Revised CNC Mill Design

In the last post I fixed some of the clearance and parts issues for the x-axis assembly for the CNC mill. I since applied these same changes to all axes and dialed in most of the components. Here is a image of the full system: 

Version 2 of the CNC mill design.

The entire assembly weighs 48 kg which is on the lighter side. To fix this I plan on casting epoxy granite around the y-axis base to add both mass and damping properties. 

The work area is:

• X travel: 240 mm
• Y travel: 180 mm
• Z travel: 110 mm

Parts

Each of the axes use SFU1204 ball screws, the only difference being the length: 500 mm on x, 400 mm on y, and 300 mm on z. Similar to this, all axes use HGR25 linear rails (a pair) and 4 HGH25-CA linear bearings (2 per rail). Again the only difference is the lengths: 500 mm on x, 400 mm on y, and 300 mm on z.

For the spindle I plan on using a 1.5 kW 110 V air cooled spindle and a VFD (found here). I modelled the dimensions in Solidworks (as seen above). The motors are just NEMA 27s, however I need to still correctly choose the torques and sizes for each axis.

For the metal/frame components, they are all 6061 aluminium bars. I have not settled on weather I will purchase precision ground bars or mill it myself yet. These will impact the price. Either way, for the x-axis it is a 25 x 150 x 500 mm aluminium bar, for the y base it is a 50 x 150 x 500 mm bar, and for the z column it is a 100 x 150 x 472 mm bar. The z-fixture is a 25 x 175 x 190 mm block while the spindle mount is a 94 x 100 x 154 mm block. I have to refine these in the design since they are not standard sizes - this will save some time and costs. 

Price

Transmission
Name	Unit Price	Amount	Total
HGR25 (2x 500mm rails)	$85.87	1	$85.87
HGH25-CA (linear bearings)	$21.24	4	$84.96
SFU1204 ball screw kit (500mm)	$37.70	1	$37.70
HGR25 (2x 400mm rails)	$79.86	1	$79.86
HGH25-CA (linear bearings)	$21.24	4	$84.96
SFU1204 ball screw kit (400mm)	$32.80	1	$32.80
HGR25 (2x 300mm rails)	$61.53	1	$61.53
HGH25-CA (linear bearings)	$21.24	4	$84.96
SFU1204 ball screw kit (300mm)	$24.76	1	$24.76
		Total	$577.40
Metals
Name	Unit Price	Amount	Total
X-Axis plate	$52.58	2	$105.16
Y-Axis base	$116.69	2	$233.38
Z-Axis column	$217.33	1.8	$391.19
		Total	$729.73
Electronics
Name	Unit Price	Amount	Total
Spindle + VFD	$230.00	1	$230.00
NEMA 23 for Z	$35.00	1	$35.00
NEMA 23 for X and Z	$28.18	2	$56.36
Stepper driver	$22.00	3	$66.00
		Total	$387.36

 

* In CAD

Here are some more images (I will upload the CAD files to drive later):