Used CNC stands for Computer Numerical Control and has been around since the early 1970's. Prior to this, it was called NC, for Numerical Control. (In the early 1970's computers were introduced to these controls, hence the name change.)

While people in most walks of life have never heard of this term, Used CNC has touched almost every form of manufacturing process in one way or another. If you'll be working in manufacturing, it's likely that you'll be dealing with Used CNC on a regular basis.

How Used CNC Works

As you might already have guessed, everything that an operator would be required to do with conventional machine tools is programmable with used CNC machines. Once the machine is setup and running, a used CNC machine is quite simple to keep running. In fact used CNC operators tend to get quite bored during lengthy production runs because there is so little to do. With some used CNC machines, even the workpiece loading process has been automated. (We don't mean to over-simplify here. Used CNC operators are commonly required to do other things related to the used CNC operation like measuring workpieces and making adjustments to keep the used CNC machine running good workpieces.)

Let's look at some of the specific programmable functions.

Motion Control

All used CNC machine types share this commonality: They all have two or more programmable directions of motion called axes. An axis of motion can be linear (along a straight line) or rotary (along a circular path). One of the first specifications that implies a used CNC machine's complexity is how many axes it has. Generally speaking, the more axes, the more complex the machine.

The axes of any used CNC machine are required for the purpose of causing the motions needed for the manufacturing process. In the drilling example, these (3) axis would position the tool over the hole to be machined (in two axes) and machine the hole (with the third axis). Axes are named with letters. Common linear axis names are X, Y, and Z. Common rotary axis names are A, B, and C.

Programmable Accessories

A used CNC machine wouldn't be very helpful if all it could only move the workpiece in two or more axes. Almost all used CNC machines are programmable in several other ways. The specific used CNC machine type has a lot to do with its appropriate programmable accessories. Again, any required function will be programmable on full-blown used CNC machine tools. Here are some examples for one machine type.

The Used CNC Program

Think of giving any series of step-by-step instructions. A used CNC program is nothing more than another kind of instruction set. It's written in sentence-like format and the control will execute it in sequential order, step by step.

A special series of used CNC words are used to communicate what the machine is intended to do. Used CNC words begin with letter addresses (like F for feedrate, S for spindle speed, and X, Y & Z for axis motion). When placed together in a logical method, a group of used CNC words make up a command that resemble a sentence.

For any given used CNC machine type, there will only be about 40-50 words used on a regular basis. So if you compare learning to write used CNC programs to learning a foreign language having only 50 words, it shouldn't seem overly difficult to learn used CNC programming.

The CNC Control

The used CNC control will interpret a used CNC program and activate the series of commands in sequential order. As it reads the program, the used CNC control will activate the appropriate machine functions, cause axis motion, and in general, follow the instructions given in the program.

Along with interpreting the used CNC program, the used CNC control has several other purposes. All current model used CNC controls allow programs to be modified (edited) if mistakes are found. The used CNC control allows special verification functions (like dry run) to confirm the correctness of the used CNC program. The used CNC control allows certain important operator inputs to be specified separate from the program, like tool length values. In general, the used CNC control allows all functions of the machine to be manipulated.