Schlieren Optical Path Tracking for Large-Area Melt Pool Spatter
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Solution Overview
Problem
Conventional schlieren imaging systems are limited by space constraints and cannot monitor spatter in a large-area melt pool during multi-layer scanning in selective laser melting, leading to incomplete capture of spatter images and increased experimental costs due to spatial limitations and difficulty in maintaining consistent conditions.
Innovation Solution
A schlieren system with an optical beam guiding system using pivoting reflectors and a synchronous controller to adjust the optical path, allowing for in-situ monitoring of spatter in a large-area melt pool by synchronizing with the laser scanning path, enabling seamless translation of the optical path without direct movement of plane mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional schlieren imaging device is used, then spatter images can be captured, but the monitored area is narrow and cannot accommodate multi-layer scanning
Solution Approach 1:
The patent applies the dynamics principle by making the optical path movable through the introduction of a galvanometer-controlled deflecting mirror. This mirror can dynamically adjust the optical path's position and angle, allowing the monitoring area to be expanded and repositioned without physically moving the entire schlieren imaging device. The dynamic adjustment capability enables the system to accommodate multi-layer scanning while maintaining a relatively simple device structure.
Solution Approach 2:
The patent implements dimensionality change by introducing a new degree of freedom through the galvanometer-controlled mirror. Instead of expanding the monitoring area in the traditional two-dimensional plane, the system adds optical path control in the angular dimension, allowing light to be deflected at different angles to cover various layers and positions of the melt pool during multi-layer scanning.
2Ease of operation
If the chamber is opened to adjust the schlieren imaging device, then the device position can be readjusted, but experimental conditions consistency cannot be ensured
Solution Approach 1:
The patent replaces the mechanical adjustment system with an optical control system. Instead of physically moving or repositioning the schlieren imaging device through mechanical means (which would require opening the chamber), the system uses a galvanometer-controlled deflecting mirror to adjust the optical path. This substitution allows for precise, repeatable positioning without breaking the sealed chamber environment, thereby maintaining experimental conditions consistency.
Solution Approach 2:
The system implements self-service through automated control. The galvanometer-controlled mirror can be programmed to automatically position the optical path at the required locations for multi-layer scanning, eliminating the need for manual intervention and chamber opening. The system serves itself by autonomously adjusting the optical path to maintain optimal monitoring conditions throughout the experiment.
3Ease of operation
If a high-speed camera is used for direct shooting, then the system is simple and easy to operate, but spatter images cannot be completely captured due to different sizes and brightness
Solution Approach 1:
The patent introduces an intermediary element - the schlieren optical system with deflecting mirror - between the light source and the camera. This intermediary processes the light by creating schlieren patterns that enhance the visibility of spatter features with varying sizes and brightness. The system remains easy to operate because the camera setup itself is unchanged, but the optical intermediary ensures complete and precise capture of spatter images.
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
The system overcomes space limitations, provides accurate spatter monitoring during multi-layer printing, reduces vibration and position errors, and allows for continuous imaging without disturbing the powder, ensuring consistent experimental conditions.
Implementation Method 1
an optical beam guiding system composed of a fifth plane mirror, an optical path deflecting mirror and a reflector group; wherein the fifth plane mirror is configured to guide any of guiding optical beams reflected by the reflector group that has been reflected by the fifth plane mirror to form schlieren optical beams
Data Source
AI summary
A schlieren system for in-situ/online monitoring of spatter in a large-area melt pool is provided, including a parallel light generation part, a parallel light deflection part, and an image acquisition part. The system can monitor spatter and other physical phenomena in the melt pool in a process of multi-layer printing and adjust a monitored area during an experiment to expand a monitored range. A reflector group composed of a plurality of plane mirrors is arranged, such that an optical path can be kept away from powder and dust areas, avoiding interference between the schlieren system and inherent devices inside a build chamber. Communication between a laser path controller and an optical path deflecting mirror galvanometer motor controller is established to automatically control the plane mirrors to change the monitored area, automatically track the melt pool, and realize online monitoring.