CNC Router: Definition and How It Works

A CNC router is a subtractive manufacturing process that uses a rotary tool to remove material from wood, expanded polyurethane foam, plastic, and soft metals. A CNC router typically has a gantry-style construction where the spindle travels left and right along the x-axis and back and forth on the y-axis. A CNC router is different from a standard CNC mill because it is not designed for high-speed cutting of complex geometries in hard metals. Gantry-style CNC routers are generally less stiff than standard CNC mills, and when harder metals are being cut. For that reason, they are limited to cutting softer materials like wood, soft metals, and, in some cases, steel. It must also be noted that routers have limited travel along the z-axis, meaning they cannot create deep holes and slots. For more information, see our guide on CNC machining.

A typical CNC router is shown in Figure 1 below:

A CNC (Computer Numerical Control) router works by moving a tool to specific x, y, and z coordinates throughout the machine's available working area. A router or high-speed spindle with a cutting tool then removes material at the desired locations. Different cutting tools can be used depending on the material and the feature being machined. These tools can be manually changed or in the case of a more advanced machine, an ATC (Automatic Tool Changer) can swap out tools.

A CNC router is controlled by a set of servo motors. These motors get their position information from a control-circuit board that converts the user-supplied G-code into precise sets of coordinates for material removal, ultimately resulting in a finished part.

Where is a CNC Router Used?

CNC wood cutting machines are widely used in the woodworking industry to produce functional and ornamental components for fine furniture. 

To What is a CNC Router Comparable?

A CNC router is comparable to a CNC mill. They both move cutting tools to pre-programmed positions to carve out a part from solid material. However, the key difference is that a CNC mill is able to machine harder materials, like steel, as well as wood and plastic while maintaining higher levels of accuracy. CNC routers also have a larger cutting area and are therefore better suited to large plants or plates.

The main benefit of a CNC (Computer Numerical Control) router is its low cost when compared to a CNC mill. Its affordability  makes CNC router’s an accessible technology that can easily be purchased by small businesses and has the potential to dramatically improve a company’s overall productivity. 

What Software Is Used in a CNC Router?

To operate a CNC router, both CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing) software packages are required. The CAD software is used to make a 3D model of the desired part. The CAM software converts the CAD model into a set of machine-readable instructions called G-code.

What are the Specific Parts of a CNC Router?

A CNC router machine is made up of four main components as described below:

1. Bed: The bed is the area where the raw stock is mounted. Some beds will have multiple holes or attachment points to make it easier to mount clamping hardware to keep the raw stock fixed in place during the cutting operations.
2. Controller: The controls typically consist of multiple stepper controller drives to control the motion of the stepper motors and the speed of the spindle/router.
3. Motors: A CNC router machine has a stepper or servo motor for each of the three motion axes. Stepper motors are typically found on cheaper hobbyist machines whereas servos provide better positioning precision and are more expensive. A separate high-speed motor rotates the cutting tool. 
4. Spindle/Router: The spindle is what is used to rotate the cutting tool to the required operating speed. The spindle is often mounted on a gantry above the bed. This gantry can move left and right along the x-axis and back and forth on the y-axis. 

For more information, see our guide on Parts of a CNC Router - CNC Router Components.

What Materials Can Be Cut on a CNC Router?

A CNC (Computer Numerical Control) router is primarily limited to cutting non-metallic materials such as MDF (Medium Density Fibreboard), plywood, acrylic, polyurethane foam, and polyethylene sheet. It can also cut softer metals such as brass, aluminum, and in some cases, steel. CNC routers are rarely used to cut harder materials like steel, as the general geometry and construction method of a router makes cutting these types of materials difficult and error-prone. CNC routing can, however, be used to engrave lettering onto harder materials like granite. 

Which Industries Make Use of CNC Routers?

CNC routers are a low-cost alternative to CNC mills and are used in a range of industries, some of which are listed below: 

1. Furniture: CNC routers are used to manufacture a wide range of furniture-related components out of wood or plastic. 
2. Molding: CNC routers are used to make wooden patterns that are, in turn, used to make sand molds for metal casting. Wooden patterns are low-cost and can be machined quickly on a router.
3. Packaging: CNC routers can easily cut foam into custom housings for sensitive or high-value products, 
4. Advertising: CNC routers can engrave custom lettering for signs and various advertising-related products. These signs can be made from wood or plastic. 

Is it Possible To Use a CNC Router in a Carpentry Shop?

Yes, CNC routers are a common feature of most carpentry shops. They have become an indispensable tool for the manufacture of components as simple as cupboard doors and as complex as 3-dimensional artworks. 

What is the Best CNC Router To Buy?

Deciding on which CNC (Computer Numerical Control) router machine is best to buy depends heavily on the type of work that needs to be done as well as the skill level of the operator. For beginners performing small-scale cutting of wood and foam, a Shapeoko is the ideal do-it-yourself CNC router. This model is extensively used in the DIY maker industry and as such, there is a wealth of information available on how to use them optimally. However, if the product mix includes large, industrial-scale components, then a more robust machine is appropriate. The ELECNC 2130, which can automatically load material, change tools and label components, would be an excellent choice. These machines require significant capital investment, so it is important to fully quantify the business case before purchasing such a machine.  

What is the Difference Between a CNC Router and a Spindle?

A spindle is typically the part of a router where the cutting tool is attached. The spindle then rotates the tool at a high rate to allow it to cut a part. In some cases, a CNC router machine has a purpose-built spindle installed whereas for lower-cost machines a standard off-the-shelf router is often installed on the machine's x-axis as a cheaper spindle alternative. 

This article presented the CNC router, explained what it is, and discussed things to consider when using it in manufacturing. To learn more about CNC routers, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities, including CNC machining and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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