Messages

1

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 24, 2018, 03:54:32 PM »

Hi,

frankly, I didn't think about the "cable load" and also didn't pay much attention to frequency depending signal disturbance. I know that HF signals usually should be transmitted via coax cables, and for avoiding signal reflexions the wave impedance of the cable should match with the connected device. But I didn't use them because there aren't coax ribbon cables available (I took the best I could get: shielded (ribbon) cables) and I never heard that not using coax cables in applications like this caused problems. If so, most people (and even many companies) would be in real trouble. It sounds little overkill to me.
I only tried to prevent any interferences from happening.
As far as I can tell though, I don't have problems with the signals itself, otherwise I would probably see some really bad and more random behavior and it would occur at other tool paths (also very fast and small little corners), too, but it doesn't.
Nevertheless I'm gonna hook up an oscilloscope (as soon as I have my own) to the drive inputs in order to see if the signal level drops when the PoKeys is firing with commands :-D

Thanks for this interesting input!

2

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 23, 2018, 03:14:10 PM »

Yes, I understood that and agree with you that at these high frequencies usually coaxial cables should be used. I only use shielded cables, though. But I think it works just fine.
I thought you talked about external radio signals interfering with my control signals.
 
All cables in my electric cabinet are arranged in a way that signal and power cables are spatially divided from one another. I did the best I could for avoiding interferences and I think it's sufficient. I mean, I don't have any real disturbances or unpredictable movements. They always happen at the same code lines and all motors behave like that, the dual axis even synchronously. If they would be out of phase, the portal would change its orientation on the linear rails by little. But I let the Gcode run several times now and measured all angles between my axes afterwards. They didn't change a bit.

It get's a lot better though by increasing the speed and playing with different accelerations.

I don't there's a fast solution now, it's probably something that has to be worked out step by step. It could be everything. Next step is that I'll update my CAD/CAM solution the next days. I see a good chance that this could vanish this weird movement as Autodesk did some severe changes to their software.
I'll take note of every change I make on my machine in the future and check if anything has changed regarding this. If so, I'll let you know.

I want to thank you, Craig, for your time and your willingness to help. I really appreciate it, many thanks!

3

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 23, 2018, 11:49:17 AM »

There are no radio signals or similar in my basement.
I exclusively used shielded cables, both for power and signal.

Reducing the  step per revolution didn’t change anything except increasing the noise level and induction of vibrations.
I stay with it: for the most part it‘‘s the toolpath generation. The installed motors are quite big, this leads to a increased noise generation. If I wouldn‘t have heard it, I would not have noticed this at all. Probably I‘ll dampen the motors‘ screw joints by adding some rubber layers between, that should minimize the noise to level where I don‘t notice it at anymore.

4

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 21, 2018, 05:29:00 PM »

Hi,

at the moment microstepping is at 6400 per revolution. I‘ll reduce it to 3200 tomorrow for test purposes.
Initially I planned with 3200 microsteps because I‘m aware of step torque loss. But I found that there‘s still a little noise/vibration improvement with 6400 steps over 3200 steps.

The Pokeys should easily be able to handle the number of steps at the driven speed, it‘s not even in the top rate area. But I will reduce the microstepping furthermore, then we‘ll see, maybe there‘s indeed another transfer problem on the line

5

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 21, 2018, 12:36:23 PM »

Hi Craig,

you‘re absolutely right. In terms of increasing the accuracy that high number of steps/rev is total nonsense, since you loose quite a lot of step torque and probably will end up being less accurate. But this isn‘t my goal. I chose this specific motor because it has a lot of holding torque and I can increase the steps/rev in order to smooth the movements and reduce the induced vibrations but without sacrificing performance (by not falling below the required application torque with the step torque).
Nevertheless I‘ll give it a try and see if that‘s the problem‘s solution (I‘ve already cut it down by half). If so, I might dampen the vibrations of each motor with a rubber pad between motor and machine.

As a side note: I programmed all drivers with the dedicated software. There are some options that aren‘t accessible from the DIP switches. For example you‘re able to set even higher steps/rev than with switches. In fact I could set steps/rev exactly to 4000 if I wanted to.

BR

6

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 18, 2018, 04:17:56 PM »

The PoKeys57CNC runs with 5V logic level, I don‘t see a problem there.
I think that this behavior is caused by the toolpath itself, not any communication errors or something like that since those jumpy movements exclusively occur at 2D adaptive toolpaths of relatively similar geometries.

Thanks for your time and help!

7

Mach4 General Discussion / Re: Jerky dual axis movement

« on: April 09, 2018, 10:18:33 AM »

Hi Craig,

thanks for your help.

I'm using Leadshine Easy Servo ES-M23480 with the appropriate drivers ES-D1008.
They are configured to a 12800 steps per revolution. In combination with 10 mm pitch ball screws that's 1280 counts/steps per 1mm.
There is no gear reduction or similar involved, both ball screws are directly driven from the motors.

I don't think the problem is to less micro stepping. I initially thought it may come from too many step commands that Mach4 or the controller can't handle.
But I did all the calculations on it. And according to that there shouldn't be a problem. The PoKeys maximum step frequency is 125kHz, with 1280 steps per mm that leads to a maximum velocity of 5859 mm/s. I don't exceed this limit.

Did you listen to the audio file? What does is sound like to you? Does is it sound rather like a software or a hardware problem?
I already thought about loose couplings, but I tightened them as hard as I could and both couplings are quite oversized, they shouldn't have a problem to transmit the torque. And if they would slip, the axes wouldn't be square anymore, but they are.

In the end, I have no idea what's causing these problems and I'm glad for every help.

Best regards,
Yannik

8

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

9

Mach4 General Discussion / Re: Huge motion steps overflows

« on: April 25, 2017, 05:20:44 PM »

Thanks for your help, Keith.
Yes, I have the newest plugin and configured everything properly. First I connected the Pokeys via USB, but ultimately swapped it for Ethernet because I had some other connection problems.
I used my MacBook via Bootcamp but maybe that didn't work out quite well. I'm gonna switch to a native Windows PC and will report afterwards if the issues are still existent or vanished.
Thanks again, at least I have a starting point now!

10

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!