Chances are if you've picked up this book (or purchased a copy), then you're probably somewhat familiar with the term CNC. But maybe not. CNC is an abbreviation for computer numerical control. A CNC machine, then, is a machine that carves out objects in three dimensions from a solid block of material. CNC machines are commonly used in industry to produce small parts such as bicycle stems and tools. Low-cost CNC machines are increasingly used by serious hobbyists, especially woodworkers, to carve creations out of materials such as wood and aluminum.
Read through this chapter and then flip through the rest of the book-you'll start seeing pictures of an unusual device being built (beginning with Chapter 7 and ending with Chapter 17). That device is the do-it-yourself (DIY) CNC machine. The DIY part is because you're going to learn how to build one in this book. When you're done, you'll be the proud owner of a three-dimensional carving machine that can fabricate parts and objects from soft materials such as wood, plastics, and even aluminum.
Computer numerical control is a very broad term that encompasses a variety of types of machines-all with different sizes, shapes, and functions. But the easiest way to think about CNC is to simply understand that it's all about using a computer as a means to control a machine that carves useful objects from solid blocks of material. For example, a CNC machine might begin with a solid block of aluminum, and then carve away just the right material to leave you with a bicycle brake handle.
CNC machines can be divided into two groups: turning machines and milling machines. A turning machine is generally made up of a device that spins a workpiece at high speed and a tool (sharp edge) that shaves off the undesired material from the workpiece (where the tool is moved back and forth and in and out until the desired form is achieved). A milling machine is a machine that has a spindle (a device similar to a router) with a special tool that spins and cuts in various directions and moves in three different directions along the x, y, and z axes.
Historically, you wouldn't actually need a computer to create forms with a turning machine or a milling machine. Adding a computer to the mix allows you to design a product on a computer first and then specify how the machine should cut this product. To design the product is to produce a computer-aided design (CAD) file. Then you specify how the machine should cut the product, and the result of that step is a computer-aided manufacturing (CAM) file (or G-Code file, or .NC file-there are many names for this type of file). This CAM file remembers all of the operations that the milling machine must follow to cut out the parts for the product. The computer tells the CNC machine how to build the part by interpreting the CAM file into signals that the CNC machine can understand.
Industrial applications for CNC machines have been chiefly based around the removal of metal to create a desired form. Metal is widely used for producing almost everything we see around us, even though these things may not be made of metal themselves. Some of the most obvious products that are made of metal are cars. The engine block and the parts within the transmission are directly produced from a CNC machine because tight tolerances are necessary (a tolerance is a range in dimensioning to which the machine must adhere). However, most of the parts of a car are not made by a CNC machine, but they have a latent connection to one. For example, how do you make a quarter panel? There is a hydraulic press with a thing called a die to create an impression in a sheet of metal. Most of the parts of the hydraulic press were made from a CNC machine. The die, the part that carries the negative form of the quarter panel and that can be replaced when design changes, was also made by a CNC machine, and then tempered for hardening and heat resistance. Even the plastic parts of a car have some connection to a CNC machine. Many of these parts were made from a mold that was created using a CNC machine.
Because CNC machines have very high precision and they can provide information back to the computer, they are also used in dimensional testing. If a switch (probe) is fastened to the location of the tool, it can analyze the measurements of a part that was produced. The machine runs this probe all over the part to confirm its desired form and measurements.
For more information on industrial uses of CNC machines, visit www.cncinformation.com
There is a large following by various hobbyists and DIYers around the globe interested in the concept of CNC machines. Roboticists, craftsmen, handymen, home machinists, small business owners, tech enthusiasts, backyard scientists, and artists have all discovered how a CNC machine can open doors to new designs and more detailed creations. A roboticist, for instance, will use a CNC machine to create the structural components of the robot with very high precision. Making these components by hand would be tedious and very time consuming. Using a CNC machine, the parts come out beautifully and fit together with great precision.
For the typical handyman, a great example of using a CNC machine might be designing and making cabinets for around the house. Typically, cabinets share many of the same dimensions and can be cut by a CNC machine over and over. Imagine cutting all of the drawers and cabinet lids by hand! The parts are numerous and the work would be quite tedious. But with a CNC machine, the individual pieces are cut and the cabinets assembled; no driving around looking for the right cabinets, having to special order them, and then waiting for delivery from the home improvement store. (The cabinets will need assembly, too, but with your own CNC machine, you'll find that the high cost of buying them in the store can be eliminated.)
CNC machines for personal use can be purchased from a variety of manufacturers, but many DIYers suffer from sticker shock the first time they begin shopping for a CNC machine. Prices of $3,000 and higher are typical for small, desktop versions that often come with a 12"×18" workspace, meaning you'll be limited to working on materials that fit in that small space. CNC machines with workspaces that allow for materials of 2'×4', for example, start around $7,000, and prices go much higher for larger workspace tables.
For most DIYers, owning their own CNC machine is still out of reach financially. But no longer-this book brings CNC within easy reach. If you can afford to spend $700 to $800, then you can afford to build your very own CNC machine.
With your DIY CNC machine, you're going to be able to do some amazing things-cut, drill, etch, and sculpt-with a variety of materials. In fact, author Patrick Hood-Daniel uses his own CNC machines to make more CNC machines! He has a machine cut and drill the MDF (medium-density fiberboard) parts used to build more CNC machines. (You can do this, too, but first you'll need to build your own DIY CNC machine-it all starts there.)
Your DIY CNC machine is made of MDF, a rigid material that holds up well to cutting and drilling, as well as being extremely strong and dimensionally stable (it doesn't shrink or expand with fluctuations in the weather or humidity). The MDF parts you'll be cutting and drilling are bolted together using a variety of sizes of bolts, nuts, washers, and other hardware. Finally, you'll be adding a mix of electronics and one computer to bring your DIY CNC machine to life and amaze your friends and family (who will, unfortunately, come up with all kinds of requests for you and your machine).
The DIY CNC machine isn't something with vague dimensions and a random mixture of hardware. We'll tell you exactly what to buy. You'll be cutting and drilling material from plans created by author Patrick Hood-Daniel and tested and used to build three machines; one by James Floyd Kelly, one by Darrell Kelly, and one by Jim Burt (not to mention the number of machines built by Patrick himself).
When you're done, however, you're not really done. CNC is a growing and changing technology, so the limits of what you can do with your machine are really up to you. While this book will give you the basic information to build and use your machine, you'll want to continue to improve your skills by delving deeper into the software and pushing the limits of your machine. (We'll provide you with some good resources for further research and learning later in the book.)
If you're like us, you're ready to begin. But trust us when we say that one of the best things you can do before starting to build your own CNC machine is this: read the entire book through at least once. Doing so will give you a glimpse of the final machine and a better understanding of how you'll get there. You may find, as we did, that half the fun of owning your own DIY CNC machine comes from building it.
Example 1.1. HISTORY OF THE DIY CNC MACHINE, FROM PATRICK HOOD-DANIEL
My desire to hop on the bandwagon of this great hobby started as a means to an end. The end has not been realized because I became more interested in the CNC machine itself and want to provide simpler designs and instruction to others who wouldn't otherwise have the means to own a traditional CNC machine.
The DIY CNC community has been around for a long time; pretty much ever since the boom of the Internet. I learned most of what I know from the information on the Internet. With my prior design training, I spent quite a bit of time improving what others had created.
Through my effort to create an initial CNC machine from resources on the Internet, I found that the materials did not hold up well with use and tended to exhibit undesirable flexing. I learned through trying and experimenting . . . and discovered many things that worked and didn't work. I quickly learned, for example, to stick with MDF as the material of choice for making my CNC machines.
Over the years, I made hundreds of trips to the home improvement store (my laboratory of ideas). The components that I used to start my CNC journey included round metal bar stock and a bunch of very cheap MDF. I thought that the metal stock would have some pretty good rigidity-I mean . . . it's metal! But I was very wrong. After putting an assembly together and using the bar stock as the rail, I noticed quite a bit of flexing in the assembly. This was not going to work, so I came up with a better way. (I was deathly afraid of trying something that was not illustrated on the Internet in fear that if it wasn't done before, it wouldn't work. But I did it anyway.) I used aluminum angles as the rails and MDF as the midsection between the rails to provide the necessary rigidity. Initially, I tried the bar stock with this technique, but the bars would still flex. The aluminum rails wrapping the MDF worked perfectly and the machine was rigid and stable-perfect! Well, perfect is a subjective word here, but it was good enough for me. And I think by the time you're done following this book's instructions and building your own machine, you'll agree.
Everything from that point on became intuitive. The mechanics and motion of the machine were all designed so that the parts could be cut, drilled, and assembled using nothing more than a few simple hand tools. (I'm not kidding-the early machines were cut and drilled with nothing more than a mitre box, a small saw, and a battery-powered drill.)
This book documents my design; you'll be able to skip the frustration that I faced because this is the design I developed that worked. The DIY CNC machine fulfills my desire to provide others with a simple, elegant, and fully functional CNC machine.
Chapter 2 is going to give you a quick introduction to the tools and equipment you'll be needing as you build the DIY CNC machine, as well as vendors for purchasing the electronics for the machine. We highly recommend, however, that you read through the entire book before purchasing any tools or equipment; if you understand what will be accomplished in each chapter, you may be able to postpone some purchases until later in the book.