Adhesive Injection for Pi-Joint Assemblies

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Solution Overview

Problem

Current methods for adhesively bonding Pi-joint designs face challenges such as difficulty in controlling adhesive quantity, potential for adhesive spillage, air pockets, and limited bond length, which result in poor bonding quality and increased cycle times and costs, not aligning with lean manufacturing principles.

Innovation Solution

An adhesive injection process that uses a vacuum to draw adhesive evenly along the gap between male and female parts, with a filler to prevent spills and a sealant to seal openings before injection, eliminating the need for tape and allowing longer bond lengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the plunge method is used to fill the female section with adhesive, then the bonding process can be completed, but it is difficult to control the amount of adhesive to avoid spill over and requires clean up

Engineering Contradiction:

Improvebonding process completionVSAvoidadhesive spill over

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

A filler material is placed at the bottom of the female section before adhesive injection to preliminarily occupy space and prevent adhesive from overflowing during the bonding process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A filler material acts as an intermediary between the adhesive and the bottom of the female section, controlling adhesive flow and preventing spill over without requiring manual intervention

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the tube withdrawal method is used to inject adhesive, then the adhesive can be injected through the tube, but the tube must be withdrawn manually making it difficult to maintain constant rate and may cause air pockets or voids

Engineering Contradiction:

Improveadhesive injection capabilityVSAvoidadhesive filling consistency

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

Manual tube withdrawal is replaced by using a vacuum system to draw the adhesive through the tube, providing controlled and consistent adhesive flow without manual intervention

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

A vacuum system is used to create negative pressure that draws the adhesive through the injection tube at a controlled rate, eliminating manual withdrawal and ensuring consistent filling without air pockets

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Ease of manufacture

If tape is used to seal openings during injection, then the adhesive can be contained, but the tape may disbond when adhesive pressure is too large causing blow-out and spill

Engineering Contradiction:

Improveopening sealing capabilityVSAvoidseal integrity during injection

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The sealing method is changed from mechanical tape to a chemical sealant that cures to form a rigid seal, changing the physical parameters of the seal to withstand high adhesive pressure without disbonding

Inventive Principle:

Principle #35Parameter changes

4Productivity

If multiple injection ports are used every 12 inches, then the adhesive can be injected throughout the joint, but the bond length is limited depending on adhesive properties and gap width

Engineering Contradiction:

Improveadhesive injection coverageVSAvoidbond length

Core Design Contradiction:

ProductivityVSLength of stationary object

Solution Approach 1:

A vacuum system is used to draw the adhesive through the entire length of the joint, enabling the adhesive to reach and fill gaps over longer distances than would be possible with pressure injection alone

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

The adhesive injection process is enhanced by introducing a vacuum dimension that pulls the adhesive through the joint length, overcoming the natural flow limitations and extending the effective bond length

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 process enhances bonding quality, reduces cycle times and costs, and improves productivity by preventing adhesive blow-outs and eliminating the need for adhesive cleanup and tape installation/removal, while enabling longer bond lengths and improved consistency.

Implementation Method 1

a vacuum to draw adhesive evenly along the gap between male and female parts

Methodology Applied

Scientific EffectVacuum: Vacuum

Data Source

PatentUS7645406B2Adhesive injection process for Pi-joint assemblies

Publication Date: 2010.01.12 THE BOEING CO

AI summary

An adhesive injection process for a Pi-joint assembly comprises the steps of: machining at least two ports into a female part of a Pi-joint assembly; inserting a filler into a gap between a male part and the female part; applying a sealant above the filler; creating a vacuum with a vacuum pump at one port; injecting an adhesive through another port; and drawing the adhesive towards the vacuum pump until the gap under the filler is completely filled with the adhesive. The adhesive injection process incorporates lean technologies that enable increased productivity during the assembly of a Pi-joint design using adhesive bonding. The adhesive injection process is suitable for, but not limited to, applications in the aerospace industry, such as the aircraft airframe assembly. The adhesive injection process may be used for the bonding of upper and lower skins to airframe structure as well as for structure-to-structure bonding.