Eco
Spool
Acknowledgements
1
Introduction
1.1 Problem Statement
1.2 Project Objective
1.3 Enabling a Circular Plastic Economy
1.4 Scope & Constraints
1.5 Plastic Demand
2
Problem Analysis
2.1 Filament Quality
2.2 Metrics of Filament Diameter
2.3 Feedstock Material
2.3.1 Post-Consumer Waste PP Flakes
2.3.2 Control Material: rPP Flakes
2.4 Key Issues
2.4.1 Issue 1: Inconsistent Rate of Extrusion
2.4.2 Issue 2: Anisotropic Volumetric Shrinkage
2.5 State of the Art
2.5.1 Typical System Architecture
2.5.2 Existing Extruders
3
Design Methodology
3.1 Design Approach
3.1.1 Sol. 1-A: Compression & Mixing
3.1.2 Sol. 1-B: Heating Gradient
3.1.3 Sol. 2-A: Circumferential Cooling
3.1.4 Sol. 2-B: Cross-Sectional Cooling
3.2 Design Statement
3.3 System Overview
3.4 System Specifications
3.5 Experimentation Methodology
3.5.1 Data Measurement
3.5.2 Data Processing
4
Compression Screw
4.1 Air-Gap and Thermal Stratification
4.1.1 Criteria
4.2 Rationale for Compression Screws
4.2.1 Elimination of the Air
4.2.2 Shear-Induced Heating
4.2.3 Forced Convection and Mixing
4.3 Theoretical Limitations
4.4 Screw Selection & CR Testing
4.5 Experimental Methodology
4.5.1 Maddock solidification experiment
4.5.2 Procedure
4.5.3 Key Experimental Findings
4.6 Results & Conclusion
5
Heating & Melting
5.1 Barrel Heating
5.1.1 Single-Zone vs Multi-Zone Heating
5.1.2 Functional Roles of Each Heating Zone
5.1.3 Thermal Limitations of Barrel Conduction
5.2 Barrel Heater Concept Selection
5.2.1 Overview of Heating Technologies
5.2.2 Selection of Heating Method
5.3 Screw-Induced Heating
5.3.1 Viscous Dissipation (Shear Heating)
5.3.2 Solid-Bed Friction
5.3.3 Combined Effect: Melt Film Formation and Radial Homogenisation
5.4 Temperature Zone Setpoint Selection
5.4.1 Literature-Derived Starting Points
5.4.2 Experimental Methodology
5.4.3 Experiment Results & Discussion
5.4.4 Final Setpoint Selection
5.5 Thermal Precision Requirements and Dimensional Accuracy
5.5.1 Viscosity Sensitivity to Temperature
5.5.2 Pressure Variation and Filament Diameter Impact
5.5.3 Implications for Zonal Heating Control
5.6 Results & Conclusion
6
Cooling Systems
6.1 Concept Selection
6.1.1 Criteria
6.1.2 Water vs Air
6.1.3 Fan Choice and Configuration
6.2 Simulation of Wind Flow
6.2.1 Evenness of Cooling
6.2.2 Effectiveness of Cooling
6.2.3 Thermal Analysis
6.3 Preliminary Prototyping
6.4 Omni-Flow
6.5 Results & Conclusion
7
Integrated Prototype Validation
7.1 Final Prototype Overview
7.2 End-to-End Filament Quality Assessment
7.2.1 Physical and Dimensional Metrics
7.2.2 System Parameters for Assessment
7.2.3 Results and Discussion
7.2.4 Printability Testing
7.3 Comparison with Commercial Filament
7.3.1 Dimensional Stability
7.3.2 Thermal Performance and Warping Tendency
7.4 Pilot Tests & Reviews
8
Limitations & Future Work
8.1 Spool-Level Diameter Uniformity
8.2 Feedstock Contamination
8.3 Scaling Throughput
8.4 Advanced Screw and Mixing Designs
9
Conclusion
Revisiting the Objectives
Addressing the Key Issues
Where Our Innovation Lies
Outlook
References
Appendices
Appendix A: Project scope thought process
Appendix B: Bulk Density Calculations
Appendix C: User Needs Analysis
Appendix D: Generic Extruder Dimensions and Material
Appendix E: Calculations for Shear Rate
Appendix F: Expected Thermal Parameters
Appendix G: Flow Simulation Parameters
Appendix H: Required Wind Speed
Appendix I: Slicer Settings
Appendix J: Bill of Materials
Appendix K: Electrical System
Appendix L: Value Proposition and stakeholder value
Appendix M: Diameter Data Acquisition and Processing Workflow
References for Appendix
EcoSpool
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