Injection Molded Product With Selective Thermal Expansion
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Solution Overview
Problem
Existing injection molded products using thermally expandable capsules face issues such as decreased rigidity and complex manufacturing processes due to thermal expansion within the mold, leading to limitations in shape design and potential surface deformation or peeling.
Innovation Solution
An injection molded product with a configuration that includes a highly expanded portion and a main body portion, where the thermally expandable capsules are only partially expanded to form unevenness on the surface, maintaining the same polymer material throughout, and a method involving selective heating post-molding to form the unevenness, allowing for a fabric-like appearance without separate surface layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermally expandable capsules are fully expanded in the mold during injection molding, then a fabric-like appearance with unevenness is achieved on the surface, but the rigidity of the molded product decreases due to reduced density
Solution Approach 1:
The invention applies local quality by creating a surface layer with thermally expanded capsules for fabric-like appearance while keeping the interior with unexpanded capsules for rigidity. The surface layer thickness is controlled to be 1/10 to 1/2 of the total molded product thickness, ensuring that only the necessary surface portion is expanded to achieve the desired appearance without compromising overall structural strength.
Solution Approach 2:
The invention uses partial action by expanding only a portion of the thermally expandable capsules located in the surface layer, rather than expanding all capsules throughout the molded product. This selective expansion achieves the fabric-like appearance effect while maintaining the rigidity of the interior structure where capsules remain unexpanded.
2Manufacturing precision
If a separate surface layer with non-foamed beads is prepared and integrated onto a hard layer, then fabric-like appearance is achieved, but the manufacturing process becomes complicated and the surface layer may deform or peel during molding
Solution Approach 1:
The invention merges the surface layer and hard layer into a single integrated structure by mixing thermally expandable capsules uniformly throughout the molding material before injection molding. This eliminates the need for separate surface layer preparation and integration steps, simplifying the manufacturing process while ensuring the surface layer and interior are bonded as one homogeneous material without risk of peeling or deformation.
Solution Approach 2:
The invention applies preliminary action by pre-mixing the thermally expandable capsules with the polymer material before injection molding, so that the capsules are already uniformly distributed in the molding material. This preliminary preparation eliminates the need for subsequent separate surface layer formation steps and ensures uniform distribution of the fabric-like appearance effect throughout the molded product.
3Ease of operation
If the mold is opened before the surface solidifies or closed after unevenness is generated, then easy mold operation is achieved, but the shape of the molded product is limited
Solution Approach 1:
The invention uses periodic action by implementing a two-stage temperature control process: first, the mold is maintained at a higher temperature during injection molding to allow the thermally expandable capsules to expand and form the fabric-like appearance; second, the mold temperature is reduced to solidify the surface. This periodic temperature variation enables both easy mold operation and versatile product shapes by controlling the timing and extent of capsule expansion.
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 configuration enhances appearance quality and design properties while maintaining rigidity by controlling the thermal expansion of capsules, preventing surface peeling, and simplifying the manufacturing process.
Implementation Method 1
an unevenness forming portion, in which unevenness is formed by thermal expansion of the thermally expandable capsules, is formed to at least a portion of a surface of the injection molded product
Data Source
AI summary
In an injection molded product of the invention, an unevenness forming portion having unevenness formed by thermal expansion of thermally expandable capsules is formed. The injection molded product includes a highly expanded portion that is formed at a surface side of the unevenness forming portion in a thickness direction of the injection molded product and in which the thermally expandable capsules are thermally expanded, and a main body portion that is a portion adjacent to the highly expanded portion in the thickness direction and in which the thermally expandable capsules are substantially not thermally expanded. The thickness of the highly expanded portion is a half or smaller than the thickness of the injection molded product in the unevenness forming portion, and a polymer material of the highly expanded portion and a polymer material of the main body portion are the same polymer material.