Random weird feedhold

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cwatson1982
Posts: 10
Joined: Tue Jun 02, 2020 11:14 pm

Random weird feedhold

Post by cwatson1982 » Sat Jun 27, 2020 1:37 am

So I finally got my post processor up to speed and was running my first real job today. After a couple of hours of running, I got a feedhold in the middle of an operation. I could not turn it off via click. So I stopped the job, checked the console and saw nothing. I tried to restart the job and could not get the spindle to turn on CW, it would turn on CCW.

After going in to kmotion and hitting Zero on the spindle axis in the step response screen I was able to get everything going again. This happened twice over the duration of the job.

Any idea where I could look? I'm running the newest version (4.35B). Spindle is set up as a servo.

I also have a similar issue where all of a sudden my Z axis will only move at extremely slow speeds. Re-running my init program allows it to move regularly again. I thought maybe it was soft limit related but no axis was very close to the limits.

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TomKerekes
Posts: 947
Joined: Mon Dec 04, 2017 1:49 am

Re: Random weird feedhold

Post by TomKerekes » Sat Jun 27, 2020 3:47 pm

Hi cwatson,
So I finally got my post processor up to speed and was running my first real job today. After a couple of hours of running, I got a feedhold in the middle of an operation. I could not turn it off via click. So I stopped the job, checked the console and saw nothing. I tried to restart the job and could not get the spindle to turn on CW, it would turn on CCW.

After going in to kmotion and hitting Zero on the spindle axis in the step response screen I was able to get everything going again. This happened twice over the duration of the job.
That sounds like a Soft Limit Condition. What are your Soft Limits set to? I would expect a couple hours of running the Spindle to accumulate about a billion counts. What does the KMotion Axis Screen show? They should be disabled by setting to +/- 1e30.

I also have a similar issue where all of a sudden my Z axis will only move at extremely slow speeds. Re-running my init program allows it to move regularly again. I thought maybe it was soft limit related but no axis was very close to the limits.
When something like this happens to troubleshoot think of motion as a chain of operations that must work correctly to achieve the desired result. Then try to determine which operations are working correctly. ie some Speed is commanded, this generates a trajectory, the servo attempts to follow the trajectory, which commands some output, the output creates a DAC voltage, which drives the amplifier, which drives the motor, which moves the axis. If you have a small Max Following Error setting and you aren't seeing an error and axis disabled, then the problem must be something causing a slow trajectory. Which axes are defined in the Coordinated Motion System?
Regards,

Tom Kerekes
Dynomotion, Inc.

cwatson1982
Posts: 10
Joined: Tue Jun 02, 2020 11:14 pm

Re: Random weird feedhold

Post by cwatson1982 » Sun Jun 28, 2020 2:23 am

Thanks! It looks like the soft limits were in fact the issue with the spindle. I had them set at +-1e+09, I changed them and ran the job again in the air with no issues.

The Z axis I will have to monitor and see if I can get the problem to repeat. The max following error is 400 counts for that axis or about .005" When I say it starts moving slowly I mean at about .01 IPM regardless of the commanded feed rate :) I wrote a quick app to monitor and keep track of max following error and when it does this the error is never more than 1 count.
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TomKerekes
Posts: 947
Joined: Mon Dec 04, 2017 1:49 am

Re: Random weird feedhold

Post by TomKerekes » Sun Jun 28, 2020 11:15 pm

Hi cwatson,
The Z axis I will have to monitor and see if I can get the problem to repeat. The max following error is 400 counts for that axis or about .005" When I say it starts moving slowly I mean at about .01 IPM regardless of the commanded feed rate :)
That would indicate the Software is commanding that slow speed for some reason.

I don't see anything unusual in the Initialization Program other than a lower case 'c' in ClearBit which makes it not compile.
Regards,

Tom Kerekes
Dynomotion, Inc.

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