[sputnikprec]

I have a bridgeport VMC412 with SEM servo motors and BOSCH drives.
we have had this machine for a good 25 years running. Some years ago I dismantled the Z motor and found the commutator segments paper thin.... I found a sem motor over e-bay and this was not exactly like the one on the machine but ran OK.
eventually started getting gross positioning error in Z and I reduced the Z max feed in parameters and it cannot go more than F5000. I tried tweaking the bosch control card but cannot get it any better. I need the machine to run faster....but can`t. what are the options? the machine parameters need modifications? I can`t use the motor I have? The machine is still giving out valuable output so worth spending a bit to get it to its original glory.... Any help appreciated.

[RMARCH]

I have a bridgeport VMC412 with SEM servo motors and BOSCH drives.
we have had this machine for a good 25 years running. Some years ago I dismantled the Z motor and found the commutator segments paper thin.... I found a sem motor over e-bay and this was not exactly like the one on the machine but ran OK.
eventually started getting gross positioning error in Z and I reduced the Z max feed in parameters and it cannot go more than F5000. I tried tweaking the bosch control card but cannot get it any better. I need the machine to run faster....but can`t. what are the options? the machine parameters need modifications? I can`t use the motor I have? The machine is still giving out valuable output so worth spending a bit to get it to its original glory.... Any help appreciated.

The SEM motor on the Z axis should be a MT30M4-24. I don't believe other motors will work.

[Muzzer]

Is it possible the new motor has a different encoder resolution? You should ideally find the datasheets for both motors and compare them. Or post them here so somebody can help you.

You will see that there were many different options for these motors. Mine had a tacho and an encoder. Look on page 3 of this document for instance:
http://www.callantechnology.com/call...quivelents.pdf

Take a picture of the nameplates on each motor as a first step....