Terahertz Detection for Metal Contamination in Polymer Sheets
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Solution Overview
Problem
Current metal detection systems in polymer sheets, such as lithium-ion battery separators, cannot accurately identify metallic particles, leading to unnecessary removal of non-metallic defects and increased costs, as they fail to differentiate between metallic and non-metallic contaminants.
Innovation Solution
A terahertz (THz) system combined with an optical inspection system is used to identify metallic particles in polymer sheets, enabling precise detection and removal of metal-contaminated areas, including both magnetic and non-magnetic metals, down to sizes of 500 μm or smaller, by generating and detecting THz beams and utilizing a computing device to determine metal contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical systems are used to identify defects in polymer films, then all defects including particles can be identified, but it is impossible to distinguish metallic particles from non-metallic particles
Solution Approach 1:
The patent introduces a terahertz detection system as an intermediary between the optical inspection system and the defect removal process. The THz system detects metallic particles by measuring changes in terahertz wave transmission through the polymer film, providing additional information about particle composition without interfering with the existing optical inspection process.
Solution Approach 2:
The patent changes the detection parameter from visible light (optical system) to terahertz waves. This parameter change enables the system to distinguish metallic particles from non-metallic particles based on their different terahertz transmission characteristics, while maintaining the ability to detect all types of defects in the polymer film.
2Reliability
If all defects are removed from polymer sheets, then product quality is improved, but manufacturing costs increase due to removal of non-metallic defects
Solution Approach 1:
The patent applies local quality by treating different types of defects differently. Instead of removing all defects uniformly, the system selectively removes only metallic particles while preserving non-metallic defects. This is achieved by detecting the specific properties of metallic particles using terahertz waves and targeting only those areas for removal.
Solution Approach 2:
The terahertz detection system serves as an intermediary that provides selective information about metallic particles, enabling the removal process to distinguish between metallic and non-metallic defects. This intermediary detection allows for selective removal of only the harmful metallic particles, reducing material waste while maintaining product quality.
3Measurement precision
If metal detection systems are added to optical inspection systems, then metallic particles can be identified, but device complexity increases
Solution Approach 1:
The patent segments the inspection system into two independent parts: an optical inspection system for general defect detection and a terahertz detection system for metallic particle identification. This segmentation allows each system to perform its specific function optimally while maintaining modular architecture that reduces overall system complexity.
Solution Approach 2:
The terahertz detection system is designed to work in conjunction with the optical inspection system, providing multi-functionality. The same terahertz system can detect both metallic particles and provide information about non-metallic particles, making it a universal addition that enhances the existing optical system without requiring separate dedicated systems.
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
The THz system provides 100% area coverage and sufficient resolution to accurately detect and remove only metal-contaminated areas, reducing waste and ensuring the safety and performance of lithium-ion battery separators by distinguishing between metallic and non-metallic defects.
Implementation Method 1
a terahertz (THz) system including a THz generator for generating a THz beam, and a THz detector
Data Source
AI summary
A sheet material measurement system includes an optical system for identifying at least a first area of a moving sheet material suspected of including at least one defect. A terahertz (THz) system includes a THz generator for generating a THz beam and a THz detector and a scanner including a scanner head for positioning the THz system over the first area. A computing device is coupled to receive signals sensed by the THz detector after interacting with the first area. The computing device determines whether the first area is a metal-contaminated area including metal particles.