Spex Logo

What is CNC Milling?

What is CNC Milling

CNC milling is a machining process that uses computerized controls and rotating cutting tools to produce a custom-designed part or product. This process is used for machining a wide range of materials, such as metal, plastic, glass, and wood, and CNC machines can manufacture a variety of precision parts.

CNC, or computer numerical control, machines are programmed with a 3D CAD model, allowing machine shops to produce large amounts of identical parts. This machining process is used for a variety of parts in industries around the world. 

Early CNC machines were used in the 1940s and 1950s. This technology was replaced by analog computing technologies. From the 1960s into the 1970s, digital technologies emerged and made the production process more automated and efficient. 

This article focuses on the CNC milling process, the capabilities of CNC milling machines, and the industries it’s commonly used in.

Brief Overview

With modern manufacturing techniques like CNC milling, the applications are nearly limitless. The milling process begins with product design using CAD (computer automated design) software.

A product designer creates a 3D model of the part and its specific dimensions. The 3D model is then converted into computer numeric controlled data that the CNC machines can understand. The data dictates how the CNC mills and lathes will move and cut away material to form the final product.

To prepare a CNC mill for production, the operator attaches the raw bar material onto the machine’s holding piece. Then the operator attaches the milling tools to the machine’s spindle to cut, drill, or shape the end product.

Once the milling machine is set up, it can be used to make high quantities of precision metal parts. These parts can be used in a variety of industries, including: 

  • Aerospace
  • Medical
  • Defense
  • Automotive
  • Industrial
  • And more!

CNC machining capabilities

The milling process is best suited as a secondary machining process to provide finishing features to a custom-designed part, but finished parts can be milled from raw material. CNC milling machines allows us to machine parts of a wide range of materials, shapes, and sizes.

The capabilities depend on the type of milling machines used. CNC milling machines with greater degrees of freedom allow for increased versatility and complexity in the milled parts produced. The capabilities also depend on the machinist’s knowledge and experience.

CNC turning is a different type of machining similar to CNC milling. The main difference is that CNC milling uses a rotating tool to cut away material to form the part, while CNC turning uses a rotating part for cutting.

CNC turning is more commonly used to make cylinder-shaped parts. CNC milling can use multiple tools to cut various angles, holes, and features to machine custom precision parts.

Compare: CNC Milling vs CNC Turning

There are two types of milling machines: horizontal and vertical. The biggest difference between these two milling machines is the orientation of the spindle. With vertical milling machines, the spindle features a vertical orientation. On horizontal milling machines, the spindle has a horizontal orientation. In other words, horizontal milling machines have a cutting tool on a horizontally oriented spindle that’s removes material to form the part.

The milling machines also have slightly different cutting tools. Vertical milling machines usually have longer, thinner cutting tools, while horizontal milling machines have shorter and thicker cutting tools.

How precise is CNC milling?

There are many factors that influence the accuracy of CNC milling. Metal parts are typically used is a system, in conjuncture with other parts which means they need to fit together properly. If one part is too big or too small, it can mess up the entire system. Part tolerances are usually within tiny fractions of an inch, and constantly checked by a quality control team.

In some industries, such as the aerospace and medical field, maintaining tolerances is even more important.

Factors like the type of milling machine, the material being milled, the machinist’s experience, and the size of the parts can affect the level of precision.

Most CNC milling machines can typically produce parts within a 5μm tolerance. 1μm (micrometer) is 1/24500 inches. So, you can expect your parts to be very accurate.

In addition to the accuracy of the technology, modern machine shops have diligent quality control teams that complete an initial inspection. This is documented and provides the customer with an expected tolerance before production begins. Then, during production, standard quality checks are done to ensure the parts are within the desired tolerance.

A higher accuracy benefits both the machine shop and the end customer. Maintaining tight tolerances saves the machine shop time and resources because more parts are useable, and the customers receive a higher quality part.

Materials used in CNC milling

Almost any type of metal can be used for CNC milling. When selecting the right metal for your project, several factors must be considered, including the cost, strength, resistance to wear, and machinability.

At Spex, we machine a wide variety of metals and polycarbonates including: 

  • Stainless Steel
  • Aluminum
  • Brass
  • Carbon Steel
  • Copper
  • Nickel Alloys
  • Polycarbonates

You can reach out to our team if you need help deciding which material is best for your project.

Related content

Contact us

Talk with one of our team members if you have any questions about ordering precision metal parts.

We would love to hear from you! Please fill out this form and we will get in touch with you shortly.
  • Max. file size: 256 MB.
  • This field is for validation purposes and should be left unchanged.
Spex Logo

Phone: (585) 467-0520

Email: sales@spex1.com

85 Excel Drive
Rochester, NY 14621