Problem- Spindle speed issues...

[rshields21]

Haas VF-2. Magnatek drive. The actual spindle speed is approximately 50% of the commanded and its erratic. example, s6000, actual bounces between 2800 and 3000.
If you command it at 10 rpms, you can count the rpms and it is off. at the very slow speed you can see the varriance in rpm as well.
I swapped the magnatek drive unit from the machine next to it, so thats not the problem.
It's not producing any alarms either.
I'm thinking the Mocon board but I wanted to see if anyone had any thoughts before I schedule a service.
Thanks

[awesome83]

It could be the mocon board, that would be the board that would send the 5v signal to the drive, but there can also be something dragging the mocon's 5vdc down. Possibly a coolant level sensor? I don't know if you have one.

If it happens during tapping i would check the spindle encoder/pulleys/belt.

[rshields21]

Well stupid me, I assumed the encoder was fine since no error was generating. Which in all fairness the local HFO agreed lol.
I pulled the covers off and basically the gear and the post assembly on the gearbox shaft was totally thrashed. Beats me how the belt never popped off which would have saved me a ton of time by generating an alarm.....
I happened to have all the spare parts so its just a matter of cleaning and reassembling.
Can anyone tell me how to orient the spindle prior to the vector drive units? I got it all back together and it works fine, but I didnt have the spindle timed when I put the piece the shot pin pops into on... Theres gotta be a way short of pulling that back off?
Thanks!!

[vlmarshall]

There's a spindle orient value in the Parameters somewhere, run an indicator across the drive lugs and tweak the setting until you get it. I've changed encoder belts on one of the Haas machines I run at work a few times, I guess once every year or two.

It's not such a bad job, sorry I can't remember the parameter for it.