Infrared Welding of Polyamide Pipes for Uniform Crystallinity
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Solution Overview
Problem
Infrared welding methods for joining crystalline resin tubular members often result in a low tensile strength due to uneven crystallinity and temperature distribution near the joined portion, leading to breakage at relatively low tensile forces, especially during low-temperature tests.
Innovation Solution
A welding joining method that controls the characteristics of infrared emission to maintain uniform crystallinity along the tubular radial direction by adjusting the heat input distribution, using a combination of low-output and high-output infrared emissions to heat and melt the resin ends, followed by slow cooling to promote uniform crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If infrared welding method is used to join crystalline resin tubular members, then the joining process is efficient and rapid, but the tensile strength of the joined body is low due to uneven crystallinity
Solution Approach 1:
The infrared emission is divided into multiple wavelength segments (first wavelength range for heating, second wavelength range for melting) to achieve different thermal effects at different stages, preventing uneven crystallinity while maintaining efficient joining
Solution Approach 2:
The patent changes the parameters of infrared emission by using different wavelength ranges at different stages: first emitting infrared in a wavelength range that heats without causing rapid melting, then emitting infrared in a different wavelength range that promotes uniform melting and crystallization, thereby improving tensile strength
2Speed
If high-output infrared emission is used to rapidly melt the resin ends, then the joining speed is fast, but the temperature distribution becomes uneven causing breakage at low tensile forces
Solution Approach 1:
The welding process is divided into two periodic stages: first emitting infrared radiation for heating, then emitting infrared radiation for melting. This periodic action ensures uniform temperature distribution and prevents premature breakage while maintaining fast joining speed
Solution Approach 2:
The patent applies preliminary infrared emission to heat the resin ends before the main melting stage. This preliminary heating action ensures uniform temperature distribution throughout the material, preventing localized stress concentrations that would cause breakage
3Device complexity
If conventional infrared welding is applied to crystalline resin, then the process is simple, but the crystallinity becomes ununiform near the joined portion
Solution Approach 1:
The patent employs dynamic control of infrared emission characteristics, switching between different wavelength ranges based on the heating stage. This dynamic adjustment maintains simple equipment while achieving uniform crystallinity through controlled thermal progression
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 achieves a high tensile strength in the welding joined body by minimizing crystallinity differences near the joined portion, preventing premature breakage and ensuring a strong bond even at low temperatures.
Implementation Method 1
heating and melting the end portions of the tubular members by emitting infrared from the infrared emission unit
Implementation Method 2
cooling down the molten end portions of the tubular members in a state where the end portions are bonded to each other by pressure
Data Source
AI summary
Provided is a welding joining method for joining end portions of first and second pipes made of polyamide resin by bonding the end portions to each other by pressure in a molten state. The welding joining method includes: a placing step of placing an infrared radiation lamp between the first and second pipes placed to face each other at an interval; a heating and melting step of heating and melting the end portions of the first and second pipes by emitting infrared; and a pressure bonding step of cooling down the molten end portions in a state where the molten end portions are bonded to each other by pressure.