Injection-Compression Molding Reduces Tool Wear and Flash
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Solution Overview
Problem
Compression-molding processes face challenges in achieving desired fiber alignment, particularly in thin or complex features, and suffer from tool wear due to relative motion between metal mold-tool surfaces, leading to issues like flash and increased manufacturing costs.
Innovation Solution
A modified compression-molding process where the volume of fiber-bundle-based preforms is less than the mold cavity volume, with a separate injection charge of neat resin or short fibers used to fill the cavity and apply pressure after mold closure, minimizing interaction between long fibers and mold surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the volume of feed constituents is increased to fill the mold cavity, then the fiber alignment and resin distribution improve, but the tool wear increases due to metal-on-metal contact during compression
Solution Approach 1:
The mold cavity is segmented into two zones: a central region containing the fiber-bundle preforms and peripheral regions filled with injection charge. This segmentation allows the long fibers to remain stationary in the central zone while the injection charge fills the periphery, preventing fiber-mold surface interaction and reducing tool wear.
Solution Approach 2:
The injection charge acts as an intermediary material that fills the gaps between the preforms and mold cavity walls. This intermediary charge prevents direct contact between the long fibers and the moving mold surfaces, thereby eliminating the abrasion that causes tool wear while still achieving complete cavity fill.
2Object-affected harmful factors
If the tool gaps are increased to reduce metal-on-metal wear, then the tool wear decreases, but flash occurs due to excessive resin and fiber flow into the gaps
Solution Approach 1:
Different regions of the mold cavity are assigned different functions: the central region is designated for containing the fiber-bundle preforms with minimal gap to maintain fiber alignment, while the peripheral regions are designated for receiving the injection charge. This local differentiation allows the central region to maintain tight tolerances (reducing flash) while the overall system accommodates larger gaps (reducing wear).
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
This approach reduces tool wear, minimizes flash, and achieves high-quality fiber alignment and surface finish, thereby simplifying post-processing and reducing manufacturing complexity and costs.
Implementation Method 1
introducing the injection charge into the mold cavity by advancing a first plunger in the first plunger cavity, the injection charge filling the void volume, thereby pressurizing the mold cavity
Implementation Method 2
consolidating the first resin, the second resin, the plurality of fibers from the fiber-bundle-based preforms, and the fibers, if present, from the injection charge
Implementation Method 3
the pressure applied by the injection charge consolidates the first resin, the second resin, the plurality of fibers
Data Source
AI summary
In an injection/compression-molding process, an assemblage of fiber-bundle-based preforms are placed in a mold cavity of a mold tool. The mold is then fully closed, but not pressurized. An injection charge, which includes resin and optionally short fibers, is placed in a plunger cavity that is in fluidic communication with the mold cavity. The injection charge is liquefied and injected into the mold cavity, pressurizing it to a pressure suitable for compression molding. If not previously liquefied, the resin in fiber-bundle-based preform is liquefied and, under the applied pressure, the resins and fibers are consolidated and then cooled to form a part.