Composite Injection Molding Weld Position Control
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Solution Overview
Problem
During overmolding with thermoplastic composite materials containing reinforcing fibers, local deformation of the sheet material occurs due to uneven solidification shrinkage of the injection molding material, particularly when the weld portion is formed over the sheet material, leading to convex surfaces and potential deflection.
Innovation Solution
The injection molding method involves injecting the injection molding material to form weld portions in regions of the frame portion that do not overlap the sheet material, orienting reinforcing fibers in a direction orthogonal to the flow direction at weld areas to minimize solidification shrinkage, and using bypass ribs or thin film portions to adjust the weld position and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the injection molding material is injected to form weld portions on the sheet material surface, then the frame portion and ribs can be molded, but local deformation and convex surfaces occur due to uneven solidification shrinkage
Solution Approach 1:
The patent applies local quality by making the mold cavity depth variable - deeper at regions where frame portion and ribs are to be molded, and shallower at regions overlapping the sheet material. This local variation in cavity depth controls the injection molding material flow and weld portion formation, allowing the frame and ribs to be molded while preventing weld portions from forming on the sheet material surface, thus avoiding local deformation and maintaining surface flatness.
2Reliability
If the weld portion is formed over the sheet material, then the injection molding material joins properly, but solidification shrinkage causes deflection and convex surfaces
Solution Approach 1:
The patent uses local quality by creating a mold cavity with non-uniform depth - deeper regions for frame portion and ribs, shallower regions for sheet material overlap areas. This controls where weld portions form, ensuring proper joining in the frame and ribs while preventing weld-induced shrinkage and deformation on the sheet material surface, maintaining surface geometry and dimensional stability.
Solution Approach 2:
The patent applies preliminary action by pre-designing the mold cavity depth distribution before injection molding. The cavity is configured with greater depth at locations where frame portion and ribs are needed, and reduced depth where the sheet material surface must remain flat. This preliminary geometric configuration guides the injection molding material flow and weld portion formation to occur only where structurally necessary, preventing subsequent deformation during solidification.
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 method effectively suppresses local deformation of the sheet material during solidification shrinkage by avoiding weld formation on the sheet surface, ensuring even distribution and efficient molding of the composite material.
Implementation Method 1
the amount of solidification shrinkage in the fiber direction in the injection molding material is smaller than that of the portions except for the weld portion
Implementation Method 2
the reinforcing fibers contained in the injection molding material (the resin 112) are oriented in a flow direction of the resin 112
Data Source
AI summary
In the present invention, it is possible to reduce the occurrence of a local deformation in a plate material during solidification and shrinkage of an injection molding material. The composite material injection molding method includes an injection step of injecting an injection molding material containing reinforcing fibers onto one surface of a plate material; and a molding step of solidifying the injection molding material to mold a frame part so as to surround the outer periphery of the plate material and to mold a rib so as to define an inner peripheral-side space on the inner peripheral side of the frame part. In the injection step, the injection molding material is injected so that a weld part at which the injection molding material converges is formed in a region not overlapping the plate material of the frame part.