Building a Box

Some time ago, a friend asked me to make a case for his Raspberry Pi 2-b. Now, a1914-01 Raspberry Pi is a miniature circuit board with some inputs on it, so there is some relevance to having a case. Electronics can be fragile. Now, when thinking about designing the idea, I decided that the case should be 100% 3D printable. This introduces and removes problems. First, it removes the need to work around predefined sizes for connectors and parts, making the only design limiter in that scope the precision with which the printer can print, which may vary greatly. On the other hand, workable 3D printed connectors of any kind are somewhat difficult to design in a non-breakable way.

DSC_0007_preview_featuredTo start off, it does look like other people have put some effort into making printable cases for various models of the Raspberry Pi. There are at least 5 different designs for the Raspberry Pi and Raspberry Pi B that I could find, but only one for the Raspberry Pi 2-b. In each case, I discovered that the makers of the cases had only uploaded the complete model, as far as I could tell, and had no variables for changing attributes of the model. I decided that I would build something paramaterized and fairly easy to modify.

My journey begins in a piece of modeling software called OpenSCAD. OpenSCAD is a program that lets the user define mathematical objects in a code-like interface that allows for extreme precision. So something like this:
cube(size=[56,89,25],center=true);
Turns into this:
Rendered yellow cube
After taking measurements from the Raspberry Pi, I started to build my model. I took the measurements and created a hollow cube that could fit the Raspberry Pi inside. I had to retake measurements several times during the process, as I ran into additional ideas on how to construct the case.

As I started to print prototype pieces to determine if I had good tolerances for my models, I found that the clips that I had decided to use to connect the pieces of the case together were a bit too small for the printer that I was using. Each of the six copies of the model I was using were “globby”, the plastic was sticking together and bunching up in places, so the models came out stretched at odd angles and with additional plastic in uneccessary places.

I had to redesign my model for the clips into something that would print at the size I was looking for without losing a lot of detail. I ended up with a pretty simple model.
module clip(x,y,z){
scale([x,y,z])
union(){A rendering of the clip code

          cube(size=[2.5,2.5,clipheight]);
cube(size=[9,2.5,2]);

           translate([7.5,0,0])
cube(size=[2,2.5,4]);
translate([7.5,0,4])
rotate([180,-90,90])
linear_extrude(height=2.5)

 polygon([[0,0],[0,2.0],[1.5,2.0]]);
}}

This model printed pretty well, and also provided simpler paramaterization for the other parts of the model and interacting with the clips.
The designs of the top and bottom parts of the case went through several revisions as I decided on what I wanted to do with connectors. The top part of the case ended up being a cube with a lot of smaller cubes subtracted from it, as well as several clip models subtracted.
In the case of the bottom part, I built it with the clips in mind. The bottom half of the case has a lip on the lower side of it for the clips to attach to. I think that there might be a more elegant way to attach the clips to the model, and make the model have a smaller profile for fitting into whatever the Raspberry Pi is being attached to.

Topbottom.
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On review of the work I have done on this project, I believe that I could refine the end product with experimentation and additional time spent on the project. I think that there are a variety of ergonomic features that I ended up skipping due to time constraints that, if I had the opportunity to expand on this project in the future that I would definitely include. As it stands, the case will protect the Raspberry Pi from damage, but has no allowances for ventilation or visual design. I think that above all, were I to do this project again, I would seek out additional resources for the design of the case. When I started this project, I did not a library of tools for modeling in OpenSCAD, and I think that starting from a stronger point would definitely help me add to the success of the final model.

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