[RICKG]

Anyone ever break a spindle encoder belt on a Mori-Seiki cnc lathe? It has a fanuc 10T control and the belt broke during a finish turn cycle in G96 mode. Spindle goes right to max rpm (3500). Seems a little odd Mori would not have some safety built in to avoid this. Any comments?

[Al_The_Man]

It is possible to monitor some conditions, but I don't see how you could check that a belt is broken, the spindle is being controlled based on encoder rate, so naturally it speeds up to try and bring the encoder revs up.
Maybe this should have been part of the prevenatitive maintenance program
Al.

[codyst]

I've been putting IFM Efector capacitive sensors on my belt driven spindles for a while. They are non-metallic proximity sensors and have a teach function that allows you to program the distance to read(4 to 60mm). If it sees the belt the signal stays high, and if the belt breaks it goes low generating an alarm. Most of the belts I've had break, start to wear away before finally breaking, and if the read is set correctly it will usually catch that the belt is going to fail before it actually does. They're about $120, but well worth it in my opinion.