cnc machining service come in different shapes and forms. This article explains the difference between CNC machining and CNC turning, two common CNC technologies.
CNC machining is a rapid manufacturing process that turns digital 3D designs into plastic or metal parts by selectively cutting away material. Many companies require CNC machining services to make parts and prototypes, and many industries use versatile technology.
But CNC machining comes in various forms. Although all CNC machining technologies follow a similar workflow — software turns the digital design into machine instructions, which instruct the CNC machine to cut material — the hardware for cutting material can differ greatly between machines.
This article discusses the main differences between two of those machines: CNC mills and CNC turning (or lathes centers).
In the article we discuss the essential features of CNC milling and CNC turning while also presenting the main advantages of each technology and a selection of common parts that companies can manufacture using each process.
CNC milling is one of the most common CNC machining services, and machinists can use it to make a wide variety of CNC machined parts. Prototype companies often use CNC mills to make one-off functional prototypes.
CNC mills use computer instructions to move a rapidly rotating cutting tool along three or more axes. When the spinning cutting tool makes contact with the workpiece, it removes material in a controlled manner. The cutting tool makes a succession of passes against the surface of the workpiece until the workpiece resembles the desired part.
Most CNC mills keep the workpiece stationary, holding it down on the machine bed with a vice. However, multi-axis CNC mills may rock or rotate the workpiece to create a greater number of cutting angles. This allows the machinist to create more complex parts without having to manually reorient the workpiece.
Providers of rapid prototyping services use CNC milling because it is a one-stop, end-to-end process with short lead times.
CNC turning is a form of CNC machining that machinists use to make rounded, cylindrical, and conical parts. Although it is less versatile than CNC milling, it is one of the most popular CNC machining services and rapid prototyping services.
Machines that carry out CNC turning are called CNC lathes or CNC turning centers. They are different from CNC mills in that they rapidly rotate the workpiece in a chuck but do not rotate the cutting tool. The cutting tool, affixed to a turret, moves towards the spinning workpiece under computer instructions and removes material where necessary.
A CNC lathe can cut the outside of the workpiece or bore through the inside to create tubular CNC machined parts.
The turret of the machine may have multiple cutting tools that can be individually engaged as required.
CNC mills offer numerous advantages to manufacturers and prototype companies. Unlike lathes, mills are versatile machines capable of creating a range of different shapes. Furthermore, a variety of cutting tools can be used to serve different operations such as roughing and end-milling.
Although they are manufacturing machines in their own right, mills are also useful for post-machining. For example, they can be used to add details to turned, molded, or 3D printed parts.
CNC milling is also fast, repeatable, and inexpensive in low volumes — partly because it does not require tooling. It is therefore found among manufacturing services and rapid prototyping services.
The biggest advantage of CNC turning is its ability to create round profiles. It is much more difficult to achieve perfect roundness using other CNC machining services like CNC milling or CNC routing.
CNC turning is also highly accurate, which makes it a valuable technology for boring holes of precise dimensions with set tolerances.
CNC milling and CNC turning can be combined to reap the benefits of both processes. In most cases, CNC turning takes place first, allowing the machinist to mill further (asymmetrical) details on the part.
Example parts made with CNC milling include:
Example parts made with CNC turning include:
As a rule of thumb, CNC turning is best for parts with round, cylindrical, or conical profiles, and CNC milling is best for everything else. If in doubt, a machining expert can guide you to the right CNC machining service for your unique project.
That being said, CNC milling and CNC turning can be combined to good effect. If a part has a predominantly round shape but also requires asymmetrical cuts or features, CNC milling can follow CNC turning in sequence. And although it is less common, CNC turning can also follow CNC milling — if a boxy or irregular-shaped part requires a large hole bored through its center, for example.
Finally, sometimes you don’t have to choose: CNC milling-turning centers integrate both technologies into a single production device.