CNC conversion pt.1

Project MiniX2D

Mechanics run down

Parts list for X-Y-Z motion control (hardware):
3 qty -16mm ballscrews with ball nuts 500mm length
3 qty -BK12 and BF12 bearing blocks
1 qty -1.5in aluminum plate. ~ 9inx9in
3 qty Nema 23 270 oz. Stepper motors. Bipolar 3A.
12 qty -M5 x .80 x 16mm cap screws (motor side fasteners)
12 qty- M5 x .80 x 2mm set screws/studs (motor plate standoffs)
2 qty - M6 x 1.0 x 35mm cap screws (Y-axis adapter bearing assy to base)
2 qty - M6 x 1.0 x 25mm cap screws (X-axis adapter bearing assy to table)
1 qty - 1.5in aluminum rod ~36 inches (motor support mounts)

Y-axis Bearing Assembly and Adapter Plates:

Using the 1/2 inch plate, the two main adapter plates can be made:

Above: The first plate to the left is sized accordingly to allow the saddle to move past the front edge of the base of the mill. This retains the original length of stock Y travel. The two holes in this plate matches the original mounting points of the stock bearing/turn-wheel assembly.

Second plate is the mounting point for the BK12 bearing assembly and the motor mount supports.

Below: The template I used to make both plates. All done via CAD program to check for clearances and alignments. The one thing that is extremely critical here is the concentricity of the large holes. This is where the 16mm ballscrew will pass through. Because of the size limits of the smaller plate, the large holes are to be at minimum 3/4 inch (19.05mm) in diameter. This means that the 16mm ballscrew only has roughly 1.5 mm clearance all around.

note:
(the holes can actually be up to 7/8" in diameter, but its really close to that upper edge. Plus I don't have a bit that big.)

Tip: Print the patterns onto 4x6in labels, cut them and then stick them onto the aluminum plate. This will give you perfect points for the center punch.

Adapter Plate Dimensions Below:

(outer dimensions aren't too critical. These were just what they ended up being after milling -no DRO)
All of the six 4.22mm (drill bit #19) holes are to be tapped for M5 .80. The two 6.35mm are 1/4" straight un-tapped.

Below: The next plate is the plate that comes into contact with the base of the mill. This acts more like a spacer that gives the y axis extra space to travel. Here are the dimensions:

This is the goal for the larger plate:

Below: Here it is mounted onto the base.

Next two pictures:
These two show the amount of travel the small plate will allow. Looking underneath the table, it seems like I can add about another 1/4 in travel if I add another 1/4 in thickness to the small plate.

Bearings:

Below: Dimension for BK12 (will need modification of bearing shown in second picture)

note: disassemble the bearing block by removing the four screws and remove the two bearings inside to avoid dust. I used an angle grinder to remove majority of the material and then cleaned up the rest on the mill.

Below: Dimensions for Ballscrews