Mechanical Push-Button Case [2024]
Summary and Key Details
Designed a mechanical push-button with a 3N actuation force and 6 mm button travel
Validated components with SOLIDWORKS FEA to ensure they withstood operational loads, achieving a FOS over 10
Applied DFA principles to the button mechanism, reducing cost by eliminating the need for adhesives or fasteners
I’ve always been fascinated by the mechanics behind everyday objects. Intrigued how something so simple and intuitive like a latch can be designed in countless ways, I was inspired to create one myself, I began thinking about a container project, where I could store something to make the latch functional - but what could it secure?.
A phone? That didn’t make sense; why box up something I use constantly?
Headphones? Too inconvenient.
A watch? An interesting idea, but not really something I’m into.
Eventually, I settled on a glasses box. It’s something I already carried around with me, and I thought creating my own personalized one would be convenient.
Project Premise
Design Specifications: Button Release Latch
When starting this project, I had two ideas in mind:
The container opens and closes with a downward push.
The container closes with a downward push and opens with a button.
I decided to design around a push button. I found this would be the most intuitive and natural choice for the design. The specifications I decided on were:
Button Actuation Force of 0.3 kg (~3 N)
After running some tests, I found that 0.3 kg allowed for a comfortable button press, without worry of accidental triggering.
Button Travel Distance of 5 mm
I wanted an emphasis on the mechanical nature of the button. This led to choosing half a centimeter of travel
Latching Force of 10 N
In order to re-latch the box, with some research I found that a range of 9-20 N would be appropriate.
Design Ideation
Preliminary sketches for the ideation on the button mechanism and box design
Force and Displacement Calculations
Prior to designing the push-button system, I derived symbolic calculations. These are later used in order to determine parameters needed for the desired actuation distance.
Button Mechanism Overview
Lid Latch Force Calculation
Button Actuation Force Calculation
Displacement in X vs Y Calculation
I selected a 45-degree angle for all interfaces because I was not significantly constrained by height or width. This also resulted in a 1:1 displacement in x-y, reducing complexity of the design. Additionally, 45 degree angles are straightforward to manufacture and commonly available in all tooling. The spring constants were calculated in the appendix.
Final Design and Specifications
Design Components
Self-Opening Hinges to lift lid on button press
Lid with hooks to latch onto the button mechanism
Interchangeable organizers, the photos show the glasses configuration
Design Specifications
Button Actuation Force of 0.3 kg
Button Travel Distance of 6 mm
Latching Force of 10 N
Finite Element Analysis (FEA)
Using PLA properties from MatWeb, I performed static FEA on the control arms and push button under maximum operational loads. Both components remained below the yield strength, ensuring no failure or plastic deformation.
For future projects, I plan to incorporate fatigue testing to evaluate the device's durability over a defined number of cycles. Fatigue analysis is a key aspect of reliability that was not addressed in this project but is crucial to ensuring long-term functionality.
Product Assembly
3D Printed Parts
Hardware
Completed Product
Product Testing
Mechanism Analysis
To observe the system in action, I assembled a temporary transparent cover. Unlike the actual front plate, this cover lacks certain guides, resulting in reduced stability. The system is significantly more stable during normal operation.
Repeatability Tests
To verify the repeatability, I conducted speed tests of opening and closing the system. Its ability to perform consistently under these conditions confirmed its stability.
Appendix: Spring Constants Calculation
Since the equations depended on the mass of the components, I began by creating initial designs. I selected PLA over ABS as the 3D printing material due to its superior dimensional accuracy and reduced warping. After assigning PLA in SOLIDWORKS, the masses of the moving components were determined as follows: the lid weighed 89.95 grams, the button 1.66 grams, and the moving arms 2.49 grams. These values were then used in the calculations below to determine the required spring constants.
Horizontal Spring Calculation
Vertical Spring Calculation
