I would like to present a little history and philosophy behind my CNC machine. First, I got interested in CNC when I tried to find ways to make many small parts for building large scale locomotives. These are built at an 1-1/2” to the foot scale. The locomotives are not live steam. I make them using mostly wood and some metals and plastics thrown in. Why wood you ask? Because my objective was to make a working model that you can ride without the high cost to build in all metals. (This will be the subject of a separate blog.)
My goal in building a CNC machine was to make it as economically as possible. To achieve that goal, I looked at designs for other machines, and looked for ways to improve upon it and at the same time keep the cost low; keeping the cost reasonable, will encourage others to make their own machines. As a rough estimate, I have $750 invested and project another $750 needed to make the machine operational (based on a 36”x72” build), Of course you will need a PC and monitor (which I already have). Additionally you will require a CAD/CAM program and a program that will connect the PC to the CNC
I have done an extensive search on the internet for components and their cost. I must confess I have a metal lathe and milling machine to aid me in making some of the components, but they are really not necessary. Ordinary woodworking tools are perfectly suitable for building a CNC machine. The materials used are quite varied.
Any CNC machine requires a flat and stable base. That base is readily available by using a torsion box construction. Those of you familiar with torsion boxes already know how to construct them, but those who don’t, there are a number of good references available over on the Fine Woodworking page and the David Marks video. Most of these utilize MDF in their construction, which is great because the material is flat and stable. As a torsion box for a CNC machine, MDF is ideal because it stays flat, it’s inexpensive and adds weight which is needed for CNC stability. MDF has also been used for the structure of the CNC machine for the same reasons noted, but it has 2 drawbacks; one. It doesn’t hold fasteners well and two. It is affected by moisture. Most have gone to a plywood construction. MDO or Medium Density Overlay is preferred for its stability, but it is not easy to come by; you usually have to get it through sign making shops and a ¾” sheet can cost $100. This is a consumer price, but if you have a resale dealers license, you can get it direct for a whole lot less. Some have been made using Baltic plywood, but this also is fairly expensive. I might add here that there are what is called “table top” CNC routers. These are small in size, usually around 24”x24” and smaller. The electronics will be the same as for a larger machine, but materials for the structure will cost much less. The most advanced designs will utilize metal in their construction. This is the way to go if you have the finances and can work with metals well. In my design, I have used aluminum as much as I can. Use of metals will result in a more sturdy machine.