During the original sleighbed project, I spent a lot of time talking with the CNC operator at work. Our machine (for wood cutting) had a table of 10' X 6', and as I continually complained about the progress Larry suggested using the CNC or building one. I had always considered such a machine a mastery of mechanics and electronics, but in truth there is not much to a CNC (which stands for Computer Numerical Control or now-a-days Computer Navigated Cutter) The first definition is right...but since NC machines are all but gone from industry, the second is accurate enough. Anyway, his comments began a very impressive internet search and contruction project that eventually caused me to build a CNC. You can build a simple machine fairly inexpensively, but you must remember two things: The first an "inexpensive" machine will be as capable as you design it (generally slow, without much cutting power) and the second and larger issue, as accurate as you construct it.

This is the reason I eventually decided to purchase a CNC from Ez-router.com (I looked at several sites including Shopbottools.com). Now that I have the CNC that is fast and accurate, I plan to rebuild my homemade one hopefully to start a cottage industry of sorts. To provide a way to get accurate results well under the $1000 mark. But, that is another story. Within the context of this site, I will try to add articles and sites I found along the way, and offer a description of the overall process.

First off, there are only a few components of a CNC.

The controller (which interprets signals from the computer and translates them to the stepper motors)

The motors that translate the electric signals into linear movement (stepper motors are most common, but servo motors are used as well).

The machine itself. A series of beariings, lead screws, ball nuts and a table that maintains the instructions detailed in the G code(we'll get to that) to produce accurate parts.

That is about it. You draw something in the computer(using a CAD program), use a CAM program to interpret it into G-code(K Cam is one of the most common, mine uses DeskCnc), then the machine is sent signals (most often through a parallel or serial port), which the driver board (controller) interprets then sends the electrical signals to the motors, which turn on and off in the required sequence to produce the part desired.

Without going into great depth at this point, the average user not knowing much about designing and building a controller, can either find plans, or buy a complete and tested board. Stepperworld.com sells complete packages for around $200-$275, but you can also seek out Gecko drives (don't have the address) which are more capable but vastly more expensive.

There are plenty of designs available for these boards, Most are for free, but if you are like me and don't know much about Stepper motor physics, buying the correct motors to run off your homemade board can be challenging.

Machine designs are available too, for free or a small fee online. www.crankorgan.com This is where I bought my set, but I didn't end up using it. Anyway, this is a great resource, you can see real detail that will start the gears of your mind turning just as they should. The real point is understanding the basics. After that, you can design a machine to do exactly what you need it to.

I'll be posting again in a couple days with a bit more detail on leadscrews, ball nuts, and the dreaded backlash. But until then, take a look at:
www.crankorgan.com
www.stepperworld.com
www.geckodrive.com
cq.cx/pcb-router.pl

That will give you some idea of the complexity. Most of the online plans and machines center around cutting airplane parts our carving sign/engraving. If you expect to build a machine out of off the shelf components to cut through 1" oak at 600 inches a minute...you better be prepared to pay for it.

Feel free to email me directly, harrigan_j@cox.net , with the questions you are too afraid to post. : )

James
Sleighbed.net