Multi-Wavelength LED Inspection for Plastic Container Wall Thickness
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Solution Overview
Problem
Current technologies for measuring characteristics of blow-molded plastic containers are limited by slow sampling speed and response time, making them unsuitable for increasing production rates.
Innovation Solution
An in-line inspection system using a vertical array of emitter assemblies that emit light energy in multiple narrow wavelength bands and broadband photodetectors to determine container characteristics like wall thickness, with a processor for real-time calibration and feedback control to adjust blow molding parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a broadband light source with a chopper wheel and spectrometer is used to measure wall thickness, then the system can provide thickness measurement capability, but the sampling speed and response time are limited and slow
Solution Approach 1:
The broadband light source is segmented into multiple discrete wavelength sources (e.g., 5 separate LEDs emitting at different wavelengths). Each wavelength source can be independently modulated and measured, allowing parallel measurement channels that increase sampling speed while maintaining thickness measurement precision through multi-wavelength absorption analysis
Solution Approach 2:
Multiple wavelength sources are modulated in alternating periodic cycles rather than continuously. This periodic switching allows each wavelength to be measured in sequence with dedicated detection windows, eliminating the mechanical chopper wheel limitation and enabling faster electronic timing control for high-speed sampling
2Productivity
If the blow molding production rate is increased, then productivity improves, but the current measurement technology becomes unusable due to insufficient sampling speed
Solution Approach 1:
The measurement system operates continuously without mechanical moving parts (chopper wheel) that limit speed. Multiple LED wavelengths are electronically switched in rapid succession, providing continuous measurement capability that keeps pace with high-speed blow molding production rates while maintaining reliable thickness data for quality control
Solution Approach 2:
The mechanical chopper wheel system is replaced with electronically controlled LED wavelength switching and photodetector measurement. This substitution eliminates mechanical speed limitations and enables measurement systems to operate at the high speeds required for modern blow molding production rates
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 fast and accurate measurement of container characteristics at high production rates, allowing for real-time rejection of defective containers and optimization of blow molding processes.
Implementation Method 1
The light sources may be LEDs or laser diodes, for example
Implementation Method 2
one that emits light energy in a narrow wavelength band that is absorbed by the material of the container in a manner highly dependent on the thickness of the material
Implementation Method 3
The broadband light is chopped, collimated, transmitted through two walls of the plastic container, and finally divided into wavelengths of interest by the spectroscope
Data Source
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AI summary
Systems and methods for in-line inspection of plastic blow molded containers. The inspection system may comprise a plurality of emitter assemblies arranged in a vertical array. Each emitter assembly may cyclically emit light energy in at least two different narrow wavelength bands at a container as the container passes through an inspection area. The system may also comprise a plurality of broadband photodetectors arranged in a vertical array, each photodetector facing at least one of the emitter assemblies with the inspection area therebetween such that the photodetectors are capable of sensing light energy that passes through the container when it is in the inspection area. The system may also comprise a processor in communication with the photodetectors for determining a characteristic of the container based on signals from the photodetectors.