CNC machining is a general term used for a variety of machining applications. “CNC” stands for Computer Numerical Control and refers to the programmable features of a machine that allow it to perform many functions with minimal human control. CNC machining is the manufacturing of parts using CNC-controlled machines. The term describes a range of subtractive manufacturing processes that remove material from bar stock or blanks to produce finished parts. There are 5 different types of CNC equipment to perform the 5 common types of CNC precision machining.
CNC precision machining is widely used in industries such as medical, aerospace, industrial, oil and gas, hydraulics, etc. CNC machining can be performed on a variety of materials, and can process metals, plastics, glass, composites, and wood.
Precision CNC machining has many advantages over machining without CNC programmable features. It can significantly reduce machining cycle time, improve surface finish, and improve quality and consistency.
Here are the 5 most common types of precision CNC machining:
1 – CNC Lathe Machining
The characteristic of a CNC lathe is its ability to rotate (turn) the material during the machining operation. The lathe’s cutting tool is fed in a linear motion along a rotating bar; this removes material around the circumference until the desired diameter and features are achieved.
A subset of CNC lathes is the CNC Swiss lathe (also called an automatic lathe). With a CNC Swiss lathe, the bar is rotated and axially slid into the automatic lathe via a guide bushing, which then automatically machines the cut part. Generally, CNC automatic lathes are suitable for machining small diameter parts.
CNC lathe machining can create internal and external features on a part: including drilling, broaching, reaming, grooving, tapping, threading. Parts manufactured by CNC lathes and turning centers include screws, bolts, shafts, joints, and more.
2 – CNC Milling
CNC milling machines are characterized by their ability to rotate the cutting tool while keeping the workpiece/block of material stationary. They can produce a variety of shapes, including face milling (shallow, flat surfaces and cavities in the workpiece) and perimeter milling (deep cavities such as slots and threads).
Parts suitable for production on CNC milling machines are typically square or rectangular shapes with a variety of features.
3 – CNC Laser Machining
A CNC laser machine has a pointed router with a highly focused laser beam that is used to precisely cut, slice or engrave materials. The laser heats the material and melts or vaporizes it, creating a cut in the material. Typically, the material is in sheet form. The laser beam moves back and forth across the material to create a precise cut.
This process allows for a wider range of design freedoms than conventional cutting equipment (lathes, turning centers, milling machines) and often produces cuts and/or edges that do not require additional finishing processes.
CNC laser engravers are often used for marking (and decorating) parts. For example, logos and company names are difficult to machine with CNC turning or CNC milling processes. However, they are very easy to engrave with a CNC laser and can be added to a component even after the machining operation is complete.
4 – CNC Electrical Discharge Machining (EDM)
CNC Electrical Discharge Machining (EDM) uses highly controlled electrical sparks to machine materials into the desired shape. It can also be called spark erosion, spark machining or wire burning.
A component is placed under the electrode wires and the machine is programmed to send an electrical discharge from the wires, generating intense heat (up to 11,700 degrees Celsius). The material is melted or flushed away by a liquid to create the desired shape or feature.
EDM is most commonly used to create precise micro holes, slots, tapered or angled features, and a variety of other more complex features in a component or workpiece. It is often used to machine difficult shapes and sizes, and is often used to machine very hard metals. An example is gears.
5 – CNC Plasma Cutters
CNC plasma cutters are also used to cut material. However, they do this using a high-powered plasma (electron ionized gas) torch that is controlled by a computer. Similar in function to a handheld pneumatic torch used for welding (up to 5,500 degrees Celsius), a plasma torch can reach up to 27,500 degrees Celsius. The plasma torch melts through the workpiece to create the cut in the material.
Whenever CNC plasma cutting is employed, the material being cut must be electrically conductive. Typical materials are conductive metals such as steel, stainless steel, aluminum, brass and copper.
Precision CNC machining offers a wide range of production capabilities for manufacturing components and finishing. Depending on the use environment, required materials, lead time, quantity, budget and required functionality, there is usually an optimal method that will provide the desired results.
