Overmolding Hollow Polymeric Insert for Vehicle Lift Gate Stiffness
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Solution Overview
Problem
Structural components like lift gates in vehicles face challenges in achieving high bending stiffness and torsional rigidity without increasing weight, which affects fuel efficiency and aesthetic quality, and existing manufacturing techniques struggle with reproducible wall thicknesses and manufacturing defects in fiber-reinforced polymers.
Innovation Solution
A method involving a hollow polymeric insert overmolded with a fiber-reinforced polymeric material to create a closed section geometry, using a mold with pressurization and inserts to ensure consistent wall thickness and increased stiffness, while maintaining a lightweight structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If panel thickness is increased or ribs are added to increase rigidity, then bending stiffness and torsional rigidity are improved, but overall weight increases
Solution Approach 1:
The patent uses a composite structure combining a hollow polymeric insert with overmolded fiber-reinforced polymeric material. This composite construction provides high bending stiffness and torsional rigidity through the closed-section geometry and fiber reinforcement, while maintaining lightweight properties by using polymeric materials instead of solid metal sections.
Solution Approach 2:
The patent transitions from two-dimensional panel reinforcement (ribs) to a three-dimensional closed-section hollow structure. This dimensional change provides superior torsional rigidity and bending stiffness with significantly reduced weight compared to traditional ribbed or solid panel designs.
2Stability of the object's composition
If metal inserts are used to provide molding surface, then structural stability is improved, but weight increases and fuel economy is negatively impacted
Solution Approach 1:
The patent replaces permanent metal inserts with a disposable hollow polymeric insert that is molded and then removed. This polymeric insert provides the necessary molding surface and structural stability during manufacturing, but is discarded after use, eliminating the weight penalty of permanent metal reinforcements in the final product.
Solution Approach 2:
The hollow polymeric insert serves as a temporary intermediary tool during the molding process, providing a surface for molding the fiber-reinforced polymeric material while maintaining structural stability. After molding, the insert is removed, leaving no permanent heavy metal components in the final structure.
3Ease of manufacture
If traditional molding techniques are used, then manufacturing is simplified, but wall thickness uniformity and manufacturing precision are poor
Solution Approach 1:
The hollow polymeric insert is pre-formed with the exact desired geometry and wall thickness before the overmolding process. This preliminary action ensures that the insert provides a precise mold cavity that guarantees uniform wall thickness in the final overmolded fiber-reinforced polymeric component, eliminating the variability associated with traditional molding techniques.
4Strength
If fiber reinforced plastic is molded against metal inserts or cores, then structural strength is improved, but fiber foaming defects occur
Solution Approach 1:
The patent uses a disposable hollow polymeric insert instead of permanent metal inserts or cores. This polymeric insert is molded and then removed, preventing fiber foaming defects that occur when fiber-reinforced plastic contacts metal surfaces. The insert provides the necessary structural strength during molding without causing the harmful fiber foaming effect.
Data Source
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AI summary
A method for manufacturing a hollow overmolded polymeric article comprising: positioning a hollow polymeric structure (10) in a mold (100); supporting the interior surface of the hollow polymeric structure; disposing a fibrous polymeric material (12) into the mold proximal to the outer surface of the hollow polymeric structure; overmolding the fibrous polymeric material onto to the outer surface of the hollow polymeric structure; opening the mold; and removing a hollow overmolded polymeric article comprising the fibrous polymeric material overmolded on the hollow polymeric structure.