## Introduction: 3D Printed 'Centrifugal Puzzle Box' - Solved With a Spin...

For this project I decided to explore the world and uses of 3D printing further after my exploration of the 3D printed iPhone cases market where I designed, created and now sell the 'TriStand iPhone Case - 3D printed iPhone cases with built in flip out stands' which stretched the capabilities of 3D printing to the max. Near to Christmas last year I also used the amazing 'trapping' capabilities of 3D printing to my advantage when I designed, created and now also sell the 'Captured Snowflake - Christmas Ornament'.

This time I have used 3D printing for the creation of a one of a kind puzzle box that is solved like no other in the world:

Centrifugal Puzzle Box (these designs were printed through a company called Shapeways based in the Netherlands and New York, a copy can also be bought and 3D printed for you here via Shapeways)- This is a unique one of a kind 3D printed puzzle box that can store anything with dimensions of less than 39x39x13mm that is opened/solved in an intriguing way, by simply spinning the puzzle box on a flat surface will unlock the lid, however this is not made to be obvious:

On the lid of the box are six sliders of different shapes, these can slide along rails in the lid, there are also three buttons that can be pressed and released, however don't be fooled, these sliders and buttons have absolutely no purpose at all in helping solve the puzzle and open the box, these sliders and buttons are simply a distraction to confuse the user.
There is one clue towards the solution of opening this puzzle box for the user, firstly, you may have noticed the numbers around the top face of the lid, these are actually coded in the format of "A=1 B=2 C=3" and actually decode clockwise starting from the number after the small circle to read "give-me-a-rapid-spin-to-unlock-my-lid", this may seem hard to notice, and it is, however I have designed an optional additional clue towards finding this clue: This 3D printed key-ring contains embedded within it, using a special wax trapped within the key-ring during the 3D printing process, a QR code and the word 'CLUE' above it (just to make it that bit more obvious), if the user is stuck while solving the Centrifugal Puzzle Box they can choose to reveal this clue by using an IOS device with a camera (iPhone, iPad, iPod Touch 4g) to read the QR code by using a bar-code reader application (tested with an app called 'Scan') to reveal the text "A=1 B=2 C=3" on the device's display which should help the user decode the message on the puzzle's lid helping them to solve the puzzle and open the lid.

The Mechanism - The mechanism used inside this puzzle box is a unique one and is best described in the video above, there are six 6mm ball bearings (sourced off eBay) placed in the slots around the top face of the bottom half of the box, these ball bearings can move freely in their short channels, the lid has corresponding loops that lower into these channels when the lid is placed on. Once the lid is placed on and the box is given a shake, the ball bearings should all be at random points in their channels, some will be across these loops in the lid which will stop that loop from being pulled out which will stop the lid being removed thus locking the puzzle. When the puzzle is spun, all the ball bearings travel to the outside of their channel so none are obscuring the loops in the lid meaning the lid can now be freely removed which unlocks the puzzle.

## Step 1: Inspiration

With the freedom of 3D printing, I wanted to design something brand new, innovative and that to my knowledge does not exist anywhere else in the world, but it also had to be small enough that is did not cost too much to 3D print (I use an online service called Shapeways to 3D print my designs as I don't own my own a 3D printer (yet?) and this can get very costly) so this is what I came up with, a puzzle box that is solved in a unique way like no other in the world, most puzzle boxes I have seen are solved in a number of moves by moving parts of the puzzle to certain precise locations in a certain order to open the box so I wanted to make mine different... by simply spinning the box on a flat surface will unlock the box's lid however I didn't want this solution to be easy to discover so many distractions were added along the way in the design process, as well as a clue towards the solution of the puzzle in the form of a key-ring.

## Step 2: Design

Above is a time lapse animation of me modelling the bottom half of the box, this was the simplest section to model so it is the easiest to show a time lapse of it's creation.

I first designed the mechanism for this puzzle box on my iPad using a simple drawing application and then proceeded to design the final box using Autodesk Inventor (CAD software), the hardest part of the design process was not the modelling itself, it was calculating all of the exact dimensions every feature such as the channels and loops should have to be so that these 6mm ball bearings would move freely within their channels and would cross the loops in the lid when the lid is on and the ball bearings are at the inside edge of their channels to lock that loop and stop the lid from being removed. I made a clearance of 0.25mm between any parts that were designed to fit into each other such as the pins/rods in the lid and holes in the box so they could fit into each other after printing with a close fit but not too much friction.

I decided that the box had to look complex on the outside to distract from the deceivingly simple solution so I decided to add 6 sliders to the top of the lid of different shapes and also 3 sprung buttons (in the second prototype) by taking advantage of the 3D printing material's flexible nature meaning I can model springs for the buttons that will be built into the design and printed as one piece, these added design features have absolutely no purpose towards solving the puzzle, they are simply a distraction for the user. Some 3D printing techniques such as the one I will be using (SLS) can print fully assembled assemblies in one print and I am taking advantage of this by designing the movable sliders and buttons within the lid of the puzzle box by making sure I leave a clearance of 0.5mm between the physically separate parts of the design (e.g. the lid and a slider) so they will actually be separate objects after printing, this removes the need of assembly after printing and also makes the sprung buttons that are part of the design possible.

Finally I decided to add a clue towards the solution of the puzzle, this is in the form of the numbers round the top of the lid, these are actually coded in the format A=1 B=2 C=3 to read 'GIVE ME A RAPID SPIN TO UNLOCK MY LID', yes, this is difficult to notice however I also modeled a 3D printable key-ring that contains a QR code which can be scanned by a smartphone to reveal the text 'A=1 B=2 C=3' to guide the user to this clue if they wish. After a few solid hours of modelling I was ready to order a prototype from Shapeways (3d printing service)

## Step 3: 1st Prototype

I learnt that a few things that needed modifying on the first design but thankfully after a bit of modification the prototype worked!

Unfortunately the design didn't work straight away, I had overestimated the grippyness of the material so even when the lid was locked, I could remove the lid as the friction between the ball bearings and the outer walls of their channels was not enough to stop the lid being removed, this was fixed by adding a lip to the inside end of the channels so now there was a physical barrier stopping the ball bearings from slipping out when the lid is locked and trying to be removed so was no longer relying on the friction of the material. This lip was created out of 1/4 mm fiberglass reinforced sheet which I glued into the channels to create a lip using cyanoacrylate (superglue).

The second failure was the text and numbers I had engraved into the box, due to the SLS (selective laser sintering) 3D printing process, the engraved letters  were unfortunately full of excess powder from the 3D printing process and this was nearly impossible to remove, this made the text quite difficult to see and overall made the puzzle box look a bit tacky, to fix this I decided to emboss all the text and the numbers so this problem of powder would not be a problem.

I also decided that on the next version to slope the front and back ends of the channels to make each ball bearing to only be in 1 on 2 positions (bistable) each channel to be either locked or unlocked making the locking mechanism more secure and reliable.

The keyring containing the QR coded clue of 'A=1 B=2 C=3' decodable using a smartphone printed perfectly and the QR code could be seen and read by using a smartphone.

I ordered a second prototype with these amendments and within 4 working days after the evening I placed the order it arrived!

## Step 4: 2nd (final) Prototype

This time the puzzle box worked like a charm with the lid reliably releasing when spun and the locks being very strong when shut. The sprung buttons on the lid worked very well and provided an excellent distraction along with the sliders from the real solution of the puzzle box. The text is also crisp and clear and the numbers around the lid can be easily decoded if wished.
If you like this project enough please vote for it in the 'UP! contest' where I can win my own 3D printer, this version is also available to buy directly from Shapeways where they will 3D print it on demand and deliver it to you world wide.

## Step 5: What's Next?

The future is upon us as we speak and with the expansion of 3D printing at a huge rate I have no time to waste before designing the next cool thing that I have the urge to make, be it an iPhone Case or Christmas Ornaments such as my previous instructables (iPhone case with built in flip out stands, Christmas ornament and most of my other instructables) however next on my list that is currently in progress of being designed is none of the above, for this next design, I want to design something completely tactile, something that has no real use but is just awesome to look at and use, and this is what I came up with...

Here is my latest project which I spent a whole solid day yesterday modelling, I wanted to make something tactile and just fun to use, It has turned out to be a Steampunk themed desk organizer which can hold paperclips etc. in the tray and maybe pencils/pens in the holes around the top or balanced on the handles when not moving:

This design consists of a cube, on each of 4 sides of the cube are 7 gears: 2 large outer ones that move in opposite directions, the outer has handles on it so it can be easily rotated, the motion between the 2 large cogs is reversed due to 5 smaller gears in a similar layout to a planetary gearbox to reverse the gear's direction on each of these 4 faces. Each of these sets of gears on the 4 faces are all liked through the big gear on each of the 4 faces meshing at 90 degrees with the big gear on each of the 2 neighboring sides. This means that theoretically if any one gear is spun, they should all spin in a memorizing pattern. Best of all it should be printable as one piece.

The design also comes with a stand so it can stand up on a desk, this stand also has a flat plaque with embossed text that I may consider allowing to be customized by the buyer.

I have also just modeled a removable lid that can be placed on the top of the cube and is locked and unlocked by rotating the cogs (the lid locks at the centers of all 4 sides below the gears on the lid) just to make it a bit more interesting and to give it a bit more functionality. This brings up the possibility of designing interchangeable mechanical add-ons that can be put in place of this lid and driven by the rest of the cogs...

Unfortunately due to the very costly nature of 3D printing services such as Shapeways and after my two recent orders of the two prototypes of the 'Centrifugal Puzzle Box' I am going to have a break from 3D printing so I don't run out of money! Hopefully one day I will own my own 3D printer so this will not be an issue.

Participated in the
UP! Contest