Tech Tips – What Are the Basics of CNC Milling and Turning?

Tech Tips – What Are the Basics of CNC Milling and Turning

CNC milling and CNC turning are two different machining processes used in subtractive manufacturing to create a part or component. With CNC milling, a cutting tool rotates around a stationary object to remove material, but with CNC turning, the work piece being created rotates around the tool. Both are operated by CNC machine (computer numerical control) and both are established and successful forms of manufacturing with their own unique features and benefits. Let’s take a closer look at the history, benefits and features of these technologies. 

What is CNC turning? 

During CNC turning, bars of material are secured in a chuck (a type of clamp that holds a usually cylindrical object in position), a tool is fed into the material as it rotates until the required shape is formed. A computer programmed turret moves towards the bar of material and removes material using its attached cutting tool or tools. 

History of CNC turning 

Although CNC machining dates back to the 1940s when it was invented by John T Parsons, the technique of turning goes beyond that to the 1700s as progress began to improve the accuracy of mechanical processes. As the turning is based on a lathe, you could say the concept of the turning process steps back even further to Ancient Egypt when lathes were used. In 1751, the first turning machine with a metal frame was invented and became the first of many similar machines. In the mid-seventies, computer aided machines started to emerge, slowly becoming the norm for manufacturing over the next decade.

What products does CNC turning produce? 

CNC turning produces important and useful electrical components and parts for industries including machinery, automotive and telecommunications. These include pins, bushings, threaded rods and screws. Metal parts created from CNC turning are very often made for the automotive sector, for example, steel components which are very strong. Brass components made through turning are commonly used for electrical hardware and consumer products, and aluminium parts which are lighter in weight and corrosion resistant are used for high-tech and multiple other different applications.

Advantages of CNC turning 

CNC turning is a favourite with manufacturers because of its ability to speed up processes efficiently and cost-effectively. Couple this with the degree of precision that is achievable and the capability to reduce waste and you can see why this is a winning choice. 

What is CNC milling? 

Like turning, CNC milling also uses computer controls to coordinate its movements, but instead of the material moving to form an object, it is the cutting tool/tools. The subtractive concept is the same because material is removed to create a finished shape. At the start of the process, the original CAD model, a CNC program is created which provides instructions for the machinery. The machine is prepared for operation before the program is activated and cutting begins. Typically, CNC milling is used for finishing processes including the creation of flat surfaces, slots, holes and grooves in objects. 

History of CNC milling

Similar, to turning, milling is also a production process with a long history, with some early machines emerging in the early 1800s. In terms of CNC milling, Richard Kegg, developed the first computer aided milling machine alongside the Massachusetts Institute of Technology. 

What materials are used in CNC milling? 

Aluminium is the primary material used in CNC milling thanks to its strong, versatile and high-grade material properties. Aluminium can also be machined more swiftly, meaning it is the most economically sound for manufacturers. Despite the prevalence of aluminium, nickel, stell, titanium, zinc, brass and thermoset plastics are also used in CNC milling. 

What products are made from CNC milling?

CNC milling produces high and low volumes of precise parts. Standard items and objects created from CNC milling include wooden parts, plastic pieces, hydraulic manifolds, control panels and landing gear components. 

Advantages of CNC milling

One of the key advantages of CNC milling is the accuracy it provides and with that, the consistently high-quality finished result making it ideal for high volume production. It is also a versatile piece of machine usable with different cutting tools and therefore able to create complex, customisable shapes. It is able to perform multiple cuts at the same time and because of its computer aided facility, there are multiple cutting options. 

 In conclusion…

CNC turning and milling each have their areas of specialisation. Milling is better equipped to produce flatter, even surfaces on larger objects, which may require secondary features like grooves, or a part that needs a hole that is off-centre. Turning is best used when working on more cylindrical pieces, plus there is an opportunity to access the wider diameter of a material for threading if needed. Despite the growing use of additive manufacturing, CNC machining is superior in producing impressive economies of scale in manufacturing with high-volume production possible for precise and accurate parts across a plethora of industries.

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