Re-designing Waste Collection System
Skills: Solidworks, Finite Element Analysis, 3D printing, Laser Cutting, User Centered Design
For my final year project in school, I worked with a group of 7 people consisting of computer science, architecture and engineering students to redesign the waste collection system in Toh Tuck Estate, a region in Singapore. Our team worked with a local waste collection company that gave us some insights into problems with the current waste collection system. The existing system involved daily collection of general waste (landfill) in the green bins and weekly collection of recyclables in the blue bins. Our research on waste collection systems in other countries revealed that there would be a need to separate waste into more categories in the future. Thus, our goal was to develop a waste collection system that could accommodate the collection of four types of waste: general waste, organic waste, e-waste, and recyclables.
For this project, I mainly worked on designing the bin attachment to allow the 120L bins located outside each house to accommodate the collection of 2 more types of waste: food waste and e-waste. I also helped with the electrical assembly and troubleshooting of the weight and volume sensors on the cargo unit.
My team decided that food waste and general waste should be collected in the same bin, while e-waste and recyclables would be stored in the same bin. This is because food waste would more likely need to be collected daily, while e-waste would need to be collected much less frequently.
There were a few iterations of the bin design, and I weighed the different iterations based on four criteria:
-
Ease of use: solution should require few additional steps for both residents and waste collectors
-
Weather-proof: waste should be protected from the elements after implementation of the solution
-
Ease of upkeep: solution should be easy to clean and maintain in good working condition
-
Ease of implementation: solution should be easily added to existing bins as a modification
The first iteration: hooked basket
The first design I prototyped was a basket that would hook onto the handles of the bin. While the idea worked in theory, I quickly realized that this solution would not work as hooking the basket on the outside of the bin would not allow the bin to close fully, leaving the waste inside exposed to the elements.
Despite the setback, the process of making this design allowed me to come up with a way to prototype a basket larger than the print area of a standard 3D printer like the Creality Ender 3. I split the basket body into four parts in Solidworks and had separate attachment points for both the handle and the hooks. This method let me print an object of about 400*400*150mm in a 3D printer with a printing volume of 220*220*250mm.
The second iteration: half basket
The next design I came up with was a basket that would attach to the inner walls of the bins. Hooks were attached via suction cups to the inside of the bin and the basket would be hooked onto the inside. I came up with a triangular and rectangular version of the basket.
To test the strength of the design, I also conducted finite element analysis on Solidworks under two loading conditions. The results are below.
Thoughts
As a side note, after going to the United States for my exchange program, I realized that the daily collection of waste from households is not a universal phenomenon. All three types of waste: landfill, recyclables and organic waste — are collected weekly. It was also interesting to see that the landfill bins were smaller than the bins for recyclables and organic waste. This way of encouraging the separation of waste in households was effective in my experience.
When I first arrived with my housemates, we did not notice that organic waste was collected separately from general waste, so we threw all our trash into one bag. We quickly discovered that since the waste was only collected once a week, our landfill bin would run out of space very easily. This led us to devise a way to separate organic waste from landfill in the house so that we would not fill the smaller landfill bin before the collection truck arrived.