[ssurfview]

We have a 1991 Fadal VMC 4020 CNC 88 control. Yesterday in jog mode the x,y,&z all moved very rough for a short 1-2 " and then the machine drops out to the manual mode with no error message (repeatedly). Giive it the HO command and x,y,&z all move normally to the home position. Start up the program and it will go through the program flawlessly. after much searching and testing the machine starts to work normal. I go home and all was well ,I thought. During the 2nd shift they ran flawlessly for about three hours then... at idle either in jog or manual all the axis would begin to move .010 then .100 then 2" I have spent the day ringing and megging cables, checking for bad solder, keyboard input connection. WTH. The wise ackers even shot me a video.

[alex gitzel]

check into the clock card and swap if you have another,also look into the cpu maybe having a glitch ,or is too full with me command must have more than 15% available.The cpu may need a zero memory to get any glitches out.also reseat the control cards.

[ssurfview]

Alex.
Saturday, I reseated all the cards in the rack. Started it up and it's been running ever since. 2nd shift will get it's first shot at it tonight. If it can make it 8 hrs with the night shift, it will survive. We did get a message about command buffer full. IF I get any more trouble, I'll check into the clear CPU option. Thanks
Steve