Spindle runaway when orienting, Bridgeport VMC800 digital

[rodgull]

Hi,

I am troubleshooting a Bridgeport VMC800 LR'22 Digital, with a Heidenhain 410MA controller. It was manufactured in March 2000.

It has had many problems, before I was brought in they had exchanged the control unit and sent the inverter away to be serviced.

I do not have a copy of the original parameters for the machine, all I have is an 8 page electrical schematic. It appears that the parameters were corrupted / modified, hence all the problems they have been seeing.

I have got the system to the point of being able to home the axis and manually control it, however whenever I attempt to orientate the spindle, the spindle speed increases until the controller reports a "Nominal speed exceeded motor S" error and locks up.

I can control the motor speed with an S command, clockwise and counter-clockwise with M commands, and move everything manually.

I have been informed of two methods of spindle orientation, however this machine does not appear to have either. The options are:

1. Seperate encoder running off a pulley on the top of the spindle - examining the system shows that there has never been one mounted.

2. Via a proximity switch which detects a flat part of the spindle pulley. The pins on the controller that I believe control this are wired to the Z-axis junction box at the top of the machine, but are not connected to anything, and don't appear to ever have been.

Does anyone know of a third way to setup the spindle orientation?
I have information on MP's and what they do from the Heidenhain documentation, however this doesn't explain the PLC values and what they do. I suspect that one of these controls the orientation method and it's setting but cannot find anything. The local Bridgeport specialist (2000km away) can't find anything so far.

I am willing to try just about anything now to get it running, as the owner needs to get this machine producing again.

Thanks for your time and any advise you can give,

Regards,
Rod Gullickson
Automation Concepts
Brisbane, Australia

[Al_The_Man]

There are basically two methods as you found, the prox type sensor and the encoder, older methods using the sensor on the spindle head would usually go into the spindle controller itself that had the orient option in it, the later methods use either the prox or more generally the encoder and the CNC controller itself would control the spindle.
If your spindle controller does not have the orient option on it, then the second method is about your only option.
It sounds like it was never quite integrated correctly from the start?.
Al.

[HuFlungDung]

How does the old 'shot pin' method work? Of course, the mechanical part is easy enough, but does the motor turn slowly, the pin drops in a groove, providing an I/O signal? I'm not sure how they make the motor 'give way' as soon as the pin drops.