CNC Milling Process and Operations

31 August 2020

Computer Numerical Control CNC milling utilises a machining process with computerised controls and rotating multi-point cutting mechanisms to successfully remove material from a certain workpiece to produce a customised part or product. This is ideally employed in machining different materials like metal, plastic, glass, and wood. Such is also employed in manufacturing a variety of customised parts and products.

CNC milling processes and operations provide multiple functions and use in precision CNC machining services. It offers significant benefits in mechanical, chemical, electrical, and thermal processes. CNC milling involves drilling, turning, and a variety of other machining processes, meaning that material is removed from the workpiece via mechanical means, such as the actions of the milling machine’s cutting tools.  

Overview of CNC Milling Process

CNC milling processes, as the name implies, makes use of computerised controls to operate and process types of machinery to cut and shape materials as desired. It also employs the basic machinery stages for CNC machining specifically – CAD model design, CAD model to CNC program conversion, CNC milling machine setup, and milling operation execution.

Normally, the CNC milling process starts with the designing of 2D or 3D CAD. Afterwards, the finished design will be exported to a CNC-compatible file format and then converted by CAM software into a CNC machine program. The CNC program manipulates how the machine would operate and how the tools would move across the workpiece.

It is a must to prepare the CNC milling machine is such a way that the workpiece is affixed to the work surface or a device that could hold the parts. Afterwards, the milling tools will be attached to the machine spindle. The CNC milling machine could operate in rotating, horizontal and vertical manner depending on the specifications and requirements of the intended product or parts.

Overview of CNC Milling Operations

CNC milling is best used if you intend to manufacture high accuracy, high tolerance parts in prototype, one-off, and small to medium production runs. Usually, CNC milling processes manufacture part with tolerances between +/- 0.001 in. to +/- 0.005 in., but some milling machines can achieve tolerances of up to and greater than +/- 0.0005 in. Its adaptability made it usable in several industries since it can produce part features such as slots, chamfers, threads, and pockets. Below are some examples of CNC milling operations. 

Face Milling – It is characterised by a cutting tool whose axis of rotation is perpendicular to the surface of the workpiece. They have face milling cutters on the periphery and tool face. The peripheral teeth primarily being used for cutting and the face teeth being used for finishing applications. Face milling is commonly utilised to create flat surfaces and contours on the finished piece and is capable of producing higher-quality finishes than other milling processes.

Plain Milling – This is also referred to as slab milling, in which the cutting tool’s axis of rotation is parallel to the surface of the workpiece. They have plain milling cutters with teeth on the periphery that performs the cutting operation.

Angular Milling – Here the cutting tool’s axis of rotation is at an angle relative to the surface of the workpiece. It has single-angle milling cutters—angled based on the particular design being machined so it can create chamfers, serrations, and grooves.

Form Milling – This is commonly used for irregular surfaces, contours, and outlines, such as parts with curved and flat surfaces, or completely curved surfaces. It has formed milling cutters or fly cutters specialised for the particular application, such as convex, concave, and corner rounding cutters.

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