Additive Manufacturing Layer Inspection via Thermal Deformation Profiles
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Solution Overview
Problem
Additive manufacturing methods face challenges in detecting defects such as pores, porosity, and surface irregularities in workpiece layers due to rough surfaces and topographical variations, which complicate the differentiation between surface effects and underlying anomalies.
Innovation Solution
A method and apparatus that utilize thermal excitation of the layer stack to analyze mechanical deformations over time, using image analysis to distinguish between surface roughness and underlying defects by examining individual temporal deformation profiles, including features like deformation increase, maximum, and decrease, and combining this with thermal analysis for enhanced defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical measurement sensors with cameras are used for 3D coordinate measurement on the topmost material layer, then surface topography can be measured, but rough surfaces and topographical variations make it difficult to distinguish surface effects from underlying defects
Solution Approach 1:
The patent applies dynamic mechanical excitation to the workpiece, inducing vibrations that propagate through the material. By measuring the dynamic response (vibrations, acoustic emissions) rather than static surface topography, the system can distinguish between surface roughness and subsurface defects based on their different mechanical response characteristics.
Solution Approach 2:
The patent utilizes mechanical vibration and acoustic emission techniques to detect defects. By exciting the workpiece with mechanical vibrations and analyzing the resulting acoustic signals, the system can identify subsurface defects such as pores and delaminations that are not detectable through static optical surface measurement alone.
2Reliability
If ultrasonic energy waves are used to detect physical properties of workpiece layers, then internal defects can be detected, but the method requires complex wave generation and analysis systems
Solution Approach 1:
The patent replaces complex ultrasonic wave generation systems with simpler mechanical excitation devices that induce vibrations in the workpiece. The detection system uses acoustic emission sensors and vibration analysis rather than complex ultrasonic pulse-echo systems, achieving comparable defect detection reliability with reduced system complexity.
3Reliability
If laser ultrasonic measurements are performed during additive manufacturing, then real-time defect detection is enabled, but the inspection process becomes more time-consuming
Solution Approach 1:
The patent implements continuous or near-continuous monitoring during the additive manufacturing process by applying mechanical excitation and acoustic emission detection in real-time as each layer is deposited. This allows defect detection without interrupting the manufacturing flow, maintaining productivity while ensuring quality.
Solution Approach 2:
The patent performs defect detection during the manufacturing process itself, identifying defects as they form in each layer before proceeding to the next layer. This preliminary detection approach prevents defect accumulation and eliminates the need for separate post-processing inspection steps.
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 reliable and early detection of anomalies in the manufacturing process, allowing for timely correction of defects and improving the quality of additively manufactured workpieces by differentiating surface roughness from underlying defects.
Implementation Method 1
DE 10 2016 110 266 A1 also mentions as an inspection method the measurement of the geometric shape and temperature of what is referred to as the melt pool. DE 10 2014 212 246 B3 discloses thermal excitation of an additively manufactured workpiece during the manufacturing process in order to detect defects in the workpiece layers early by thermographically capturing and analyzing the thermal radiation from the topmost workpiece layer.
Implementation Method 2
DE 10 2016 110 266 A1 discloses a method and an apparatus for the additive manufacturing of workpieces, wherein laser ultrasonic measurements, absolute measuring interferometry or laser pulse thermography are proposed for inspecting workpiece layers.
Implementation Method 3
DE 10 2016 110 266 A1 also mentions as an inspection method the measurement of the geometric shape and temperature of what is referred to as the melt pool.
Data Source
AI summary
A method for additive manufacturing includes obtaining a dataset that defines the workpiece in multiple workpiece layers arranged one on top of the other. A layer stack of multiple workpiece layers is produced based on the dataset. The layer stack has a respective topmost workpiece layer at a defined instant of time. The layer stack is thermally excited at the defined instant of time and a sequence of images of the respective topmost workpiece layer is recorded. The layer stack is inspected using the sequence of images. The inspection involves evaluation of an individual temporal deformation profile of the respective topmost workpiece layer in response to the thermal excitation. The individual temporal deformation profile has multiple characteristic features including an individual deformation increase, an individual deformation maximum, and an individual deformation decrease. The inspection result is determined by evaluating at least one of the characteristic features.