You're almost done with the building and construction phase of your CNC machine. At this point, your machine has lead screws inserted through all three axes. You can turn these by hand (or use a drill) and watch as the individual axes move up and down, side to side, and front to back. But now it's time to bring your machine to life. Back in Chapter 6, you wired up the electronics and motors; in this chapter, you'll be mounting those motors to your machine.
This will be the last time you hear us say this, but please read through the entire chapter before beginning so you'll have a better understanding of the work that's ahead.
Note
Refer to the MDF Plans and Cut List PDF files for cutting and drilling dimensions of all MDF parts-these files can be downloaded at www.buildyourcnc.com/book.aspx
Your CNC machine will have three motors-one per axis. The motor will be bolted to the machine using a set of motor mounts, two per motor. Refer to the CNC plans for cutting and drilling these parts. Figure 17-1 shows a single motor mount cut and drilled with only the 2 1/2" large hole and the 1/4" holes used to bolt it to the CNC frame. (You'll be drilling four additional holes that will be used to mount the motor to the motor mount shortly.)
Note
The motor mounts are Parts G, H, I, J, K, and L. Although all the motor mounts are cut and drilled identically, you will hear us refer to a motor mount as the "top motor mount" or the "bottom motor mount" because you will be using two motors mounts, stacked on top of one another, throughout the chapter. The top motor mount will be the motor mount that is closest to its attached motor; the bottom motor mount will, obviously, be the one underneath.
Take three of the motor mounts (write T on them if you like to indicate "top") and place a motor on top of each of them so that the motor's shaft is centered in the large hole. Insert a drill bit (1/4") into the four corner holes on each motor and make four marks in the motor mount for drilling. Figure 17-2 shows each of the four corners of a motor being marked on a motor mount. You will be using #8 screws to bolt each motor to the motor mounts.
Clamp a bottom motor mount piece to a top motor mount and drill 1/4" holes through both pieces. Figure 17-3 shows a top motor mount and a bottom motor mount with the holes drilled to match the motor's four corners.
Next, take the three bottom motor mounts and counterbore the four holes for mounting the motors so that the four #8 nuts you will use to secure each motor are flush with the surface (or slightly below). Figure 17-4 shows two of the bottom motor mounts-one with the #8 nuts inserted and the other with the holes counterbored. (We used a hammer and lightly tapped them into the holes. You want to make sure that they fit nice and tight so they won't spin.)
Next, place a top motor mount over a bottom motor mount and use 1/4" bolts (3" length) to secure the motor mounts to the CNC frame. Attach one motor mount pair to the front leg of the CNC machine (see Figure 17-5), another pair to one of the gantry sides (see Figure 17-6), and the remaining pair to Part C, the top of the z-axis (see Figure 17-7). After bolting on the motor mount pairs, attach a motor/lead screw coupling. Use an Allen wrench to tighten down one end of the couple to the lead screw-that end will have a 1/2" hole (the other end will eventually be tightened down on the motor shaft). Figures 17-5, 17-6, and 17-7 all show the motor mount pairs bolted and the motor/lead screw couples.
Next, insert four #8 bolts (2 1/2" length) into the four corners of a motor. Screw two #8 nuts on to each bolt (don't tighten them, but screw them on until they're almost to the head of the bolt).
Take the motor, insert its shaft into the couple, and use an Allen wrench to tighten down the small screw to the shaft, as shown in Figure 17-8. (If you look carefully, you can see two nuts on each of the four #8 bolts.)
For each of the #8 bolts, use your fingers to screw down the nut closest to the motor mount, but don't tighten completely yet. Use your fingers to screw the nut closest to the motor up to the motor's bottom. Figure 17-9 shows this done for the z-axis motor; perform these same steps for the remaining two motors.
Examine the motor to make certain it is level and then use a wrench to tighten down the #8 nuts. Tighten them slowly and alternate frequently to keep the motor from becoming unbalanced. When done, the motor should be securely fastened to the motor mount.
Figure 17-10 shows the motor tightened down and secure on the x-axis front support (leg).
Tip
You may find adding a third nut on each #8 bolt to be useful. The third nut can be used to tighten down and hold the nut that is pressing against the motor mount (which may tend to loosen over time as the machine moves and shakes).
We know you're anxious to apply some power and get those motors spinning, but you've got one more task to accomplish before you can begin testing. You need to mount your router to the router base, Part V.
The steps for mounting your router to Part V will obviously depend on the brand and model of router you purchase. We chose to use the Bosch Laminate Router (Colt model), also known as a hand router. This router comes with a thin black plastic base that is bolted to the router's metal shell-this plastic piece makes the router easier to slide along whatever material it is cutting . . . and it's a piece we don't need. So we removed it, exposing the four holes in the corners of the router (see Figure 17-11). We'll use these four holes to bolt the router to Part V.
Our first step is to drill the hole for the router's collet (and milling bit). We've marked the center point for drilling this hole on Part V, but this point will vary depending on the size and shape of the router you use (you can see that in Figure 17-11); Figure 17-12 shows Part V drilled with the four small holes used to bolt the router to the MDF and the larger hole for the collet and milling bit. (Again, the center point was marked based on where we wanted the final mounting of the router to be-as long as you drill your center point so that the router is not touching or interfering with any moving parts, it should be OK, but be sure to leave enough room on the router base for a vacuum hole if you wish to connect a hose for collecting dust.)
Note
Read the instructions carefully for the router you have purchased. Each router is different, and the method used to raise and lower the collet may be different from one router to the next. We set our router's collet at the lowest level-that is, as close as possible to the material it will be cutting and drilling. You'll also want to cut or drill a vacuum hole in the router base that doesn't interfere with the router's function but allows for proper suction of the dust created.
Next, we counterbored the four holes on the bottom of Part V; Figure 17-13 shows how the bolts we used for attaching the router to the base are flush with the surface (actually, just a little bit deeper).
Finally, we bolted Part V back to the z-axis frame, as shown in Figure 17-14.
Note
You may have to get creative when it comes to mounting your router. If you've purchased a router without holes in its base, you may cut some additional pieces of MDF to be used as a clamp to hold the router in place. These pieces would most likely be bolted to Parts W and X (one behind the router and one in front) and prevent it from moving. Be sure to check out our forum for reader suggestions and alternative methods for securing routers to the CNC machine at www.buildyourcnc.com/book.aspx
Now take a step back and admire your new CNC machine. Figure 17-15 shows our machine, ready to go.
Tip
You'll definitely want to come up with some method for keeping the router's power cable and the motor wiring from getting tangled or caught up in the moving parts. One way to do this is to use a metal wire (with two large hooks on the ends-e.g., cut and bend a coat hanger) above the machine-we hooked one end to a rafter in the ceiling and used the other end to hold all the cables up and out of the way of the machine.
At this point, you should have the following items completed:
Six motor mounts cut and drilled
Pairs of motor mounts bolted to CNC frame
Motor/lead screw coupling attached to lead screw (for all three axes)
Three motors bolted to the CNC frame (one per axis)
Motor/lead screw coupling attached to motor shaft (for all three motors)
Router base (Part V) drilled for collet/milling bit
Router bolted to router base (Part V)
For the work performed in this chapter, you will use
#8 nuts; quantity: 12
1/4" bolts; 3" length; quantity: 6 (for attaching motor mount pairs)
1/4" nuts; quantity: 6
#8 bolts; 2 1/2" length; quantity: 12 (for bolting motors to motor mounts)
#8 nuts; quantity: 24 (for adjusting distance of motors from motor mounts)
Motor/lead screw coupling; quantity: 3 (1 per motor)
The hardware required for mounting your router to the router base will vary based on the model of router you use.
Congratulations! Are you ready to power up your CNC machine and test it out? Well, we'll keep this short, then-Chapter 18 is all about getting the software configured so you can test out your motors and try out a few cutting operations.