Continual Intermittent 'Lost Sync' errors with PMDX-424 SmartBOB-IsoUSB on Mach4

[epoch80]

We have a PMDX-424 SmartBOB-IsoUSB with break out board.

We are having continual intermittent issues which show in Mach4 as below.

PMDX: Communication error 'Lost Sync'
PMDX: Communication status 'Sync'd to Device'

Communication seems to be lost and the re-gained straight away, but in that time our program is completely lost leaving us no option but to re-boot the entire machine, re-home and restart the program. Nightmare.

I have performed the following mitigation tips previously recommended via support.

Measure 1: Provide a common ground between the board and the PC - this was completed as instructed. 

Measure 2: Adding a magnetic ferrite filter - We added ferrites to both ends of a high quality shielded 50cm USB and installed conduit around the cable to further mitigate possible interference.

Measure 3: Replace 424 - We replaced the 424 as instructed.

Any insight anyone could offer us as to why we are continuing to receive this error would be appreciated.

[Walter]

From my research, your symptoms seem consistent with EMI noise.  Without knowing your whole setup, it is difficult to know for sure. Is there a condition or sequence of events that it always occur?  Does it occur when the spindle motor/VFD is off or on?

The biggest culprit for noise is the VFD.  It is advised to put an EMI filter between your main power supply and the inputs of your VFD to prevent noise from bleeding back to the power supply.  If your computer is on the same circuit as your VFD, then the noise can definitely reek havoc. 

The next thing is to be sure your shielding is grounded.  All signal carrying wires should be shielded with proper grounding.  The description of the PMDX-424 says the USB port is isolated electrically.  This by itself should help with EMI interference, so I suspect there is a strong EMI source somewhere. 

Lastly, be sure no signal wires run parallel to any power carrying wires.  If they need to cross, cross them with a 90 degree joint and if they need to run parallel, be sure they are separated the recommended distance or run them in separate conduit.  My experience with EMI is limited, and there are plenty of resources on the internet on the effects of EMI and how to minimize it. 

Hopefully, this is the issue and you can easily correct it.   

[epoch80]

Thanks for your reply. Unfortunately the error is completely random, which is making troubleshooting difficult. We can run the machine for days without issue, then have 3 in a few hours. It is a custom machine that is not running a standard VFD and spindle. It has 4 axes. 2 x 48v stepper motors and 2 x AC servo motors. I have done all the standard EMI related fixes.

[David.k]

Hello. I have exactly the same problems with 424 and it happens randomly. I also want to add that I have a problem with the fact that 424 refuses to work with the encoder. Now I'm trying to solve the problem with the touch probe "PMDX: No synchronized position from motion planner" When I tried to solve the problem with the support service (problem with the encoder), I was asked to provide a standard set of files, which I did. After that I was just ignored. I got the impression that 424 is not a finished product and I was deceived.