Wiring is a pain. One of my friends at the hackerspace that had built his Shapeoko2 mentioned that assembly was the easier part, the hard part was wiring it up and he was right. Included in this work was also figuring out how the power supplies and the other bits would be arranged. OK, it wasn’t that much of a pain. It was fun trying to figure out the layout of the power supplies and the control boards, as well as where the emergency shutoff switch was going to be located. It was one of those moments where you look around for what you have on hand, because you need to solve problems you didn’t know you had until you run smack into them. McGyver moments if you will. A few examples are the fan shroud, the cable strain relief, limit switch mounts and the e-stop button.
It starts with a slab of particle board as the base of the layout. This section of board is meant to be somewhat detached from the table, so that I can move it in and out as needed to service various parts.
I had to figure out how to mount the e-stop switch as well as the spindle speed controller’s pot. I decided to make myself a slanted control panel. I had some of the black plastic you see in the picture, already cut at a slant. I grabbed a piece of clear acrylic and slapped it together with some glue. The best solution isn’t always the prettiest. Over time this panel has grown to include the master power switch, the lights, motors and spindle switches. At some point, I may re-engineer this panel, including using the CNC to machine it’s own panel, complete with engraved labels. But that’s off in the future.
Cable strain relief
Had to get inventive on this one. I needed a way for the cables sticking out of the side of the machine to be strain relieved so they didn’t damage the motor controller board if they accidentally got yanked on. It doesn’t happen that often that something falls or something gets caught on the wires, but once is enough if there’s nothing there to hold it in. The mounting board is a bit of acrylic, which I solvent welded a thicker chunk of acrylic to. With some holes in the thicker acrylic, wire ties can now be used to keep the bundles from being yanked out of the screw terminals. To date, it’s saved the controller board terminals at least three times. The bluish colored blobs are epoxy putty (love the stuff, so useful) which the aluminum stand offs are stuck into. This solves the problem of mounting the circuit board to the acrylic strain relief board, without having to counter bore the underside to use screws. Simple and effective.
The NEMA23 motors for the X and Y axes required a gauge that could take a continuous load of 2 amps. I decided to use a flexible 16ga speaker wire, I needed the flexibility for movement, and although I technically could use 18ga, I tend to over engineer. Monoprice had a wonderful deal on a 100′ roll of 4 conductor speaker wire for $40. This gave me enough with spare. I used 12ga solid core conductor from the power supply to the motor controller board, because it could carry a max of 34 amps.
Cable chain mounting
I finally figured out that I could use a salvaged block of HDPE to mount to the side of the X gantry and attach the cable chain head to that. A bit ugly, but it works well. The cable chain for the X carriage is less sophisticated, and at some point in the future, I’d like it to be a proper cable chain, but at the moment the woven cover is good enough.
The limit switches I bought came on these little circuit boards and while they looked nice, there were two problems: they were wired up wrong for my electrical setup, and they got in the way. I had to throw them out, they just wouldn’t work. So I desoldered the switches off of them and decided to mount them myself with a few pieces of plastic. I over engineered the switches mounting plates. I figured you couldn’t just glue them to the plate that you screwed onto the rail, because over time the pushing on the switch might crack the glue. Thus I used #1-72 screws. If I’d thought harder, I’d have realized that it’s total overkill because if your limit switches are taking enough strain to crack glue, then you’re doing something wrong. 😉
Stepper drivers get hot. Like burn your fingers hot, and that’s even well before they hit their melt down temp. They definitely need cooling if you want to use them long term (longer than a few runs of the CNC that is). My first attempt was poor, because even though the fan was sitting on top, it wasn’t blowing across the heatsinks in a way that would maximally remove the heat. Eventually I threw out this shroud in favor of a shroud I created from some scrap ABS, a server fan and a bit of glue and epoxy putty. Even at full tilt, the motor drivers are kept well ventilated and they do well.