Thermoplastic Bonding Member Protrusions for Ultrasonic Welding

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Solution Overview

Problem

Existing methods for joining fiber-reinforced thermoplastic resins, such as those using energy directors or fabric meshes, face challenges like high costs, instability in shape and size, warping issues, and difficulty in achieving stable and high joint strength, especially for large-sized members and in cases where joined surfaces separate.

Innovation Solution

A method involving a joining member with a sheet part and protrusion parts made of thermoplastic resin, where the protrusion parts have a maximum height of 100 to 500 µm and a specific ratio of projected areas to the sheet part area, applied between two members to be joined, allowing for efficient ultrasonic welding and stable joint formation even with warped surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If energy directors are formed integrally with joining object bodies to achieve stable and high joint strength, then joint strength is improved, but manufacturing cost increases due to fine processing of molds

Engineering Contradiction:

Improvejoint strengthVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

A separate joining member with protrusion parts is introduced as an intermediary component between the two fiber-reinforced thermoplastic resin bodies. This joining member serves as the energy director, eliminating the need for complex mold processing on the main components while achieving stable and high joint strength through ultrasonic welding.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If energy directors are formed on large-sized members, then joint strength is improved, but shape and size stability deteriorates due to pressure distribution issues during shaping

Engineering Contradiction:

Improvejoint strengthVSAvoidshape and size stability

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The energy director function is segmented from the main joining objects and transferred to a separate joining member. This allows the protrusion parts to be independently formed with controlled geometry, avoiding the pressure distribution problems that occur when forming energy directors directly on large-sized members during their shaping process.

Inventive Principle:

Principle #1Segmentation

3Strength

If joining surfaces with energy directors are used, then joint strength is improved, but adaptability deteriorates when members warp and deform making joining surfaces contact impossible

Engineering Contradiction:

Improvejoint strengthVSAvoidadaptability to warped surfaces

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The joining member with protrusion parts acts as a flexible intermediary that can accommodate warped and deformed joining surfaces. The protrusion parts make initial contact and concentrate ultrasonic energy, enabling welding even when the joining surfaces cannot achieve full contact due to warping.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Device complexity

If traditional ultrasonic welding is used without joining members, then process simplicity is maintained, but productivity decreases due to insufficient joint strength requiring rework

Engineering Contradiction:

Improveprocess simplicityVSAvoidproductivity

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The joining member with protrusion parts is a simple-to-introduce component that significantly improves joint strength and welding reliability. This small increase in complexity leads to substantial productivity gains by eliminating rework and ensuring consistent joint quality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables cost-effective, high-productivity joining with stable and strong joints, allowing for easy repair of separated surfaces and is suitable for mass production with a high degree of design freedom.

Implementation Method 1

a resonator called a welding horn is pressed against the joining object bodies while high-frequency mechanical vibration is given from the resonator, and the mechanical vibration transferred to the joining object bodies is converted into heat energy to heat and melt a part of the joining object bodies

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Implementation Method 2

the mechanical vibration transferred to the joining object bodies is converted into heat energy to heat and melt a part of the joining object bodies

Methodology Applied

Scientific EffectMechanical vibration converted to heat energy: Viscous Heating

Data Source

PatentEP3466652B1Method for producing bonded body

Publication Date: 2021.03.31 TEIJIN LTD

Figure 1~4

AI summary

The present invention provides a method for producing a bonded body, wherein a bonded body, in which a member A containing a thermoplastic resin and a member B containing a thermoplastic resin are bonded with each other, is obtained by arranging a bonding member between the member A and member B and melting at least a part of the bonding member. In this connection, the bonding member has: a sheet part containing a thermoplastic resin; and a plurality of projection parts containing a thermoplastic resin, which are on at least one surface of the sheet part and are integrated with the sheet part.