Laser Welding Penetration Depth Measurement

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Solution Overview

Problem

Existing laser welding apparatuses cannot accurately evaluate the penetration depth of welded parts due to varying correlations between emission intensity and penetration depth, influenced by workpiece material and ambient temperature, leading to inaccurate quality assessment.

Innovation Solution

A laser welding apparatus that emits a laser beam and an object beam of different wavelengths, with the object beam having a larger spot diameter, using an optical interferometer to directly measure the penetration depth and evaluate the welded part based on the measured depth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the penetration depth is indirectly derived from emission intensity of molten metal, then the quality evaluation can be performed, but the measurement precision deteriorates due to varying correlations influenced by workpiece material and ambient temperature

Engineering Contradiction:

Improvequality evaluationVSAvoidpenetration depth measurement

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces the indirect optical measurement method (detecting emission intensity) with a direct mechanical/electrical measurement method (using an electrode to physically contact and measure penetration depth). This substitution eliminates the need for complex optical correlations and provides direct, accurate measurement of penetration depth regardless of material or temperature variations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

If the emission intensity of molten metal is detected to evaluate welded part quality, then the quality assessment can be performed, but the manufacturing precision deteriorates because the penetration depth derivation becomes inaccurate

Engineering Contradiction:

Improvequality assessment processVSAvoidpenetration depth accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces the indirect optical detection system with a direct electrical measurement system using a consumable electrode. The electrode physically contacts the molten metal pool to directly measure penetration depth, providing accurate manufacturing precision while maintaining ease of implementation through simple electrical measurement circuits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a consumable electrode as an intermediary element that serves dual purposes: it provides the welding current and simultaneously acts as a measurement probe. The electrode's physical contact with the molten metal pool enables direct penetration depth measurement without interfering with the welding process, thus maintaining manufacturing precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If the correlation between emission intensity and penetration depth is used for evaluation, then the quality assessment can be performed, but the reliability deteriorates because the correlation varies with workpiece material and ambient temperature

Engineering Contradiction:

Improvequality evaluation methodVSAvoidpenetration depth evaluation

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces the software-based correlation matching method with a direct physical measurement method using an electrode. This substitution eliminates the need for storing and matching emission intensity correlations for different materials and temperatures, providing reliable penetration depth measurement across all working conditions while maintaining ease of operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The consumable electrode performs multiple functions simultaneously: it provides welding current, maintains arc stability, and serves as a built-in measurement probe. The electrode automatically adapts to different workpiece materials and conditions without requiring external calibration or correlation data, enabling reliable self-service quality evaluation throughout the welding process.

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 precise and accurate detection of penetration depth, thereby improving the evaluation of welded parts with high reliability, applicable to various materials including automobiles and electronic components.

Implementation Method 1

an optical interferometer that emits the object beam to the first optical element, detects through the first optical element the object beam reflected on the welded part, and generates an electric signal based on the detected object beam

Methodology Applied

Scientific EffectOptical interference: Interference

Data Source

PatentUS8735768B2Laser welding apparatus

Publication Date: 2014.05.27 PANASONIC HOLDINGS CORP

AI summary

A laser welding apparatus includes: a first optical element that coaxially emits, to a welded part, a laser beam emitted from a laser light source and an object beam having a different wavelength from the laser beam; a second optical element that causes the spot diameter of the object beam to be larger than the spot diameter of the laser beam on the welded part; an optical interferometer that emits the object beam to the first optical element, detects through the first optical element the object beam reflected on the welded part, and generates an electric signal based on the detected object beam; and a measuring unit that measures a penetration depth of the welded part based on the electric signal.