Plastic Bottle Shredder
Sensor-triggered shredding machine
Demo · The prototype at work
“Drop the plastic in. The sensor sees it, and the blades start on their own.”
— Shaikh Farhan
Plastic goes into the feed slot, the ultrasonic sensor picks it up, and the Arduino starts the cutter. The shredded flakes collect in the basket below.
A low-cost plastic bottle shredder that starts on its own: an ultrasonic sensor spots a bottle at the inlet, an Arduino switches the motor on through a relay, and interlocking steel blades cut it into small flakes ready for reuse.
Level · Intermediate · Why it’s here
A first-year engineering design project that went past the basics: interviewing users, comparing real industrial machines, scoring three concepts and then building a working, sensor-controlled prototype with mains power, gearing and a microcontroller.
The problem
A municipal corporation wanted to reuse plastic bottles in road construction, but industrial shredders cost lakhs of rupees and need a factory floor. The brief: a compact, safe machine that shreds PET, HDPE and PP bottles for under ₹10,000.
Highlights
- 01Hands-free operation: the HC-SR04 sensor detects a bottle at the feed slot and the Arduino drives a 5V relay to run the AC motor only while there is plastic to cut.
- 02Dual-shaft cutter with 14 + 14 hardened interlocking blades, driven by a ~120:1 multi-stage gear train that turns a high-speed motor into high cutting torque.
- 03Shredded flakes drop straight into a collection basket under the cutter, keeping the machine compact and easy to empty.
- 04Followed a full engineering design process: stakeholder interviews, benchmarking against Vecoplan, WEIMA, Shred-Tech and Precious Plastic, an objective tree, a pairwise comparison chart and a weighted Pugh chart to pick the final concept.
- 05Team: Shaikh Farhan, Avnish Choudhari, Harshwardhan Limkar, Darshani Gunjal, Aditi Kalushe and Mridul Pardeshi.
What’s inside
Bottle detection
An ultrasonic sensor on the lid measures the feed slot and tells the Arduino the moment a bottle goes in.
Relay motor control
The Arduino switches the mains AC motor through an isolated 5V relay, so the cutter never idles.
Dual-shaft cutter
Two shafts of hardened blades turn towards each other, pulling the plastic in and tearing it into flakes.
High-torque gearing
A multi-stage plastic and metal gear train trades motor speed for the torque needed to cut tough PET.
Built-in collection
A mesh basket under the cutter catches every flake, ready to be bagged for recycling or road material.
Design by the numbers
Three concepts (manual, semi-automatic, fully automated) scored on a weighted Pugh chart; the simple, durable one won.
On the ground
Next project
Line Tracing Robot