This document describes the process of using a CNC milling machine to create a rear bearing housing for a formula one go-kart. The process involved using SolidWorks to design the part and generate G-code, setting up tools and work coordinates on the CNC machine, and then milling the part from an aluminum billet through a series of operations including center drilling, hole drilling, rough contouring, finishing cuts, boring, and contouring to add fillets. The finished part housing is intended to house the rear bearing of the go-kart.

1.
Allen E. Paulson College of Engineering & Information
Technology
Automation and CIMS
MENG 5331
FINAL­ Rear Bearing Housing
Ibrahim Ahmed
Ross Campbell
Bradley McDonald
Indigo Pinto
Casey Sheppard
Steve Soto
Submitted to : Submission Date:
Mr.Spencer Harp 10/21/2014

2. Abstract:
The purpose of this lab was to use the large CNC milling machine to create a rear bearing
housing for a formula one go cart.
Procedure:
Before the CNC milling
The first step of the process was to open the part file in SolidWorks. We then proceeded to
make a sketch slightly bigger than the part which would represent our aluminum billet where the part
would be machined from. After defining the stock material, we then set a coordinate system in order
to give the CNC machine a reference point for all the coordinates in the G&M code. The first job we
defined in HSM Works was a center drilling operation for all the holes on the part’s surface. This
process was required so when the actual holes were drilled, the drill bit wouldn’t “walk” on the part
surface. This is the same as a normal drilling operation, except the depth was set just enough to start
the holes. The next job was the actual drilling of the holes, after the center drilling. Our bearing
housing had 4 holes of a larger diameter, and 27 lightening holes around the actual bearing housing.
These two jobs, while basically the same, needed to be separate due to the different drill bit size. So
the 2 jobs were defined separately and the correct tools were selected. An adaptive clearing job was
then created in order to start carving out the part from the solid aluminum billet. We set the cutting
depth to be 0.4” in order to make it a faster process while still being within the capabilities of the CNC
machine and the tool selected. For the center hole which houses the bearing, the entry for the flat
mill bit was set to a helical entry. Also, since this was a rough cut and not a finishing cut, we left a
small amount of stock material during this step in order to make the finishing cuts on a separate job
which would provide a smoother finish. A horizontal clearing step was performed in order to remove
the last small amount of stock material left during the rough cut in the adaptive clearing step, along
with a vertical clearing for the vertical surfaces. These two jobs then provided a smooth finish for the
part. A boring operation was performed in the center bearing hole in order to provide a smooth finish
with no entry or exit tooling marks. This process removed the small amount of stock material left
during the adaptive clearing and made the part to the specified final dimension. The last two jobs
involve using a ball tipped bit in order to form the smooth fillets around the bearing housing hole.
The 2D contour job was created in order for the tool to create the fillets and get rid of the stepping
effect created during the adaptive clearing step. While it is basically the same job, this process had to
be split into two jobs because the fillets were on two different planes, one higher than the other.
After SolidWorks
1. Turn on the system.
2. Power up restart.
3. Check tooling by jogging over to clear area on the table and bring the tool down 4” off the
table.
4. Switch to hand wheel jog mode and 0.001 increment mode.
5. Use a 123 block to set the tool 1” above the table.
6. Press tool offset measure.

3. 7. Enter -1.0 and press enter.
8. Repeat steps 3-7 for all new tools.
9. Switch to new tool by pressing the MDI button on the CNC control box.
10. Enter the desired tool number (eg.T-5) then press ATC FWD button on the control box.
11. Press the offset key to switch between tool offset and fix offset.( machine must be in jog
mode).
12. Scroll over to the desire coordinate.
13. Press the part-zero button to automatically insert the measure values.
14. Jog and use the edge finder to locate x and z zeros on the mill and enter appropriate values
accounting for the diameter of the edge finder.
15. Set the tool to zero by jogging 3” above the part.
16. Switch to hand wheel jog and 0.001 increment mode.
17. Use a 123 block to set the tool 1” above the part.
18. In the correct cell, press part zero set in the highlighted Z cell.
19. Enter -1.0 and press enter.
20. Subtract the measure tool offset.
21. A warning will appear just press enter.
22. Upload the program to the CNC controller using a USB jump drive. Press select programs then
followed by the up arrow key followed by a right arrow key and select the program.
23. Place the aluminum bar securely on the table.
24. Make sure the coolant pump is pointed directly on the drills.
25. Close the doors and press start.

4. Fig 1. Stock piece defined from a sketch.

5. Fig 2. Coordinate system set in order to orient the machine.
Fig 3. Center drilling the holes before deep drilling

6. Fig 4. Drilling holes

7. Fig 5. Adaptive clearing, creating the general shape of the part from the aluminum billet. Helical entry
for the center hole
Fig 6. Horizontal clearing the surfaces to give it a smoother finish after the rough cutting.

8. Fig 7. Boring operation done to give the large diameter hole a cleaner finish after rough cutting

9. Fig 8. 2D contour operation to cut the fillets using a ball tipped tool.
Fig 9. Another 2D contour in order to do the same but on a different plane

10. Fig 10. showing tool selection

11. Fig 11. showing the aluminum stock on secured

12. Fig 12. showing holes being drilled into the part

13. Fig 13. showing the CNC controller

14. Fig 14. showing access material being milled off part

15. Fig 15. showing center hole being milled will coolant.

16. Fig 16. showing center hole being milled without coolant

17. Fig 17. showing part that is completed in the front

18. Fig 18. showing back pocket being milled

19. Fig 19. showing front completed part
Fig 20. showing back of completed part

20. Fig 21. showing top view
Fig 22. showing side view

21. Fig 23. showing part with rear bearing front view
Fig 24. showing part with rear bearing back view

22. Fig 25. showing two finish parts one with a sand blast finish