Happy Easter!

Are you tired of traditional Easter egg hunts with real eggs you have to try not to break while you color them? Or maybe you're tired of worrying about what the one or two eggs you didn't find will smell like in a few weeks?

3D printing to the rescue! This year impress your friends and family with this cutting edge Easter technology! Yes, this limited edition, Easter Bunny approved, 2016 3D printed Easter egg has not 1, not 2 but 4! YES 4, moving parts!

But wait, that's not all! Act now and not only do you get the 4 spinning parts, but you also get the 2 integrated legs that snap out of the case to easily turn this cutting edge egg into a beautiful centerpiece fit for any occasion!

Quick, act now!!! Easter is this Sunday, Sunday, Sunday!!!

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Ok, had to do the fun sales pitch. Hope you all got at least a chuckle or two out of that. Here's the official story for the design inspiration:

The design for this spinning Easter egg gimbal was inspired somewhat by this thing: http://www.thingiverse.com/thing:1228453

I made a handful of these 2016 gimbals for our new year’s party and people really like them. It was the first movable print in place object I made. The concept of a single print piece with moving parts was pretty interesting, so I started to experiment more with print in place objects of my own design. My first design was round like normal. My second design used circles and squares. From there I was thinking of a way to get out of the round and symmetrical designs. With Easter approaching an egg made sense. And, if you own a 3D printer, you inevitably end up with remnants from a roll of filament and sample filaments in all kinds of colors. So, here’s a fun, festive way to use up some of the filament remnants or samples you have laying around!

The part of the story I left out:

Somehow I ended up with a bright pink PLA sample from ColorFabb… It prints great, but it’s bright pink. There not many things I can think of that need (or want) to be printed in bright pink. Hmmm… What to do, what to do…

Ah ha! Easter! Pink goes well with Easter!

Must. Design. Something. For. Easter.

Enter 3D printed spinning Easter egg. Check and mate.

Step 1: Tools and Materials

To make the 3D printed egg in this instructable you’ll need:

The .stl file(s) from step 2
A 3D printer, or access to one.
At least .03 lbs of filament.

To design and print your own you’ll need:

A computer
CAD software of some sort (more on this in step 4)
A 3D printer or access to one
Filament for the printer

Step 2: The Design

I ended up making five different iterations before being satisfied with the results.

Proof of concept. Also included an offset piece and a non-symmetrical piece. Passed proof of concept, offset parts didn’t spin well.
Added grass and legs to the case, made things symmetrical so they would spin better.
Revised the legs to snap in place better, beefed up some of the pins on the middle, added text.
Revised the Happy Easter text to print cleaner, minor fine tuning of the pins and sockets.
Rounded the tips of the grass blades to make them less likely to warp, small revision to the text.

Attached here are the rev 5 files. There’s one zip folder with everything assembled and then there’s another zip file with all the parts broken out so you can print individual pieces if you want. I’ve also started playing with some dual extrusion prints of this, so far so good!

If you find you have further design questions, please reference the attached technical specification drawing. I’m sure it will answer the rest of your questions ;-)

Step 3: 3D Printing

This egg was designed so it can be printed in once piece without supports. You can also print copies or pieces in different colors and then mix and match colors. Take care when removing it from the print bed, these pieces are relatively solid but I did have one of the circles prints break. The legs are also a little stiff the first time you fold them out, try to press as close to the inner bump on the leg to break it free.

Settings will vary a lot from printer to printer. For a baseline here are my settings.

Infill: 15% infill worked great.

Extruder temp:

PLA, about 195 *C
Wood filaments, about 200 degreesC
*ABS (white), about 225 degrees C
*XT copolyester (blue) 245 degrees C**

Bed temp and prep: PLA 45*C, XT copolyester 70*C, ABS 90*C. All printed on a clean PEI sheet

Cooling: First layer - no cooling for all materials. Following layers - full cooling for PLA, no cooling for ABS or XT.

Speed: 50 mm/s worked well.

* Note - These materials shrink. I recommend scaling the models 101%-103% If you plan to mix ABS and PLA.

**My RH hotend is all metal. Printing above 230*C with a PTFE lined hotend isn’t usually recommended.)

Step 4: CAD Tips

Pick your CAD platform of choice. If you don’t have a preference yet, I like OnShape (even though the file storage for the free version is a little limited). Autodesk Fusion360, Sketchup and Tinkercad are also popular. I’d encourage you to try a few different ones and pick your favorite.

Overall, this design isn’t too complicated. Some egg shapes, some circles, a wavy line and a zig zag. The tricky parts are getting holes and cones lined up and attached in the middle of curved surfaces, and getting the parts to fit together but still spin.

Making the egg

Pick your drafting plane.

I picked the front plane since this is the orientation the final product will be in. Most of the sketches will be done on this plane. Make a sketch of the shape you want on the plane you selected (front plane for me). When the sketch is finished, to make your solid object extrude the sketch from mid plane. This puts the sketch plane for following features in the middle of the part.

Making the pins

To make the pins we’ll use the revolve feature instead of extrude. So sketch half of a 2D cross section of you pin onto the plane . Click revolve and select the axis. Done! (reference pictures 1-3 in this step)

Interface pin interface cuts

Making a revolve cut for the interfacing pins uses pretty much the same steps. This will work ok, but I used a different approach since I wanted the ends of the pins to be flat for better clearance. From trial and error, flat ends seem to make the parts print cleaner and spin better than using cones with sharp points. Use the perpendicular plane, extrude cut mid plane. Continue with the design. (reference pictures 4 and 5 in this step).

Make things fit

My target offset for pin to hole clearance was 0.5mm. This worked pretty well for the rotating joints. Minimum engagement of 1mm for the joints was a good target.

Clearance for the egg to case was about 1.5mm. This gave enough clearance for the parts to pass each other without clashing. Thickness of parts of about 3mm

There was some minor tweaking, but this got my proof of concept working. (reference pictures 6-10 in this step)

Once you’re happy with your design. Export it as an .stl file and drop it into your favorite slicing program to prep for printing.

There are always different ways to design things and not all CAD platforms have the same tools. This was the easiest path without creating extra reference geometry.