Polymer Injection Molding with Buffer Zone for Surface Quality
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Solution Overview
Problem
Conventional molding processes for thermoplastic parts, especially those with visible faces on vehicles, often result in defects like hot spots and shrinkage due to material flow issues at the start of filling, making the parts unsuitable for visible applications.
Innovation Solution
A process involving the injection of polymer material into a mold with additional parts extending over a specific length to manage material flow, followed by cutting to form a clean edge, using techniques like temperature reduction and mechanical failure at the junction to achieve precise separation without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional molding process is used, then production efficiency is maintained, but surface defects occur making parts unsuitable for visible applications
Solution Approach 1:
The mold cavity is divided into a main part and at least one additional part. The additional part acts as a buffer zone that captures defects at the material flow entry point, separating them from the visible surfaces of the main part. This segmentation allows the visible faces to be defect-free while maintaining conventional molding processes.
2Productivity
If material flow is increased to improve filling speed, then productivity increases, but hot spots and shrinkage defects worsen
Solution Approach 1:
The harmful effects of high-speed material flow (hot spots, shear disruption, shrinkage) are extracted and confined to the additional part of the cavity. This allows rapid filling to continue while the defects are isolated in the non-visible additional part, which is later separated from the main part.
3Manufacturing precision
If visible faces are required, then appearance quality improves, but production cost increases due to material restrictions
Solution Approach 1:
Different regions of the cavity serve different functions: the additional part is designed to accommodate defects and is not visible after assembly, while the main part produces the visible surfaces with high quality. This local differentiation allows use of conventional, cost-effective materials like polypropylene throughout, avoiding the need for expensive materials like ABS/PC.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process ensures parts with visible faces have minimal defects, meeting automotive appearance standards with clean cuts and no beading or roughness, suitable for large-width parts and various applications like spoilers.
Implementation Method 1
when the junction between the part and the additional part has a temperature less than or equal to the embrittlement point of the polymer material
Implementation Method 2
lowering the temperature of the junction to a temperature less than or equal to the embrittlement point of the polymer material
Data Source
Figure 1A~1B
Figure 2~4
Figure 5~6
AI summary
The invention relates to a method for producing a part consisting of a polymer material, said method involving injection-moulding said polymer material in a mould comprising a main section for forming the part and an additional section for forming an add-on for the part. The additional section is arranged between the injection point and the main section. The part and the add-on are separated by cutting.