What is a CNC machine? First lets start of with what CNC stands for: Computer Numerically Controlled.
Computer is the device that you are currently using to read this article and normally you will find that CNC machines are controlled by older model computer hardware and software. Most shops still run their machines on Windows XP though some even still have Windows 95 computers running some milling machines. Be prepared to see some technology that most would consider dead when you see a CNC machine as cost to upgrade would be much higher then just training technicians to use the older software.
Some specialized machine have the software program built right into the machine themselves which can be controlled either from a remote computer or you can upload a main program through a USB port. These machines allow the engineer to make changes to speed and other features on the fly.
The second piece of the puzzle is Numerically Controlled (or Numerical ) means the automation of machine by precisely programmed commands encoded on some storage media. In the past programs were stored on punch card but today USB drives/Hard drives store the code for a machine to use to follow a set of instructions.
So what is a CNC machine? It is a device that is computer controlled to follow a set of instructions that will allow the creation of a product. There are multiple types of CNC machines that can create many things that we use today. From multi axis systems that create parts for cars out of metal or plastic to the milling machines designed to shave away nano-meters of metal to get the perfect radius. CNC machines in industry vary to great degree and you can specialize in a certain type of CNC machine programming or device type.
There are many types of CNC machines that have different methods of creating products for customers. Some use metal razors to shave bits of material away at a time. Some machines have multiple bits ready to switch out as needed by the programmer (Swiss Machining). Other machines use magnetism combined with electricity (Electrical Discharge Machining) to melt away bits of material as needed in a super precise manner.
CNC machines can be made to create items from all types of mediums. The most common is metal, plastic, wood, granite, or stone. Each of these CNC machine will range in capabilities and this will change the price. Basic used machines can be as low as $500 while complex multi-axis systems designed for mass production could go into the millions of dollars.
One thing is clear, our world today would not be what it is without CNC machines.
Pictures taken from http://www.mwmachinery.com/