What does CNC stands for and what is cnc machining?

What does CNC stands for?

CNC stands for machining by "Computer Numerical Control", in other words, the machining tools are controlled by software codes that pre-programmed in machines. CNC machining tools move or rotate with the command of the codes, cutting the material from the material block, thus to achieve desired part.

Types of CNC machines

Here are some commonly used cnc machines:

CNC milling machines:

Cnc milling machines are very popular, the tools moves along x,y,z axis to cut material from the workpiece to achieve complex geometry parts..

CNC routers:

A cnc router moves its machining tools to remove materials just as cnc mlling machines, but it cannot cut deep holes or slots as a cnc milling machine, and it is limited to processing softer material like wood, plastic, and soft metals. cnc milling can achieve highier accuracy than cnc routers. Cnc routers are often used in furniture, packaging, and advertising.

CNC lathes

A cnc lathe spins the workpieace, while the cutting tools are held stationary, the cnc lathes can create cylindrical or conical parts such as shafts, pins.

CNC bending machine:

CNC bending machines are used to bend or fold cold sheet metal into various geometry and cross-sectional shapes. CNC bending machines can produce different kinds of sheet metal parts, such as brackets, product covers, and clamps, which are used in manufacturing,automobile, aircraft, etc.

CNC grinding machine

CNC grinding machine, or cnc grinders, remove material by cnc high speed abrasive grinding tool, achieving unmatched surface precision on work piece.

CNC drilling machine

Cnc drilling machines are capable of drilling holes precisely with cnc drilling bits.

CNC laser cutter

High power laser beams moves by CNC to cut the work piece, achieving intricate shapes. Multiple materials can be cut, such as, steel, aluminum, leather, plastics, wood, etc. However, reflective metal like brass and copper reflects laser beam, causes damage to the machine. Moreover, cutting materials like polycarbonate can create harmful gases. As you might have thought, CNC laser cutters can achieve only 2d effects and limited cutting depth compared to milling or turning machines

CNC EDM machines

EDM stands for electrical discharge machining, also known as spark machining, it removes material by a series swift recurring current electrical discharges (sparks) between two electrodes. High electrical conductive materials like brass are perfect for EDM. Hard materials, like  titanium, and heat treated steel can be processed by EDM machines easily when compared to conventional turning or milling machining.

CNC plasma cutters

Plasma refers to a hot substances ejected from the cutting torch. CNC plasma cutters are designed to cut electrically conductive materials by computerized numerical controlled hot plasma, the temperature of the plasma can reach up to 45,000 degrees Fahrenheit and 25,000 degrees Celsius, thus precise cut can be done..

CNC water jet cutter

CNC water jet cutter uses high pressure water jets to cut through materials like aluminum and plastic, compared to laser and plasma cutters, water jet cutters are slower.

3d printing machine

3d printing machine, or 3d printer, unlike other machining process that removes material from a work piece, 3d printers add material layer by layer to create an item. 3d printing is relatively slow process, often used to build prototypes.

How does CNC machining work?

There are 4 steps to describe how cnc works.

1. Get a CAD model ready.

To get cnc machined parts, a proper CAD(computer aided design) model is necessary. there are some popular CAD software used by product designers or engineers for example: AutoCAD, SolidWorks.

In prototyping stage, product appearance, function, and manufacturing feasibility should be taken into consideration. A good CAD drawing should show operating features like holes, threads, critical dimensions indicated with tolerances, etc

2. Model be converted to CNC readable code

CNC machines can only understand codes. Some CAD software can transform the files into G code. In other cases, CAM(computer aided manufacturing) software is needed. Production engineer or mechanics uses CAM software to create machining tool path and other machining instructions for CAD models, and converts them into codes readable to cnc machines.

There are some CAD software with CAM functions, i.g: AutoCad, SolidWorks, Fusion360, NX/UG. Commonly used CAM sorftware, i.g. Mastercam.

3. Setting up the cnc machines

Before machining, there are several set up steps to complete. For example, determining the most suitable machining method and machines according to part quantity, cost, complexity, placing the work piece, fixture and machining tools accurately, setting up a series of machining parameters like cutting speed/depth, feed speed, adjusting and optimizing machining procedures...

4. Machining

When machine is set up correctly, machining process can get started. Based on cnc program codes, the work piece can be processed automatically in the cnc machines:

Rough machining: removing most of the material to shape the final structure.

Half-precision machining: improving dimensional precision and surface finish

Precision machining: Obtaining the required dimension and surface finish.

When machining completed, the part will be inspected before any post processing.