Laser Cut Break Detection via Slag Drop Monitoring

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Solution Overview

Problem

During high-energy beam cutting processes, such as laser cutting, cut breaks occur due to insufficient energy per section, leading to incomplete cuts and slag accumulation, which existing methods struggle to reliably detect and address.

Innovation Solution

The method involves recording images of the interaction area to detect slag drops at the end of the cutting front, using thermal or externally illuminated images, and recognizing cut breaks based on the occurrence of these slag drops, which are indicative of insufficient energy for complete cutting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high-energy beam cutting is performed with increased feed rate or reduced power, then productivity increases, but cut quality deteriorates leading to cut breaks

Engineering Contradiction:
Improvefeed rateVSAvoidcut completeness
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent implements real-time monitoring of the cutting process by detecting slag drops in the interaction area between the high-energy beam and workpiece. When slag drops are detected, the system generates a signal indicating a cut break condition, enabling immediate feedback to adjust cutting parameters or alert operators, thus maintaining cut quality at higher feed rates

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent replaces traditional mechanical measurement methods with optical detection using image recording devices (cameras) to monitor the cutting process. By capturing and evaluating images of the interaction area, the system detects slag drops that indicate cut breaks, substituting physical contact measurement with non-contact optical sensing for real-time quality control

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If laser power is increased to prevent cut breaks, then cut quality improves, but energy consumption increases

Engineering Contradiction:
Improvecut completenessVSAvoidlaser power
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The real-time detection system provides continuous monitoring of cut quality through slag drop detection. This feedback mechanism allows the system to maintain optimal cutting parameters only when needed, rather than continuously operating at high power, thus reducing overall energy consumption while ensuring cut completeness when quality issues arise

Inventive Principle:
Principle #23Feedback

3Measurement precision

If real-time monitoring of cut quality is implemented, then detection reliability improves, but device complexity increases

Engineering Contradiction:
Improvecut break detection accuracyVSAvoidmonitoring system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and monitors only the critical indicator of cut quality - slag drops - from the complex cutting process. By focusing detection efforts on this specific phenomenon in the interaction area, the system achieves reliable cut break detection without needing to monitor all aspects of the cutting process, thereby limiting the increase in device complexity

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses an intermediary substance - slag drops - as a visible indicator of cut break conditions. These slag drops serve as a mediator between the invisible thermal processes and the detection system, allowing indirect but reliable monitoring of cut quality through optical detection of the slag phenomenon

Inventive Principle:
Principle #24Intermediary (Mediator)

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 reliable detection of cut breaks, enabling real-time adjustments to cutting parameters or process interruptions to prevent incomplete cuts, thereby improving cutting efficiency and reducing rejects.

Implementation Method 1

capturing a thermal image of the interaction area... the thermal image, particularly in the NIR-A range, e.g. at wavelengths around approx. 800 - 1100 nm, has proven to be particularly favorable for the detection of the slag droplets based on the lack of thermal radiation in an area of the thermal image shielded from the slag droplets

Methodology Applied
Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentEP2805791B1Method and device for detecting a cut section
Publication Date: 2018.09.26 TRUMPF WERKZEUGMASCHINEN GMBH & CO KG
  • EP2805791B1 patent drawingFigure 1
  • EP2805791B1 patent drawingFigure 2~3c

AI summary

The invention relates to a method for detecting a cut interruption when cutting a workpiece with a high-energy beam, in particular with a laser beam, comprising: recording an image of a monitored area (21) of the workpiece, which includes an interaction area (22) of the high-energy beam with the workpiece; evaluating the recorded image to detect slag droplets (25) at an end of the interaction area (22) opposite a cutting front (23); and detecting the cut interruption based on the appearance of the slag droplets (25). The invention also relates to an associated device for detecting a cut interruption.