Conceptual Design of a Low-Cost Extrusion-Driven Injection Molding Device for Polymeric Materials

Abstract

Conventional polymer injection molding achieves high part quality and productivity; however, equipment and tooling costs frequently restrict its use in educational laboratories and early-stage research settings. This study introduces a requirement-driven conceptual design for a low-cost injection molding device that uses readily available filament-extrusion hardware to fabricate ASTM D638 Type I specimens. The methodology translates functional requirements into integrated subsystem decisions for the injection unit, mold unit, and structural frame, supported by first-order flow, thermal, and mechanical analyses. The design process establishes a feasible low-throughput operating window and addresses key risks through targeted solutions: guideline-based venting to minimize gas entrapment, conduction-focused mold heating with cartridge heaters and optional cooling channels for thermal regulation, and a stable clamping and alignment strategy for precise nozzle-to-mold positioning. Sprue and runner alternatives were assessed as coupled variables, with the constant-cylindrical sprue selected as the most robust option for maintaining quality consistency, mitigating defects, and maintaining dimensional stability under laboratory constraints. Material screening and preliminary sizing criteria identified aluminum tooling as suitable for the reference configuration. The resulting framework offers a practical pre-prototyping approach for low-volume comparative testing, educational use, and early laboratory validation, while excluding industrial high-throughput operation from its intended scope.