Pre-molded Insert Resin Bonding Gap Prevention

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Solution Overview

Problem

In molded parts with inserts, resin contraction during the molding process leads to internal distortion and gap formation at the interface between the insert and the molded part, affecting the bonding process and productivity, especially in multiple molding processes where the use of thermoplastic resin and injection molding methods are common.

Innovation Solution

A composite molded part is formed by pre-molding an insert composed of metal, ceramic, or a combination of materials with a thermoplastic resin having crystallinity, and then applying heat treatment below the crystalline melting point of the resin, followed by an insert molding process using thermo-setting resin to surround the pre-molded part with an over-molded part, ensuring a firm interface without gap formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple molding process is used to increase productivity, then productivity is improved, but gap formation at the interface between insert and molded part occurs due to resin contraction

Engineering Contradiction:

ImproveproductivityVSAvoidinterface gap

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The insert is pre-molded with the resin before the final molding process. This preliminary action ensures that the insert and resin are already bonded together, preventing gap formation during the subsequent molding process even when resin contraction occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The insert and resin are merged into a single integrated structure through the pre-molding process. This merging ensures that they move and contract together as a unified structure, eliminating the interface gap problem that would occur with separate components.

Inventive Principle:

Principle #5Merging (Combining)

2Strength

If heat treatment is applied during over-molding to integrate parts, then bonding is improved, but resin contraction of the pre-molded part occurs causing internal distortion

Engineering Contradiction:

Improvebonding strengthVSAvoidinternal distortion

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The insert and resin are pre-molded together before the heat treatment and over-molding process. This preliminary bonding ensures that the insert and resin are already integrated, so when heat treatment is applied during over-molding, they contract together as a unified structure rather than causing relative distortion between separate components.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If adhesive material is coated and hardened on insert surface after over-molding to seal interface, then interface sealing is improved, but productivity decreases due to additional coating and hardening time

Engineering Contradiction:

Improveinterface sealingVSAvoidproductivity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The sealing function is extracted from the post-molding adhesive coating process and integrated into the pre-molding process itself. By pre-molding the insert with the resin, the sealing function is achieved during the molding process rather than requiring a separate post-processing step, thereby eliminating the additional coating and hardening time.

Inventive Principle:

Principle #2Taking out (Extraction)

4Manufacturing precision

If uniform resin thickness is maintained to prevent void generation, then void generation is reduced, but the ability to accommodate inserts with increased thickness is limited

Engineering Contradiction:

Improvevoid generationVSAvoidinsert thickness accommodation

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The insert is pre-molded with the resin in a controlled environment before final assembly. This preliminary action allows the resin to be applied uniformly around the insert, preventing void generation even when the insert has increased thickness, because the pre-molding process can accommodate varying insert dimensions while maintaining proper resin distribution.

Inventive Principle:

Principle #10Preliminary action

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 method enhances the reliability and stability of the bonding process by preventing gap formation between the insert and the resin, improving the efficiency and cost-effectiveness of the molding process while maintaining high precision and productivity.

Implementation Method 1

applying heat treatment below the crystalline melting point of the resin

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 2

an insert molding process using thermo-setting resin to surround the pre-molded part

Methodology Applied

Scientific EffectCuring: Chemical Bonding

Data Source

PatentUS8784715B2Structure of parts made from plural composite pieces and method of building those parts

Publication Date: 2014.07.22 ASTEMO LTD

AI summary

A pre-molded part is formed by pre-molding an insert with a pre-molded member, and then the pre-molded part is inserted into an over-molded member composed of thermo plastic resin. After applying a heat treatment with a temperature lower than a crystalline melting point of the pre-molded part to the pre-molded part surrounding the insert, a firm contact between the insert and the resin surrounding the insert without a gap at the interface between those parts is obtained.