The scientific study Of metal-cutting and automation techniques is products of the tieth century. Two pioneers of these techniques were Frederick Taylor and Henry During the early 1900s, the improving U. S. standard Of living brought a new high in person. al wealth. The major result was the increased demand for durable goods. This increasd i, demand meant that manufacturing could no longer be treated as a blacksmith trade, and the use of scientific study was employed in manufacturing analysis. Taylor pioneered studies in k. scientific management" in which methods for production by both men and machines were studied. Taylor also conducted metal cutting experiments at the Midvale Steel Company that t lasted 26 years and produced 400 tons of metal chips. The result of Taylor's metal-cutting experiments was the development Of the Taylor tool-life equation that is still used in industry today. This tool-life equation is still the basis of determining economic metal cutting and has been used in adaptive controlled machining.
Henry Ford's contributions took a different turn from Taylo's. Ford refined and developed the use of assembly lines for the major component manufacturer of his automobile. Ford felt that every American family should have an automobile, and if they could be manufactured inexpensively enough then every family would buy one. Several mechanisms were developed at Ford to accommodate assembly lines. The automation that Ford developed was built into the hardware. and Ford realized that significant demand was necessary to offset the initial development and production costs of such systems.
Although manufacturing industries continued to evolve. it was not until the 1950s that the next major development occurred. For some time. strides to reduce human involvement in manufacturing were being taken. Specialty machines using cams and other —hardwired' logic controllers had been developed. The U. S. Air Force recognized the development time required to produce this special equipment and that the time required to make only small sequence changes was excessive. As a result, the Air Force commissioned the Massachusetts Institute of Technology to demonstrate programmable or numerically controlled ( NC) machines (also known as —softwired" machines). With this first demonstration in 1952 came the beginning of a new era in manufacturing. Since then, digital computers have been used to produce input either in a directed manner to many NC machines. direct numerical control (DNC), or in a more dedicated control sense. computer numerical control (CNC). Today' machine control languages such as APT (Automatic Programming Tool) have become the standard for creating tool control for NC machines.
It is interesting to note that much of the evolution in manufacturing has come as a response to particular changes during different periods. For instance. the technology that evolves in the nineteenth century brought with it the need for higher-precision machining(This resulted in the creation of many new machine tools. a more refined machine design, and new production processes. ) The early twentieth century became an era of prosperity and industrialization that created the demand necessary for mass-production techniques. In the 1950s it was estimated that as the speed of an aircraft increased, the cost of manufacturing the aircraft (because of geometric complexity) increased proportionately with the speed. The result of this was the development of NC technology.
A few tangential notes on this history include the following. As the volume of parts manufactured increases, the production cost for the parts decrease (this is generally known as economy of scale" ). Some of the change in production cost is due to fixed versus variable costs. For instance, if only a single part is to be produced (such as a space vehicle) , all of the fixed costs for planning and design (both product and process) must be absorbed by the single item. If, however. several parts are produced, the fixed charge can be distributed over several parts. Changes in production cost. not reflected in this simple fixed-versus vari- able-cost relationship. are usually the result of different manufact uring procedures— transfer-line techniques for high-volume items versus job-shop procedures for low-volume items.
Automated Manufacturing Systems
An automated manufacturing system consists of a collection of automatic or semiauto• matic machines linked together by a "intrasystem" material-handling system. These systems have been around since before Henry Ford began to manufacture his Model T on his moving assembly line. These automated systems have been used to produce machined components, assemblies, electrical components, food products. chemical products. etc. The total number of products produced on a single system varies with the production methods. However, the principles of designing the production systems are the same independently of the product being manufactured. The workstations in a production system can be manual, semiautomatic or fully automatic. The automatic stations can be programmable or hardwired.
The purpose of any production system is to produce a product or family of products in the most economical manner. Automated production systems are no different from any other type Of manufacturing system. In order to employ any form of automation, the implementa• tion must be economically justifiable. Automation has traditionally been most appropriate for high-value products. However. flexible automation equipment has brought automation to some relatively low value products. Selected from "Modern Manufacturing process Engineering". Benjamin W. Niebel. rt. al. , McGraw• Hill Publishing Company, 1989.
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