COVID Christmas Bauble

This Instructable is to design and print a COVID-19 style Christmas Bauble. What could be more 2020 than that!

Using Fusion 360, this Instructable teaches some basic techniques for creating, copying and moving component parts to form a bespoke Christmas decoration.

Once the objects have been created, export to slicing software print and assemble.

3D Printer - I'm using a Prusa Mk3s
Fusion 360 - Sign up for a free hobbyist license

As a hobbyist, I have signed up for the free version of Fusion 360. You are limited on what can be done as a hobbyist, but for a project like this, the missing items are not required.

Looking at the official (artist impression) renderings of the virus, I doodled some designs, and added some rough angles and sizes. All of the values are added as parameters so we can tinker with the look and feel later on.

The following parameters are created with the starting values:

• ballRadius - 20mm
• pinHeight - 10mm
• pinMinRadius - 3mm
• pinMaxRadius - 4mm
• baseRadius - 8mm
• baseHeight - 2mm
• pegRadius - 1.5mm
• pegHeight - 2mm

The positions and numbers of the pins will be

• 0 deg - 1 pegs
• 30 deg - 5 pegs (360/5 = 72 deg)
• 60 deg - 7 pegs (360/7 = 51.4 deg)
• 90 deg - 9 pegs (360/9 = 40 deg)

1. Start by creating a new design
2. Add some basic parameters to make the rest of the process easier
   1. Select MODIFY-->Change Parameters
   2. Select the + next to the 'User Parameters'
   3. Add separate entries for the parameters defined in Step 3. This will make subsequent steps easier
3. Create a new sketch by selecting the 'Create Sketch' icon at the top of the screen
   1. Create a centre circle using the origin as the centre, and the diameter as ballRadius*2
   2. Draw a line through the centre of the circle
   3. Select 'Finish Sketch' in the Sketch Palette
4. Select half of the circle and revolve it around the centre axis, this creates a sphere
5. Rename the sketch accordingly
6. Create a new Sketch by selecting the 'Create Sketch' icon at the top of the screen.
   1. Draw a line from the origin that is ballRadius in length. This will be the offset we draw the peg at. This is useful if we change the size of the ball in the future
   2. Using the design, draw the peg, utilising the parameters created previously
   3. Once the base of the peg has been drawn, draw an arc from the origin, with a radius of ballRadius. This allows a smooth transition of the peg to the ball
   4. Select 'Finish Sketch' in the Sketch Palette
7. Select half of the peg and revolve it around the centre axis. This creates a solid peg. You may wish to adjust the size and shape of the peg.
8. Copy the peg to another location, this is done by
   1. BROWSER-->Peg-->Right Click-->Move/Copy the peg
   2. Set the pivot point by clicking the button in the dialog
   3. Select the origin
   4. Click on the green tick next to Set Pivot
   5. Click the 'create copy' option
   6. Using the drag icons, move the copy to the new location. The locations are defined in the drawings earlier
9. Repeat step 8 for all of the pegs. It is possible to select multiple pegs to move and copy. This speeds up the process dramatically
10. If a single object is required, you can export now
11. When all of the pegs have been created, select MODIFY-->Combine
    1. Select the ball as the 'Target Body' and all of the pegs for the 'Tool Bodies'. Make sure the Operation is set to Cut
12. Once all of the pegs have been cut from the ball, export the ball and pegs separately as STL files

The body should be sliced using your standard slicing software and 3D printed with supports on the build plate only.

This only requires a basic 15% infill to maintain the structure.

Once the body has been printed, print a single peg to check for sizing.

My first attempt did not fit properly, so I adjusted the peg size by removing 0.15mm from the bottom peg radius. This allows the peg to snugly fit into the ball. I suspect I have an 'elephants foot' that was causing the issue. Each printer will need its own adjustments.

Support is required for the pegs. Due to the delicate nature of the pegs, I used the following parameters:

1. Support on the build plate only
2. Increased perimeters to 4 to build strength
3. Only printed 9 at a time, otherwise if 1 fails, they all fail
4. Spaced them out so the supports do not overlap
5. First layer was reduced to 30% speed. I didn't get a failure at this speed
6. Added a layer change at the end of the peg to look more like the virus

I added a hole to the peg so that I was able to tie thread to the object, but this isn't necessarily needed.

I did glue in the pegs, but the fit was tight enough not to necessarily need it.

The models are available on Thingiverse to print. Enjoy!