What Is CNC?
Computer Numerically Controlled (CNC) machines are capable of carving complex patterns out of a wide range of materials. Essentially CNC is the attaching of a computer-controlled device that allows the user to program a part, and have the computer drip feed the information straight to the machine. The information is coded into what is called G-code, which gives the programmer control over every aspect of the machine such as the starting point, stopping point, speed, cut rate, ect.
Stepper Motors: How They Work
Stepping motors come in a wide range of angular resolution. The coarsest motors typically turn 90 degrees per step, while high-resolution permanent magnet motors are commonly able to handle 1.8 or even 0.72 degrees per step. With an appropriate controller, most permanent magnet and hybrid motors can be run in half-steps, and some newer controllers can handle smaller fractional steps or micro-steps. All this basically means is that a stepper motor has a center rotor that spins encased in a cylinder that has several (usually 20) teeth, which are also commonly called windings. If a controller sends an electrical signal to one of the teeth, the rotor (under no load) will snap to that point. If the next winding in sequence is then given the signal, the rotor turns to that position. It is possible, however, to energize two windings at different amounts and micro-step the drives.
Benefits of Retrofitting
If you compare the costs of retrofitting versus purchasing new equipment, the benefits are in favor of retrofitting by a long shot. A typical new CNC mill might run $30,000-60,000 while a similar retrofitted mill might cost a third to a sixth of that amount. Another important benefit is accuracy, which new computer controls can handle up to ten times more accurate signals than other OEM CNC controls. The downside of retrofitting is that it is not always easy to find suitable machines for the process as they are often thrown out or junked due to their age. Assuming a person was comparing the two options for a new machine purchase, retrofitting can be quite a cost-saver.