What is CNC Milling?

CNC Milling is a machining step during a product manufacturing process in which a cutting tool is moved on the surface of the product in an angular direction to the axis of the product. This automated machining process is similar to cutting and drilling, in that the milling process also uses a rotary cutting tool. However, in CNC milling, the cutter is able to move along multiple axes, unlike the drill which moves along a single axis. Also, in the drilling process, the cutter is advanced along the rotation axis, whereas in milling the cutter is usually moved perpendicular to the rotation axis so that the cutting occurs on the circumference of the cutter.

During this operation, material is removed by making several separate cuts on the product. The speed at which the cutter cuts as it rotates is known as feed speed, and this, along with the number and sharpness of the teeth or blades of the cutter will determine how much material is removed.

CNC Milling can be divided in two categories

Face Milling
Cutting occurs as the ends of the milling cutter. This process is used to cut faces or flat surfaces into the job piece, or to cut flat-bottomed cavities into the item.

Peripheral Milling
Cutting occurs along the circumference of the cutter, and the cutter teeth are in effect scooping out the material from the work piece. Thus, the shape of the cutter is received on the cross section of the milled surface, to create slots, threads or gear teeth, for instance.

A CNC (Computer Numerical Control) machine is controlled via software programs built into computer controls. These machines operate on a number of axes, and most machines offer between 3 to 5 axes, with 5-axes CNC milling centers being able to create parts of very complex geometries. In addition, these machines can be used in diesinking, engraving applications and in making 2.5D surfaces such as relief sculptures. The use of computers allows for the production of shapes that are almost impossible using manual methods.

Differences between Turning and Milling:

  1. In the CNC turning process, the workpiece rotates, whereas in the milling process, the tool rotates.
  2. The cutting tool moves parallel to the workpiece axis, whereas in milling the tool moves perpendicular to the axis of the workpiece.
  3. The turning process usually uses a single point cutting tool, whereas multi-point cutting tools are used during CNC milling services.
  4. Turning is usually performed on cylindrical pieces, whereas milling can be performed on any shape.