Introduction to CNC machines

What is a CNC Machine?

• CNC: Computer and Numeric Control

Conventionally, an operator decides and adjusts various machines parameters like feed, depth of cut etc. depending on type of job, and controls the slide movements by hand. In a CNC Machine functions and slide movements are controlled by motors using computer programs.

For a CNC machine control unit (MCU) decides cutting

Speed, feed, depth of cut, tool selection, coolant on off and tool paths. The MCU issues commands in form of numeric data to motors that position slides and tool accordingly.

•A numerical control, or “NC”, system controls many machine functions and movements which were traditionally performed by skilled machinists.

•Numerical control developed out of the need to meet the requirements of high production rates, uniformity and consistent part quality.

•Programmed instructions are converted into output signals which in turn control machine operations such as spindle speeds, tool selection, tool movement, and cutting fluid flow.

• By integrating a computer processor, computer numerical control, or “CNC” as it is now known, allows part machining programs to be edited and stored in the computer memory as well as permitting diagnostics and quality control functions during the actual machining.

• All CNC machining begins with a part program, which is a sequential instructions or coded commands that direct the specific machine functions.

• The part program may be manually generated or, more commonly, generated by computer aided part.

Types of Machine

Lathes for metal and plastics Used to produce 3D product shapes and moulds for plastic products.

Milling machine for mould making and surface milling. Used to produce dies for die cutting printed products.

CNC Lathe:-

Automated version of a manual lathe.

• Programmed to change tools automatically.

• Used for turning and boring wood, metal and plastic

CNC Milling Machine:-

Has 3 to 5 axes.

Used for wood, metal and plastic.

Used to make 3D prototypes, moulds, cutting dies, printing plates and signs.

How CNC Works

Controlled by G and M codes.

These are number values and co- ordinates.

Each number or code is assigned to a particular operation.

Typed in manually to CAD by machine operators.

G&M codes are automatically generated by the computer software.

Features of CNC Machinery

The tool or material moves.

Tools can operate in 1-5 axes.

Larger machines have a machine control unit (MCU) which manages operations.

Movement is controlled by a motors (actuators).

Feedback is provided by sensors (transducers).

Tool magazines are used to change tools.

For more information about CNC machines:-

• https://en.wikipedia.org/wiki/Numerical_control

• http://www.brighthubengineering.com/manufacturing-technology/55787-what-is-the-cnc-machine-how-cnc-machine-works/