CNC Milling is a machining process used to progressively remove material like aluminum, glass, or wood. CNC milling uses computer controls and rotating multipoint cutting tools in order to remove the material from the workpiece and produce a custom-designed part or full product.

A CNC machine refers to a machine that uses Computer Numerical Control. It can either be used for prototyping or in full production. Aluminum is one of the most commonly machined material and it is the most preferred material in most of the manufacturing sector.

Milling is a mechanical machining process that comprises rotating multipoint cutting tools around the workpiece in order to remove some material from it. The workpiece is fed in the same path as the rotation of the cutting tool. Some processes that are used in the CNC milling operation involve face milling and peripheral milling.

A CNC Mill is a CNC machine that translates programs that consist of specific numbers and letters to move the spindles or cutting tools around the workpiece to various different locations and depths. Most of them use G-Code and are compatible with different milling operations.

Overview of the CNC Milling Process

The CNC milling process makes use of computer controls to manipulate and operate machine tools on the mill which shape and cut up stock material. The process follows the same production stages that all CNC machining process go through, which are;

  • Designing a Computer-Aided Design (CAD) model
  • Using Computer-Aided Manufacturing (CAM) software to create the machine program that is used by the CNC machine
  • Setting up the CNC machine
  • Executing the operation

The process starts with the creation of a 2D or 3D CAD design, which is converted by CAM software into a CNC machine program that directs the machine’s actions and the movement of its tools. The CNC milling machine is then prepared by affixing the workpiece to the work surface and the milling tools to the spindle of the machine.

As soon as the machine is set up, the operator can launch the program using the interface and the machine executes the program. The machine then rotates the tool at high speeds. The machine also either feeds the workpiece into the stationary tool, moves the tool across a stationary work piece, or moves both the tool and workpiece simultaneously.

In CNC milling, the machine normally feeds moveable workpieces with the rotation of the cutting tool rather than against it, which is the case in manual milling processes. This is known as the climb milling process while other processes are called conventional milling processes.

Milling is best appropriate as a finishing or secondary process for a machined workpiece, thereby providing some features of parts or more definition. It can also be used to shape a workpiece from beginning to end. The milling process will in both cases gradually remove stock material to give the desired shape or form.

The tool cuts off small pieces from the stock material in order to form an approximate shape. Then it makes it go through the process again at higher accuracy to finish the piece to its exact specifications. Normally a workpiece requires several machine passes or setups to reach the required precision.

Once the milling operation has been completed and the piece produced to specifications, the piece can then move on to other stages of production.

CNC Milling Operations

The CNC milling process is suitable for producing parts with high accuracy and tolerance in prototype, one-off, or small and medium production runs. It is used in a wide range of industries and for a vast array of part features and designs. The most common milling operations are;

Face Milling

This is a milling operation that makes the cutting tool’s axis of rotation to be perpendicular to the surface of the workpiece. It uses face milling cutters that have teeth on the periphery and the tool face. It can be used in both vertical and horizontal milling machines.

Plain Milling

This is also known as slab or surface milling. Here the cutting tool’s axis of rotation is made parallel to the surface of the workpiece. The plain milling cutters only have teeth on the periphery of the tool and are divided into narrow and wide cutters.

Angular Milling

It is also known as angle milling. The cutting tool’s axis of rotation is at an angle to the workpiece. It is used to produce angular features like dovetails, chamfers, serrations, and grooves at different angles.

Form Milling

This milling operation involves irregular surfaces, contours, or outlines. It uses special cutters specialized for each particular operation.

It is used to produce intricate designs and complex parts

The CNC Milling Process in the Rapid Prototyping Industry

The CNC milling process is commonly employed in the rapid prototyping industry to produce different prototypes. It is used to also produce one-off pieces and in production runs. It is ideal when manufacturing high-quality pieces with high tolerances and excellent surface finishes than other prototyping methods.

It is used when producing pieces with complex features and designs that will be shown to potential investors and customers. It can also be used to show how features and other designs affect and come into shape in a piece.

The Aluminum CNC Milling Machine

When it comes to milling aluminum, the CNC milling machine commonly uses aluminum as a commonly machined material due to its because of its excellent machinability, thermal, and mechanical properties. The aluminum is a soft, lightweight, malleable, durable, and non-flammable metal.

There are a lot of milling machines in the world, but they mostly share basic machine parts like the machine interface, column, knee, etc.

The Machine Interface; is the component of the machine used to load and execute the CNC program.

The Column; provides support to all parts of the other machine components.

The knee; is the adjustable component that provides support to the saddle and worktable.

The saddle; is located above the knee and supports the worktable.

The worktable; is where the workpiece or the work holding device is fastened


The CNC milling process is an important one in creating complex pieces with intricate designs. It is used in various industries especially in the rapid prototyping industry. It involves various processes and materials to produce its pieces.


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