Belt Molding Step Design Conceals Sink Marks
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Solution Overview
Problem
Resin molded products with different shrinkage ratios exhibit sink marks at material boundaries, leading to aesthetic issues due to visible depressions, which existing methods can only partially mitigate.
Innovation Solution
A belt molding design featuring a design portion with a step between its surfaces facing the molding body and design lip, where the step's boundary is within the depression caused by sink marks, making the depression unnoticeable and improving appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a design portion is formed to cover both the molding body and design lip, then the appearance is improved, but sink marks become visible at the material boundary causing aesthetic deterioration
Solution Approach 1:
The patent applies preliminary action by forming a step structure in advance during the molding process. The design portion is designed with a step that creates a level difference between the first and second portions, positioned so that the boundary of the step coincides with or is within the depression area. This pre-formed step structure proactively conceals the sink mark before it becomes visible on the final product surface.
Solution Approach 2:
The patent uses dimensionality change by introducing a step structure that creates a vertical level difference between the first portion (covering the molding body) and the second portion (covering the design lip). This level difference adds a dimensional feature that redirects visual perception away from the horizontal boundary where sink marks occur, effectively concealing the defect through a vertical dimension.
2Ease of manufacture
If the design portion is made of a resin with higher mold shrinkage ratio than the molding body, then the design portion can be properly formed, but sink marks are caused at the boundary between different materials
Solution Approach 1:
The patent applies preliminary action by incorporating a step structure into the design portion during the molding process. This step is formed in advance with a specific boundary position that aligns with the depression area caused by differential shrinkage. By pre-positioning the step boundary, the patent anticipates and compensates for the sink mark formation that occurs when resins with different shrinkage ratios are used.
3Shape
If the boundary of the step is positioned within the depression area, then the sink mark becomes unnoticeable, but the design portion structure becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the design portion into two distinct portions: a first portion covering the molding body and a second portion covering the design lip. The step structure creates a clear segmentation between these portions, with the boundary strategically positioned within the depression area. This segmentation approach simplifies the overall structure compared to trying to create a completely flat, uniform surface that would require complex compensation techniques.
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 step formation between the design portion and molding body surfaces conceals sink marks, enhancing the belt molding's appearance and preventing water from flowing between the design lip and molding body, thus maintaining a clean and aesthetically pleasing surface.
Implementation Method 1
A molten resin shrinks as it cools, and then a depression called a 'sink mark' is formed on the surface of a resin molded product molded by extrusion molding or injection molding when a molten resin shrinks
Implementation Method 2
Bristles 11a and 13a to remove dust (dirt) and water attached to the surface of the sliding glass 9 are formed on the side surfaces on the interior side, of the upper sealing lip 11 and the lower sealing lip 13
Data Source
AI summary
A belt molding includes: a molding body, which includes an inner wall, an outer wall, and a connection wall that connects an upper end of the inner wall and an upper end of the outer wall; a design lip, which is formed at the upper end of the inner wall of the molding body; and a design portion, wherein the design portion includes a first portion, which covers at least a part of the molding body, and a second portion, which covers at least a part of the design lip, and wherein a step is formed between the first portion and the second portion, such that a level of a surface of the first portion is different from a level of a surface of the second portion.