Line Scan Camera Array for Metal Bar Surface Defect Detection
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Solution Overview
Problem
Conventional inspection methods for metal bars, particularly those produced through reducing processes, face challenges such as high temperature, fast traveling speed, non-flat surface geometry, and limited access, which hinder effective detection of surface defects in real-time, leading to increased costs and customer complaints due to undetected defects.
Innovation Solution
An imaging system utilizing multiple digital line scan cameras and a light line assembly with uniform light intensity, capable of imaging a metal bar's circumference while moving, and a computing unit to process image data for defect detection, allowing for real-time inspection of surface defects on non-flat surfaces at high speeds and temperatures, with a compact design that minimizes the need for additional handling or moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection methods are used on metal bars, then the inspection can be performed with simple equipment, but the detection capability is insufficient due to high temperature, fast traveling speed, and non-flat surface geometry
Solution Approach 1:
The inspection system is divided into multiple independent line scan cameras, each responsible for capturing a specific angular sector of the bar surface. This segmentation allows the system to handle the complex inspection task through multiple specialized components rather than a single complex device, enabling precise defect detection on high-speed moving bars while maintaining manageable system complexity
Solution Approach 2:
The system transitions from conventional 2D area imaging to 3D volumetric data acquisition by capturing images at multiple angular positions around the bar circumference. This dimensional approach allows the system to reconstruct complete surface information from multiple perspectives, overcoming the limitations of single-view inspection on rotating, non-flat surfaces
2Productivity
If the metal bar travels at high speed (100 m/s), then productivity increases, but conventional inspection approaches cannot accommodate such speed
Solution Approach 1:
The inspection system operates continuously without interrupting the bar production flow. Multiple line scan cameras capture images in rapid succession as the bar moves through the inspection zone, ensuring that inspection coverage remains continuous and complete even at speeds up to 100 m/s, thereby maintaining both high productivity and reliable defect detection
Solution Approach 2:
The system replaces mechanical contact-based inspection methods with non-contact optical imaging. This substitution eliminates the need for physical interaction with the high-speed moving bar, allowing inspection to occur without slowing down the production line or risking safety issues associated with contact measurement at such speeds
3Temperature
If the metal bar is at high temperature (1,100°C), then the reducing process can be maintained, but many inspection technologies cannot be used
Solution Approach 1:
The system replaces contact-based or heat-sensitive inspection technologies with non-contact optical imaging. The line scan cameras and light sources are positioned to interact with the bar through radiation and reflection without physical contact, enabling inspection to proceed at high temperatures where conventional mechanical or electronic sensors would fail or be damaged
Solution Approach 2:
The system introduces light as an intermediary medium between the inspection system and the hot metal bar. By using optical radiation to carry information about surface defects from the bar to the cameras, the system avoids direct thermal interaction, allowing inspection components to remain at safe temperatures while the bar maintains its process temperature
4Measurement precision
If area cameras are used to inspect bar surfaces, then the bar must be stationary during imaging, but this requires additional handling
Solution Approach 1:
Instead of moving the camera with the bar or stopping the bar for imaging, the system inverts the approach by using multiple fixed cameras that remain stationary while the bar moves through their fields of view. Each camera captures a specific angular sector, and the combination of all camera views provides complete surface coverage without requiring bar stopping or complex camera movement mechanisms
5Productivity
If line scan cameras are used requiring the bar to spin, then the lighting design must be flat, but this limits applicability to non-flat surfaces
Solution Approach 1:
Each line scan camera is equipped with dedicated lighting optimized for its specific angular viewing position rather than requiring uniform flat lighting across the entire bar surface. This localized lighting approach allows each camera to capture high-quality images of its assigned sector regardless of the bar's cross-sectional shape, making the system adaptable to round, square, hexagonal, and other non-flat geometries while maintaining high inspection speeds
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 real-time, quantitative detection of surface defects on metal bars traveling at speeds up to 100 m/s and temperatures over 1,100°C, providing detailed defect information and reducing the need for additional handling or moving components, thus improving product quality and reducing costs associated with defective products.
Implementation Method 1
a light line assembly configured to project a light line belt having a second predetermined width onto the surface of the bar
Implementation Method 2
an image acquisition assembly having a field of view configured to image a first predetermined width over a circumference of a surface of the bar
Data Source
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Figure 8~12
AI summary
The present invention is directed to solving the problems associated with the detection of surface defects on metal bars as well as the problems associated with applying metal flat inspection systems to metal bars for non-destructive surface defects detection. A specially designed imaging system, which is comprised of a computing unit, line lights and high data rate line scan cameras, is developed for the aforementioned purpose. The target application is the metal bars (1) that have a circumference/cross-section-area ratio equal to or smaller than 4.25 when the cross section area is unity for the given shape, (2) whose cross-sections are round, oval, or in the shape of a polygon, and (3) are manufactured by mechanically cross-section reduction processes. The said metal can be steel, stainless steel, aluminum, copper, bronze, titanium, nickel, and so forth, and/or their alloys. The said metal bars can be at the temperature when they are being manufactured. A removable cassette includes various mirrors. A protection tube isolates the moving metal bar from the line light assembly and image acquisition camera. assembly and image acquisition camera. A contaminant reduction mechanism applies a vacuum to remove airborne contaminants.