Modified Easy Mill
Based on Tom McGuire's Easy Mill Instructable, found here.
When I set out to make this CNC mill, I told my dad. I knew I'd need some help; I didn't think I could do it alone. When I first asked my dad, he basically said that we couldn't make one because it was too complicated. He was worried that he didn't have the tools or abilities to make such a machinist-quality machine. But. I didn't want to give up so easily. I started scouring the Internet looking for an easy to make, fairly accurate CNC mill that didn't require a large amount of precision. That's when I found Tom's Easy Mill. It looked simple enough, and the Instructables claimed it was precise enough, so I brought it to my dad. He agreed that we could probably do it with the tools we had, so we set out to make it. This happened last Winter. We made the frame of it during my Winter Break, and we've worked on it extensively this summer (2 full days a week), and we finally finished!
This page right here will detail what we changed from Tom's mill, what went wrong, what we did well, and what we'd do next time.
What I Changed
- The driver board - Tom's driver board required five wire stepper motors, and I had already bought these 4-wire motors. Also, I didn't care for how Tom used incandescent bulbs to change how fast the motors moved. The board I used was this one, which ended up being a problem to configure due to its poor documentation.
- The motors - I had already bought mine by the time I realised Tom used something else. I used this motor
- The channel - Tom used 3/4 inch aluminum U-channels, and I used 1/2 inch. This was because, 1) I didn't read the manual carefully enough when I was getting it, and 2) Even if I had read it more carefully, Lowe's didn't have the right kind. If I could only change one thing for the next time I made one of these, I'd change this. When I got to the Y axis, I had to raise the channels with wood pieces so the plexiglass platform wouldn't hit the motor.
- The piping - Tom used 1 inch water pipe, and I used 1 1/2 inch. This turned out to be a benefit because I could tap and drill into it easier.
- The position of the Z motor - Tom had his running through the rail, which made it harder for him to hold on the aluminum channels, and also to mount the motor. My solution ran into a tiny bit of trouble because the brace that holds the all-thread hit the bolts holding the whole Z axis to the pipe flange (frame).
- The bearing/s that keeps the axis held against the other aluminum channel - Tom just tightened his on with a screw and it held magically. My dad and I had no such luck, and it would always come loose on the slightest pressure. We ended up having to manufacture a piece of metal that held two bearings and mounting that on the pieces of plexiglass. This was very difficult, and we needed to redo it more than 5 times. (Still, we aren't happy with it.)
- The bearings for the Z axis - Again, Tom's bearings Just Worked™, but I couldn't get it to work like that. We ended up folding a ruler around the whole thing and attached bearings to either side. When the Z axis still jiggled, we added another one a few inches up.
- The dremel mount - Tom used a generic dremel and held it on with two plastic posts. My dad and I decided that it would be stronger and hold the dremel sturdier if we fully wrapped around the dremel, and sure enough, our solution was very sturdy. Tom also used a different kind of spring to hold the dremel in place.
- The milling bit - Tom doesn't really say what bit he uses exactly, but I used a Dremel diamond point tool for engraving. It works really well, according to my less-than-extensive testing.
- Limit switches - Tom doesn't use limit switches, but I got some at Fry's, and my driver board supported them, so I wired them up one day. They integrated well with the CAM program I used, LinuxCNC.
What I'd Do Differently Next Time
First of all, I just wanted to say that I'm happy that I did it this way, for the first time. I know that mine could be improved, but this one was a terrific learning experience. All of the things I want to change after the fact would have added cost to my project, and because I was (and still am) learning about this (and thus wasting materials), it would have cost a lot more to start out with those materials. That aside, here's what I'd change:
- I'd get rid of the aluminum U-channels and bearings that held them on. They just caused a ton of friction, and the bearings were extremely difficult to put on. I'd replace them with some slide bearings. It would make everything so much easier to work with and it'd perform better.
- I'd replace the Dremel with a dedicated CNC spindle so the driver board and the CAM software can turn the spinner on and off. This would also remove the problems we encountered with trying to fit the dremel to the mill.
- I'd replace the pipe with some of that extruded aluminum T slotted framing. It would make it easier to level (we had some problems with keeping the whole thing level).
For the software, I used a dedicated computer running a modified version of Ubuntu Linux called LinuxCNC, and it worked really well. I had a bit of trouble configuring the whole apparatus due to the less-than-well documented driver board I got, but I pulled it off. The configuration files can be found here.
I brought this device to the Orange County Mini Maker Faire, and I was interviewed by a small tech Internet TV station called QGITS about my project. The interview can be found here.