How does CNC routing work?
by Brian Bell, Owner, Rocky Mountain CNC Works
February 20, 2024
Consider a two-inch-long cutting tool with razor-sharp edges. Now spin it at 24,000 revolutions per minute and use computer control to guide it. A tool like this can slice away wood or plastic with exceptional accuracy. In fact, accuracies of 0.001 inches or greater are possible. It can also glide through materials at speeds exceeding 800 inches per minute. This is CNC routing. It offers a versatile means of cutting and shaping wood, plastic, and other materials. CNC routers offer outstanding flexibility and efficiency in manufacturing applications. Because of this, they are in widespread use across numerous industries around the world.
What is A router?
But first, what the heck is a router? At its core, a router is simply an electric motor outfitted with handles. Positioned on the motor’s shaft is a collet, allowing the operator to affix a cutting tool, known as a router bit. Upon activation, the electric motor spins the router bit at a high velocity. This spinning cutting edge can then be directed through the material, facilitating the creation of various shapes and profiles. What distinguishes a router from a rotary carving tool is its inclusion of a base, which typically rides on the surface of the workpiece.
The array of router bits available is virtually limitless, offering the ability to cut a myriad of profiles and shapes in the workpiece. Among the most straightforward is the straight bit, characterized by a single cutting edge aligned parallel to the axis of spin. Such a bit serves well for basic material cuts and is also adept at fashioning rabbets, dados, and grooves. At the opposite end of the spectrum are router bits featuring multiple shaped cutters capable of intricately carving and shaping complex profiles on both sides of the workpiece simultaneously.
A basic router and three router bits
What Makes a CNC Router Special?
Welcome to the world of computer numerically controlled (CNC) routers, where precision and practicality converge to redefine fabrication. These machines elevate the router’s capabilities by integrating advanced mechanisms that guide its movements with precision. Think of it as a choreographed routine directed by a computer program.
Larger CNC routers typically use a spindle instead of a router. A spindle is much more powerful than a router and is designed to run quieter and for hours on end. The purpose is the same, though – to spin a cutting tool, thus allowing it to do something useful.
The picture shows a three-axis CNC router that uses a gantry (the elevated beam above the work table) to move the spindle in the X, Y, and Z directions. In CNC routing, X is generally side-to-side, Y is forward and back, and Z is up and down. The entire gantry moves forward and back over the workpiece (the Y direction), a carriage with the spindle attached moves side-to-side along the gantry (the X direction) , and the spindle moves up and down on the carriage (the Z direction).
Other CNC router designs may move the workpiece in the X and Y directions instead of the spindle, thus eliminating the gantry. There are also CNC machines with more than three axes, allowing the workpiece to be rotated in various directions during machining.
The CNC Routing Design & Manufacturing Process
To transform raw materials into something functional, a CNC router relies on a guiding program that directs its movements, shaping and cutting as needed. But where does this program originate?
Typically, the journey starts with a designer or engineer crafting a digital blueprint of the desired object using computer-aided design (CAD) software. These CAD programs range from simple tools for hobbyists to complex suites costing thousands, even tens of thousands of dollars per user.
Once the digital model is complete, it serves as the foundation for a computer-aided manufacturing (CAM) program. Here, an engineer leverages the CAM software, equipped with details about the CNC machine’s capabilities, available router bits, and the chosen material, to generate a numerical control (NC) program. This NC program outlines the precise bits and toolpaths necessary for the CNC router to execute, dictating its movements during production.
The digital model from CAD, generated toolpaths from CAM, and the finished product.
Types of CNC Routed Parts
Using a three-axis CNC router, the different parts that can be cut can be classified as either 2D, 2.5D, or 3D parts.
2D Parts
As the name suggests, 2D parts are simply cutouts. The CNC router lowers the cutter far enough to cut through the material, and thereafter moves the cutter in only two dimensions, the X and Y dimensions. This doesn’t mean, however, that all cuts are either vertical or horizontal. By moving X and Y at different speeds simultaneously, complex shapes can be created. Most plywood parts are 2D, and many plastic and metal parts are also 2D in nature.
2.5D Parts
Parts that are 2.5D add features that have depth. Adding a rabbet, counterbore, or chamfer to a cutout part makes it a 2.5D part. When cutting a 2.5D part, the cutter will be moved to different depths (Z) to cut different features, but creating the feature itself does not require moving in the Z direction during the cut.
3D Parts
3D parts require simultaneous movement in the X, Y, and Z directions and are usually machined with ball nose router bits. Dome and bowl shapes are 3D, as are irregular curves and surfaces. There are many machining strategies that can be used for 3D shapes, the best for each case being determined by the material, the shape itself, and the bits being used.
Materials Used in CNC Routing
CNC routers are incredibly versatile, able to cut and shape a wide variety of materials. This is just a small sampling of the materials that can be used:
Wood & Wood Derivatives
CNC routers find extensive application in crafting 2D and 2.5D components from materials such as plywood, particle board, and MDF. Their precision cutting capabilities make them indispensable for furniture and cabinet makers, interior designers, and the signage and construction sectors, where engineered wood parts are a staple.
Moreover, CNC routers excel in shaping, carving, and engraving solid woods. In the realm of furniture production, where solid wood components demand intricate 3D techniques CNC routing stands as the go-to solution for achieving impeccable results.
Plastics & Foams
A vast array of plastics are utilized across industries today, each presenting unique properties and challenges, yet CNC routers stand ready to cut and shape nearly every variant.
From acetal and ABS to HDPE, PVC, and polycarbonate, CNC routing accommodates the diverse range of industrial plastics. Automotive, aerospace, medical, and industrial sectors all benefit from the precision crafting of plastic parts facilitated by CNC routers, whether in 2D, 2.5D, or 3D configurations.
Additionally, CNC routers are adept at handling various types of foam. Cross-linked polyethylene (XPLE) foam finds widespread use across industries, while high-density urethane (HDU) foam is a preferred material for signage and architectural applications. With CNC routing, these foams, alongside others, can be seamlessly machined to meet the demands of diverse projects.
Non-Ferrous Metals
Delving deeper into the realm of CNC routing, one discovers its remarkable versatility extends beyond wood, plastics, and foam to encompass a wide array of non-ferrous metals. Among these metals, aluminum, brass, and copper emerge as prime candidates for precision machining with CNC routers.
Aluminum, renowned for its lightweight yet durable properties, finds extensive use in aerospace, automotive, and architectural applications. Brass, with its distinctive golden hue and excellent machinability, lends itself to intricate designs in industries ranging from jewelry to musical instruments. Copper, prized for its conductivity and corrosion resistance, plays a vital role in electrical components, plumbing fixtures, and artistic endeavors.
Through the artful manipulation of CNC routers, these metals are transformed from raw material into meticulously crafted components. Whether it’s carving intricate designs into brass for ornate fixtures or shaping aluminum for aerospace components with utmost precision, CNC routing unlocks a world of possibilities for the fabrication of non-ferrous metal parts.
Composites
Expanding the horizons of CNC routing, a plethora of composite materials stand ready to be cut and shaped with precision. Among these, carbon fiber, fiberglass, and aluminum composite materials (ACM) emerge as prime contenders for CNC routing applications.
Embracing Tomorrow: The Impact of CNC Routing
In conclusion, CNC routers represent a significant advancement in manufacturing technology. Their ability to precisely shape materials with efficiency and versatility has revolutionized various industries. From their basic form to the sophisticated systems seen today, CNC routers continue to play a crucial role in modern fabrication processes. As technology progresses, these machines will likely become even more integral to manufacturing, driving efficiency and innovation across the board.