Denford Software & Machines

Hello,
I have a few issues with my NOVATURN DENSTEP lathe (with VR Turning 1.45.0.0):
1. The automatic toolpost has stopped working.
- when trying to change tool in the Tooling window the program hangs up and throws out a timeout error - no output change on the TPFR relay or the control board output.
- "Auto changer" option in machine parameters is set to "1",
- toolpost brake is getting hot when the machine is turned on,
- when trying to run the toolpost motor by hand - by bridging INPUT 6 and 7 on the toolpost control board the motor runs well and sensor LEDs TB0I, TB1I, and TB2I light up correctly,
- there doesn't seem to be any visible damage on the U28 ULN2803 and U35 chips.

2. The spindle encoder - British Encoder 33DEN2 982664 shows incorrect RPM values:
- when running the motor with 1145 RPM the encoder shows stable 3718 RPM in the Machine control window,
- running at 220 RPM - encoder shows 459 RPM,
- There were bits of dust on the encoder disc - I've cleaned them out with IPA per manufacturer instructions - no change in displayed values.

3. When starting up or changing spindle speed the motor audibly overrevs and then settles down to the correct speed.
- this issue was present since I bought the machine - It's an old one from 2000,
- I've checked the board output voltage and it's ~150 V @ 1150RPM,
- brushes on the motor are fine.

I'll be grateful for any help with troubleshooting.

Can you confirm the RPM on the chuck using an external Tacho?

I think the first thing to do is actually check the actual speed and compare to the encoder.

You say : I've checked the board output voltage and it's ~150 V @ 1150RPM and the encoder is saying the spindle is running at 3718 RPM

The spindle would be normally running at top speed around 160-180V DC which should be 3500RPM so I suspect that the spindle motor is demagnetised and the RPM on the encoder is reading correctly.

The N max on the drive already seems to be at minimum. Could you supply another photo of the spindle drive and also monitor the spindle analogue to the spindle drive.

Analogue is 0-10VDC on pins 2 and 3 of the spindle drive NVT-D7C