EMC linux + CNC mill + CNC Lathe

[VEI Dude]

Leav,

Does your mill & lathe have drivers already? Or do you need those?

Here's my summary of how all the pieces work, in reverse order. I'm basing my values on general hobby/training-sized machines, which it seems is what you have. Note that this is a bare scratch of the surface of info on these devices...
(1) The stepper motors move in very small, but well defined increments with each "pulse" it receives from the driver -- common is 1.8 degrees per step (200 pulses per rev). Some motors are bi-polar and others are uni-polar, and some of these motors can be wired as the other type.
(2) Once you determine what type of motors you have, you need matching drivers. The drivers put out a (relatively) high voltage to power the stepper motors. The drivers usually take a 2-wire signal -- one is the direction (high or low digital level), and the other is a step (one pulse for each step). If you don't have drivers already, look into Geckos (a bit pricey, but very capable), IMS, Xylotex, and others.
(3) The drivers require a high-voltage, high-current motor power supply (usually 30V to 70V and a few to 10A or 20A, depending on the driver and motor), and a low-voltage, low-current control power supply (usually like 12V or 5V).
(4) The drivers get the step and direction signals (one pair of signals for each axis of your machine) from a parallel port (usually). You can get a breakout board to simplify extracting the signals from the parallel port. Some of these cost as low as $10. Note that some laptops have very low signal levels from the parallel port, so get a buffered breakout board for a bit more $$$. Check out places like cnc4pc.com .
(5) If your machines have control of the spindle, or coolant, etc, you will can also get the control signals for those from the breakout board.
(6) For software, as much as I am a Linux guy first, I must admit that setting up Mach3 with Win2000 was much easier than EMC. The free version is limited in number of lines, but it's still a LOT of lines. You might try that to get started much quicker.
(7) You can write g-code manually for now, then later get a decent cad-cam program to generate the code for you.


Some other notes...
- Common convention is ... On the mill, X is left to right, Y is forward and back, and Z is up/down. On the lathe, X is forward-back, and Z is left to right. Yes, it's odd, but Z is always considered to be along the axis of spindle rotation.
- You'll come across "microstepping". This is the ability of the driver to step the motor only partially for each step pulse. You get smoother operation and better resolution, but the PC needs to send out many more pulses per second. 8 microsteps is usually good enough. 4 is decent, but 16 or more is usually not noticed.
- Steppers may show a few volts listed on the label (like 2 or 3 volts), but you would power it with a supply about 20 to 25 times that (yes, going up to 70 volts or so). Reason is that the high voltage gets current to the motor windings much faster, and the current-limiters in the driver will switch the voltage off accordingly at the right time to not overdrive the motors.
- A CNC machine does not absolve you of learning to machine (endmill types, speeds, feeds, depths-of cut, workholding, etc.).
- Get on cnczone.com and machsupport.com . Good info there.

Cheers,
-Neil.