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The Challenge
Replace an obsolete, labor-intensive quality control inspection system for flat glass distortion  analysis with an automated system which performs the motion control, data acquisition and analysis tasks with  greater accuracy, repeatability, and efficiency. 

The Solution 
Data Science Automation uses National Instruments LabVIEW, PXI, SCXI, Database  Connectivity Toolkit, and the Signal Processing Toolkit to create a custom application that combines flexibility and ease-of-use with reliable motion control, data acquisition, high speed accurate analysis, comprehensive reporting,  trending, and archiving capabilities.

Introduction 

Flat glass is manufactured worldwide and used in products as diverse as automotive windshields, furniture and  architectural glazing. Optical quality requirements are critical for safety and aesthetics alike.  

In glass manufacturing, two aspects of the analysis of the distortion in flat glass are important. Expedient and  accurate measurements are required for routine determinations of conformance to quality specifications. And, in  the event that excessive optical distortion is found, it is essential to ascertain the most likely causes of the  distortion in the manufacturing process.  

A multi-laser scanning system with obsolete electronics, inaccurate measures, and manual data processing was  used to detect, characterize and correct surface and internal inhomogeneities in the glass. Although these  objectives were being met using the obsolete manual system, numerous hardware problems and labor-intensive  operational requirements resulted in the loss of efficiency and reliability of the system. With increasing quality  standards, reduced staff at manufacturing and research facilities, and the need to correct quality problems with  urgency, Data Science Automation was contracted to overhaul the system and put more diagnostic capabilities in  the glass manufacturing facilities. 

Data Science Automation, Inc. (DSA) replaced an existing manual analysis system with a LabVIEW-based  system that exploits state-of-the-art computer-based instrumentation techniques for improved performance,  greater reliability, and reduced maintenance. DSA’s flat glass distortion processing system offers expedient and  accurate data acquisition, extensive data analysis and process correlations, flexible trending, full database  archiving capability, and comprehensive reporting features combined with an intuitive user interface.  

System Configuration 

The new distortion analysis system developed by DSA includes National Instruments LabVIEW, DAQ, PXI, and  SCXI, as well as various third-party manufacturer’s components for interlocks, motion, and laser position  detection. 

Using the graphical user interfaces, operators can easily configure the production data, printing parameters, and  data acquisition settings; align the detector beams; acquire the distortion data; edit and analyze the acquired  waveforms; archive selected raw and processed data sets; trend the archived data; and produce diagnostic,  quality, spectral, and summary reports, and learn from the comparison of samples produced with similar or  different process parameters. 

Upon startup, the application titlebar (Figure 1) offers several option buttons that are used to navigate the primary  application features appears. Flexible configuration screen allows users to modify many of the default data  collection and process variable display and printing parameters.  

Figure 1: Application title bar enables users to navigate the primary application features. 

Alignment of the laser beams in the center of the position-sensitive photodiode detectors is an important  procedure that should be performed regularly to ensure the accurate and reliable distortion results. The Beam  Alignment option enables users to perform this task quickly and easily. For example, beam position palettes  (Figure 2) indicate each laser beam’s position relative to the center of the corresponding photodetector. If the  beam is centered on the detector, within some radius of tolerance, the center LED will show green, while if the  beam is outside the radius of tolerance, red LED’s will indicate the direction to which the beam is deviated,  enabling operators to take corrective actions in the right direction.

Figure 2: Beam position palette indicates the position of the detector beam and guides users in centering it. 

Acquisition/Analysis user interface (Figure 3) manages the data acquisition, editing, analysis and file storage  tasks. Users can view one set (or channel) of distortion data at a time or two channels superimposed for  

comparison purposes. Distortion analysis can be performed on the data acquired from a current run or on a set of  saved data. Displayed data can be edited automatically to remove noise spikes from the waveform or manually to  remove any other anomalies.  

With only a few I/O points for top surface reflection, bottom surface reflection and transmitted laser signals, this  application generates and analyzes a significant amount of data for thoroughly characterizing glass distortion  quality. Available analysis techniques include diagnostic, quality, contour, spectral and JTFA. Together these  provide long wavelength and other visual distortion characteristics that simulate the human eye’s response, and  time domain and frequency domain information for accurate correlation to manufacturing processes for  continuous improvement.  

The complicated and time consuming manual calculations, correlations and reporting requirements kept these  capabilities isolated in the hands of skilled researchers with limited time to provide remote support to the  manufacturing facilities. The automated analysis and reporting available in the LabVIEW system, with expanded  capabilities, provided immediate, on-site diagnostic capabilities to the plants.

Figure 3: Acquisition/Analysis user interface. 

Utilizing the Database Connectivity Toolkit, the flat glass distortion processing system software enables users to  archive selected group of raw and processed data into a Microsoft Access database. Once the data are stored in  the database, users can easily access them using Access’s built-in query functions or the historical trending  option of the analysis software. Flexible and comprehensive trending user interface allows users to compare  distortion data from different plants and study the fluctuations in various production variables over time for better  quality control and assurance. A versatile print manager interface lets users produce thirty pages of publication  quality reports for any data set.  

Conclusions 

This solution offers a robust and state-of-the-art data acquisition and sophisticated analysis system. Also the  versatile database application and reporting option provide the ability to store and review the analysis results fast  and easily. Finally, the intuitive and aesthetically pleasing user interfaces bring these factors together and  provides users with a comprehensive optical distortion analysis tool that is easy to use, robust, extremely flexible  as well as requires little maintenance and permits easy accommodations of any future improvements. The  system was demonstrated in the research environment and proved sufficiently stable and valuable to be installed  in multiple primary glass manufacturing facilities.