CNC machining can be used for small production runs and also larger runs, depending on the level of automation. Because machined parts do not require special tooling, such as in injection moulding, it is often the economical choice for singular custom parts.
Stainless steel is a low carbon content steel with high strength. It is valued for its high corrosion resistance, which makes it suitable for a wide range of sectors including the oil & gas, chemical, maritime, aerospace and atomic energy industries. Any steel alloy with a minimum of 10.5% chromium can be considered as a stainless steel.
There are four main families of stainless steel that can be categorised according to their microstructure. These are martensitic, austenitic, ferritic and duplex.
Austenitic stainless steel has higher corrosion resistance and toughness, but lower strength and hardness than martensitic stainless steel. Due to the lower hardness of austenitic stainless steels, it is preferred for use in CNC machining.
CNC-manufactured stainless steel parts include surgical instruments, medical tools, cookware, industrial machine parts, gears, tractor parts, pressure vessels and measurement tools.
Aluminium is strong and lightweight, yet soft and ductile. This makes it easier to work with due to the lower power to cut when compared to steel.
Due to its lightweight nature, it is used extensively in the aerospace and automotive industries.
There are different grades of aluminium that are used in CNC machining.
6061-T6 is a commonly used alloy in CNC machining, due to its versatility, cost, and good specific strength. It is available in a range of different heat treatments.
While it is strong, it does not perform well under high levels of mechanical stress or fatigue.
It is used often in car chassis components, bike frames, heat sinks, and even satellite structures.
For more high-performance needs, 7075-T6 grade aluminium is the more optimum choice. It has superior specific strength compared to 6061-T6 and is better suited for high stress applications such as aircraft structures and missile components.
All steel has some carbon inside, but when the carbon is the main alloying element, it is considered to be carbon steel.
Carbon steel comes in four different types, which are:
Carbon steel is the most commonly used type of steel and makes up about 90% of all steel used.
Low-carbon steel is best suited for sheet metal work.
Medium carbon steel is commonly used in CNC machining and is used in axles, gears, rails, fluid pipe couplings. It has excellent strength, and high heat resistance, so it is often used in demanding applications such as in automotive engine crankshafts. Crankshafts can be forged, or manufactured with CNC.
High carbon steel (tool steel) has a much higher tensile strength than medium and low carbon steel. It is difficult to cut, and wears cutting tools much quicker than lower carbon steels.
Special consideration must be made when cutting high carbon steel with a CNC machine, especially with regards to tool selection, cutting speed, and cutting depth. It is possible to cut with CNC if these factors are taken into consideration though, and many parts such as bolts, kitchen knives, and aircraft components are made this way.
Ultra high carbon steel is hard and brittle and very hard. It is used to manufacture punches, dies, springs and high-strength wire. It is difficult to form with CNC and many parts manufactured with ultra high carbon steel are done so with powder metallurgy processes.
Brass has a high tensile strength, an attractive colour, and is very soft. Because it is a softer metal, it is also easy to machine. It is often chosen over other metals due to its comparatively low price.
Brass is an alloy made from copper and zinc. It can also contain other elements such as lead, which reduces the friction and increases wear resistance. This makes it especially good for components requiring low-friction such as lock mechanisms, bearing faces and gears.
Brass also has high corrosion resistance, which is why it is used in plumbing, and has traditionally been widely used in maritime applications where salt corrosion can be an issue.
CZ121 grade brass is harder and stronger than usual grades. The addition of lead to this alloy makes it softer, and reduces the chipping during machining operations.
For this reason, CZ121 is often used in security devices such as multipoint lock mechanisms.
Sometimes, it is not required to use metal components, especially in lower stress applications, or applications in lower temperature environments.
In these cases, it is often acceptable to use plastics instead of metals, especially for production runs that are too small to be economically viable for injection moulding.
For smaller production runs, plastic parts can be produced on CNC systems such as mills or lathes.
Plastics are often selected for applications requiring reduced weight, such as in aerospace or automotive. Prototypes in these areas are often made with machined plastics.
There are a wide range of plastics that can be CNC machined, including ABS, PEEK, polypropylene, POM (Delrin), polycarbonate, Nylon, PTFE and many more.
CNC made plastic parts are often used in custom fluid applications where a non-standard replacement part is required. Such parts can include pipe fittings such as unions, nozzles, flanges, diaphragms, threaded fittings, reducers, inserts and solenoid casings.
If there is a product requiring precision, repeatability, and a relatively low capital expenditure, then CNC is an ideal solution for parts ranging from prototypes, to parts intended for end use.
Surgical instruments used during medical procedures are often made with CNC processes. They require high levels of precision, repeatability, surface finish and they need to be made from sterilizable materials.
Such instruments include cutters, laparoscopic graspers, blade handles, forceps, scissors and implant holders.
Smaller medical parts can be made with micromachining, which can produce components as small as 50 microns.
Parts made with micromachining include miniature screws for implants, catheters, stents, pacemaker components, and ophthalmic devices.
CNC parts are often found outside of the operating theatre also. Larger machines such as MRI scanners and X-ray machines can often contain hundreds of CNC-made components. Medical implants are often designed as custom parts, unique for the patient.
For cases like these, CNC is an ideal solution as parts manufactured with CNC can be produced economically in small production runs.
Implants are often fabricated from machined titanium, and even from biocompatible plastics such as PEEK. 3D printing can also be used in combination with CNC machining to produce highly custom implants such as spinal implants.
Other materials used for CNC produced parts in the medical industry include stainless steel, tantalum, platinum, palladium, and other plastics.
Industrial machinery is used to produce accurate parts, and are required to be highly reliable in order to reduce machine downtime and increase profits. CNC machines are industrial machines, and they themselves contain a large number of CNC machined parts inside them.
Many industrial machines use linear motion systems, and the linear rails and bearings that form the basis of these motion systems must be CNC machined and finished with precision. Often the surface finishes require post processing with CNC-controlled precision grinding systems.
Other CNC-made components inside industrial machines include gears, cams, lifters and other precise components to create and convert motion.
Industrial machines are not simply limited to the manufacture of other machines. There is industrial machinery in all aspects of industry, ranging from agriculture to food processing, to production lines.
Wherever there is precision required in manufacturing, assembly, or resource harvesting, there will largely be components manufactured by CNC.
CNC machining is used extensively in the automotive industry. Engine blocks are often manufactured with casting, but require CNC for surface finishing, especially for the internal components which must have high dimensional accuracy.
And it’s not just the vehicle components that are manufactured with CNC machining.
Often, the tools used to fabricate other components must be made with a CNC system.
Components such as body panels are often formed on a die stamping press or other forming tool, which must be made with CNC.
There can be hundreds of plastic components on a car also. These can be found on the trim, on the exterior (such as door handles) and throughout the entire interior of the car. Most of these plastic components are made with plastic moulding processes, and require CNC made mould tooling, to allow for the high production runs.
A car dashboard is often made from a single moulded plastic part, and the mould used to manufacture the dashboard is a huge CNC machine part.
The moulds for producing dashboards can often cost over a million dollars to produce.
Pretty much every single part of a car has been manufactured with the use of CNC machining, either by directly machining the part, or indirectly, by machining the tooling to make the part.
The alternative energy (or “new energy”) industry is focused on the manufacturing and operations of renewable energy sources, as opposed to traditional non-renewable fossil fuel based technologies.
Turbines contain many CNC made parts, and even parts that have been cast (such as turbine blades) require CNC finishing to produce high quality surface finishes.
Solar PV (photovoltaic) systems, or solar panels, are manufactured by forming molten silicon into ingots, before they are sliced into wafers. Many of the silicon forming tools and machining tools for creating the wafers are created with various CNC methods.
Robots come in many different types, and are used in a variety of industries from automotive welding robots, to surgical robots, to military robots such as drones and bomb disposal robots.
They require predictable, accurate and controllable motion, often needing micron levels of precision. This precision is related to the accuracy and tolerances of the component parts.
These parts, especially metal parts, are often manufactured with CNC machining.
A core part of many robotic systems is the stepper motor. Many parts within the stepper motor, from the shaft to the housing, are all manufactured with CNC machining.
Naturally, robotic systems perform a lot of motion-based activities, and so the mechanisms for these motions such as gears, cams, and linear systems are all manufactured with CNC processes. Linear systems require a high degree of precision, and so can be manufactured with numerous CNC processes such as milling and CNC-controlled precision grinding, to obtain the best surface finish.
The end effectors of robots, such as graspers on a surgical robot, are CNC machined also.