In May 2021, I invested in a 3D space mouse to see what effect it would have on my solid modelling experience. A 3D mouse or "space mouse" is a device that allows a designer to rotate three-dimensional models on a computer with all six degrees of freedom simultaneously.
By manipulating the upper puck, you can rotate a virtual model as if it were in front of you. I ended up using it quite a bit, both for my job and for the projects I work on in my free time. I started to take it to and from work every day, and to keep it in good condition, I needed a protective case for it.
At the time, I worked for Formlabs in Somerville, Massachusetts. One perk of working for an advanced fabrication company is that you can access advanced tools, including in this case, a 3D scanner and our own 3D printers. I decided to design and print a custom case for my space mouse, with some extra features built in to improve the user experience: cable management, a small form factor, and ease of handling.
I wanted the case to have a near-perfect fit for my space mouse, but I didn't have any accurate measurements of the device itself. The overall strategy was to take a 3D scan of the mouse, use that scan to design a case, and then 3D print it out of a flexible resin. I started by fixturing my 3D mouse inside a high-precision dental 3D scanner at Formlabs headquarters. This scanner projects a uniform grid of light onto the mouse from different angles, collecting millions of data points of the surface of the object.
From there, I opened the raw data in GOM Inspect, a point cloud analysis application. This software allowed me to see the data that was collected and measure the dimensions of relevant geometry. The scanner didn't capture some of the reflective surfaces on the mouse, because this method of scanning depends on light diffusion onto matte surfaces. However, the scan was accurate enough for me to gather the information I needed.
I recreated the mouse in Solidworks. From this model, I could easily design a form-fitting case.
I began implementing other features to give the case the appearance and operation I was looking for. The biggest offender with this mouse is the cable. I wanted to integrate some sort of cable management and protection into the case. The first solution I came up with had two flexible pockets within it, with a gap just larger than the diameter of the cable. I drew inspiration from the floor cable protectors I used when I mixed sound for musicals and plays. The cord would fit into this pocket and coil inside a hollow chamber within the case, simultaneously keeping the case closed and protecting the mouse even further.
I 3D printed the mouse case using a Form3 3D Printer. This type of printer utilizes a different process from the more common FDM (Fused Deposition Modelling) type printer. Instead of melting thermoplastic filament which then cools to form the final shape, this machine uses a process called stereolithography to selectively cure photopolymer resin. I elected to use Formlabs Flexible 80A resin, because it has the perfect blend of protection, toughness, and flexibility. I needed a material that would deform enough to accept the spacemouse, but resilient enough to keep functioning after thousands of cycles.
The lattice structures connecting the case to the build plate are supports used to print the object in space. They are automatically generated by the slicing software, and they're incredibly easy to remove:
Once I removed the print from the build plate, I needed to post-cure it to improve the material properties. When exposed to UV light at 60°C for ten minutes, Formlabs 80A resin experiences a 140% increase in tensile strength.
I tested the case out, and thankfully, it fit perfectly! However, as I used the case for the next two weeks, I noticed several issues with the design.
This version had two separate pockets for the cable to wind in, with the entrance point located between them. Because of this, it was difficult to use both pockets to store the wire, and as a result, it was not practical to wrap the cable around the case. The top loop of the case was too thin and did not have large enough fillets, so it tore off after just a few days. Further, the radius of curvature of the compliant joint was too small, and during the frequent openings and closings, a crack began to propagate. I decided to fix all of these issues with version two:
I made some changes to the design, and printed another version a couple of weeks later. The new design has only a single pocket for cable management, larger fillets on protruding features, and larger radii on living hinges.
I printed this version, and it was finally good enough for me to feel comfortable using it! I began carrying my mouse to and from work with it, and to this day I still use it to store my mouse when not in use.
Here is a video of the case's operation in action:
I learned many new manufacturing techniques during this project, and I am happy with how the final result has performed. I referenced my knowledge of materials science, compliant mechanism design, and industrial design to produce multiple iterations of a product I had a demonstrable need for. I first created a functional prototype, and then beta tested the product for a short time before solving the issues I experienced with it.
The final result I created is robust, protective, and maintains a small profile. With a built-in carrying loop on top, it is easy to handle--you can easily remove it from a tightly-packed backpack without needing to grab the external diameter. So far, it has held up for five months (as of February 2022) without any discernable issues. I make an effort to apply this same engineering mindset to all of my projects. I believe that a product should include all sorts of minor details (some even so small as to go unnoticed by most) and that every aspect of a product's design has potential for improvement. Thank you for reading, and feel free to check out my other projects!
