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Machine Vision Systems

Pellet Inspection System

A computerized Machine Vision Based Inspection System is developed in order to perform visual surface inspection of cylindrical fuel pellets.

This inspection system includes an imaging system that gives a high quality unfolded image of the pellet surface. The imaging system includes a high resolution camera, machine vision lens and custom designed illumination. To process the obtained image, image processing software is developed for automatic detection of defects on the pellet surface, its quantification and analysis.

Pellet Inspection System
[Fig. : Machine Vision Based Inspection System]

The system generates a throughput of 2.5 second/pellet. Among the pellets accepted by the system, correct decision was made in 98.3 % of the pellets. Among the pellets rejected by the system, correct decision was made in 85 % of the pellets.

The system is advantageous over human eye due to its reliability, high speed and accuracy, ability to quantify defects for qualitative assessment.

Machine Vision based Metrology Systems

Industrial production houses such as nuclear, automotive, aerospace, defence, etc. impose very stringent dimensional tolerances for critical components and systems. This imposes extreme challenges during fabrication, assembly and final product qualification too. Complex systems usually involve hundreds of different components of various sizes and complex geometries which demand precise component dimensions. Machine vision plays a pivotal role in inspection of components, their assemblies due to very high measurement resolution (down to few microns). Machine vision based measurements are non-contact hence remote inspection is possible. Automated inspection of components with high throughput can be easily achieved with this method.

LCID, RRCAT has developed expertise in machine vision based metrology systems for dimensional inspection. These systems have been specially designed and developed as per the custom needs to maximize the inspection throughput and fulfil the accuracy and repeatability requirements of the user. These systems are based on shadow graph technique. These systems are provided with suitable component holder/jig. The software developed provides component accept / reject decision along with complete report of all the measurements carried out for the component.

The metrology system mainly consists of two sections viz., illumination optics (on one side of component under measurement) and imaging optics (On other side of component under measurement). The component whose dimensions are to be measured, is kept between these two sections (usually component holder or glass plate is used). Illumination optics generates shadow of component under test which is captured by imaging optic. The system has in built embedded processor. Image processing & measurement software running on this processor measures different dimensions of component under test with customized report for the user. The dimensions are measured by sampling the specimen at many locations and typically min, max and average values of the dimension are reported.

Industrial components have variety of sizes. Depending on component measurement requirements and accuracy differ widely. Thus we have developed customized solutions keeping in mind the size of the component and accuracy and repeatability requirements.

Following metrology systems for end plate, end plug and various test specimens have been developed.

End plate dimension measurement system

Field of view 100 mm x 94 mm
Resolution 30 microns
Repeatability 15 microns
Throughput 3 plates/ minute

Photograph End Plate Inspection System
Photograph End Plate Inspection System

The outer diameter of end plate is a critical parameter. Hence it is measured at 100 different locations. Using these 100 readings average diameter of the end plate is calculated and displayed to the user. Apart from this, software reports maximum and minimum diameter as well. On basis of these measurements accept / reject criteria can be set by user. Software also provides calibration procedure to calibrate the instrument.

End plug dimensional inspection system

Field of view 46mm x 38mm
Resolution 20 microns
Repeatability 20 microns
Accuracy ±20 micron
Throughput 4 plugs/ minute

Photograph End Plug Inspection System
Photograph of end plug Inspection System

Metrology System for Industrial Components

This system measures the dimensions of different industrial test specimens of varying geometry and size for studying different mechanical properties of the specimen under test. The system has embedded processor running customized image processing & measurement software for measurement of different dimensions of specimen under test with customized report for the user.

Field of view 60 mm x 45 mm
Resolution 13 microns
Repeatability 10 microns
Accuracy ±13 microns
Throughput 3 Specimens / minute

Shadowgraphs of different test specimens
Shadowgraphs of different test specimens

Photograph of Metrology System for Industrial Components
Photograph of Metrology System for Industrial Components

These systems can work in semi-automatic mode with operator feeding the components or can be easily integrated with the pick & place, SCARA robot or any other suitable multi axis robotic manipulator to automate the entire inspection task.

The machine vision based systems use commercially off the shelf industrial components, and are thus suitable for inspecting any industrial component or system. The knowledge base and expertise developed over the years at LCID can be leveraged for developing inspection system of any other component as well.

High throughput machine vision based metrology system for end caps

A machine vision based metrology system based on non-contact shadow graph technique has been designed and developed for automated dimension measurement of End Caps of elements. System has telecentric optics with high resolution GigE camera to capture high contrast, silhouette of component placed between camera and light source. Use of telecentric optics improves repeatability and accuracy of measurements. This system has field of view of 45 mm x 35 mm and optical resolution of better than 10 micron.

A sample holder is designed to hold four end caps in front of light source. The image of these end caps is acquired simultaneously. This image is then processed by inspection software. Inspection software measures the dimensions of four end caps on a single click. It measures the dimensions of each end caps with accuracy of ± 10 micron and repeatability of better than 10 micron. Overall through put of system is 12 end caps / minute. A user friendly graphical user interface facilitates operation of system even by unskilled operator.

PHWR Fuel Tubes Inspection System
PHWR Fuel Tubes Inspection System
System Photograph
GUI of Software

PHWR Fuel Tubes Inspection System

Machine vision based inspection system to detect surface defects on PHWR fuel tube is developed for NFC, Hyderabad. NFC has defined defects categorised as dents, pits, handling defects, tool mark, flattening, burning chattering and handling defects. The system comprises of 2 no. 8K line scan cameras and 2 no. 12” line lights to image full 500mm length of the tube. The tube is rotated on a rotating mechanism. Software is developed and deployed on PC to analyze the defects on the tube.

PHWR Fuel Tubes Inspection System PHWR Fuel Tubes Inspection System

OCR based End plate Inspection System

Software with imaging setup is developed for the reading of end plate identification number. This system is standalone system where pre-processing and execution are done inside the smart camera. Results are transferred using serial communication to master PC or master data logger.

OCR based End plate Inspection System
OCR based End plate Inspection System
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