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Author Topic: Machine Freezes Followed by Unwanted Offset  (Read 253 times)

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Machine Freezes Followed by Unwanted Offset
« on: November 02, 2020, 08:05:35 AM »
Hello Mach4 Forum

We are currently running 3 AVID CNC Pro 2448 Machines that all show a similar issue that occurs on an intermit basis.

We will be running a known and tested file but the machine will suddenly pause (on its own) mid cycle for 3-4 seconds followed by an offset usually X and Y. Understandably this will ruin the work and is quite disruptive. The offset is not 'programmed' rather the machine has lost steps and lost position. This lost position seems to be due to some kind of digital interruption - the machine is certainly not mechanically overloaded at the time that it looses steps.

Admittedly the PCs that we are using seem to be underpowered in terms of graphics card (Mach4 states 256 to 512 of dedicated graphics RAM) and I don't think our PC actually has a dedicated graphics card. (PC spec here: https://www.amazon.co.uk/gp/product/B07MPPW7JY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1).

My question is does this seem to be a symptom of underpowered graphics or is this likely to be coming from somewhere else?

Any pointers would be very helpful.
Re: Machine Freezes Followed by Unwanted Offset
« Reply #1 on: November 25, 2020, 08:28:26 AM »
When I first got my CNC machine running I would notice that during testing the GCODE would run and then throughout the cycle the head would pause briefly and then resume.   Sometimes for a split second sometimes longer.  This machine uses a PoKeys57CNC controller.  I thought it was interference on the wiring so I ensured that all of my cables were grounded appropriately. These by no means were cheap cables either they were all sourced from IGUS.  The however didn't fix the problem.  I then tried changing PCs thinking it was a PC issue.  Adding more RAM didn't fix the problem, A SSD drive didn't fix the problem, A 16 core PC didn't fix the problem.  Then I upgraded my video card, same problem.  I contacted Pokeys, they have excellent support by the way, and I explained the issue.  After some back and forth they suggested that I watch the command buffer to the PoKeys 57CNC.

They have a utility that can inspect when the buffer is full. What did you know as I was watching the program run the GCODE buffer to the device would goto 100% the machine would stop briefly and then resume.  Sometimes loosing where it was left off.  And when the machine stopped it sometimes was violent depending upon the GCODE instruction.  Rapid moves were the worst.

Now the issue was identified that the buffer was filling up to fast.  Onto the solution.  While watching Windows processes I noticed that the processor would hit 100% utilization each time the buffer was full.  I then sorted the process list from worst offender to least offender by processor percentage.  There was one windows process that is used by Windows which causes this to occur.  When I shut that down (and didn't allow it to ever start up again), this was in the services control panel mind you, the problem went away.  Now what that service was I don't know off hand, but maybe this will help you diagnose your problem.
Re: Machine Freezes Followed by Unwanted Offset
« Reply #2 on: November 25, 2020, 07:01:37 PM »
i dont think its pc issue ,because pc or buffer problems not loose position ,maybe just give you deley
its sound more like the worst word in control system"noise"
in any case ,which hardware do you use?
check all yours ground
avoid ground loop
ground all "0" from all supplier to the main ground
try use Ethernet  not usb cat7 cable