Nuts and Volts - October 2013

CNC 101

CNC — or Computer Numeric Control — is applied to milling in the form of a computing device that is capable of converting machine tool language into physical motion. The complexity of the CNC computing device is directly related to the CNC mill’s desired function.

A simple CNC mill can be driven by a microcontroller. More complex CNC mills are normally driven by PC-class systems running specialized CNC software.

PCs are wonderful application execution platforms. However, the performance of a standard off-the-shelf computer is horrible when it comes to high speed I/O operations required by CNC applications. To offset the PC’s lack of I/O speed, a typical computer-based CNC system will include a drive which sits between the PC’s limited I/O subsystem and the mill motor. Drives can be endowed with intelligence or simply act as dumb high-current motor controllers. In that a PC is not designed to supply pulse trains that roam in sub-millisecond space, an computer-based CNC systems. A popular intelligent motor drive is squirming around in Photo 1.

We are not going to get into CNC motors. However, the most commonly used motors in the CNC environment are servo motors and stepper motors.

CNC 201

Since the GECKODRIVE you see in Photo 1 is dedicated to driving stepper motors, there isn’t much more movement information we can provide to the stepper drive. All we are able to configure is the upper amperage limit by placing the

What does your cell phone have in common with a CNC machine? Your cell phone enclosure was manufactured in a mold that was crafted using a CNC machine. Taking that thought a bit further, a specialized CNC machine drilled the holes in your cell phone's circuit board while yet another specialized CNC machine stuffed the phone's printed circuit board (PCB)

with electronic components.

If you have an inkling that we will be talking about CNC machines this month, you're close but no cigar. We are going to focus on programming the silicon brains behind the milling tools and motors.