Laser Machining Head Distance Sensing With Optical Coherence
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Solution Overview
Problem
Capacitive distance measurement methods in laser machining systems are prone to inaccuracy due to lateral sensitivity issues, especially when the nozzle approaches a three-jaw chuck or when cutting metal sheets, leading to unstable machining processes and potential jamming or misalignment of cut-out parts.
Innovation Solution
A laser machining system with a machining head that employs optical coherence tomography for precise distance measurement using a reflective reference and a continuous measurement beam, allowing for parallel or coaxial operation of the optical and laser beams to determine the distance between the machining head and the workpiece, and optionally the machining ground, thereby ensuring accurate and error-free measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive measurement method is used for distance measurement, then the measurement can be performed, but the measurement precision deteriorates due to lateral sensitivity issues when the nozzle approaches the three-jaw chuck or when cut-out parts protrude from the metal sheet
Solution Approach 1:
The patent replaces the capacitive measurement method with an optical measurement method using a laser beam and optical coherence tomography. The optical measurement beam travels parallel to the laser beam through the same opening, eliminating the influence of lateral objects like the three-jaw chuck or protruding cut-out parts on the measurement signal.
Solution Approach 2:
The patent introduces a reflective reference surface arranged in the opening through which the laser beam passes. The optical measurement beam reflects off this reference surface to provide a stable reference signal for distance measurement, separating the measurement function from the machining function and eliminating interference from surrounding objects.
2Measurement precision
If the optical measurement beam and laser beam run coaxially through the same opening, then the measurement precision is improved by eliminating lateral sensitivity, but the device complexity increases due to the need for precise beam alignment
Solution Approach 1:
The patent merges the optical measurement beam path with the laser beam path by having both beams travel coaxially through the same opening in the machining head. This shared path eliminates the need for separate openings and reduces the overall structural complexity despite the precision requirements for beam alignment.
Solution Approach 2:
The opening in the machining head serves dual functions: it allows the laser beam to pass through for machining and simultaneously allows the optical measurement beam to pass through for distance measurement. This multi-functionality reduces the number of components and simplifies the overall device structure.
3Measurement precision
If the distance measurement is performed using reflections from both the reflective reference and the workpiece, then the measurement accuracy is improved, but the calculation complexity increases
Solution Approach 1:
The patent uses the reflection from the reflective reference surface as a stable feedback signal for distance measurement. By comparing the reference reflection with the workpiece reflection, the system can accurately determine the distance to the workpiece surface while compensating for variations in the measurement system itself.
Solution Approach 2:
The reflective reference surface is pre-positioned in the opening at a known location. This preliminary arrangement provides a fixed reference point that simplifies the calculation of workpiece distance, as the reference reflection serves as a known baseline for measurement calculations.
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 approach provides a stable and precise measurement of the distance to the workpiece, maintaining a constant distance during machining, which enhances the stability and accuracy of the laser machining process, especially at long distances and reduces the risk of collisions or misalignment.
Implementation Method 1
a laser machining system with a machining head that employs optical coherence tomography for precise distance measurement
Implementation Method 2
configured to determine a distance between the machining head and the workpiece based on a first reflection of the optical measurement beam from the reflective reference and a second reflection of the optical measurement beam from the workpiece
Data Source
AI summary
A machining head is provided for a laser machining system configured to machine a workpiece using a laser beam. The machining head includes a housing having an opening for emitting the laser beam from the machining head; at least one reflective reference at the housing; and a measuring device configured to direct an optical measurement beam towards the opening and the at least one reflective reference. The measuring device is further configured to determine a distance (d1) between the end portion and the workpiece on the basis of a first reflection (A) of the optical measurement beam from the at least one reflective reference and a second reflection (B) of the optical measurement beam from the workpiece.