It's my first post here so first of all hi to everyone!


I have a problem with Mazak VTC800/30SR rotary tables. We are producing a part which is mounted on two rotary tables which are supposed to work in a synchro mode. The rotary tables have fixtures that are separate from each other and are only connected together when a part is mounted on them.
The problem is that from time to time one rotary table moves while the other doesn’t and before the controller reaches electrical current alarm level, the rotary table twists the mounted body and all machined tolerances are gone.In the beginning I thought this might be a problem of the fixture and that after rotating the forces on rotary tables are uneven and the machine tries to compensate that by moving one rotary table while the other doesn’t.
But when I was checking the fixtures without the part mounted on them with a renishaw touch probe one of the rotary table moved while the other didn’t, so this means this happens without any realtion to the forces on the rotary tables.

This is more or less how this happens:
1. I move both rotary tables to the zero position in the nonsynchro mode.
2. I turn the synchnro mode on.
3. I'm rotating the rotary tables by moving the master rotary table, the slave table follows.
4. After some time (once it happened after an hour, once after 2 days of work) the master table moves, the slave doesn't. The master moves although the program is not running and I'm not moving it manually.
5. When I move the master back to zero in the synchro mode, the master shows positon 0 deg, the slave for example 2,6 deg. To move both of them back to zero position I have to unsynchronize them, move them to 0 and synchronize them again.

The other clue is that every time I connect the rotary tables after few days of them being unplugged I get the nr 10 detector alarm and I have to make the procedure with changing bit 7 in the M18 parameter of the rotary tables. In this machine there are no batteries in the MDS, there is a central battery on the door of the electrical cabinet and it is connected with all MDSes in the machine. It shows 3,6V when we checked. If the battery was dead I guess I would have the nr 10 alarm on all axes.

Anyone had a problem like that? Any clues?