[forhire]

Today I decided to check the brushes on the Z axis motor. This required pulling the motor out of the machine. Brushes looked fine so I cleaned out the carbon dust and decided I'd test it on the X axis using the open loop battery box. Hookup is fairly simple. 0V (red & black) is hooked up to 1 & 2. Enable (yellow & green) is hooked up to 16 & 17. Encoder loop from velocity controller 21 & 22 must be removed. 5 & 6 are the tachogenerator voltage.

Attachment 423830

Unfortunately the Z axis motor ramped right up to 2500 rpm on the X axis. The X axis motor had barely moved in open loop. Obviously there was something different about the two motors. After carefully comparing the two I found a short on one pole of the tachogenerator to the body. Oddly both motors generated similar +/- voltages when tested. I used a little liquid electrical tape to correct the short. After the repair the Z axis motor behaved properly on the X axis.

Attachment 423832

Following the motor repair I swapped the axis drives. The Z axis drive performed correctly on on the X axis. At this point I am confident both motors work along with both axis drives are good but there is clearly something not right with the Z axis wiring. I suspect the tachogenerator wiring. The voltage looks ok but I didn't have time to check for a short to ground. That's the next thing to check. I guess.

I'm getting closer...

[forhire]

After many months of working on this lathe I have finally been able to get it fully startup. Turned out the tachogenerator connections were cold and only held in place by the heat shrink. Good enough to see a voltage with a multimeter and watch it with the scope but not enough current for the axis drive to behave. Resoldered the connections and the axis drive finally started working. Some genius had soldered them on the outside rather than using the solder cup. :devious:

I verified both X and Z axises both move, the spindle runs nice and quite, turret rotates as it should, hydraulic chuck clamps and un-clamps correctly. Now all I have to do is fine tuning. Yeah!

Thanks for all your help and suggestions. I have learned a TON about DC servers and I'm a lot more comfortable working on them.

Attachment 423936