Junk Jenius

Playful Recycling Bottle Crusher | Oct – Dec 2024

Mechanical Engineering

Product Development

Solidworks & Woodshop

TOOLS/SKILLS

TOOLS

SolidWorks, Shop Tools, Arduino, FEA (Ansys), Rapid Iteration

MADE FOR

Carnegie Mellon Senior Mechanical Engineering Capstone:

Product Development Course

Carnegie Mellon Senior Mechanical Engineering Capstone:

Product Development Course

MY ROLE

Led CAD design, mechanical prototype, and shop fabrication

TEAM

4 students (MechE + Business)

Overview

Overview

Junk Jenius is a plastic bottle recycling machine designed for our college campus. It simplifies and elevates recycling by automating the cutting, draining, and crushing of bottles into one fluid, satisfying motion.

Recycling is often overlooked because it's messy, tedious, and inconvenient. Our goal was to remove that friction — and even make the process fun.

I collaborated with a multidisciplinary team to take this idea from user research and sketches to a fully functioning, interactive prototype. I led all CAD development, mechanical analysis, and physical fabrication. Our project was awarded Best Prototype at CMU's 2024 Engineering Design Expo by popular vote.

Recycling is often overlooked because it's messy, tedious, and inconvenient. Our goal was to remove that friction — and even make the process fun.

One-Touch Operation

Story-Driven Design

Interactive Prototype

CMU Design Expo '24

1st Place - Best Prototype

Low Recycling Rates on Campus

At Carnegie Mellon, every campus meal comes with a free plastic water bottle — and most students take one by default.

Students throw them out without finishing them, much less emptying or crushing them. Even with recycling bins everywhere, they, along with trash cans, are overflowing with uncrushed, half-full bottles.

Why aren’t these being recycled properly?

“I get a new one with every meal, so I don’t even think about it.”
“If there’s stuff still in the bottle, toss the whole thing.”
“The bins are always full anyway."

They aren't lazy, they're busy people dealing with tiny points of friction:

Leftover liquid
No clear instructions
No obvious place to crush a bottle
Overflowing bins

Our challenge wasn’t just technical, it was behavioral. We needed to make the "right" way the easiest way. Our insight: to improve recycling behavior, we didn’t need to remind people — we needed to make the process easier, cleaner, and more satisfying.

At Carnegie Mellon, every campus meal comes with a free plastic water bottle — and most students take one by default.

Why aren’t these being recycled properly?

“I get a new one with every meal, so I don’t even think about it.”
“If there’s stuff still in the bottle, toss the whole thing.”
“The bins are always full anyway."

They aren't lazy, they're busy people dealing with tiny points of friction:

Leftover liquid
No clear instructions
No obvious place to crush a bottle
Overflowing bins

Competitor Analysis & User Studies

To understand the biggest barriers to recycling, my team conducted a competitor study on a compacting Joseph Joseph trash can by deconstructing, documenting, and analyzing its mechanisms, then doing user tests in a real college kitchen over 48 hours.

We tested the Joseph Joseph Titan Trash Can with real users in a dorm kitchen and dissected its internals.

Pain Points:

Unintuitive - Confusing interaction model (too many levers)

Fragile - Key mechanisms broke after 48 hours of normal use

Unhelpful - Manual operation same efficacy as using hands

—

User Likes:

Interactive/Fun - The satisfaction of crushing something "I wanna try!"

Interactive/Fun - The satisfaction of crushing something -"I wanna try!"

Hygienic - Not having to touch the trash

💡 Key insight - Recycling needs to be automatic, durable, and engaging.

User Needs

Satistying to watch

Easy & Intuitive Use - 1 button operation

Durable

Automatic

Drain leftover fluids

Ideation - Exploring our Options

Brainstorming improvements for current trash compactors and waste management

Crushing Mechanism

After confirming our problem space and user needs, we explored different mechanical approaches to the crushing mechanism. Options included a manual lever, cam system, and motorized linkage, but after evaluating cost, force output, and ease of integration, we determined that a linear actuator would give us the best balance of performance and simplicity. It was strong enough to crush bottles, relatively affordable, and easy to source.

linkage mechanism

cam system

off-the-shelf linear actuator

To test feasibility early, I built a rough proof-of-concept using a 200 lbf actuator wired to a breadboard and mounted in PVC. It worked reliably, confirming our direction.

Proof of concept using linear actuator - successfully crushes bottle!

Lo-Fi Prototyping for System Configuration

Next, we tackled layout. Our team debated vertical vs. horizontal configurations. I quickly created CAD mockups and cardboard prototypes of both to test ergonomics and drainage. We chose a slanted horizontal layout, which:

Allowed gravity-assisted drainage
Aligned better with actuator motion
Made bottle insertion and visibility easier

This decision became the foundation for our mechanical structure and user-facing interface.

Sketching out the entire user process for each layout configuration:

using lo-fi prototypes to test layout feasibility:

Prototyping

Once our layout was locked in, I led the entire mechanical build from rough proof-of-concept to final prototype.

Confirm Linear Actuator Reliability

The first step was confirming that a linear actuator could reliably crush a water bottle. I wired a 200 lbf actuator through a breadboard and 3-way switch, mounted it to scrap PVC and wood, and tested it with empty bottles—some with caps, some without, in various shapes. It worked. That early success gave us confidence to move forward.

Iteration with CAD & FEA

I transitioned to CAD to model the actuator mount, bottle path, and enclosure. I went through several iterations of the actuator mount specifically, refining hole placements, fastener clearances, and bracket dimensions to improve alignment and rigidity. If the actuator wasn't sitting flush or started to flex under load, I updated the CAD, re-cut parts, and remounted them in the shop to get it right. The structure had to match the actuator's stroke and allow easy fabrication with the shop tools and materials available to us.

Validating Design with Stress Analysis & FEA

Machine Shop Fabrication

I built nearly everything by hand in the woodshop: cutting the PVC chute, assembling the frame from acrylic and wood, laser-cutting panels, and aligning parts using clamps and jigs. I added a slanted acrylic drainage ramp that directed liquid toward a filter bin.

The blade was machined out of stainless steel. I designed its mounting geometry, installed it, and iterated the positioning and pierce angle through testing. I revised the CAD multiple times to adjust hole placements and support dimensions, returning to the shop to machine or re-cut parts as needed.

custom blade geometry designed to pierce bottle without getting stuck

all components were hand fabricated and assembled in machine shop

I handled all fitting, fasteners, and assembly, adapting in real time when parts didn’t align. If holes were off, I re-drilled them. If the chute sagged, I reinforced it. Every part was hand-fit, and the entire system was built from scratch and refined through testing.

We validated:

Reliable crushing for standard 16.9 oz bottles
No liquid leaks due to slanted ramp and filter bin
Smooth one-button interaction

We validated:

Reliable crushing for standard 16.9 oz bottles
No liquid leaks due to slanted ramp and filter bin
Smooth one-button interaction

Visual & Emotional Design - Pittsburgh-Made

While our prototype focused on functionality, I additionally designed and CAD-modeled a playful, Pittsburgh-inspired aesthetic for a future version:

Blade housing as a red bus (like a snowplow)
Actuator rails styled after city bridges
Outer frame mimicking Pittsburgh’s hilly skyline

These features weren’t fabricated, but they helped us imagine how a utilitarian object could feel emotionally resonant and locally relevant.

Results

We showcased our working prototype at the 2024 CMU Engineering Design Expo. We gave live demos throughout the event, crushing various types of plastic bottles on the spot and walking attendees through the mechanism. We encouraged people to test it themselves, which sparked a lot of engagement and curiosity. The sound of the actuator and the visual feedback from the clear crush chamber created a uniquely satisfying experience.

Feedback from users and visitors emphasized how intuitive and tactile the machine felt, even in its prototype form. Many noted that they hadn’t expected something so mechanical to feel so interactive and approachable. Several commented on how the one-touch interface made it easy to trust and use.

Our project was awarded Best Prototype by popular vote, standing out among dozens of other capstone projects for its functionality, relevance, and the clear opportunity it represented.

Successfully cut, drained, and crushed plastic bottles in live demos
Built for safety: all moving parts enclosed, momentary switch prevents misuse
Designed to fit into real public spaces, especially campus recycling systems
Received strong interest for continued development and deployment

jjj

Download Full Documentation

Reflection

This was my capstone project, and one of the most rewarding experiences of my time at CMU. I loved getting to work on something tangible, solve engineering problems hands-on, and see users light up when they interacted with the final product.

It reminded me that good design isn’t just about performance—it’s about clarity, ease, and emotional impact. If we make it intuitive, people will use it. If we make it delightful, they’ll want to.

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