5 Common Materials used for CNC Machining: Which is Best?

Various metals - Challenge Engineering CNC Machining Sydney

Before the invention of CNC machine tools, the potential of machining was very limited. Many of the machined elements of parts manufacturing we see today would be nearly impossible to conceive through manual machining, while also taking longer to complete.

The use of CNC machine tools revolutionized manufacturing and the field of engineering. Both straight lines and complex contours are now just as easily machined, with much more consistent quality.

At the early design stages of a part, material choice remains a critical decision - one that can be quite complex. Do you need something that’s malleable? Corrosion-resistant? Would a heat treatment make this material more suitable for your needs?

There are so many options and considerations, that unless you’re an expert in the materials engineering field, it can easily become overwhelming. In this article, we’ll go over some basics that will help point you in the right direction.

Which Material best suits your Application?

Copper and Copper Alloys

Not only is copper the best electrical conductor, its heat conductivity makes it suitable for products like cooling system elements and heat exchangers in the automotive industry. These heat conductivity properties also make it easier to shape through CNC machining.

  • C11000 copper is a great choice for transformers, electrical contacts and fittings, since it has high corrosion resistance and conductivity. C14700 copper is an even better choice for electrical contacts due to its superior conductivity. C14700 copper is often used for magnetic housings, bushings, electrical contacts, pump components, and bearings. It stands out as the option with some of the lowest permeability, as well as non-magnetic properties.

  • Brass is a copper-zinc alloy. C38500 brass is an excellent choice for parts that require knurling and threading due to its strength, resistance to corrosion and wear, and great machinability. It is a great choice for electronic hardware and contacts, fittings, and a number of commercial products, thanks to its low strength combined with weight, as well as its low cost (its machining produces high scrap returns, which translates into cost savings).

Aluminium and Aluminium Alloys

Aluminium is a popular choice for CNC machining. Aluminium machined components are completed in less time than any other metal, making aluminium and its alloys very economical to machine. The applications of aluminium and its alloys are virtually endless.

  • 2011 aluminium is designed for machining, and is commonly used in all kinds of commercial products, especially in electronic hardware. However, 2011 aluminium cannot be anodized or welded.

  • 6262 aluminium is a great all round alloy, which has good machinability, can be welded and also anodized.

  • 6061 aluminium has good resistance to corrosion, weldability, and formability. Just like the previous two alloys, it is common in electronic hardware, but also in piping, recreational equipment and aircraft components.

Steel

Most Steel alloys (e.g. 1020, 1030, S1214) can be case hardened, and are designed to provide excellent machinability.

  • S1214 steel is designed for excellent machinability, which gives it an immense range of uses in commercial products, and it is probably the most varied of the steel alloys spectrum. Or S12L14 steel was developed for high volume production, repetition engineering.

  • 1020 steel is a low-carbon steel with good machinability and excellent weldability, so it is used for rivets and parts that require strong welds. A Ø50mm round bar, cold drawn is normally supplied as a h10 tolerance, or +0/-0.1mm (or +0/-0.004”).

  • 1030 steel has higher carbon content, but also higher strength. It’s meant for applications that require higher stress resistance, like shafts, gears, studs, etc.

  • 4140 steel stands out for its fatigue resistance, toughness, and strength, machinability, hardening characteristics which are all the reasons why it’s so often used in commercial and industrial applications. It is commonly supplied in black, straight from the mill, or for repetition engineering, in a peeled or centreless ground bar. Typically, a Ø38.1 round peeled bar would be a k12 (+0/-0.25mm) tolerance or centreless ground would be a h8 (+0/-0.039mm) tolerance, which covers most industrial applications.

  • 4340 steel is a good selection for highly stressed components and possesses all the characteristics of 4140, but takes it up a notch.

Titanium

Titanium has a high melting point, is very strong, lightweight, and resistant to corrosion, water and salt. These are all unique characteristics for a number of industries and applications.

  • Ti-6Al-4V is particularly strong and lightweight, which makes it perfect for aircraft and aerospace applications.

  • Ti-6Al-4VEli is very similar, but with added good bio-compatibility, which makes it the number one option regarding medical implants. The tolerance for a ground and polished ½” bar of any of these two titanium alloys is set at +/-.002.

Plastics

Most machined plastics are used for insulators, bushings, and bearings.

  • Extruded Nylon offers great machining and high friction resistance. It’s commonly used for bearings, insulators, and short runs of projects to be converted into injection moulding.

  • Acetal is similar to nylon, but offer improved machinability. They are also commonly used for insulators and bearings, as well as for gears and bushings.

  • HDPE or High Density Polyethylene is used for a number of domestic and industrial applications.

  • PTFE and Teflon both have an impressive set of benefits such as weathering, flame, heat, frictional wear, radiation and chemical resistance, as well as high durability, impact strength and low moisture absorption rate. Recommended for wet environments, insulators, spacers, bearings, and valve components. The expected tolerance for a ½” PTFE or Teflon bar is between +/- 0.005 and 0.

  • PVC is a very low-cost and lightweight plastic. It’s very commonly used for the manufacture of insulators, bushings, fittings, and components for valves and pumps.

  • UHMW or Ultra High Molecular Weight Polyethylene provides one of the highest resistances to abrasion and wear. It’s commonly used in the manufacture of bushings, sprockets, and bearings.

At Challenge Engineering, in Sydney Australia, we machine custom metal and plastic components, and pride ourselves on great customer service. We can manufacture and deliver anywhere in Australia. Please contact us and find out how we can assist your business.

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