Laser Tear Line Control Using Transmitted Pulse Feedback
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Solution Overview
Problem
Existing methods for producing tear lines in planar workpieces, such as airbag covers, face challenges in achieving consistent tear strength and residual wall thickness due to variations in material thickness and transmittance, leading to inaccurate deactivation of laser beams and inconsistent tear resistance.
Innovation Solution
A method involving a pulsed laser beam with a predetermined pulse amplitude and pulse length, where a reference signal curve is generated without a workpiece to establish a deactivation criterion for space-resolved termination of laser pulses, ensuring consistent residual wall thickness and reproducible tearing behavior, using an array of sensors to detect transmitted pulse amplitudes and adjust pulse length based on measurement signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pulsed laser beam is used to produce tear lines by material removal, then tear strength can be controlled, but variations in material thickness and transmittance cause inconsistent residual wall thickness and inaccurate laser beam deactivation
Solution Approach 1:
The patent employs a sensor array that detects transmitted laser radiation to provide real-time feedback on material thickness and transmittance variations. This feedback enables dynamic adjustment of laser pulse parameters (amplitude, duration, repetition rate) to compensate for material variations, ensuring consistent residual wall thickness and accurate beam deactivation across the workpiece
Solution Approach 2:
The system dynamically changes laser pulse parameters (amplitude, duration, repetition rate) based on detected material properties. By adjusting these parameters in response to material variations, the system maintains consistent material removal characteristics and achieves uniform residual wall thickness despite variations in the workpiece material
2Manufacturing precision
If multiple scanning movements are repeated to achieve minimum residual wall thickness, then tear line quality improves, but production time increases
Solution Approach 1:
The system performs preliminary detection of material thickness and transmittance before the main material removal process. This preliminary action allows the control system to pre-calculate optimal laser pulse parameters, reducing the number of iterative scanning movements needed to achieve the desired residual wall thickness and thereby shortening production time
Solution Approach 2:
The patent implements dynamic control of laser pulse parameters during the scanning process based on real-time sensor feedback. This dynamic adjustment allows the system to adapt to material variations on-the-fly, achieving high-quality tear lines in fewer scanning passes compared to static parameter approaches, thus improving productivity
3Strength
If space-resolved deactivation of laser beam is implemented based on transmitted laser power detection, then constant tear strength is achieved, but device complexity increases
Solution Approach 1:
The patent introduces a sensor array as an intermediary between the laser beam and the material removal process. This intermediary detects transmitted laser radiation and provides information about material properties, enabling space-resolved deactivation control. The sensor array acts as a mediator that translates material characteristics into control signals for the laser system
Solution Approach 2:
The system replaces mechanical measurement methods with optical detection using sensor arrays that measure transmitted laser radiation. This substitution enables non-contact, real-time detection of material thickness and transmittance, facilitating precise space-resolved deactivation control without mechanical intervention
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 allows for precise control of material removal, achieving consistent tear strength and reduced residual wall thickness tolerance, enabling the production of tear lines with predictable and uniform properties across different contours and workpieces.
Implementation Method 1
the parameters of the laser pulse are selected such that the laser pulse causes an energy input which leads to heating of the covering material at the respective removal location to a temperature above an ablation threshold and, thus, to material removal
Implementation Method 2
heating of the covering material at the respective removal location to a temperature above an ablation threshold
Implementation Method 3
an array of sensors below the tear line then detects the transmitted laser radiation. The achievement of the minimum allowable residual wall thickness is determined by detection of a predetermined amount of transmitted laser power
Data Source
AI summary
A method and device for producing a tear line on a planar workpiece by material removal by means of a pulsed laser, wherein machining cycles are preceded by a method step for generating and storing a reference signal curve which is formed by reference signals, causing the pulse amplitude of the laser pulses, via removal locations along the contour of the tear line. The achievement of a respective predetermined percentage of the reference signal or of an absolute distance from the reference signal by a measurement signal is used as the space-resolved deactivation criterion for each removal location, which measurement signal is obtained from a transmitted part of the pulse amplitude at the respective removal location.