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Bistable Mechanism

Foundations of Product Realization - Spring 2019

Partner: Rachel Wallstrom

Create a mechanical device​ that switches between and displays two unique states. 

Concept Sketches

With our bistable device, we ideated different scenarios in which it could be utilized. We hoped that our device would be able to spark joy in the user, and we settled on the goal of having the toggle switch slide a board to release a gum ball during the device's unstable transitional stage. We also ideated different design aesthetics and fun features that the mechanism could have.

Early Prototypes

To the left is the prototype that we decided to move forward with for our final project, as it was the most consistent and elegant in design. However, as you can see, there were many different designs that we conceptualized and rapidly prototyped before coming to this decision. This phase was a hugely important part of our ideation process, as it gave us a greater understanding of the real-world limitations for the various bi-toggle mechanisms and a greater confidence in the design that we eventually settled on.

CAD Exploded View and Assembly Drawing

CAD Assembly

In the assembly stage, we were able to get the components to move with one another. We were even able to test our hard stops within SolidWorks to determine where the arm should ideally stop.

IRL Assembly

After the print, support material had to be dissolved in order for the toggle arm to be usable.

The holes for the shoulder screw were a bit tight, so we used a drill bit to widen them.

We tested placement on scrap acrylic to optimize the location of each component.

Finished Product

Bill of Materials

¼’’ shoulder screw, 1’’ L (McMaster 91259A542) x 2 - $3

2-56 x ¾’’ machine screw (McMaster 90272A084) x 2 - $0.16

4-40, hex standoff, 1’’ L (Jameco 139185) x 2 - $1.10

D-profile precision shaft (McMaster 8632T132) - $1.50

Compression spring 1.5’’ L, 0.3’’ OD, .256’’ ID (McMaster 9657K347) - free, provided

¼’’shoulder screw, ¾’’ L (McMaster 91259A540) - $1.50

4-40 x ¼’’ machine screw (McMaster 90272A106) x 2 - $0.04

4-40 threaded brass heat-set insert (McMaster 93365A120) x 2 - $0.30

10-24 hex nut (McMaster 90480A011) x 2 - $0.04

10-24 threaded brass heat-set insert (McMaster 93365A150) x 2 - $0.50

3D black nylon prints on Ultimaker 3 - $6.06

- Toggle arm, shaft support, shaft holder

Acrylic (¼’’ clear) - $1

Total - $14.76

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