3D Optical Focal Length Measurement for AM Laser Drift Control
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Solution Overview
Problem
Additive manufacturing machines face challenges in maintaining precise focal length of the laser, leading to build failures, part weakness, and instability due to thermal lensing and other factors, which are not detected until service intervals.
Innovation Solution
The implementation of a closed-loop feedback system that uses a measurement laser to capture backreflected signals, which are then analyzed by a sensor to measure focal distance errors, allowing for real-time adjustments to maintain the desired focal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser is used to fuse powder material in additive manufacturing, then material fusion and shape creation are achieved, but focal distance drift due to thermal lensing occurs leading to build failures
Solution Approach 1:
The patent implements a feedback control system where a measurement laser continuously monitors the actual focal distance by analyzing backreflected signals from the powder surface. The sensor detects focal distance errors and feeds this information back to a controller that adjusts the Z-axis position of the measurement laser to maintain the desired focal distance, thereby preventing build failures caused by focal drift
Solution Approach 2:
The patent introduces a measurement laser as an intermediary tool that does not directly participate in material fusion but serves to monitor and measure the focal distance. This separate measurement beam interacts with the powder surface and optical system to provide real-time focal distance data without interfering with the primary manufacturing laser's function
2Device complexity
If focal length calibration is performed only at service intervals, then device complexity is reduced, but focal distance errors are not detected until failures occur
Solution Approach 1:
The system continuously measures focal distance errors in real-time during operation and provides feedback to maintain accurate focusing, eliminating the need for complex periodic calibration procedures while ensuring continuous measurement precision
Solution Approach 2:
The measurement laser and sensor system automatically monitor and detect focal distance errors without requiring external intervention or complex calibration procedures, enabling the system to self-diagnose and maintain optimal performance throughout operation
3Reliability
If real-time focal distance measurement is implemented, then build failure rate is reduced, but device complexity increases due to additional measurement components
Solution Approach 1:
The measurement laser shares the same optical path and focusing optics as the manufacturing laser, allowing the existing optical components to serve dual purposes. The backreflected signal measurement technique uses the same optical system infrastructure, reducing the need for entirely separate measurement hardware
Solution Approach 2:
The patent uses a separate measurement laser as an intermediary that operates independently from the manufacturing laser system. This measurement beam serves solely for focal distance monitoring and can be integrated into the existing optical path without requiring complex modifications to the primary manufacturing 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 continuous monitoring and adjustment of the focal distance, reducing the likelihood of build failures and part weaknesses, thereby improving the reliability and stability of additive manufacturing processes.
Implementation Method 1
A measurement laser beam is sent through a focus unit of an additive manufacturing (AM) machine. The beam reflects off of a powder surface
Implementation Method 2
The backreflected signal is separated from the measurement laser beam. A sensor element measures a focal distance error from the backreflected signal
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
Methods, apparatus, systems, and articles of manufacture are disclosed to implement and operate an additive manufacturing machine (200) with focal length error determination and correction. An example apparatus includes a main laser (112) to create a main laser beam of the AM machine, the main laser beam used to fuse particle powder together in an AM process; a focus unit (108) to focus the main laser beam at a specified distance, the focus unit also including a measurement beam; a semi-transparent mirror (118) to split a backreflected signal, created from a reflection of the measurement beam from a powder surface, from the measurement beam; and a sensor element (128) to measure a focal distance error from the backreflected signal. The example apparatus can also include a measurement laser (120) to generate a measurement laser beam with the main laser beam.