STEPPER MOTORS
I am trying to select a simple CNC system and would like to ask your opinion on the following. I am building a lathe to my own design; it is about Myford ML7 size. I intend to drive the leadscrew and cross slide by stepper motors. These stepper motors can be dis-engaged so that normal manual operation is also possible. I would like the stepper motors to be driven at a selectable fixed speed and engaged or disengaged by the operator in a similar manner to conventional lathes for fine 'X' feed (cross slide movement) and 'Y' feed (along the lathe bed). The lathe spindle will be belt driven from a 3-phase inverter controlled motor. The lathe spindle can also be separately driven by a further stepper motor ('A' drive), which can also be engaged and disengaged by the operator. I intend these stepper motors to be controlled by a cnc program, which will allow simple settings for the relative speeds of the motors. The 'A' drive motor will have two modes: 1) as a dividing system for indexing the lathe spindle. 2) As a slow speed drive which can be coordinated with the 'Y' feed for screw cutting. The cutting tool would be engaged/disengaged in a conventional manner whereby the carriage drive is coordinated via a screwcutting dial. I would like to ask your opinion on whether you think this will work? Will the leadscrew and spindle be coordinated enough by the cnc program without a further device to sense the spindle position? I also intend to use a fourth stepper motor to drive a small milling spindle mounted on the cross slide ('B' drive). Do you see any problem with using a stepper motor for this purpose? (Speeds approx 200 to 2000 rpm). It would be desirable to operate these stepper motors individually as well as in combination with each other. Therefore would it be better to use individual stepper motor drivers rather than one four way driver because this would allow stepper motors that are not being use to be switched off? I can give you further details of the stepper motor drive conditions if you require. I would be grateful for any advice.
Regards Alan Jackson