Weird movement / output to DYN4 - slow jerky rotation

[jj80909]

I'm starting a bench setup of a Acorn and DMM DYN4 drives. This is for a 3 axis knee mill.

So far, I have done the following:

1. Ran the DMM/DRV software to set up the drives for each axis (Gear Number, Pulse/DIR, Position).
2. Changed the command input to RS232 and ran the autotune software to tune each motor mounted on the mill.
3. Reset the command input to PULSE/DIR and saved on each drive.
4. Ran the setup wizard and made the appropriate settings (DriveOK to NO, Steps/Rev, invert drive enable).
5. Started CNC12 and set parameter P991=1.

I have only the X axis setup in the wizard with a simple home, and the motor is disconnected from the mill. Once I start CNC12, I cycle the E-stop and hit cycle start, the motor starts to turn very slowly, but in a weird jerky rotation. It sort of rotates in spurts.

I can jog the motor in both directions in fast and slow jog, but when I release the button, the motor continues to creep and this continues in either the CW or CCW direction.

I have re-confirmed the pinouts for the the 25 pin D-sub connector and the wiring to the Acorn board. I used twisted pair cable with foil shield and they are not near high voltage lines.

I tested the line voltage and it is a clean 239 VAC (running through a line reactor).

I also checked the 24 volt power supply. The voltage measures 21.1VDC and the 5VD side measures 4.7VDC. Is this too low?

Any suggestions are appreciated.

[cut2cut]

Add a ground jumper from either the DYN4's DB9 (JP5) or DB25 (JP4) nut to the ground terminal on the DYN4. See enclosed picture, the nut is partially obscured in the picture. The black wire with red arrows pointing to the connection points. I am fairly certain your issue will vanish.

p.s. hopefully this topic becomes a sticky.

Jake

[jj80909]

Thanks Jake!

I put a ground jumper on like you posted and it works great now...even homes good

It did sound like some ground issue, but I thought I had all the bases covered.

Thanks again!