THE TYRANNY OF LARGE NUMBERS

e [Music] [Applause] [Music] [Applause] the rapid development of today's electronic Sciences has brought along problems which did not exist in the simple old days a few short years ago engineers and scientists today are concerned about what can be called The Tyranny of large numbers electronic equipment as is used in direct dialing systems and carrier telephone circuits has become so complex that a single longdistance telephone conversation may involve literally hundreds of amplifiers thousands of electron tubes and millions of other circuit elements if ordinary components were used like those entirely satisfactory for radio and television receivers we could anticipate a failure about once an hour a failure in a telephone system would be annoying and expensive to repair a failure in a complex military weapons system could be disastrous the increasingly complex electronic equipment used in defense often has to work under extreme conditions of cold heat humidity vibration and shock and not fail one of the components that is a vulnerable part of electronic systems both civilian and military is the deposited carbon resistor small unglamorous looking items like these are used by the millions in applications that range from telephone transmission to the Army's Nike Zeus anti-missile missile systems in some defense applications these resistors must be built to have a failure rate of no more than one failure per 200 million hours of operation the deposited carbon resistor is basically not a complicated device it consists of a short ceramic Rod or core which is first Co with carbon to each end of the core is applied a conducting termination and caps and leads are attached a helical Groove is cut into the carbon film to change the electrical path on the core and raise the resistance to the desired value finally the resistor is given a cover for protection from the environment in spite of the deceptive simplicity of the deposited carbon resistor manufacturing them manually has many disadvantages manual handling and storage of large process inventories raises the danger of contamination human controls have definable limitations and increase the possibility of latent defects but most of all because manual manufacturing is slow a greater time must elapse before an error can be observed and the information fed back to the operator for correction to shorten this feedback control Loop requires increased speed to meet higher reliability requirements demands more critical care together these need a higher level of performance than has been previously attained it became clear that to appreciably shorten the feedback control Loop required a radically new approach a number of years ago a few of the creative minds at Western electrics North Carolina Works began to find ways to meet this challenge chenge this was a search that led into areas not explored before in manufacturing technique it presented problems in the fields of physics chemistry mechanics and electronics problems such as developing a carbon deposition furnace simultaneously open and sealed shut or compressing 16 hours for termination paint curing to 50 seconds or more than 200 separate transport problems since these were things not tried before there were occasional clashes of ideas when neither side could be proven right or wrong there were contributions from a number of Engineers One By One The conflicts were resolved and finally the members of the engineering team developed a solution to the problem [Music] a solution was a precise automated production line completely controlled by a single computer with feedback of information from three key points along the line making possible rapid closed loop operation the brain of the automated line the digital computer performs basically in three areas to start at the beginning it programs production control A month's requirements can be fed into the computer at random it completely schedules and programs the work arranging it according to the four power sizes and nearly infinite number of resistive values it is capable of handling the second area is statistical quality analysis at three stations along the line each unit is inspected each five units are analyzed and the average is plotted in the computer's memory statistical tests are applied to determine if a trend is developing a statistical trend is handled in the third and most important area rapid feedback control here the computer formulates the information to detect any Drift from the accepted Manufacturing tolerances stored data is used for calculating new setup information which is disseminated to the appropriate station [Applause] the nucleus of each resistor is the tiny ceramic core these are transported through a plastic tube to the carbon coating furnace historically carbon coating was applied to large numbers of resistors tumbled in a batch type furnace cores are individually fed through three separate Chambers where speed temperature and coating gas flow are closely controlled by the computer first the cores enter a heating area where temperature is controlled at 21 200° F nitrogen gas is continually flushed through it to prevent oxygen from entering a central deposition area there methane gas is heated until it decomposes to form crystalline carbon after coating the cores pass to a cooling area where they are reduced to room temperature leaving the furnace each resistor is subjected to its first quality control inspection the carbon coating is electrically checked by four probes analog voltage proportional to resistance is digitized and sent to the computer as a basis for feedback control of the Furnace the results of the inspection can also be visually monitored a compressed air tube carries the cores to the next station where ends are coated with gold particles a mask is fitted over each core protecting the center [Applause] section both are placed under a bell which is pumped to a vacuum the ends of the resistor are sputtered with particles from a gold cathode gold termination eliminates silver paint with its 16-hour curing cycle at the next station caps into which leads have been welded outside the line are fed through tubes to capping Chucks the Chucks place them over both ends of the resistor core simultaneously the resistor is then deposited on a pallet which carries it through the remainder of the operation [Applause] pallet carries the resistor to the helixing machine where a helical Groove is cut along the core to obtain the desired [Applause] resistance a computer controlled Bridge monitors the cutting the bridge balances when the desired resistance is reached disengaging the lathe the bridge senses any nonlinearity indicating chipping or other defects and such units are automatically rejected again the resistor is inspected its resistance is precisely measured by a wheat Stone Bridge unbalanced voltage is digitized and fed to the computer which makes the necessary corrections to the helixing machine again closing the feedback loop defective resistors are automatically rejected the next step is encapsulation two epoxy pellets are inserted over each lead and an epoxy sleeve is fitted over the core retain between two resilient Chucks the resistor is fed into an oven since the sleeve is fully cured and rests on the gold caps of the resistor it does not melts and retains an air space along the body but the partially cured pellets soften in the 350° heat forming an effective seal with a sleeve the resistance are transferred to Clips which immerse them in a water bath containing a wetting agent instead of manual inspection a series of 10 photoelectric cells watch for air bubbles which would indicate a leak in the capsule the special memory device rejects a defective component as it leaves the tank resistors which pass the leak test go to a marking machine control by the computer which stamps on the wattage resistance value production Lot number and [Music] date the final inspection a feedback control point resets the preceding inspection station compensating for shifts in resistance value due to the heat of encapsulation the line supervised by three or four highly trained technicians manufactures inspects and tests Precision resistors at the rate of 12200 units per hour in 1 qu to 2 watt sizes and a nearly infinite number of resistor values although the new facility will cut resistor cost substantially its primary objective is to provide large quantities of ultra reliable units needed for Bell system and defense purposes a number of versatile computers are available to Industry many already used to control Al materials like chemicals metals and oils this computer application is unique for the first time a computer has been used with a statistical quality control system with rapid feedback loops to control a series of fabricating machines making individually distinct components capacitors transistors inductors all can now be considered for automated production an engineering hypothesis is now a fact a giant step towards breaking the tyranny of large numbers [Music] be for