In this instalment we are going to add the Z-carriage assembly. It is similar to the previous two assemblies, but instead of the basic shaft supports we will be using pillow block supports.
Z Carriage Components
The Z-Carriage consists of a Z-Carriage Plate, Z-Carriage spacer, two 16” 8mm shafts, four 8mm sliding bearing trucks, and four 8mm pillow block shaft supports.
In addition we will be attaching the ACME drive nut.
The Z-Carriage plate is supported by the two shafts and four bearing trucks, while the 8mm pillow blocks are used to secure the shafts to the X-Carriage. As with the previous carriages, I had to find the sweet spot for the distance between the two trucks. The further apart they are the more rigid your table will be. The down side is that you lose travel.
The trucks on the Z-Carriage are 4-1/4" from outer edge to outer edge. The shafts are 2" apart. This will yield 3" of Z travel.
The Z-Carriage spacer (not shown above) is a 1/8" thick plate that sits between the main carriage plate and the trucks. This allows the plate to clear the pillow block spacers without the need to machine slots in the back of the plate.
Z Carriage Components
- 2, 8mm x 16" long shafts
- 4, 8mm pillow block shaft supports
- 4, 8mm sliding trucks
- Z Carriage Plate
- Z Carriage Plate Spacer
- 1, 8mm drive nut
Z Carriage Hardware
In addition to the carriage components listed above, the following hardware fasteners were used to secure the Z-Carriage plate to the bearing trucks and the pillow blocks to the X-Carriage plate:
- 16, 4mm x 16mm machine screws
- 16, #8 washers
- 16, #8 lock washers
- 10, #10-24 x 1-1/4 machine screws
- 10, #10-24 hex nuts
- 12, #10 washers
- 10, #10 lock washer
Please note that I used #8 washers for the 4mm machine screws. This is only because they are cheaper and easier to find than their 4mm counterparts.
The Z-Carriage Plate
The Z carriage is cut from 3.75" x 5.5" stock.
The thickness of your stock can be 3/4" or 1/2". For 1/2" I recommend acrylic or Corian, but 1/2" MDF will also work.
I recently upgraded my Z carriage from 3/4" particle board to 1/2" Corian (shown here) and it is a little stiffer and more durable.
The depth of the pockets should be:
- 3/8" for 3/4" thick stock
- 3/16" for 1/2" thick stock
Start by cutting out the two templates. Set the Z Motor Plate aside as you will be using it a little later in this series.
Tape the Z-Carriage Plate template to the stock as shown here.
Mark your holes with a punch and drill the holes and pockets. A drill press will be the most acurate, but a portable drill will work if you keep the bit perpendicular with the stock.
Drill your pockets first.
The Z-Carriage spacer sits between the Z-Carriage plate and the bearing trucks. As stated before, it allows the plate to clear the pillow blocks without having to machine the back of the Z-Carriage plate.
Its made from 3.75" x 3.1875 x 1/8" stock. 3mm thick stock will also work.
Baltic birch plywood or hard board works well. Here I am using a piece of hardboard.
Cutout and use the Z-Carriage spacer template just as you did with the Z-Carriage plate template.
The first step is to install the pillow block shaft supports, as shown in Figure 2. The supports are held in place with two #10-24 x 1-1/4" machine screws.
The screws are secured (Figure 3) with a #19 washer, #6 washer, #10 lock washer, and finally a #10-24 x 1-1/4” hex nut. At this point the nuts should only be finger tight. The shaft supports should look like the ones shown in Figure 4.
Next, the shafts are inserted through the upper pillow blocks, and two 8mm trucks are added, as shown in Figure 5.
The shafts are pushed through to the lower pillow blocks and secured with the set screws on the shaft supports, as shown in Figure 6. The bottom of the shaft should be flush with the bottom side of the lower pillow blocks. Don’t worry about the excess shaft that is sticking out above the upper pillow blocks. Later you will install a motor mount on these shafts.
Place the Z-Carriage spacer on the back of the Z-Carriage plate. Note that the back of the plate does not have pockets.
Place the 8mm ACME nut on the spacer and secure them with the two #10 1-1/4" machine screws as follows.
Place a #10 washer on the machine screw then insert through the front of the Z-Carriage plate.
Add another washer, lock washer and secure with a #10 hex nut.
Finger tighten only.
Secure the Z-Carriage assembly to the four trucks with the 16, 4mm x 16mm machine screws you removed earlier. Remember to add the lock washer/washer combo to the screw, as shown in Figure 8.
Once the carriage plate is secured to the four trucks, move it all the way to the top and snug the upper screws. Next, move the carriage plate to the bottom and do the same with the lower screws. Once you are happy with the movement of the carriage, tighten all the screws.
Once the carriage plate is secured to the four trucks, move it all the way to the top and tighten the screws on the upper pillow blocks. Next, move the carriage plate to the bottom and do the same with the lower pillow blocks. Once you are happy with the movement of the carriage, tighten all the nuts.
This completes the KReduCNC Z-Carriage assembly. As stated earlier, the excess shaft lengths on the top of the Z-Carriage will be used to support the Z motor mount and later to secure hoses and/or cables.
The drawing files for the Z carriage can be found here:
Please note that these files are subject to change. You will need some sort of CAD software that can import eps or pdf files to use them. They are raw 2D drawing files without annotations.
The templates can be purchased here:
Please note that there are cheaper linear motion components available. These are the ones I used. Almost all shafts and supports will works, but don't cheap out on the bearing trucks, as you get what you pay for.