Injection Molded Article With Localized Surface Roughness
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Solution Overview
Problem
Injection molded articles with protrusions of varying inner diameters often develop sink marks due to uneven cooling and shrinkage, leading to reduced visual quality, leakage issues, and inaccuracies in flow channel height, especially when attempting to prevent sink marks on the product's visible surface.
Innovation Solution
The solution involves processing the mold to create a mirror surface region and a projected region close to each other, with the projected region having a surface roughness greater than the mirror surface region, ensuring the resin adheres well to the mold and preventing sink marks on the visible surface while maintaining accuracy on the invisible surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If roughening is applied to the entire region of the product visible surface to prevent sink marks, then sink marks are prevented on the visible surface, but the surface properties deteriorate causing liquid leakage and flow channel height inaccuracies
Solution Approach 1:
The patent applies different surface treatments to different regions of the mold. The first region (where sink marks would form) receives roughening treatment to increase adhesion and prevent sink marks, while the second region (requiring accuracy) maintains mirror finish to ensure liquid tightness and flow channel precision. This local differentiation resolves the contradiction by allowing roughening only where necessary.
Solution Approach 2:
The mold surface is segmented into distinct regions with different surface properties. The patent divides the mold into a first region for roughening treatment and a second region for mirror finish, allowing independent optimization of each region's surface characteristics to meet different functional requirements.
2Temperature
If the core-side portion in the fixed mold is separated earlier due to faster cooling, then the visible surface is protected from sink marks, but post-shrinkage occurs causing sink marks on the visible surface
Solution Approach 1:
The patent changes the adhesion parameter of the mold surface through roughening treatment. By increasing the surface roughness in the first region, the adhesion force between the resin and mold is enhanced, which compensates for the earlier separation caused by faster cooling and prevents sink marks on the visible surface.
Solution Approach 2:
The mold surface is pre-treated with roughening in the first region before injection molding. This preliminary action increases adhesion in advance, ensuring that when the resin cools and shrinks, it remains firmly attached to the mold surface and does not form sink marks.
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 effectively prevents sink marks on the visible surface, ensuring the product's surface properties are maintained, preventing liquid leakage, and achieving the required accuracy in flow channel height.
Implementation Method 1
the mold surface on the product visible surface side that would cause sink marks has a higher adhesion force to resin than the mold surface on the invisible surface side
Implementation Method 2
A molten thermoplastic shrinks while being cooled and solidified in a mold
Implementation Method 3
A molten thermoplastic shrinks while being cooled and solidified in a mold
Data Source
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AI summary
An injection molded article is obtained by injection molding a molten resin into a mold. The injection molded article includes: a base as a thin plate-shaped member that is connected to a gate of the mold; and a plurality of protrusions each integrally molded on the base and having a thickness greater than a plate thickness of the base. The plurality of protrusions have holes each extending through the base, and the holes in the respective protrusions are connected through another component to form a flow channel. A processed region processed to have a surface roughness greater than a surface roughness of a mirror surface region including a region between the holes on the base is formed in a projected region where a region having a predetermined thickness value is projected on the base.