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Topics - cncnc

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1
Mach4 General Discussion / Jerky dual axis movement
« on: April 08, 2018, 04:28:55 PM »
Hi guys,

I have a problem with a jerky axis movement on my home built machine (with PoKeys 57CNC controller) and don't quite know where it comes from.
The only affected axis is the Y. It is a dual axis (two ball screws, two 8Nm closed loop steppers). Both bearings on the Y axis are quite preloaded but this shouldn't be a problem for the stepper motors.
During the milling cycle the Y axis starts to bang when it accelerates. At first I expected the worst, that both axis motors didn't move synchronously and the gantry is put under heavy stress. But turned out not to be the case, I measured the flatness of my X axis and it was just fine. If both Y motors would have moved different from one another, the gantry would bent. This shouldn't even happen though, because both stepper motors do have encoders and the same input signal. If they wouldn't move in sync, an alarm would be triggered.
So I watched both motors during a job and noticed that both seem to jerk simultaneously.
I don't think this comes from overload of the motors, they have plenty of power and in general they aren't equally strained during a job so a simultaneous jerking movement is quite unlikely.
Additionally these jerky movements don't appear when I jog the Y axis. This leads me to the assumption that there must be something wrong with Mach4 or the way I set it up.

I already thought this may come from too many steps per unit, but according to my calculations it should be ok and Mach4 (PoKeys plugin) didn't complain.
But I don't know how these step frequency calculations apply to a dual axis or when more than one axis is moving.

In order to give you an impression of what I mean I uploaded a short mp3 file where I face off my slot table. From 2,5 - 4 seconds you can clearly hear the banging of both motors in the background. AudioYaxismotors.m4a



I hope you have some ideas and can help me out!

Many thanks and best regards,
cncnc

2
PoKeys / Pokeys motion steps overflow
« on: April 24, 2017, 05:48:59 PM »
Hey there,

I already posted the following problem in another sub forum but I think this concerns the PoKeys side, too:

I was up to configure Mach4 for my CNC machine and hit on some troubles with "motion steps overflow".
As a controller I'm using a Pokeys57CNC v1.1 via Ethernet and the newest Mach4 version (no third party screen installed, just the Pokeys plugin).
As long as I ran just one axis everything was fine. But as soon as I drove two axes simultaneously and stopped at least one of them I went into some problems. By the moment I stop one of the two axes, Mach4 gives a fault alarm of motion "steps overflow". According to Mach4 the system is losing several hundreds or even up to a few thousand (!) steps. Sometimes even the stepper driver (Leadshine EM 806) gives an alarm signal back to Mach4 after stopping one Motor which I set up to trigger the emergency stop. This doesn't happen when starting the motors. I don't have a clue where this behavior comes from. First I thought the problem is maybe caused by too high back EMF which my power supply capacitor can't handle and which disturbes the control signals, but it seems not to be the actual number of driven motors but the number of driven axes (no matter how many motors are driven) because my Y axes is driven by two motors (slave mode via hardware, Mach4 doesn't know that Y is a dual motor axis).
Motor parameters are 500mm/s² acceleration and 10000 mm/min rapid speed, so nothing special here and according to my calculations it should be an ease for the pokeys to handle. This phanomena applies for both high and low speed.
I also recognized similar problems while incremental jogging. When I try to jog any axis with low speed (<5% of max) in 1mm steps in negative direction, it won't do anything. Error alarm "motion steps overflow (160)" (160 steps per 1mm) pops up. In the opposite, positive direction on the other hand jogging works perfectly fine.
Another minor problem which doesn't really apply for this topic is that I can't change the step size at incremental stepping. I have different values in the settings, but pushing the designated incremental step button won't change anything, it sticks at 1,000.

Any help and/or suggestions are very welcome, cheers!

3
Mach4 General Discussion / Huge motion steps overflows
« on: April 24, 2017, 03:45:17 PM »
Hey there,

I was up to configure Mach4 for my CNC machine and hit on some troubles with "motion steps overflow".
As a controller I'm using a Pokeys57CNC v1.1 via Ethernet and the newest Mach4 version (no third party screen installed, just the Pokeys plugin).
As long as I ran just one axis everything was fine. But as soon as I drove two axes simultaneously and stopped at least one of them I went into some problems. By the moment I stop one of the two axes, Mach4 gives a fault alarm of motion "steps overflow". According to Mach4 the system is losing several hundreds or even up to a few thousand (!) steps. Sometimes even the stepper driver (Leadshine EM 806) gives an alarm signal back to Mach4 after stopping one Motor which I set up to trigger the emergency stop. This doesn't happen when starting the motors. I don't have a clue where this behavior comes from. First I thought the problem is maybe caused by too high back EMF which my power supply capacitor can't handle and which disturbes the control signals, but it seems not to be the actual number of driven motors but the number of driven axes (no matter how many motors are driven) because my Y axes is driven by two motors (slave mode via hardware, Mach4 doesn't know that Y is a dual motor axis).
Motor parameters are 500mm/s² acceleration and 10000 mm/min rapid speed, so nothing special here and according to my calculations it should be an ease for the pokeys to handle. This phanomena applies for both high and low speed.
I also recognized similar problems while incremental jogging. When I try to jog any axis with low speed (<5% of max) in 1mm steps in negative direction, it won't do anything. Error alarm "motion steps overflow (160)" (160 steps per 1mm) pops up. In the opposite, positive direction on the other hand jogging works perfectly fine.
Another minor problem which doesn't really apply for this topic is that I can't change the step size at incremental stepping. I have different values in the settings, but pushing the designated incremental step button won't change anything, it sticks at 1,000.

Any help and/or suggestions are very welcome, cheers!

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