Ultrasonic Weld Quality Testing via Frequency Analysis

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Solution Overview

Problem

Ultrasonic welding technologies lack a simple, non-destructive method to assess the strength of ultrasonic welded joints between a fabric flap and a thermoplastic product, leading to issues with faulty connections due to sonotrode wear, which affects the quality and reliability of the welding process.

Innovation Solution

A method involving the measurement of structural data from ultrasonic welds using non-destructive techniques such as microscopic reflection, X-ray, infrared, or terahertz methods to calculate a frequency distribution, which determines a quality index by comparing values at the sonotrode and fabric spatial frequencies, allowing for the assessment of weld strength and detection of potential faults.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If non-destructive measurement methods are used to assess ultrasonic weld strength, then quality control capability is improved, but device complexity increases

Engineering Contradiction:
Improvequality control capabilityVSAvoidmeasurement system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical disassembly and direct strength measurement with non-destructive optical measurement methods. The system uses optical sensors and image processing to detect structural characteristics of the weld, substituting mechanical testing with optical field-based measurement to achieve quality assessment without physical contact or destruction of the welded joint.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces structural characteristics (optical patterns, surface topology, or material distribution features) as an intermediary parameter. Instead of directly measuring weld strength, the system measures these intermediate structural features and correlates them with weld quality through analysis algorithms, enabling indirect but reliable quality assessment.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of operation

If simple quality testing methods are implemented, then ease of operation is improved, but measurement precision deteriorates

Engineering Contradiction:
Improvequality testing simplicityVSAvoidweld strength assessment accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The measurement system is designed to automatically capture structural characteristics and perform quality assessment without requiring manual intervention. The optical sensors automatically detect weld features, the system processes the structural data, and generates quality results autonomously, maintaining simplicity of operation while ensuring precise measurement through automated analysis algorithms.

Inventive Principle:
Principle #25Self-service

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

Enables continuous quality control of ultrasonic welds, detects faulty connections, and ensures consistent quality by monitoring sonotrode wear, thereby improving the reliability and security of the welding process.

Implementation Method 1

measuring structural data of the ultrasonic weld, wherein the measurement is carried out by means of a non-destructive measuring unit, in particular by means of a measuring unit which uses microscopic techniques in reflection

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 2

Two- or three-dimensional structural data can be generated based on differences in composition using transmissive methods, such as those in the X-ray, infrared, or terahertz range

Methodology Applied
Scientific EffectX-ray transmission: X-Ray

Implementation Method 3

Two- or three-dimensional structural data can be generated based on differences in composition using transmissive methods, such as those in the X-ray, infrared, or terahertz range

Methodology Applied
Scientific EffectInfrared radiation: Infrared Radiation

Implementation Method 4

Two- or three-dimensional structural data can be generated based on differences in composition using transmissive methods, such as those in the X-ray, infrared, or terahertz range

Methodology Applied
Scientific EffectTerahertz radiation:

Implementation Method 5

highly sensitive surface analysis techniques (e.g., scanning electron microscopy with integrated X-ray analysis and/or MHz ultrasonic reflection)

Methodology Applied
Scientific EffectAcoustic wave detection: Ultrasound

Implementation Method 6

calculating a frequency distribution of the structural data; and using a value of the frequency distribution to determine a quality indicator

Methodology Applied
Scientific EffectFourier transform:

Implementation Method 7

The thermoplastic material is briefly melted by introducing an ultrasonic wave into the thermoplastic element using a sonotrode

Methodology Applied
Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Implementation Method 8

The thermoplastic material is briefly melted by introducing an ultrasonic wave into the thermoplastic element using a sonotrode

Methodology Applied
Scientific EffectUltrasonic heating:

Data Source

PatentEP3511152B1Quality testing of an ultrasonic welded connection
Publication Date: 2021.03.03 BUNDESDRUCKEREI GMBH
  • EP3511152B1 patent drawingFigure 1~2
  • EP3511152B1 patent drawingFigure 3A~3C
  • EP3511152B1 patent drawingFigure 4A~4C

AI summary

The invention relates to a quality control method for an ultrasonic weld between a fabric flap (102) and a product (106), wherein the fabric flap (102) comprises a fabric with threads, the threads having a fabric spatial frequency in one direction, wherein the product (106) has a thermoplastic material at least in an overlap region (104) with the fabric flap (102) comprising the ultrasonic weld, wherein the ultrasonic weld has weld points arranged one after the other in the direction with a sonotrode spatial frequency different from the fabric spatial frequency, wherein the method comprises: - measuring structural data of the ultrasonic weld; - calculating a frequency distribution of the structural data;and - using a value of the frequency distribution to determine a quality indicator, wherein the value includes at least one value of the frequency distribution at the sonotrode spatial frequency and/or at the tissue spatial frequency, wherein the quality test is passed if the quality indicator lies within a predetermined range of values.