Eddy Current Sensor Array for AM Welding Defect Detection

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Solution Overview

Problem

Additive manufacturing (AM) continuous welding systems face challenges such as prolonged production time, high costs, material waste, and difficulty in inspecting work pieces due to issues like layer deviation, separation, and porosity, leading to defective products and reduced throughput.

Innovation Solution

An AM continuous welding system that uses eddy current sensors to monitor material layers in real-time, allowing for immediate action to be taken if undesirable characteristics are detected, such as location deviations, porosity, or separation, by altering operational parameters or halting the process, and presenting alerts on a display device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If post-processing inspection is performed after AM completion, then defects can be detected, but material waste increases and manufacturing throughput decreases

Engineering Contradiction:

Improvedefect detection capabilityVSAvoidmanufacturing throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The eddy current sensor array performs inspection during the additive manufacturing process before the work piece is complete, allowing defects to be detected in real-time rather than after manufacturing. This preliminary detection prevents defective parts from completing the entire manufacturing cycle, reducing material waste and improving throughput by enabling immediate corrective action.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An eddy current sensor array is introduced as an intermediary inspection mechanism that can probe the work piece during manufacturing without requiring completion. The sensor array acts as a mediator between the manufacturing process and quality assurance, enabling continuous monitoring without halting production.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If complete manufacturing is performed before inspection, then the work piece is fully formed, but inspection becomes difficult or impossible due to geometry and thickness

Engineering Contradiction:

Improvework piece completionVSAvoidinspection accessibility

Core Design Contradiction:

Manufacturing precisionVSDifficulty of detecting and measuring

Solution Approach 1:

Inspection is performed preliminarily during the manufacturing process when the work piece is still being built layer by layer, rather than attempting to inspect the complete finished part. This allows the sensor array to access internal structures and thin sections that would be inaccessible or impossible to measure after final assembly and post-processing.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If real-time monitoring is implemented during AM process, then defects can be detected early, but system complexity increases

Engineering Contradiction:

Improvedefect detection accuracyVSAvoidmonitoring system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical contact-based inspection systems with an eddy current sensing system that uses electromagnetic fields to detect defects non-contactly. This substitution reduces mechanical complexity while maintaining high detection accuracy, as eddy current sensors can probe through materials and detect internal defects without physical contact or complex positioning mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution enables concurrent monitoring and adjustment of the AM process, reducing material waste, improving manufacturing throughput, and ensuring higher quality work pieces by addressing defects as they occur, thereby enhancing the efficiency and reliability of the AM process.

Implementation Method 1

a first eddy current sensor array that is configured to generate a first plurality of sensor signals while in current-sensing proximity of a re-solidified feedstock segment

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Implementation Method 2

a heat source, such as a laser or electron beam, that heats the feedstock, forming a melt pool

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS10780523B1Eddy current monitoring in an additive manufacturing continuous welding system

Publication Date: 2020.09.22 LOCKHEED MARTIN CORP

AI summary

An AM continuous welding system (AMCWS) is provided. The AMCWS includes a feedstock dispenser that configured to emit feedstock at a designated location, and a heat source configured to heat the feedstock. The AMCWS also includes a first eddy current sensor array that is configured to generate a first plurality of sensor signals while in current-sensing proximity of a re-solidified feedstock segment. A controller is coupled to the first eddy current sensor array and is configured to determine, based on the first plurality of sensor signals, a first characteristic of the re-solidified feedstock segment. The controller determines that the first characteristic is a first undesirable characteristic, and initiates an action based on the first undesirable characteristic.