Thermal Cutting Cut Break Detection via Phase Shift Measurement
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Solution Overview
Problem
Current methods for detecting cut breaks during thermal cutting, such as those using optical sensors or LC resonant circuits, face challenges like high installation space requirements, thermal stress exposure, and poor signal-to-noise ratios, making early detection difficult, especially for smaller workpieces.
Innovation Solution
A method that uses a difference measurement approach by determining the phase shift between a reference signal and a measurement signal from a measuring electrode, allowing for early detection of cut breaks and adjusting energy input to prevent complete breakage, involving a phase discriminator and control unit to manage energy input based on phase shift signal limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical sensors are used to detect cut breaks, then detection capability is improved, but installation space requirements increase and sensors are exposed to high thermal stresses
Solution Approach 1:
The patent replaces optical sensor systems with an electrical measurement system using a measuring electrode connected to the workpiece. This electrode detects changes in electrical properties (capacitance, resistance, or inductance) during the cutting process, eliminating the need for optical sensors that require installation space and are exposed to thermal stress. The electrical measurement system can be integrated directly into the workpiece or cutting machine structure.
2Measurement precision
If optical sensors are placed close to the workpiece for better signal detection, then signal intensity is improved, but thermal stress exposure increases
Solution Approach 1:
The patent substitutes optical sensors with an electrical measurement system that uses a measuring electrode. This electrode can be electrically connected to the workpiece without being physically exposed to the same thermal environment as optical sensors would be. The measurement is performed through electrical contacts that remain outside the high-temperature cutting zone, eliminating thermal stress exposure while maintaining measurement precision.
3Reliability
If LC resonant circuit amplitude detection is used, then cut break detection is achieved, but signal-to-noise ratio deteriorates due to background noise and amplitude variations
Solution Approach 1:
The patent changes the measurement parameter from amplitude detection to frequency or phase detection in an oscillating circuit. Instead of measuring amplitude variations which are affected by background noise and distance changes, the system measures frequency or phase shifts of the oscillating signal. These parameters are more stable and less susceptible to noise, improving the signal-to-noise ratio while maintaining reliable cut break detection.
Solution Approach 2:
The patent implements a feedback mechanism where the measured electrical parameters (capacitance, resistance, or inductance changes) are continuously monitored and fed back to control the cutting process. When a cut break is detected through parameter changes, the system can immediately adjust cutting parameters or stop the process, providing real-time feedback control that improves detection reliability and reduces noise impact.
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
Enables early detection of impending cut breaks and effective countermeasures to prevent damage, reducing machine downtime and wear by adjusting energy input and cutting speed, with improved signal-to-noise ratio and reduced risk of false signals.
Implementation Method 1
the capacity of which is determined by the capacity between the processing head and the workpiece
Implementation Method 2
the electrical properties (capacitance, resistance or inductance) of the workpiece
Data Source
Figure 1A~1B
Figure 2
AI summary
The aim of the invention is to allow a potential incomplete cut to be detected during the cutting process when thermally cutting a workpiece (208). According to the invention, this is achieved by a method for detecting an impending incomplete cut or an incomplete cut which has already occurred, wherein energy is input into a cutting region, and the method has the following steps: a) applying a first alternating signal to the workpiece (208), b) detecting a second alternating signal caused by the first alternating signal in a measuring electrode (207) arranged at a distance from the workpiece (208), c) ascertaining the phase offset between the first and the second alternating signal, thereby outputting a phase offset signal, and d) comparing the phase offset signal with a specified upper threshold and a specified lower threshold for the phase offset signal.