Why did I create this? I recently decided I wanted to really test 3D printing's potential as a manufacturing technique, this did not mean see how well it can just print a boring plastic part that could have just be injection molded for a fraction of the price like many 3D pieces printed we see now through services such as Shapeways, this meant designing something that could only be produced using 3D printing (and it had to be awesome!) while showing 3D printing to be a potentially very useful technology in the future due to one of it's two main advantages; the first has already been well documented about; this is about how 3D printing can be used to produce complex 3D geometries that would be impossible to produce using any other manufacturing technique, however these complex 3D geometries are generally just created for their aesthetic appearance and while they are generally very impressive, they have no real potential use or meaning that could portray 3D printing as a more practical manufacturing technique than current techniques for mass production.
In this instructable, I attempt to explore this second advantage of 3D printing and this is it's ability to print moving parts by printing whole assemblies in one print with all moving parts printed fully assembled, unlike the other advantage, this advantage really has a potential to change the way we mass produce devices which have moving parts; by 3D printing all moving parts in place, this completely removes the need for assembly, either by the manufacturer, which costs them money to employ people, as well as the time for the assembly to take place, or by the buyer which is again time consuming and can be complicated.

What is it? To fully test out 3D printing's ability to produce complex mechanical parts fully assembled I designed the '28-Geared Cube' which is a 3D printed desk toy which, as it's name suggests, is a cube with 28 gears on it; by rotating any one of these 28 gears, the other 27 gears also turn in a mesmerizing pattern. This was 3D printed using the 3D printing service Shapeways in the White, Strong and Flexible material. While I did want to test 3D printing, I also wanted to design something that I felt looked good and really made you question what was going on when you turn the gears.
To achieve this, the 28 gears are arranged so on each of 4 sides of the cube are 7 gears: 2 large outer ones that move in opposite directions, the outermost gear has handles on it so it can be easily rotated, the motion between the 2 large cogs on each face is reversed due to 5 smaller gears set within the cube in a similar layout to a planetary gearbox to reverse the big gears' direction on each of these 4 faces. Each of these sets of 7 gears on the 4 faces are all liked through one of the big gears on each of the 4 faces meshing at 90 degrees with one of the big gears on each of the 2 neighboring sides. This means that if any one gear is spun, they all spin in a memorizing pattern.

Step 1: Designing

First you need an idea which requires moving parts, whether this has a practical use, or no real practical use at all and is just designed for fun (like my design) and then you need to design it in such a way on CAD software that it can be 3D printed and move as intended in your design:

When designing assembled moving parts for 3D printing, the main design constraint you have to follow is the required clearance between parts within the design that you wish to print as separate solid bodies, such the distance between meshing gears, so that these actually print as separate parts, this value can usually be found for various 3D printing techniques, for example, Shapeways, who I use to 3D print, clearly publish the minimum clearance between moving parts for each of their materials they 3D print in on the 'Material Portfolio' pages (white, strong and flexible material requires a 0.5mm clearance); if this value is used, the moving parts should print without an issue and should be able to move as designed (as long as the other design constraints are followed for the intended material such as minimum wall thickness).

My design took many hours to make, first as sketches on my ipad, then modelled using Autodesk Inventor Professional 2013. I decided to model this design as separate pieces and then virtually assemble the separate moving pieces to create the final design, this allowed me to animate the design to make sure everything would work as I wanted it to.  

The design was then uploaded to Shapeways where it was 3D printed in their 'White, Strong and Flexible' material and then it was posted to myself...
<p>It is very nice, but for Instructables I think you should include links to the cad files and/or stl files. Of course, it is your design (and quite awesome) and you are free to do anything with it.</p>
Do you have the file available for download?

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