COLLAGE OF TECHNOLOGY AND BUILT ENVIROMENT
Thesis progress
DEVELOPMENT OF AN AUTOMATIC ENERGY-EFFICIENT PLASTIC
SHREDDER WITH A MODULAR BLADE DESIGN FOR RECYCLING SOLUTION.
No
Student Name
ID Number
1
Petros Lidetu Goshu
UGR/3246/13
2
Dereje Desta Ordolo
UGR/8189/13
3
Cherinet Bezabih Ganta
UGR/9583/13
Adviser: Mr. Micheal
INTRODUCTION
• Plastics are widely used due to their durability, versatility, and low cost,
but their non-biodegradable nature causes environmental issues.
• Millions of tons of plastic waste are generated globally, polluting
landfills, waterways, and open environments.
• PET is commonly used in single-use items, and its recycling requires
effective shredding.
• Effective recycling requires shredding, but conventional shredders are
often energy-intensive and not optimized for small-scale use.
GENERAL OVERVIEW OF PLASTICS
• Plastics are synthetic or semi-synthetic materials made from polymers,
offering a wide range of properties.
• They are classified into thermoplastics (can be reshaped) and thermosets
(harden permanently).
• Major types include PET, HDPE, PVC, and LDPE used across various
sectors.
PET
HDPE
PVC
LDPE
Focused Overview: Polyethylene Terephthalate (PET)
• PET is a thermoplastic polyester known for its strength,
transparency, and recyclability.
• It has specific chemical and mechanical properties relevant to
shredder design.
Properties of
PET
2. Mechanical Properties
Property
Typical Value
Design Relevance
Density
1.38 – 1.40
Helps determine blade force and energy
g/cm³
requirements
1.Chemical Properties
• Resists dilute acids, alcohols, oils;
weak against strong acids, bases,
alkalis.
• Degrades in hot water/steam
(hydrolysis).
• Stable, low reactivity, recyclable.
• Safe unless burned (releases CO2,
water, trace toxins).
Tensile Strength
Modulus
70 – 80 MPa
of
Elasticity
Impact Strength
Hardness
2.8 – 3.5 GPa
Indicates PET’s resistance to tearing
blades must be sharp and robust
Reflects
affecting
shred
response and flake size
~3 – 5 kJ/m²
Important for evaluating shock loads on
(notched Izod)
blades
~Rockwell R
Guides blade material selection for wear
85–95
resistance
PET
Melting Point
stiffness,
~250°C
softens
well
temperature—safe
shredding
above
for
ambient
mechanical
Application Areas of PET Plastics
• PET is used in packaging, textiles, automotive, electronics,
construction, and 3D printing.
• Recycled PET (rPET) is used in new packaging, textiles,
construction, and automotive components.
plastic used in textile
plastic used in automotive
Food packaging
3D printing materials
Environmental Impacts of PET Plastics
• PET is non-biodegradable, contributes to marine pollution, uses fossil fuels, causes
visual pollution, and has low recycling rates.
• Effective waste management strategies like shredding are important.
Problem Statement
Plastic waste, especially PET, poses an environmental threat due to lack of accessible
and energy-efficient recycling equipment.
Existing plastic shredders on the market present several challenges:
•High energy consumption: Most machines run continuously regardless of material
input, leading to unnecessary power usage.
•Lack of automation: Manual operation and absence of sensing systems limit energy
optimization and ease of use.
•Non-specialized blade systems: Many shredders are designed for hard plastics and are
not optimized for processing soft materials like PET.
•Complex maintenance and inflexibility: Conventional blade configurations are often
difficult to maintain or replace, especially with locally available resources.
Literature Review - Overview of Plastic
Waste and Recycling Needs
• Global plastic production is high, with single-use plastics like PET being a major
concern.
• PET is often mismanaged due to a lack of affordable and energy-efficient recycling
systems, especially in developing nations.
• Plastic shredding is essential for recycling, enabling size reduction for further
processing.
Geyer, R., Jambeck, J. R., & Law, K. L.
(2017). Production, use, and fate of all
plastics ever made.
works:Dual-shaft shredders offer high power
limitation: energy-intensive and costly, for hard plastics
Duflou, J. R., Kellens, K., Devoldere, T., & Dewulf,
W. (2012). Energy related process improvements
in mechanical recycling of plastics
works: Granulators produce small particles.
limitations: require pre-processing and energy.
has fixed blade arrangement.
Liu, H., Zhang, Y., & Li, W. (2018). Design and
analysis of modular blades in recycling machines
works: Individual blades to be removed, replaced, or reconfigured with
minimal disassembly, enhancing operational flexibility and serviceability.
limitations: blade has less gripping ability.
cont...
While advancements have been made in shredding and recycling technology, the
following research gaps remain:
•
•
•
•
A lack of low-cost PET-specific shredders for soft plastics.
Minimal use of modular blade systems in small-scale shredders.
Absence of sensor-based automation in energy management.
Poor adaptability of existing designs for low-resource environment.
Objectives
1. General Objective
To design and construct a
plastic shredder that operates
automatically, consumes
minimal energy, and effectively
processes soft plastics for
small-scale to medium
recycling applications.
2. Specific Objectives
• To integrate a proximity sensor-based system for
automatic motor control.
• To develop a modular blade system optimized for
soft PET materials.
• To ensure minimum energy consumption and
reduce idle running time.
• To design a simple, affordable, and
manufacturable shredder using local materials.
• To improve operational safety, maintainability,
and flexibility.
• To contribute to sustainable waste management in
resource-constrained communities.
Scope and Limitations Limitations:
The project focuses on designing
and developing a semiautomated, energy-efficient
shredder for soft plastic waste,
mainly PET.
Scope:
Includes automatic motor control,
modular blade system,
mechanical design,
electromechanical component
integration, and documentation.
•The shredder is designed only for soft
plastics like PET, not for hard plastics or
mixed waste.
•The control system is limited to on/off
switching, and the design does not include
additional processing units.
Conceptual Design and Methodology
working mechansim
cont...
Explanation:
• Hopper: Plastic Waste is fed into the shredder.
• Proximity Sensor: It detects the presence of plastic
waste.
It sends an Analog Signal to the Arduino indicating whether
plastic is present or not.
• Arduino: This is a microcontroller that acts as the
"brain" of the automatic control system.
It receives the analog signal from the proximity sensor.
It sends a Digital Signal to the Servo Motor.
• Servo Motor: the servo motor likely controls the Switch
Control. The digital signal from the Arduino dictates the
position or state of the servo motor, which in turn
operates the switch.
• Switch Control: This acts as an intermediary to
control the power flow to the main shredder motor.
It is turned on or off by the servo motor based on
the Arduino's signal.
• Power Supply: This provides the electrical energy
needed to operate the entire system, including the
electric motor.
• Electric Motor: This provides the rotational
power for the shredding mechanism. It receives
power through the Switch Control.
cont...
• Gear Box: The Rotational Power from the electric motor is fed into a gear box. The
gear box's purpose is to increase the Torque (rotational force) available for shredding.
• Shredder Chamber (Modular Blades): The increased torque from the gear box
drives the shredding mechanism within the shredder chamber.
• Shredded Flakes: The output of the shredder chamber is Shredded Flakes of PET.
Next work
Selection of Components and methodology...