Pencil Holder

After learning our way around Fusion 360, we were taught how to make that design a reality. The Fab Lab has a small and a large ShopBot, but the process for milling is pretty much the same on both. For this project, we followed steps from a powerpoint to make a pencil holder and then milled it on the ShopBot. The design files, manufacturing files, and powerpoint (PDF, PPXT, and Google Slides) are in the google drive folder above.

WORK FLOW for ShopBot:

1. Grab goggles and ear muffs
2. Prepare SBP file (save from Fusion 360 and upload to shared google drive folder)
3. Move the tool out of the way (J2 x,y)
4. Get a block of wood and secure it on the table using hammer and wedge
5. Zero out the Z axis (C2)
   1. Clip zeroing plate to machine using alligator clip and set the plate on the table underneath the tool bit (Don't forget to unclip the plate and put it away after Z axis is zeroed)
6. Raise Z axis by 4 in (JZ, 3)
7. Home X and Y axes using proximity switches (C3)
8. Jog machine to origin of wood block (J2 6,6)
9. Make that your new origin (Z2)
   1. On the yellow keyboard, the X and Y axis should read 0
10. Check vent and make sure it is open
11. Check that frequency is set to 300 hertz (digital display on the side of the machine)
12. Turn on vacuum (big green button)
13. Load file into ShopBot
    1. Air cut (3D offset) first, re-zero Z axis, and change it back to "no offset"
    2. Announce out load when turning on spindle and router
14. After milling is finished, turn off vacuum and move tool up and out of the way
15. Use table saw to cut off excess, sander, and router table to round edges

NOTE: Always have two people in the room so that one person can always be next to the red switch in case of emergency.

DESIGNING pencil holder on Fusion 360:

First, we set up the document by changing the units to inches and turning on the origin.

We created a rectangle that was 5 in. x 5 in. on the XY plane and used the extrude (e) to pull it out 1.375 in.

Now we had a cube (5 x 5 x 1.375) that would serve as the base of our pencil holder. The next steps would create the toolpaths needed to make the holes/compartments. We started making the multiple holes by creating one .5 in. circle (c) on the front face and using the "rectangular pattern" to create 3 more identical circles equidistant apart. The same process was used to create the two columns of four .375 in. circles.

We selected the eight smaller circles and pressed e to extrude them by .75 in and set operation to "cut". For the bigger circles, we extruded them by 1 in. and selected "cut".

The last technique we used was the spline tool to make a curved shape which would serve as a coin pocket or a miscellaneous compartment. We extruded (e) it .25 in. and set operation to "cut".

GENERATING TOOLPATHS in CAM:

It was important that we stopped our sketch before switching from "model" to "CAM" and that our units were still in inches. We began by creating a new setup (first drop-down menu). Under setup we changed origin to "model origin", and under stock we changed the "Stock Slide Offset" to .25 in. and "Stock Top Offset" to .125 in.

The first toolpath we created was the face toolpath, which levels the top of the material (Click the 2D drop-down menu at the top and choose "face").

For the face toolpath, we only had to change things under Tool (nothing under Geometry, Heights, Passes, or linking). We selected the tool we wanted (1/4'' fFat Endmill) from "samples", 1/4 in. Lastly, we changed the spindle speed to 18,000 rpm and the feedrate to 300 in./min.

The next toolpath we created was the bore toolpath, which is used to mill cylindrical pockets (choose "bore" under the 2D drop-down menu).

For the bore toolpath, we had to change the geometry and passes, but the tool stayed the same and nothing had to be changed under heights or linking. Under geometry, we selected each hole so that all 11 are blue. Under passes, we changed the "pitch" to .375 in. and unchecked "Stock to Leave".

The third toolpath we created was the pocket toolpath to cut out the coin pocket (Click on "2D Pocket").

We changed the geometry, passes, and linking. The tool shouldn't change and nothing under heights needs to be modified. Under geometry, we selected the bottom of the pocket which should highlight red when selected. Under passes, we checked "multiple depths" and changed the "maximum roughing stepdown" to .25 in. Under linking, we selected ramp and changed the ramp type to "plunge".

The last toolpath we had to create was the contour toolpath, which basically cut out the entire pencil holder from the block of wood. For contour toolpathing, we changed the geometry, heights and passes, but kept the tool and linking the same. Under geometry, we selected the bottom so that it highlighted red and the red arrow was outside the box. Under heights, we changed the bottom height to .25 in. Under passes, we checked the box named "multiple depths" and set "max roughing stepdown" to .25 in.

The last step before bringing the file over to the ShopBot was creating the gcode for the ShopBot. We right clicked on the setup and clicked on "generate toolpath". Before post processing the toolpaths, we simulated each toolpath (right click on setup -> click simulate -> change tool to shaft -> check stock). When we clicked on "post process" we changed the post processor to "ShopBot Open SBR" and renamed it.

SUMMARY:

Overall, I thought this project taught us a some important skills that will be used in the future. Because it had been a while since I had last used the ShopBot, this was a good refresher on the basics. There were also some new techniques that we learned on operating the ShopBot and designing in Fusion 360. One of the most helpful tips I learned was the typing commands on ShopBot. Instead of having to click around under the drop-down menus, you just have to type in two letters/numbers, and it does exactly what you want. Furthermore, the way that the C commands are ordered gives a good guideline/checklist when prepping for the file.

My only setback was that I had to redo the milling a second time because during the first time, I thought that the bit was going too far down, so I hit the emergency switch. At the time, I didn't realize that I could have just hit the space bar to stop the spindle, and I wanted to be extra-cautious. After stopping the ShopBot using the emergency switch, the origin and z-axis got all messed up, so we couldn't just resume. We had to reset the origin and z-axis, home the X and Y axes, and start from the beginning. This wasn't too much of a problem: the face toolpath ran its course and just didn't touch the top since the surface was already leveled from the first time. A video of the ShopBot milling the pencil holder and a picture of the final product is below. If I had more time, I would learn how to use the table saw to cut off the excess and the router table to round the edges.