Obtaining Zero-Defect Production Quality with NI Machine Vision
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Author(s):
Shahzad Sarwar - Averna Technologies Inc.
Daniel Cox - Averna Technologies, Inc.
Industry:
Imaging Equipment
Products:
PXI/CompactPCI, Machine Vision, LabVIEW
The Challenge:
Inspecting packaging tubes with machine vision cameras distributed along the production line with stringent dimensional tolerances of a few tens of microns along with color matching and print defects.
The Solution:
Using National Instruments PCI frame grabbers, image processing software, and LabVIEW, along with robust electromechanical design and disciplined system integration, to implement a highly successful inspection and process control system.
"By using flexible and high-performance PC-based machine vision technology for our implementation approach, we saved more than $100K in capital investment, several months in integration time, and a potential hundreds of thousands of dollars every year during production."
The Need for High-Speed Inspection Systems
Many of the production lines in pharmaceutical and other industries were originally designed and implemented a few decades ago. Production competitiveness has constantly pushed the speeds of these lines, and lately, there has been an ever-increasing emphasis on product quality control. Recent advancements in PC-based machine vision provide industrially rugged and cost-effective visual inspection systems to add to and interface with the infrastructure of these aging production lines. Such high-speed inspection systems can ensure real-time identification and rejection of production defects and serve as valuable process feedback and control utilities.
Averna Technologies successfully integrated one such system for packaging tubes for cosmetic and pharmaceutical use. The inspection requirements included extensive dimensional measurements with tolerance as stringent as a few tens of microns carried out at different locations along the production process as tubes traveled through the line at a high speed of 150 parts per minute.
Each station along the production line used two area scan cameras with 2 million pixels and provided 10 MB of image data to Camera Link frame grabbers housed in PCI slots of a PC. The PC ran Microsoft Windows and National Instruments LabVIEW software to acquire and process images. We performed dimensional measurements on tubes with efficient and precise image processing algorithms designed using NI machine vision software. We used an LED illumination, with the exception of one of the cameras where we used a laser line, to perform 3D depth measurements. At each station, signals from tube proximity sensors triggered image acquisition.
At the beginning of tube production, the vision system downloaded the tube specifications from a central database and automatically configured the inspection mechanism. Image measurements imaged and evaluated the quality of each tube. If a tube did not meet the quality criteria, it activated a tube-rejecting pneumatic valve, which removed the tube from the production conveyer.
The inspection system showed measurement averages, defect occurrence statistics, and images of good and bad tubes as live displays for process monitoring and as a tuning aid. It then accumulated and transferred inspection results to a remote station for logging and report generation.
Line Scan Inspection
For high resolution and complete print quality inspection, a line scan camera with 2,000 pixels imaged the tubes with station details. Spindles picked up the tubes from the conveyer. Twelve of these spindles rotated the tubes at 300 rpm as a line scan camera acquired a flat image of the full tube surface. The system transferred the image to the NI PCI-1428 image acquisition board and processed it using NI LabVIEW software for print quality inspection. Similar to area scan inspection, the system rejected any defective tube in real time and showed live measurement statistics and images for process monitoring while transferring the results to the remote logging and report generation desktop over the network.
Statistical Process Control and Inspection Integration
The system transferred visual inspection results to a remote networked desktop that also automated acquisition of inspection measurements, including product weight, wall thickness, and others. We acquired this information using an NI PCI-232/8 serial interface board. Our inspection product, Proligent, provided an integration platform for vision and other product measurements as well as for comparisons to quality criteria. Proligent also offered data logging, statistical process monitoring graphs, and report generation capabilities, making the inspection system a comprehensive production assistant useful for process monitoring and tuning.
Industrial Robustness
We designed the rugged PC-based visual inspection system to withstand an industrial operating environment by housing all the hardware in enclosures that met the temperature, vibration, and electrical isolation requirements. On the software side, LabVIEW and Proligent provided reliable ease of use for shift operators and extensive analysis and quality reporting functionalities.
PC-Based Machine Vision Technology Saves Time and Money
This application shows how inspection systems using machine vision are making inroads into industrial production and ensuring unprecedented quality control. This specific system integrates five machine vision cameras, illumination and triggering hardware, and instruments for nonvision measurement. It successfully provides a networked and integrated inspection system with extensive process control and monitoring capabilities. By using flexible and high-performance PC-based machine vision technology for our implementation approach, we saved more than $100K in capital investment, several months in integration time, and a potential hundreds of thousands of dollars every year during production.
For more information, contact:
Shahzad Sarwar
Director of Industrial and Real-Time Solutions
Averna Technologies Inc.
Tel: (613) 230-0283
Fax: (613) 236-3754
E-mail: shahzad.sarwar@averna.com
Web: www.averna.com
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