Segmented Pyrometer Monitoring for Laser Welding Fields
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Solution Overview
Problem
Conventional sensors, such as pyrometers and cameras, inadequately monitor temperature profiles and gradients during the laser metal fusion (LMF) process due to limited spatial resolution, measuring rate, and sensitivity, which hinders effective closed-loop control of the welding process for producing three-dimensional components.
Innovation Solution
An irradiating device equipped with multiple pyrometer segments, including a first pyrometer segment and several second pyrometer segments, which image thermal radiation from the machining field to enable contactless temperature detection at multiple positions, achieving high measuring rates and real-time monitoring by using segmented diodes with different wavelength-dependent sensitivities and filter devices to attenuate thermal radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pyrometers with single-point detection are used, then high sensitivity and measuring rate are achieved, but spatial resolution is insufficient to capture temperature gradients across the machining field
Solution Approach 1:
The pyrometer sensor surface is divided into multiple segments, each corresponding to a specific spatial position in the machining field. This segmentation allows simultaneous temperature measurement at multiple locations with high precision, resolving the contradiction between single-point sensitivity and multi-point coverage by creating a array of focused detection zones that collectively map the entire machining area.
2Area of stationary object
If cameras with high spatial resolution are used, then temperature distribution across the machining field is captured, but measuring rate and sensitivity are insufficient for high-speed LMF processes
Solution Approach 1:
The patent replaces camera-based optical imaging systems with a pyrometer-based segmented detection system. This substitution leverages the high temporal response characteristics of pyrometers while achieving spatial resolution through segmented sensor surfaces and optical focusing, thereby attaining measuring rates suitable for high-speed LMF processes while maintaining adequate spatial coverage.
3Area of stationary object
If the measurement spot diameter is increased to 1 mm for pyrometer detection, then spatial coverage is improved, but the resolution becomes significantly larger than the focal spot (50-100 μm) reducing measurement accuracy
Solution Approach 1:
The pyrometer sensor is segmented into multiple small detection elements, each with a small effective measurement area that matches the focal spot size (50-100 μm). This segmentation allows the system to maintain high spatial resolution at each measurement point while collectively covering a larger area through the array of segments, thus resolving the contradiction between measurement spot area and resolution.
4Loss of information
If thermal radiation from low temperature regions is detected, then complete temperature profile is obtained, but detection difficulty increases due to low intensity of thermal radiation
Solution Approach 1:
Different segments of the pyrometer are optimized for detecting thermal radiation at different temperature ranges. This local optimization allows each segment to effectively measure the temperature characteristics of its corresponding region, whether high or low temperature, thereby capturing the complete temperature profile while maintaining adequate detection sensitivity across all regions.
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 setup allows for precise monitoring of temperatures and temperature gradients around the machining beam, enabling improved process control, including powder heating, cooling rates, and material properties, thereby enhancing the quality of three-dimensional components produced.
Implementation Method 1
The imaging device images thermal radiation which emanates from the machining position in the machining field on a first pyrometer segment, and wherein the imaging device images thermal radiation which emanates from a position in the machining field being situated ahead of or behind the machining position
Implementation Method 2
filter devices to attenuate thermal radiation
Data Source
AI summary
An irradiating device for irradiating a machining field with a machining beam, in particular with a laser beam, for carrying out a welding process, is provided. The irradiating device includes a beam scanner for aligning the machining beam to a machining position in the machining field. The irradiating device has an imaging device for imaging a part-region of the machining field on a pyrometer which has at least two pyrometer segments. The imaging device images thermal radiation which emanates from the machining position in the machining field on a first pyrometer segment, and images thermal radiation which emanates from a position in the machining field being situated ahead of or behind the machining position along an advancing direction of the machining beam in the machining field on at least one second pyrometer segment. A machine tool having such an irradiating device is also provided.