Insert-Molded Article Gate Mark Defect Prevention
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Solution Overview
Problem
In insert-molded articles with metal and resin components, reducing the thickness of the resin covering part can lead to molding defects such as sink marks and voids due to insufficient holding pressure, and cold slugs may enter the injection mold, affecting the article's dimensional accuracy and strength.
Innovation Solution
The insert-molded article design includes a metal component with through-holes or blind holes opposing the injection gate, ensuring the resin component fills these features, providing sufficient thickness to prevent premature solidification and maintaining holding pressure, while the gate mark distance is optimized to prevent cold slugs from entering the mold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the resin covering part is reduced to achieve weight reduction or space saving, then the weight and size are improved, but molding defects such as sink marks and voids occur due to insufficient holding pressure
Solution Approach 1:
The through-hole or blind hole is formed in the metal component beforehand, positioned opposite the gate mark. This preliminary structural preparation ensures that when resin is injected, it flows through the hole and creates a filler part that maintains adequate thickness at the gate region, preventing premature solidification and ensuring sufficient holding pressure even when the overall covering part thickness is reduced
Solution Approach 2:
The resin covering part has non-uniform thickness distribution: thinner in non-critical regions for weight reduction, but maintains sufficient thickness at the gate region due to the filler part formed by resin flowing through the through-hole or blind hole. This local quality variation allows weight reduction while preventing molding defects at critical areas
2Volume of moving object
If the thickness of the resin covering part is reduced, then space is saved, but cold slugs formed in the last shot may enter the cavity and deteriorate appearance and strength
Solution Approach 1:
The through-hole or blind hole in the metal component acts as an intermediary structure that guides resin flow. The filler part formed by resin passing through this hole creates a physical barrier and flow path that prevents cold slugs from the last shot from entering the main cavity, while still allowing the covering part to be thinner for space savings
3Quantity of substance
If the resin thickness below the gate is insufficient, then material usage is reduced, but sufficient holding pressure cannot be applied resulting in molding defects
Solution Approach 1:
The through-hole or blind hole is pre-formed in the metal component to create a predetermined flow path for the resin. This preliminary action ensures that resin material efficiently fills the cavity and creates a filler part with adequate thickness at the gate region, maintaining sufficient holding pressure and strength while using less overall resin material
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 design stabilizes the dimensional accuracy and strength of the insert-molded article by preventing molding defects and ensuring the resin component solidifies properly, while preventing cold slugs from entering the injection mold, thus maintaining the article's appearance and strength.
Implementation Method 1
closing the mold, and injecting a molten molding resin material from the pin gate to form the resin component through injection molding
Implementation Method 2
the thin resin immediately below the gate is solidified before the gate is solidified
Data Source
Figure 1~2A
Figure 2B~3A
Figure 3B~4
AI summary
An object is to inhibit occurrence of molding defects even when the thickness of a covering part, of a resin component, covering the surface of a flat plate-shaped part of a metal component is reduced, thereby stabilizing dimensional accuracy and strength of an insert-molded article. Another object is to inhibit a cold slug formed in the last shot from entering a cavity of an injection mold, thereby preventing the appearance and strength of the insert-molded article from being deteriorated. A metal component 1 has a shape including a flat plate-shaped part 3, and the flat plate-shaped part 3 has a through-hole 7 formed therein. A resin component 2 has a shape including a covering part 5 that covers a surface E of the flat plate-shaped part 3, and the covering part 5 has a surface in which a gate mark B is present. The through-hole 7 formed in the flat plate-shaped part 3 of the metal component 1 is located opposite to the gate mark B. The resin component 2 has a filler part H with which the through-hole 7 is filled.