As manufacturing engineers, we've made significant advancement in machine tool technology. in the past 20 years. We are well into the learning curve when it comes to the application of mini-computers, micro-processors, solid. state relay technology and optical measuring scales. Efficiency continues to increase and equipment up time ranges into the high ninety percents. In less than ten years, we can envision the complete obsolescense of the traditional magnetic relay control devices in use today.
Traditionally, optical devices have served to enhance the capability of human eyes to see smaller or distant objects better, to improve the precision of some measurements or to make other kinds of measurement possible. More recently, new optical and opto-electronic devices, sometimes in conjunction with computers, have made possible optical systems that function without the intervention of human beings. They are capable of executing the key step of drawing conclusions from "scenes" automatically, often without a conventional "image" even being formed. This kind of automation adds increased speed and reliability to the advantage that optical techniques usually have in being non-contacting (not to mention non-destructive). These factors now make optical techniques suitable for use directly on the production line. 100% on-line inspection for quality control is one such use. Making pertinent measurements further upstream - to control the process - can be even more useful than automated quality control at the end of the line, which only sorts scrap from good production without affecting the amount of scrap made.
There are many opportunities for the potential use of optical techniques in nondestructive testing in the Army. However, there has been relatively little use of optical approaches in NDT which has traditionally favored instead, X-ray, ultrasound, eddy current, magnetic techniques, and penetrants. The large number of items procured in some Army systems requires automated and high rate testing systems with which optical approaches can be very compatible. The basic principles of optics could be applied to NDT requirements in a number of Army applications including testing of large composite panels, frame alignment, elimination of mechanical gages, and NDT of large structural load-carrying assemblies and bridges.
The most common application of optics to nondestructive quality evaluation of raw product is for color and appearance analysis. An application less familiar to consumers is automatic sorting, where each unit is evaluated and the defective units are removed. Devices for sorting beans, peanuts, and other small products by comparing the reflectance of the product to a standard have been in use for more than 30 years. With these devices each bean is examined on both sides while in free-fall and accepted or rejected. The operation is sufficiently rapid so that it is economically feasible to sort commercial volumes of these crops.
The various manufacturing activities nave receivea the primary emphasis curing efforts to improve productivity through automation. Inspection activities, especially electronic module inspection, have received only secondary emphasis. This has resulted in a trend which has developed where the cost of manufacturing an item is decreasing with the cost of inspection rising due to inflationary causes. This trend increases the ratio of the cost of inspection to the cost of manufacturing. Quality Assurance activities must recognize that the cost of inspection is becoming an increasingly significant percentage of unit cost and make a concerted effort to reverse this trend. This paper describes some of the problems we are faced with in Aerospace electronics manufacturing (small lot size, highly complex designs, reliability requirements, personnel requirements) and some of the areas in which we think an optical system may be developed to meet our needs.
The various significant optical gauging concepts are identified and references are given that describe in detail the concepts and their hardware implementation. Other general references in the field of optical metrology are also provided.
The Helium Neon laser operating at 633 nm has taken its place as a custom or off-the-shelf component in the industrial environment. It is low cost, rugged and reliable. Some of the peculiar properties of Helium Neon lasers are discussed with emphasis on the consid-erations necessary to specify and use the lasers routinely. The topics covered are: beam properties, electrical characteristics, noise, mechanical requirements and lifetime.
Optical sensors are rinding increased usage in inspection and quality assurance applications. The versatility and high speed data gathering capabilities of imaging sensors lend themselves to complex applications such as pattern recognition and gray-scale defect deter-minations. Applications of this type usually require computer capability to mandLutte and digest the data but optical scanning rates usually outpace the instruction cycle rates of microcomputers. This paper discusses a method of handling high speed imaging data to pro vide real time computer analysis, decision and control. Methods and technical designs are described that provide data compression, formatting and preprocessing. Hanipulative tech.- niques for both digital and analog (video) signals are discussed.
A real-time, digital, video processing system offers a flexible means for performing high-speed, on-line, automated product inspection. With the capability to digitize and store a 512 x 512 multi-gray level image in 1/30 second as well as subtract a reference image from a new image in a TV frame time, it is possible to perform high-speed inspection of parts, packages and labels. Such a unit can operate as a stand-alone unit or as a pre-processor for a dedicated or time-shared computer. Design trade-offs and examples of specific applications will be discussed.
Programmable electro-optical measuring systems are being readily introduced to industrial inspection applications. Major improvements in the operation, measuring power and speed of the devices have served as impetus to the increase in their popularity and acceptance. The majority of system improvements have come on the wings of technological advances in individual component members; microcircuitry has dimished the size and price of components yet increased their performance and reliability. Presently solid state scanners employ dense CID matrix arrays to reduce or eliminate many of the problems associated with CCD arrays or imaging tubes. The CID lacks the resolution of either vidicon or image dissector sensors, however, measuring accuracies achieved using tube devices can be approached by the lower resolution CID through proper application of quality optics. Inexpensive floppy disk storage has further enhanced the usefulness of the newer machines by providing capacity for unlimited programs and data storage.
An instrument is described for measuring both particle and droplet size distributions. Based on Fraunhofer diffraction of laser light, the measurement is fast, reliable, and easy to make. Hardcopy results include a characteristic diameter, distribution width, and a 15-segment histogram of the size distribution. Following a brief review of sizing techniques and the importance of measuring size distributions, a technical discussion is presented on the principles of the instrument. Configuration of the instrument is discussed. Five examples of commercial application are presented covering spray and particle samples.
In the past, electro-optical inspection technology met with little success in the automotive industry's production environment. Service, maintainability and reliability were high on the list of problems. A credibility gap between the industrial minded plants and the laboratory oriented suppliers developed through a lack of understanding on both sides. Recent social, economic and competitive pressures have made increased quality demands of the automotive industry. Advanced technology can be an effective tool in solving quality problems if that old credibility gap is bridged. The Transmission and Chassis Division of Ford Motor Company has developed an Advanced Gauging Program in an attempt to bridge that gap. Program funded feasibility demonstrations provide manufacturing plants with a technical awareness, and suppliers with a knowledge of industrial conditions and requirements. Currently installed advanced gauging systems are paving the way for future inspection needs.
An optical system, based on automated triangulation, has been designed to inspect the final configuration of diesel engines. This system, which inspects for the correct location and orientation of approximately one hundred external engine components, has a spatial resolution of 2 millimeters and can perform a complete inspection in less than two minutes.
Monitoring product color has become an increasingly important part of production. Both colorimeters and spectrometers offer the potential for automating this process. Color measurement may be needed to match all items to the same color, as in production of colored plastic caps. Sorting almonds from debris can be performed by using color as an indicator. Systems for both of these applications are discussed and compared to illustrate examples of bringing color measurement technology onto the factory floor.
The application of electro-optics to industrial metrology is discussed. Principles of operation and methods of implementation are illustrated by a detailed examination of three electro optical microprocessor based gaging systems. One system inspects and sorts precision springs. Features measured by the machine include spring rate, free length, and end sqthiireness. The machine accommodates over 80 different part number springs and main-tains a gross throughput of 1,000 pieces per hour. Also described, is a small parts measuring machine used to measure features such as diameter, taper, roundness, sphericity, concentricity, length, thread quality, etc. on parts such as ball studs and bearings used in automobile steering systems. The third machine measures the location and diameters of each of three fuel ports in-side the bore of a diesel fuel injector barrel. The machine can handle any one of four different part numbers with an inspection cycle time of six seconds. A description of the mechanics, optics, software, calibration, and operation on each of the machines is given.
Laser scanning techniques in conjunction with a dedicated micro or mini computer can perform many inspection operations more accurately and more rapidly than visual inspection. Examples of typical systems are given.
The paper describes the control problem in terms of the constraining parameters: the nature of the process plant environment, the process and its constituents, methods of sensing the process, spectral characteristics of the process infrared emission and absorption, and the time lag between a process adjustment and the resulting change in the observed characteristics. Considered in detail is the manner in which the process control system operates within the sphere of these constraints together with the transfer of data and control signals. Examples are included of system operation in laboratory, plastic and gas process analysis and in an experimental coal gassification unit.
One of the major tasks confronting the designer of chemical processes is the evaluation of the ability to measure and control process parameters. The availability of instrumentation is discussed in terms of performance, reliability, safety, and economy. The potential contribution of devices capable of monitoring spectral irradiance is discussed. Also covered is recent application based on the development of an integrated radiometric system for use in a coal-related process.