[WC56]

Hi, earlier this year I posted about a problem I was havingwith the spindle of my 1984 Okuma LB15 (OSP5000L control). Through thehelp of forum members & a local technician the fault was eventually foundto be the spindle motor speed sensor.

To prove this the technician told me to remove some covers& place a small heater fan so that it was blowing on the motor & leave itthere for a couple of hours. This worked & the spindle ran fine for therest of the day.
I then pulled the motor out & closed the gap between thesensor, which is a Fanuc A20B-9000-0010 & the toothed wheel by a couple ofthou, cleaned a few things & put it back together & all seemed ok.
This machine does not get much use; although I do run awarm-up program through it once every week or two. The other day I ran it for astraight 10 hours with no issues, however the following morning the originalproblem reappeared.
As we are into spring here in Australia the weather is startingto warm up, so I thought I would wait & try it later in the day…shefired up without a problem.

Based on this I have a couple of questions that I hopesomeone can answer:

1. How does the ambient temperature affect thespeed sensor?
   
2. Is it worth getting the sensor output signalcheck with a scope?
   
3. If the sensor is stuffed, where can I getanother one or is there another ‘fix’?

Any help would be much appreciated
Thanks WC56

[Henrik Adler]

Hi There in the outback.
The Fanuc drive is supplying two lines with about 2.5 volts to the sensor, which overrides theese voltages with two sinus signals depending on the speed. This overrided signal around 2.5 volts comes bask to the drive as A and B channel. Depending og the drive there is adjustments to make theese signals square waveforms, and the levels must be adjusted so they are symmetrical and twisted 90 degrees in comparison to each other. Yes You will need to use a dual channel ocilloscobe to do this calibration.
Your description of the problem indicates that the adlustment is at the edge of OK.

Best
Henrik Adler
DK.

[WC56]

G'day Henrik Adler, thank you for replying. The machine was recently moved 650Klms by truck so I wonder if this could have effected it. I will find someone who can check the signals as you have sugested & report our findings. Regards WC56