[Ascobie22]

I have an early 90's Hurco BMC-20 with an Ultimax Monitor. The machine runs fine in manual mode. We can turn the spindle on, adjust the speeds with the override and move it on the XYZ axis without a problem. However, when we try to run a program the spindle sounds like its constantly changing speed. It starts at the speed we programmed, offhand 1700 RPM I think, then it loses speed jumps back up then loses it again. The monitor actually said the spindle was a solid 3850 RPM (or some number close to that) rather than increasing and decreasing with it. It almost makes me think that maybe it's losing power then getting it back then losing it again. The error that comes up on the screen is SPINDLE FAULT- ZERO SPEED SIGNAL ERROR. Any help with this would be greatly appreciated!

[Bob La Londe]

My first guess would be a bad connection between your signal source and your VFD. Possibly a bad connection at your switch or maybe even a bad switch. Could also be a bad speed sensor or a bad speed sensor connection if it has closed loop spindle speed control.

[Spooner]

I had a similar issue on a VMX30U--

along with a number of other problems. I'm pretty convinced we had a really poor installation with our particular machine.

The side panel of the trunion was not sealed properly and had begun to fill with coolant and oil. This led to the encoder cables for the A axis to start shorting out (giving us some A axis alarms every once in a while)-------and we also figured out that the voltage draw was pulling power from the entire back board of the machine and causing power fluctuations for the spindle speed.

The trunion side panel got pulled off, cleaned out and properly sealed, and our variable spindle speed seemed to go away. We did however have to have another wiring harness replaced in the back to prevent the 20 control freeze ups during tool change that we were getting each day.

I have to be honest--I'm not too impressed so far.

[powerr]

Check the SER Spindle Enable Relay. We have seen the contacts go bad and not get the signal to the spindle drive. Also check to see if there is a error on the spindle drive when it errors out. For A quick test you can swap it with the Lube relay.