Here is a way to make a computer controlled milling machine. That puts the real power of a computer control machining into the hands of the average human. Small enough to set on the desk but scalable to any size. As inexpensive as possible without sacraficing accuracy (too much). All most all the parts can be purchased in local retail stores. And above all CHEAP you can be up and running for well under $200. With it you can do 2 Dimentional engraving and PC board etching and 3D milling and modeling in Foam, Wood, Plastic and other soft materials. Also try watching the YouTube movie at the end (the last frame).New information on the Motor Driver Circuit is (HERE).
Step 1: The Frame
The frame needs to be a flat base that you can mount everything on horizontally and a goose neck of some kind to hold the Z axis (the up and down part with the motor tool)firmly in place. I used one inch pipe just for fun but as it turned out it was pretty handy too. When I needed to make adjustments I could just tap it with a hammer. As you can see the post that holds the Z axis doesn't have to be in the center. It just needs to be firm and the water pipe does a good job of that. Later, after you are sure all the pipe joints are in the right place, you can add a drop of thread sealer to the joints and it will be a good solid structure.
Step 2: The X Stage Rails and Motor
Next its time to add the rails for the X axis stage. These rails are 3/4 inch U chanel aluminum that you can get from the hardware store. Put a washer under each end to space the rail off the pipe just a bit. Don't worry about the rails being perfectly parallel. You'll see why later. Now mount the stepper motor with a bracket like you see here. Connect a length of 1/4 by 20 threaded rod to the motor shaft with a short piece of rubber hose (1/4 inch fuel line). Now your ready to set the movable part of the X axis(the stage).
Step 3: X it Stage right
Take a piece of plastic(I used Plexiglas) or metal, something strong and flat and mount a piece of the U channel to it. Now the tricky part. The round thing is a bearing. You can get them out of motors or buy them at a hardware store. Mount it to a short piece of aluminum like so. Then take a 1/4 in. coupling nut(a long nut) and wrap it with aluminum like so(see pic.) The bearing will hold the X stage to the X rail and the coupling nut will allow the motor to run the satge back and forth. It wouldn't hurt to grease the skids a little and the nut too. Here's a video on making the bearing fixture.
Step 4: The Y stage
The Y stage is just like the X stage but turned 90 degrees. Mount two rails and a motor on the X Stage and then take another piece of flat material and a U channel and make the moving Y stage. Make the little bearing thing and a coupling nut for it too. When your done it should look like this.
Step 5: Zee Z Axis
Again we are going to reproduce the X and Y Stage to create the Z axis stage. Take a flat piece, here I used a piece of white Plexiglas. Mount some rails and a Motor to it. Then make a moving stage piece with a u channel and a roller bearing. We'll do something a little different with the nut(see picture). The four posts you see on the stage will hold the motor tool. Now since this stage is going to move up and down the weight of the motor tool will make it want to come off of the rails so lets add a few more roller bearings to each side to keep it together.
Step 6: Get it together
Now we slap the motor tool into the Z stage. Then its time to mount the stage to the frame. And there you have it. This is the mechanical structure. From here we will need to hook up the stepper motors to a controller and get some software running on the computer but I'm going to save that for future articals.
Step 7: What's it Do
If you were interested in this project it's likely you have already seen what can be done with an 3 axis(XYZ) computer controlled milling machine. What is suprising is what kind of accuracy you can get out of this thing after you tinker with it a little bit. Make sure all the rails are held firm and straight. Tighten the roller bearings so the stage doesn't shift.
I used it to make PC boards. It's real good for engraving name tags and signs. And it's pretty exciting to see it carve a 3D object out of a block of foam or plastic.
WARNING there's a lot to learn about the software. Some venders offer package deals of motors, drivers, and software. That makes it easier but you pay for it.
I'll add more to this later. Send me comments and questions.