Milling About

Unit Overview

In this unit, Milling About, students aimed to explore the basics of milling, in which they learned about the different types of milling machines and how to utilize computer aided manufacturing (CAM) on Fusion 360 to generate a g-code. To begin, I was tasked with designing a custom dog tag in CorelDraw, following a set of instructions that covered the fundamentals of CNC machines. Next, students were required to design, simulate, and mill a wax mold in Fusion 360; in this process, we learned how to utilize the "Manufacturing" workspace of Fusion 360 effectively (CAM). The ultimate end product of this project involved the laser cutting of a chocolate box through CorelDraw - both of which were completed with partners. 

I first traced a bitmap (detailed logo) of the .png reference image in CorelDraw, before creating a text box and converting the text to curves. In order to trace the bitmap, I hovered over the "bitmaps" drop-down menu and selected the "Outline trace" feature. In the pop-up menu, I clicked ok. Then, to create the text, I used the CorelDraw text box feature and typed in my desired phrase (I selected the phrase, "very gud-e," to reflect the character, gudetama). Converting the text to curves allows the user to manipulate the text more effectively. To finish, I saved the file as an .SVG. 

Milling Machine Workflow

Tools:

• OtherMill Pro

• 80 degree bit 

• Bit changing wrenches

• Foam for bed when changing bits

• Nitto Tape

1. Download file fromCorel Draw

   1. 1. Make sure that the design is measured in millimeters

      2. Export as an SVG file WITHOUT template

2. Locate a 80º engraving bit (will depend on the type of engraving)

   1. Analyze under the microscope for any signs of chipping/damage

3. Turn on the milling machine by clicking on the switch 

4. Home the machine by pressing the home button

5. Open up the Bantam software

6. Change the engraving bit

   1. Select the “change” button in the top right corner of the screen (should be located next the the “tool:” option)

   2. Remove all acrylic screens from the milling machine

   3. Place a foam board on the milling bed

   4. Place two wrenches on the bolt above where the bit is located

   5. Twist inward to loosen the grip

      1. The left hand should twist to the right, and the right should twist to the left

   6. Twist the bolt until fully loose

   7. Carefully insert bit into the hole 

   8. Tighten the bolt until the bit is moderately supported

   9. Twist outward to tighten the grip

      1. A similar motion to before, except it's the opposite

   10. Place the previously removed acrylic screens back onto the milling machine

7. Select the 80º tool (metal engraving bit)

8. Click the locate button

9. Measure the material for width (x) and length/height (y) using digital calipers

10. Apply the tape onto the material

    1. Use Nitto tape (double-sided tape)

    2. Use scissors to trim off the excess tape

    3. Peel off the back layer

11. Measure the thickness of the material (z) including the Nitto tape

12. Select the “loading” button next to the “move” options

13. Remove the front acrylic screen

14. Tape down the material on the bottom left corner of the bed

15. Place the acrylic screen back

16. In Bantam, click file and import the svg. File of the design

17. Make sure “custom size” is selected on Bantam

18. Adjust the dimensions according to the width, length, and thickness of the dog tag

19. Click the “placement” button

    1. Choose “Re-Home” to move the bed back to its original position

20. Click “Mill All Visible”

    1. Be careful to not touch the bed while it is actively milling as it could cause metal splinters

21. Remove the front and side acrylic screens

22. Click on the “loading” button

23. Use a scraping tool to carefully scoop up the material off of the bed

    1. Do not put your hand directly in front of the scooper

    2. Once it is successfully removed, avoid touching the engraving

24. Moisten a paper towel using sanitation spray

25. Gently wipe the material using the paper towel

    1. Make sure the excess pieces of metal are removed

26. Peel off the Nitto tape from the back

Problems Encountered and Solutions

• One of the first issues I encountered was in Fusion 360, in which the x, y, and z axes were incorrect. At first, we tried to fix this issue by redefining the axes in the work coordinate system of the setup tab (for instance, under the "y axis" selection box, I changed it from "z" to "y"); however, whenever I tried to change it, it kept switching back to the original. My second approach, which was successful, involved changing the physical orientation of the design. To do this, I changed the workspace back to "Design" and rotated

• Another issue regarded the estimated time to mill. When I simulated the toolpath for the first time in Fusion 360, the estimated total time was around 5-6 hours. To cut the time down, I went back into the Design workspace and un-extruded a part of the frog design; the original was extruded inwards by 8 mm, but I changed it to 2.5 mm. When I returned to the Manufacturing workspace, the total time was around 51 minutes.

• The last issue I encountered was the size of the milling bit. Whenever I simulated the toolpath (or when I actually milled), the bit consistently skipped over a particular section of the design (the arm of the frog). Similarly, when I dragged the view cube to the side perspective, the bit never created the facial features of the frog. This was due to the size of the bit, which was too large to complete the design's fine details. In the future, if I made a similarly precise design, I would generate a separate toolpath using a smaller bit (this would be done in Fusion 360).

CAM and CNC Milling Machine (wax)

Tools:

• CNC Milling Machine

• 1/8" R1/16" milling bit (1/8" ball end mill)

• Nitto Tape

1. Design a 3D design in Fusion 360 

2. Change the workspace to “Manufacture” in the drop down menu from “Design”

   1. This will allow the user to prep the design for milling, simulate the process, and generate a g-code

3. In the set-up drop down menu, select “new set-up”

4. In the dialogue box, in the setup tab, select machine as Autodesk Generic 3-axis

5. In the stock tab, changed the mode to “fixed size box”

6. Under height, change the model position to offset from the top

7. Change the offset to 0

8. Click ok in the dialogue box to complete the setup

9. In the toolbar, under the 3D tab, select the option “pocket clearing”

10. In the dialogue box, in the tool tab, select the tool as “⅛’ R1/16” (⅛” Ball End Mill)” from the other mill tool library.

    1. Install the other mill tool library. (Extract only other mill libraries after downloading the file. Right-click on the local library to import only that file).

    2. If you need to use a smaller bit (i.e. 1/64”) for finer detail, you will need to complete a second toolpath

       1. If you change the bit, you will need to create a new g-code 

11. Make adjustments in the Passes tab, changing the minimum diameter, minimum cutting radius, maximum step over, and minimum stepover to .0625 mm  

12. Click ok the in the dialogue box 

13. Under the pocket toolpath on the left side of the screen, simulate the milling process of the design

14. Under the Info tab of the simulation window, view the estimated length of time for the file to be milled. 

    1. Ensure that the time is appropriate - if it isn’t make changes to the original file in the Design workspace

15. In the Action tab of the toolbar, choose Post Processing to convert the Fusion 360 file into a g-code, which is a computer numerical control (CNC) programming language. 

16. Under Post Process, set the Post to Othermill (OtherPlan), 

17. Name the file under the Program and make sure the Unit is Millimeters.

    1. The NC extension should say “gcode”.

18. Load your .g-code into engproj from your computer and then download the file onto an OtherMill desktop computer

19. Import the design into the Bantam software by clicking on the “open file” button

20. Under initial set-up, install the appropriate tool used for milling (select the appropriate “wax” bit (ends with “-wax”).

21. Under the material setup, change the dimensions for the design

    1. Change the material offset the (z) to .05 mm under the material placement tab

22. Under the plan setup, change the plan offset “z” value to a negative value or until the milling tool fits the center of the material (it should directly align with the top of the milled object.

23. Click mill all to begin the milling process 

Problems Encountered and Solutions

• When I completed the test cut on cardboard, I noticed that the design was too small; as a result, the scored areas were difficult to locate, and I was unable to assemble the box. Thus to solve this issue, I sized up the entire design by 2-3x in CorelDraw. I followed the same process in sending the design to the laser cutter, adjusting the bed, etc.

• After I finished laser cutting the box, I noticed that the flap wasn't completely secured - part of this was caused by the size of the design; despite increasing the dimensions, certain flaps were still fairly small and delicate. In the future, I would change the design to have longer flaps similar to the ones glued on the inside (those didn't fall off).

• Another modification would involve changing the design to market "Valentine's Day" a bit more -- potential changes include adding a separate text box and/or selecting a more relevant design.