff was wired or whatnot please don't hesitate to reach out!
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Re: Acorn + Clearpath success stories?

Post by teknic_servo »

slodat wrote: Thu Feb 18, 2021 10:23 pm Tom - then why not use the 5v DB25 step/direction outputs on Acorn?
This should work well but has not been tested by Teknic. But as Gary mentioned, driven 5VDC signals are less susceptable to the step timing error that open collector.
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Re: Acorn + Clearpath success stories?

Post by teknic_servo »

Gary Campbell wrote: Fri Feb 19, 2021 10:56 am
The ClearPath motor inputs are optically isolated and current limited. This design provides exceptional noise immunity even in the most difficult EMI environments like plasma CNC machines and applications that use a VFD.
I have 2 instances in the field where the "Step Input Timing Error" does not occur when the VFD is powered down. (Delta VFD & low rpm motor)
The optical isolation hardware of the ClearPath motors provide enough noise immunity that shielded and twisted pair cables between the CNC motion controller and the ClearPath motor are not required.
Yet the Teknic supplied control wiring is now appears to be twisted pair
Gary,
It is true that there are two twisted pairs in the Teknic controller cables. These twisted pairs were not implemented for the SD series of ClearPath most often used on CNC machines. The twisted pairs were implemented for the SC (software control) series of ClearPath motors because of the high frequency of data transmission required (much higher data transmission than with the SD series). Rather than have two different sets of controller cables, we just offer one set of cables that can be used with all ClearPath series (SC, MC, and SD).
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Re: Acorn + Clearpath success stories?

Post by teknic_servo »

carboncymbal wrote: Fri Feb 19, 2021 11:29 am
Gary Campbell wrote: Fri Feb 19, 2021 10:56 am
The ClearPath motor inputs are optically isolated and current limited. This design provides exceptional noise immunity even in the most difficult EMI environments like plasma CNC machines and applications that use a VFD.
I have 2 instances in the field where the "Step Input Timing Error" does not occur when the VFD is powered down. (Delta VFD & low rpm motor)
The optical isolation hardware of the ClearPath motors provide enough noise immunity that shielded and twisted pair cables between the CNC motion controller and the ClearPath motor are not required.
Yet the Teknic supplied control wiring is now appears to be twisted pair
I’m curious about this as well. Do those panels have the recommended pull up resistors installed?

This mirrors some of my experience. I had no issues at all with timing errors (without resistors ) until I ran the VFD at low frequency. High frequency (say, above 120 hz) had no issues and VFD off had no issues. But immediate issues at 30hz. I installed the resistors and had the same issue. Then I added ferrites to the VFD output and the issue was fixed. (These tests were done before I decided to tear the panel down and rebuild)

From this I arrived at my possibly over engineered approach when I rebuilt the panel. Resistors, EMI power filters on all power supplies and VFD, zero phase reactor for the VFD output, and a load reactor on the VFD output output, and Shielded twisted pair wires with proper drain.

So far with limited testing it is working without issue. Time will tell if the issue is resolved.

There was one user of here who converted a boring machine. He said that twisted pair, shielded cable resolved his issue, and didn’t use resistors.

Something doesn’t add up it seems to me. Even with all of the suggested countermeasures suggested above, it seems
Some people still have issues with A VFD causing I put timing errors.

"Is it possible that the actual outputs from acorn are being effected due to noise in the cabinet? Possibly in a way that only clearpath servos are sensitive to?"
Clay,
Yes, this is the most likely reason. Most servo systems are susceptible to emitted EMI noise sent through the air. That it why shielded, twisted pair cabling is required for most systems. This emitted EMI does not have a lot of energy (i.e. current) but does have significant voltage.

The optically isolated, current limited I/O for the ClearPath motors are designed to operate based on current versus the standard approach of voltage. So EMI noise that is sent through the air that gets onto the controller cables of the ClearPath motors is not "seen" by the motors even if they are not shielded or twisted pair. This is called noise immunity.

That said, if EMI gets to the conttoller and a signal is sent by the controller to the ClearPath motor that violates the step timing minimum requirement of 715ns, you will get a step timing error. So the motor is noise immune, but it can't make the controller noise immune. Hope that helps.
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Re: Acorn + Clearpath success stories?

Post by teknic_servo »

Dave_C wrote: Fri Feb 19, 2021 2:53 pm Question:

At one one time were we not told to use 1K ohm resistors? [Page 47 of the Clearpath manual] Now I see they are saying 10K Ohm resistors.

Edit: I'm using the SDHP series, not the "stepper Killer" version.

Dave C.
Dave,

The ClearPath manual is being updated this week with the following information:

* Use 1k ohm resisitors for 5VDC and 10k ohm resisitors with 24VDC
* The Step Input Timing error is being added to the Blink Code chart starting on page 156.

Thanks,
Tom T
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