CNC routers have been employed by commercial woodworking shops for decades. These big machines cut, drill, dado and route parts for cabinets and furniture in facilities all over the world. And because the technology that drives these machines has become available to consumers, CNC routers are becoming popular with hobbyist woodworkers. You can buy a ready-to-run machine from any of several different manufacturers, but it’s easy to design and build your own.
A three-axis CNC router is a fairly simple machine, and anyone with basic woodworking skills and a few tools can build one. If you’d like to add CNC to your shop, you just need to know a few things about the best materials to use, how a CNC machine works and what software you’ll need.
How a CNC Router Works
It’s important to understand how a CNC machine converts circular motion from a spinning motor into linear motion before you design your own router. Each axis of a CNC router can move back and forth in a straight line by traveling along a pair of guide rails. These rails are like train tracks, and all three axes of a CNC router are equipped with bearings that operate like the wheels of a train. Depending on the type of bearings, they either slide or roll along the shafts (or tracks, if you prefer the train analogy)
Small stepper motors provide the power that pushes/pulls each axis forward or backwards via a lead screw and lead nut. The screw is mounted to the motor at one end and supported by a bearing at the other. It can spin freely but cannot move lengthwise. The nut is secured to the axis, and when the screw turns, the axis moves towards one end of the screw.
By turning the screw in the opposite direction, you can reverse the direction the axis travels.
For each axis of a CNC machine, you need two shafts (train tracks), four bearings (wheels), one lead screw and one lead nut. That means you should buy 6 shafts, 12 bearings and 3 lead screws/nuts for a three-axis router.
CNC Router Types
There are two popular designs for CNC routers. Your budget, shop size and woodworking skills should help you determine which type to build. The first type of CNC router is called a fixed gantry. The gantry is essentially a bridge that supports the y and z axes. It spans the width of the machine (or length, in some designs). The y axis travels from one end of the gantry to the other. The gantry itself does not move. Instead, the x axis travels from end to end.
The other type of CNC router design is called a moving gantry. As you can probably guess, this design incorporates a mobile gantry, which moves along the x axis. The advantage of this type of machine is that it can accommodate longer workpieces than a fixed gantry router of the same size. A fixed-gantry router needs to be more than twice as long as its maximum cut length. So, if you want to be able to route workpieces up to 48” long, your machine needs to be over 8’.
Think about it this way: the moving part of the x axis is 48” long. It has to travel 48” to make a full-length cut. To allow for that much travel, you need 48” for the length of the axis, plus 48” for the length of travel. That comes out to 96” overall, or 8’.
Because a moving gantry travels from one end of the x axis to the other, it can cut parts almost as long as the x axis itself. That means you can build a machine with a smaller footprint that’s capable of the same cut length.
Best CNC Router Materials
MDF or Plywood
To build a machine that can make accurate, repeatable cuts, you need to use flat and sturdy materials. MDF is super flat, easy to machine and available at just about any home center or hardware store. It’s about $40 for a 4’ x 8’ sheet and is the choice of many CNC builders on a tight budget.
One disadvantage of this material is that it tends to split when nailed or screwed together. If you’re going to build a CNC router with MDF, you’d be wise to avoid mechanical fasteners as much as possible. Instead, use dowels or biscuits and yellow glue.
Plywood is light and super strong, but it’s not usually as flat as MDF. It holds screws and nails much better, but its tendency to warp means it’s not the most suitable material for use in a CNC router.
Plastic: HDPE and UHMW
Plastic sheets are ideal materials for a CNC. Two of the best options are HDPE (High Density PolyEthylene) or UHMW (Ultra-High Molecular Weight polyethylene). PVC works well, too. You can cut, route and drill all of these materials with standard woodworking tools and bits. To join plastic parts, just drill and tap holes in the material and connect with bolts. This gives you the option of easy disassembling your machine later if you want to make modifications or move it to another location.
If your budget allows, consider using extruded aluminum profiles to build your machine. You can buy a variety of different profiles that are made to work with special fasteners. Some manufacturers will even pre-cut the profiles for you and provide machining services so that you can assemble the parts with a hex key or wrench.
Steel and aluminum tubing are also great choices. They’re rigid and fairly easy to work with, if you have the right tools. If you don’t, ask your local metal fabrication shop if they will pre-cut, drill and tap parts for you. It usually doesn’t cost much to get steel tubing cut to size and drilled.
CNC Electronics: Motors and Controllers
To power your new CNC machine, you need stepper motors and a controller. Each axis requires its own motor, and anything with 269 oz/inches to 485 oz/inches of torque is probably sufficient for most projects. Search for stepper motors online and view the seller’s documentation to find the right motors for you.
You also need a controller to provide signals to the motors. Think of a controller as a circuit board that communicates between your computer and the CNC router. Get up and running fast by purchasing a kit that contains all three motors and the controller. There are some excellent options online from sellers like Xylotex, Probotix and StepperOnline.
Software is often the most confusing part of a CNC router for new users. There are several different types of software involved in CNC, and you need at least two different applications to run your machine.
The first application you need is the controller software, which provides signals to the motor controller and steppers. Every time you cut a part with your CNC, you’ll use the controller software to open and execute a program.
Mach 3/Mach 4 is one of the most widely used applications for hobby CNC machines. It’s inexpensive, powerful and fairly easy to use. Artsoft, the company that develops the software, provides free tutorial videos that will get you started quickly.
Before you can cut anything with your new router, you need some way to create CNC programs. You can generate a program manually with G code, the programming language that directs your motor controller. But it’s easier to start with software that allows you to simply draw parts and convert them into G code. That software is known as CAD/CAM (Computer Aided Drafting/Computer Aided Manufacturing).
CAD/CAM programs can get extremely complex, but you don’t need much to get started. Some of the best programs for beginners are even free. Check out the browser-based application Jscut at jscut.org. It lets you import an SVG file and convert it to G code right in your browser. You can find lots of free SVG files online.
Fusion 360 is a powerful and free CAD/CAM application from Autodesk, the makers of AutoCAD. There’s a fairly steep learning curve with this software, but you can do just about anything with it once you’ve familiarised yourself with the user interface and features.
CNC Router Plans
The easiest way to build your own CNC router is to start with plans from someone who has already designed and built a machine. You can find dozens of plans online, some free and some available for just a few dollars.
You don’t have to build your machine according to someone else’s plans, but you’ll learn a lot about how to design a CNC router by studying plans other people have developed. It’s easy enough to tweak another design to fit your needs. Your best bet is to download several plans, study them and incorporate the features you want into your own design.