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« on: February 03, 2018, 09:28:35 AM »
Hi,
The situation im in is with a retro fit on a customers Wadkin fabricated industrial router.It was fitted with a bosch pmdc system running at 150volts.
I have scrapped all of that system and saved the servos which I have fitted 360ppr chinese single ended encoders on the back (they had tachos on).
I am using ucnc dg4s 180 drives and there uc 300 motion controller, all of which im happy with.
The ancillary power supplies have there 0 volts commoned to the computer 0 volts and then to machine ground, but not commoned to the servo main power supply.
The servos have twisted power leads, the encoders have 4core 0.5mm with an overall shield which is grounded only at the drive end.
Interestingly i can disconnect the grounds etc. and it makes no differance.
The issue :
Z axis - runs perfectly really smooth encoder/motor leads approx 4 ft long.
X axis - holds position on start up but if you touch the pulley or give it a command it judders like a crazy thing and creeps forward,uncontrolable and wont stop unless you reset drive. encoder/motor cables approx 12 foot long.
Y axis - behaves exactly as X again 10 foot encoder /motor cables.
I have tried swapping drives and motors around with no differance, so I have come to the conclusion its possibly cables, or at least the length of them.
I have sopken to Balazs at CNC drive and got this answer:
"I think the jumping is caused by electrostatic charge, likely the body of the encoder is statically charged with the motor and maybe even the machine frame"
But im afraid he gave me no solution to it.
I have read that putting 2 capacitors at the encoder power end (0.1 +0.001 uf) can help filtering
Also using pull up or pull down resistors on the A B channels can help (will need some clarity here)
Or should I try to totally insulate the encoders from ground.?
I shall be going back on site tommorow to have another go at it, Any thoughts?
Regards
Tony
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