Optimizing Compass Covers for 3D Printing

Have you ever wished you could do multicolor 3D prints with your single nozzle extruder and not have to buy $600 worth in equipment? In this instructable we're going to do just that. This multicolor method is so versatile that it can be used in almost every project. For example, I used it on a compass case to improve it's design, and personalize it.

Backstory : One day I took my compass to school and the front cover cracked and broke. Only then did I notice how flimsy the clear plastic of the cover was. My sister's case also had cracks in it and it was just a few months old. Maybe they created the covers with planned obsolescence in mind, or just bought a brittle kind of clear plastic. Either way, I decided to remake the cover, to be stronger, optimized for 3D Printing, and personalized.

I am a 7th Grade student at the Maria von Linden Gymnasium

• 3D Printer
• PLA Filament
• Fusion 360

The cover was thankfully not completely broken so I took some measurements from the parts that were still whole and wrote them down on a piece of paper.

First I created a sketch on the xy plane and drew a rectangle using the length and width dimensions of the original cover.

Then I offset this rectangle 2 mm (the wall thickness).

After that I extruded the smaller rectangle up 2 mm (the wall thickness)

Next I chamfered the edges (as seen in the picture)

The original lid has a hinge on it and I decided to recreate this next

First I created a sketch on one wide side of the cover

Then I created a small cutout rectangle to allow for free rotation without it jamming up. I used the measured dimensions from Step 1

Subsequently I created another rectangle beside it which is going to be revolved to form a hinge

I also filleted one edge of it

Next I sketched a small triangle which is going to be the tip of the hinge that interfaces with the back

Finally I mirrored this sketch to also be on the other side (as seen in the picture)

First I extrude-cut the small rectangles to allow the part to fit

Then I revolved the small triangle and the upper rectangle around the front edge of the case

The original cover had a little slot where a small lump on the back lid would interface with it, essentially locking the lid in place

I created a sketch on the face opposite to the hinge face and on the inner wall (as seen in picture)

Then I created 2 small wide rectangles (using the measurements from step 1)

After that I extruded the upper rectangle out 0.5mm and the lower rectangle was extrude cut in 0.5mm

Finally I chamfered the edges of the upper prism

Next I decided to add my name on the interior of the case.

To do this, I created a sketch on the interior of the case.

After that, I added a text box (found under create) and input my name

Then I changed the text size and font (I used Kefa font)

Afterwards I extruded the sketch up 0.6 mm

To personalize the front cover I decide to design and print a picture on it

First, I cut off 0.4 mm (2 x 3D Printing layer height) from the bottom

Then imported a picture as a canvas (or a decal) I used a picture of some clownfish.

While choosing a picture, remember that a 3D printer can't really do gradients and that you have to use discrete colors

Next I created a sketch and, using the spline tool, I traced the outlines of the picture (It's very tedious, I know). Be sure to create full regions or closed loop (not open lines)

Then I selected all the profiles that I wanted to have one color (ex. blue) and extruded all of them 0.4mm, while making sure to create a new body

Then I grouped each color and using the appearances colored each body it's specific color

I repeated this until I extruded all the profiles

To get the picture to show we are going to use a technique developed by Devin Montes called the multipass multicolor technique.

To do this we split the print into several g-codes and print them one after another.

I printed the largest parts from the picture to the smallest parts from the picture to optimize the chances of success and then finally printed the main case.

To create the g-codes,

• Import all models into cura
• Select all models and merge all models (option+command+g / right click and then merge models)
• Center the model group at (0,0,0)
• Ungroup models (right click and then ungroup models)
• Delete every model except 1 (the one you want to create g-code for)
• Slice with mostly regular settings (1mm z-hop and no brim/skirt/raft)

First print the g-code for the largest part on the picture.

Then, making sure to keep your print bed heated, switch to another filament color and print the next largest part in the picture

Repeat this until you have printed all the g-codes for the picture

Finally print the top plate on top of all the small parts of the picture.

You're done