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Study on Iterative Design and Development of Bottle Caps
Study on Iterative Design and Development of Bottle Caps
What Is Design Iteration?
What Is Design Iteration?
Iterative design is a process where a product is developed through repeated cycles of design → test → evaluate → improve. Instead of trying to get the perfect design in one go, engineers refine it step by step. We here at NESA followed a similar procedure to 3D print a perfect bottle cap which not only fits the threads perfectly but also doesn't leak. It took us a lot of iterations to reach that perfection.
FIG 1
Problem Statement
Problem Statement
The objective of this project was to design and develop a bottle cap that meets key functional like leakage-proof, matching threads of a common PET bottle, easy griping which were the required functionalities of our project . A systematic iterative design approach was required to identify design inefficiencies, refine critical parameters such as thread geometry, material selection, and grip features, and ultimately achieve an optimized and reliable bottle for our project .
Design Iterations
Design Iterations
This was the first iteration for bottle cap the threads were internal and the threads were cut instead of extrude .
The wall thickness of the cap is also very less hence the cap was not sturdy
This was the second iteration of the bottle cap
The wall thickness was increased to make the bottle cap sturdy
There was air leak from the threaded area of the bottle cap
The dimensions of wall were decreased and the threads were extruded in the third iteration
There was still water leakage through the threads and also there was gaps in between the 3d printed layers
This was the fourth iteration
The nozzle temperature was increased so the extrusion would be more smoother this would reduce the gaps in the layer
The threads were continuous hence it was slightly tilted when installed
The thread design was changed in this iteration
Instead of one continuous thread it was split into 3 different threads which would follow individual tracks on the PET BOTTLE
A wall was designed on the base of the cap so that the leakage will decrease as the mouth of the bottle will be pushed against it.
This wall was designed in such a way that it would seal the mouth of the bottle from the inside.
The overall height of the cap was reduced by 2mm to increase the force between the mouth of the bottle and the top portion of the cap
The diameter of the inner wall were reduced and the thickness of the wall was increased.
This way the walls were more sturdy
As water was still leaking from inside the wall the diameter was increased so that the tolerance between the mouth of the bottle and the wall will be reduced to the point that water would stop leaking
The height of the wall was increased to make the sealing mechanism more effective
The thread height was also increased in this iteration.
The wall height was changed in this iteration to seal the mouth of the bottle
The threads were aligned and the iteration was perfectly fitting but due to leakage when pressure was applied i decided to change the height of the threads
The threads were changed in this iteration to stop leak from the threads but it did not work and the alignment failed .
The wall radius was reduced but this lead to cap not fitting properly. Hence the wall radius was reduced in the next iteration
The threads were reiterated to the 11th iteration as the leakage was due to the wall and not the threads
This iteration the threads were aligned and the wall was also not blocking the mouth of the bottle
But whenever pressure was applied the bottle was leaking
FIG 2
Overall Critical Design Elements
Overall Critical Design Elements
1. Thread Geometry
1. Thread Geometry
The threads of the cap play a crucial role in ensuring proper engagement with the bottle neck. Optimizing thread profile, pitch, and alignment was essential to achieve a secure fit and minimize leakage. Iterations demonstrated that accurate thread matching significantly improves sealing performance and prevents misalignment during installation.
2. Internal Sealing Wall
2. Internal Sealing Wall
An internal wall feature was introduced to enhance the sealing mechanism. This wall is designed to interact directly with the mouth of the bottle, creating a compression-based seal from the inside. Its height and tolerance were critical parameters, as they determined the effectiveness of leakage prevention, especially under static conditions.
3. External Grip Features (Ridges)
3. External Grip Features (Ridges)
To improve usability, external ridges on the outer surface of the cap were identified as an important design addition. These ridges enhance grip, making the cap easier to open and close, particularly when higher torque is required. Although not directly related to sealing, this feature contributes significantly
Testing Methodology
Testing Methodology
The testing methodology for each design iteration was structured to evaluate alignment, sealing , and pressure resistance of the bottle cap. Initially, the cap was examined for proper alignment during application. This involved verifying that the cap engaged with the bottle threads uniformly and progressed downward in a parallel manner without tilting or cross-threading. Ensuring correct alignment was critical to achieving an effective seal.
Following successful alignment, the bottle was inverted to assess leakage performance under static conditions. The cap was observed for any signs of fluid leakage, indicating potential deficiencies in thread fit or sealing surfaces. Finally, a pressure test was conducted by manually compressing the bottle to simulate real-world handling conditions. This step evaluated the cap’s ability to maintain a leak-proof seal under internal pressure. The absence of leakage during this stage confirmed the robustness and reliability of the design.
These three sequential tests were consistently applied to each iteration to ensure systematic evaluation and progressive improvement of the bottle cap design.
Fig 3&4
In the above images Iteration no.12 was used ,as it can be seen that there is a missed layer in image 4, hence there was a minor leakage.
Fig5&6
In the above image iteration no.13 was used u can see that there are no missed layers or leakages in the above image .
The videos below are the testing videos of bottle cap no.13 .
NOTE- These are a few more testing videos that were taken for documentation purpose BOTTLE CAP TESTING VIDEOS
Result & Conclusion
Result & Conclusion
The iterative design process resulted in significant improvements in the sealing performance of the bottle cap. Initial prototypes exhibited noticeable leakage under both static and applied pressure conditions, indicating deficiencies in thread engagement and sealing geometry. Through successive design refinements, the cap achieved reliable sealing under static conditions, with no leakage observed when the bottle was inverted. This demonstrated improved alignment and effective thread compatibility with the reference PET bottle.
However, during pressure testing, minor leakage was still observed when external force was applied to the bottle. This indicates that while the design successfully meets basic sealing requirements, further optimization is required to enhance pressure resistance, potentially through improvements in material properties, sealing interfaces, or thread tolerances.
Overall, the results highlight the effectiveness of the iterative design approach in progressively improving performance, while also identifying areas for continued development.
References
References
https://www.bisleri.com/home Overall the design was made so that it would fit the mouth of the bottle made by this brand.
Author & Designer - Siddharth Shidid
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