6 Parts of a CNC Router - CNC Router Components

It’s critically important that the frame of a CNC router is as stiff as it can be. Precision is impossible if the position of the workpiece or the cutter is uncertain because of the flexure of the frame. The consequences of an insufficiently stiff structure in a router vary, depending on the degree of flexibility, including: chatter, cross-bridge flexing, and displacements on any one axis.

Tables vary in their construction and locating systems for workpieces. The most adaptable tables are those made with vacuum pull-down or integrated T slots (or both), so a wide variety of workpieces can be clamped anywhere. Aluminum extrusion construction is very common and offers a good mix of adaptability, stiffness, and low weight. Alternatively, a range of strong materials can be machined to make a T-slot table with slots on two axes, making a checkerboard pattern of mount points.

The spindle is the single most critical component of a CNC router. In most machines, the spindle is integral to the motor shaft and relies on the motor bearings. This is a low-cost construction method, but unless the motor bearings are sufficiently robust, premature wear problems may result.

Spindle/motor bearings come in various qualities; they wear items that require periodic replacement. Loose bearings mean a loose cutter, and accuracy is lost. Stiff bearings add hard work and more heat to the process. Bad quality or worn bearings add a lot of noise to a fast-turning cutter.

The ways or slides are the motion tracks that enable X-Y-Z movement. It is from these (and a stiff frame and good quality lead screws) that any router derives its precision …or lack of it. The most common ways are precision-ground stainless steel rods on which either plain bushes or recirculating ball collars run. An axis requires at least two such rods – and the further apart those rods are, the more precise the axis motions will be. Plain bushes are lower cost, recirculating ball bushings are freer moving but more expensive. Free motion means more precise positioning. 

More expensive machines tend to employ V-form tracks with grooved, sealed ball races locked onto both sides of the track. This track provides equal stiffness but requires less height to maintain the motion. Recirculating ball slides are harder to protect from dirt than sealed ball races. They have wiper seals that clean the ground shaft way, but some material will often get past this.

The axis drives convert the output of the stepper motors that drive the machine from rotary to linear motion. Lower-cost machines often use toothed or timing belts for this. While that may sound less than optimal, toothed belts have been used in robotic positioning systems in this way for decades and can be durable, when kept clean.

More expensive machines tend to have recirculating ball screws. These offer the advantages of freer motion and lower hysteresis. But they pose the same contamination/wear issues that similar systems in the sliding ways suffer, so cleanliness is essential for long machine life.

The control computer module is the brain of any CNC machine. It takes G-code and turns it into motion by driving/controlling the various axis stepper motors and the spindle motor. These devices are sophisticated I/O control devices that control a range of outputs – from simple 3-axis and cutter speed up to 5-axis, with coolant pumps, motor cooling systems, automated cutter/router changers, and more.

CNC controllers are generally single-board computers. They are composed of processors, memory, integrated self-protection mechanisms, and power supply. CNC controllers are designed to turn the input G-code the user provides into precise and repeatable movements that cut a complex net shape from a material blank.

CNC routers are automated machine tools that are widely used for cutting 2D and shallow 3D profiles from generally soft materials. A CNC router uses three motion axes that transport a rotating cutter to remove material in a programmed pattern. This motion is driven by the point-to-point instructions of the G-code. Cutting tools can be changed (either manually or automatically) to remove material in progressive and generally small-depth cuts to maintain higher accuracy and better surface finish. For more information, see our guide on CNC Machining.

Some Common CNC Router Accessories

CNC router accessories include many categories of equipment, including a surprising number of tools and accessories – of wide-ranging cost and usefulness. These are:

1. CNC Router Bits

“Bits” is a catch-all term for a wide range of drills and cutters. This accessory includes the face or shell mill, square and bull nose end mills, and ball end mill. Bullnose and ball end mills are good for cutting the surfaces of curves, as they don’t create grooves and can blend surfaces to a smooth roundness.

2. CNC Collet

A collet is a simple clamping system that uses a split tube (with a tapered nose). It forms a close fit with the straight tool shank and has a lock nut that clamps the taper to squeeze the split tube onto the tool. The collet will sit within a tool holder, often called a collet chuck, which is generally fitted to the router with a taper locator and spring locator to lock it in place. In many simpler setups, the collet chuck is not removed from the spindle but is fixed in place, so new tools and collets to suit them are handled in place.

3. CNC Tool Holder in Place

Collet clamped tools that are fitted to a removable collet chuck can be quickly fitted to the machine's cutter drive, using a variety of locating and locking systems. For auto tool change setups, each required tool will be placed into its collet. The machine will pick up new tools from fixed positions on the table when required. Each of these collets will have a quick-release upper portion that the router can attach to without difficulties.

4. Automatic Tool Changer Tool Forks

Tool changer forks are devices in which a collet chuck sits when not in use. These devices are usually placed in a line to make a tool rack. The position of each collet chuck is fixed, and the machine can deposit the used tool in an empty fork and then acquire the next from another position.

After each tool change, the machine confirms the tool position and cut depth. If the tool has been incorrectly set in the collet, this will result in over- or under-cutting the part. A tool sensor, a low-cost touch-and-go detector, helps ensure tools are set correctly.

5. Vacuum Suction Pods and Cover

Vacuum clamping devices, or suction pods, are a convenient way to locate and retain workpieces on the table. They can be clamped down using the T slots or other table-clamping systems and allow quick release of the parts. This part is particularly useful when a run of parts is being produced, as it allows precise and fast repositioning of the next workpiece without tools. Suction pods come in a wide range of shapes, sizes, and heights.