You should now have a better understanding of how the various axes are going to be used to get the machine's router bit to the material for cutting and drilling. Up to this point, you've built the x-axis and y-axis, including the y-axis frame that will move forward and backward on the x-axis aluminum rails.
You should also be much more comfortable with cutting, drilling, and measuring MDF, as well as creating the very useful bearing-rail assemblies (BRAs). Well, you're almost done.
The z-axis frame is next. This frame will ride side to side along the y-axis frame you put together in Chapter 12. In addition, this frame will contain another set of rails, mounted vertically, that will allow the router to move up and down. Once this frame is built and attached, you'll have the makings of a real CNC router with full motion on all three axes.
We know you're anxious to complete your CNC machine, so we'll jump right into it. Before we begin building the z-axis, however, there are two more parts related to the y-axis that must be cut. These two parts are needed to make a critical key measurement for cutting and assembling the final z-axis frame.
In order to mount your z-axis frame to the y-axis frame, you'll be cutting and drilling two parts that make up the top and bottom "caps" of the z-axis frame.
The two MDF parts you will be cutting are
Part C | Y-Axis Linear Bearing Support-Top (BRA Support) |
Part D | Y-Axis Linear Bearing Support-Bottom (BRA Support) |
Note
Please refer to the MDF Parts Layout 1 and MDF Parts Layout 2 PDF files available for download at www.buildyourcnc.com/book.aspxwww.buildyourcnc.com/book.aspx
Figure 13-1 shows these two parts outlined; Part D is partially obscured in the figure because it is on the bottom of the z-axis frame.
Please note that Part C has a single BRA mounted on the underside that rides along the top y-axis frame rail. Part D has a matching BRA that is mounted on the top that rides the bottom y-axis frame rail.
Figure 13-2 shows a portion of the MDF Parts Layout 1 PDF file. You can see that Parts C and D are side by side.
Caution
The part layouts found in MDF Parts Layout 1 and MDF Parts Layout 2 are not to scale; refer to the MDF Plans and Cut List file for actual dimensions.
The dimensions of Parts C and D are fixed; cut these pieces to 4"×6 7/8" (6 and 7/8 inches).
You're also going to need two BRAs after cutting and drilling Parts C and D. So, go ahead and cut two pieces of angled aluminum rail to a length of 4" each. Use your BRA template to drill pilot holes and then tap both pieces to make two BRAs. Set these aside until you're done drilling Parts C and D.
Figure 13-3 shows Parts C and D and two 4" lengths of rail.
Tape Parts C and D together (we used blue painter's tape) and mark the top piece for drilling using the dimensions provided in the CNC plans. Because Parts C and D will be drilled identically, drilling pilot holes through both pieces first will ensure that the holes in both parts match up later. For now, do not drill the larger hole or the two small 1/4" holes above and below it, as indicated in Figure 13-4. That will be covered in a later chapter. We used a 3/4" Forstner bit for the larger counterbore holes and a 1/2" Forstner bit for the smaller holes.
Figure 13-5 shows Parts C and D taped together and marked for drilling. The goal is to drill using a 1/8" bit to create pilot holes. Note that the blue painter's tape is applied over the spot where the larger hole will be drilled. Go ahead and drill the pilot holes in Parts C and D.
Caution
After taping, label both of the exposed surfaces with "CB" to indicate the surface where the counterbored holes will be drilled. (The surfaces of Parts C and D that are touching and hidden between the two taped parts will not have counterbored holes drilled, but will instead hold the BRAs.)
After drilling the pilot holes, remove the tape to drill the counterbore holes.
Tip
The surfaces of Parts C and D with the counterbored holes will face away from the z-axis frame. This means that Part C (the top) will have the counterbore holes facing up, away from the machine. Part D's counterbored holes will be facing down. This is why you need to label each surface with "CB" so you don't forget which side is which.
Figure 13-6 shows us drilling the six counterbored holes in Part C. You'll need to experiment with the proper depth so that the bolt heads that go into the counterbored holes sit completely below the surface. For our Part C, the counterbore depth was approximately 1/4".
Drill both Parts C and D with the counterbored holes. Figure 13-7 shows the two pieces of MDF with all the counterbore holes drilled.
Notice in Figure 13-7 that the center of the counterbored holes still have the 1/8" pilot holes. Use these as guides to drill 1/4" holes in the center of all the counterbored holes. Figure 13-8 shows Parts C and D with the 1/4" holes drilled.
Next, mount one BRA each on Parts C and D. Mount the BRAs on the side that does not have the counterbored holes drilled. Figure 13-9 shows the BRAs mounted.
You've now completed the two caps that will hold the z-axis frame to the y-axis frame. All that's left is to drill the large hole in both parts to hold the lead screw bearing. Refer to the plans for the locations for drilling the large bearing holes (and for Part C, the two 1/4" holes that will hold the square nut). Drilling these large holes is identical to the method described in Chapter 10. You'll use a 1 1/8" Forstner bit to drill the larger hole and a 1" bit for the inner hole. Figure 13-10 shows Part D with the lead screw bearing hole drilled. Note that the counterbored hole is on the same side as the counterbored holes for the nuts that hold the BRAs.
Figure 13-11 shows Part C with the bearing inserted along with a test piece of lead screw. After drilling the lead screw bearing holes for Parts C and D, set these parts aside.
Before we finish building the z-axis, we've got to take a measurement using Parts C and D. This measurement is critical when it comes to the assembly and movement of the z-axis, so take your time and maybe even have someone else double-check your numbers.
There are three parts that you're going to cut in the next few chapters; these are Parts A, B, and F. Two of these parts (F and A) are indicated in Figure 13-12; Parts F and A are partially visible, but Part B is completely obscured in the figure. Part B is mounted vertically next to Part A and has the same dimensions as Part A.
Figures 13-13 and 13-14 show the final parts installed. Ignore the assembly for now and just focus on the distances that must be measured, as indicated in each figure.
Now here's the tricky part-we highly recommend an assistant for this task. Place Part C on top of the y-axis frame's aluminum rail and place Part D under the rail. This task is much easier if you use two clamps-one in the front and one in the back-as shown in Figure 13-15.
It will help if you use a small (torpedo) level to make certain that Parts A and B are as parallel to the floor (or tabletop surface) and each other as possible. Adjust the clamps until the distance on the front (for Part F) matches the distance you've measured on the back (for Parts A and B). Once you have Parts C and D clamped to the rails and the front and back measurements are equal, write down that measurement here:
Height/length of Parts A, B, and F: ____________
At this point, you should have the following items completed:
Part C and D cut and drilled
Two BRAs assembled using a 4" rail length
One BRA bolted to Part C and one bolted to Part D
Parts C and D clamped to the y-axis frame rail for measuring
Height/length of Parts A, B, and F measured
For the work performed in this chapter, you will use
Bearings; 1/2" inner diameter, 1 1/8" outer diameter; quantity: 2 (for lead screw)
Bearings; 5/16" inner diameter, 7/8" outer diameter, 1/4" thick; quantity: 8 (for BRAs)
1/4" bolts; 1" length; quantity: 8 (for BRAs)
1/4" nuts; quantity: 16 (for BRAs)
Up next in Chapter 14, you'll begin cutting the parts required to build the z-axis frame. You'll be building another set of BRAs and cutting Part F and chamfering its edges to hold two pieces of aluminum rail.