Understanding the Manufacturing Process

Key to Successful Cad/cam Implementation

Joseph Harrington Jr.

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000146493
• Edition: 1
• Topic: Commerce
• Subtopic: Production

This book approaches manufacturing as a basic problem of making a desired end-product from bulk raw materials. It encompasses the entire gamut of activities from product concept to maintenance of past products in the field, and everything in between.

Chapter 1
Introduction

Manufacturing is evolving from an art or a trade into a science, an important one. A quarter of the population is involved in some form of manufacturing activity, and the rest of the population benefits from the products. When manufacturing was still an art, or rather a collection of very different arts, each had its own unique technology. We now see manufacturing as a science whose fundamentals are independent of what is being made, or when it is being made. It has a structure that is the key to understanding the science, and understanding is the key to profitable application of the science. Most important, this structure is invariant, so that once understood, the knowledge may be applied to any of the many technologies.

Learning is, in the ultimate analysis, the transfer of experience gained in the past to problems of the present. When we understand the scientific principles that govern manufacturing we can profitably apply that knowledge in many ways to the problems of today’s highly integrated manufacturing technology. We can expedite the production of goods; we can adapt designs to changing needs more readily; we can increase the profitability of the enterprise; we can conserve materials and labor. The role of manufacturing in the economy, and in society, is changing with the times. With such a scientific understanding of the subject, we can analyze the effects of proposed changes and select optimum courses of action.

This understanding is essential for everyone involved, whether an old timer or a novice, whether a top level manager or an apprentice worker; it is essential for those in marketing and in production, for those acting as legal counsel or financial managers, for those in personnel or in data processing. It is most certainly essential for students preparing to enter the field of manufacturing in any of its phases.

It is the objective of this book to explain this structure of the science of manufacturing, and to show how it works and how to use it. Because the science described is generic to all the many various forms of manufacture, it may be applied profitably to any manufacturing enterprise.

MANUFACTURING DEFINED

Manufacturing is the conversion of naturally occurring raw materials into desired end-products. The word derives from two Latin word roots meaning “hand” and “make”-almost literally “handmaking.” In early civilizations products were indeed hand made; human muscle power and mental control moved crude tools over materials gathered by hand. Today, few products are made by human, or even animal muscle power. Other sources furnish the power, but humans still conceive the products and guide the operations of production.

In the broadest sense, manufacturing begins with the acquisition of raw materials, and extends throughout the whole gamut of activities of production to the distribution and, if necessary, the maintenance of the end-products. It is convenient to think of this sequence as having three parts—extraction of the naturally occurring materials from the environment, culling, and concentration; the conversion of these materials into a specialized form in bulk; and the conversion of bits of the bulk materials into discrete parts which, when assembled with other parts, constitute the desired end-products. For example, iron ore is dug from the ground, cleaned, and concentrated; it is smelted and converted to steel which is rolled into bars and sheets; pieces of steel are machined into pistons, connecting rods, and crankshafts which are assembled into engines.

In the first step, to take other examples, trees may be cut, limbs and roots removed, and the trunks taken to a sawmill; or aluminum ore (bauxite) may be dug up, cleaned, and shipped to an aluminum refinery; or cotton may be grown, picked, ginned, and shipped to a cotton mill; or oil and gas may be pumped from a well, separated, and piped to an oil refinery.

In the second step, logs may be cut into boards or lumber, seasoned, sorted, or milled into plywood; or the bauxite may be smelted, refined, alloyed, and rolled into aluminum sheets, slabs, or drawn into wire or tubing; or bales of cotton may be carded, spun into thread, woven or knitted into fabric, and dyed or printed; or oil may be refined, fractionated and used as bulk fuels, or the gas may be chemically combined with other elements to produce the monomers for plastics.

In the third step, a factory may acquire a variety of bulk materials from the second step and shape individual pieces which are assembled into end-products, tested, and distributed to the end users. These end-products may be infinitely diverse-ships, airplanes, automobiles, telephones, radios, typewriters, computers, clothing, carpets, shoes, lights, cameras, clocks, furniture, and toys. The variety of consumer goods is seemingly endless. Some products are produced in large quantities-paper clips, for example; other products are produced in smaller numbers-fine automobiles, for example. Similarly, the end-products may be machinery to be used in making other products - printing presses, looms, metal working machines of all sorts, conveyors, retorts - again, the list of capital goods is seemingly endless in its variety.

It is not necessary that the ultimate product of this long sequence be either essential to life, or even useful in our daily affairs. Products may serve only to satisfy our aesthetic senses - fine art of all sorts, for example; or fine foods. If a product is desired, and is physically created by a sequence of acts, it is in the ultimate sense a manufactured product.

This book must confine itself to a manageable size and a limited field. It will concentrate on the third step of the three outlined above. This activity has become known as the “discrete parts industry” to distinguish it from the second step activities which generally produce bulk quantities of materials - feet of lumber, yards of cloth, rolls of steel strip; or pounds of molding compound.

How shall we define the word “manufacturing,” which we shall be using so frequently? Word usage in this field is as diverse as the segments of the field, if not more so. Individual companies in a single segment may give the same word quite different meanings. The word manufacturing itself is a good example: in some instances it refers to everything the company does; in others it refers to everything except marketing; in still others it refers only to the fabrication department and excludes product design as well as marketing.

In this book, manufacturing will encompass the entire gamut of activities from product concept to maintenance of past products in the field, and everything in between. It will include product conception, product design, manufacturing engineering, fabrication of parts, assembly, test, distribution, and support. It will include all of the managerial functions necessary to integrate and operate the activity reliably, profitably, and in a timely manner.

In short, we will treat manufacturing as an indivisible, monolithic activity, incredibly diverse and complex in its fine detail. The many parts are inextricably interdependent and interconnected, so that no part may be safely separated from the rest and treated in isolation, without an adverse impact on the remainder, and thus on the whole.

This book is written to expound this complex structure, to trace its origin, to explore the interaction of the parts, and to understand how to measure, and therefore control, manufacturing. So understood, manufacturing will advance from an art to a science. This book is written, not to discuss how to perform one part of the task, but how to understand and manage the whole, or how to participate more intelligently in some part of the whole.

THE HISTORY OF MANUFACTURING

That manufacturing is indeed a monolithic function can be seen in its origins. Anthropologists suggest that one of the things that distinguished early man from other forms of life was the opposable thumb, which made it possible for a man to grasp and manipulate a tool. Early tools were probably no more than a sharp edged rock fragment or a conveniently shaped stick. With these tools and his muscles, early man was able to skin and cut game for food and for leather clothing, to erect shelters, and to defend himself.

The Bronze and later the Iron Age introduced metals for tools -swords and spear points, axes and saws, planes and chisels, needles, pots and pans, and many other tools. Wood working and stone working skills evolved, and civilization moved forward. At the time of the Roman Empire, manufacture was well advanced in ship building, weaving, metal working, housing, leather working, jewelry, and the fine arts. Tools were refined, but motive power was still largely human. Animals, water, or wind powered the grist and saw mills.

So it remained to the end of the eighteenth century. Tools and skills were progressively refined, and some of the products were exquisite works of art or precision mechanisms. However manufacture was the province of a master craftsman. He was a gun smith or a weaver, a shoemaker or a cabinet maker, a printer or a cooper. He conceived his product, procured his materials, made his tools, and fashioned the product. He performed the entire function of manufacture.

From the earliest times, extra workers were added by the master craftsman to do the routine labor, and thus specialization of labor was introduced. As market sizes increased, marketing of mass-produced products was spun off to someone else, and the first of many divisive barriers within the fabric of manufacturing was introduced. When steam power arrived in the early 1800s, it became desirable to have larger factories, with many more people in an establishment. This, in turn, required several echelons in the hierarchy of supervision. While the owner or master retained overall control, department heads divided up the responsibilities and authorities over the several stages of the work, and more divisive barriers and compartments were created in the fabric of the organization.

In the late 1800s, the function of product development was split off as a separate unit with its own staff, separated by another organizational barrier from production. Research, as distinct from development, made its appearance in the early 1900s.

As volume of production grew, plants grew, and the number of echelons in the managerial hierarchy also grew. Multiplant companies appeared. The result of the last two centuries of evolution and expansion in manufacturing is a structure of great complexity - a fractionated and divided structure, with each little part trying to protect its turf and optimize its own performance. This of course has led to suboptimization of the whole. It has also led to communications barriers between the units at every level, horizontally and vertically.

The result is that today people see manufacturing, not as a single continuum, but as an aggregation of factions, and not always cooperative factions. There are differences in the training, education, and even in the cultural background of the people in these compartments. There has been a loss of perspective on the part of many. This is not good.

Basically these changes were the result of the division of the original one-man craftsman structure as the scope of the enterprise grew. Skills were specialized and divided. Authorities were specialized and divided. Now it is obvious that, if a function in manufacturing is divided into two parts, and the two together are to be the equivalent of the undivided whole, then the partial functions are interrelated. So, no matter how complex the product, nor how much is made, nor how many different products are to be produced, nor how intricate the process, manufacturing is still a monolithic, indivisible continuum.

In spite of the fact that manufacturing is, and always has been an indivisible continuum, the mode of operation has changed from time to time. In the earliest times, manufacturing was labor intensive. The cost of tools was small compared to the cost of the many man hours of labor that went into the simplest product. Cloth for clothing was, for example, produced by first spinning the wool or flax into thread-a hand operation using only hand tools. Next, the thread was woven into cloth on a loom which was a simple device available in many homes. The weaving operation required many hours of repetitive labor as the shuttle was thrown from side to side of the warp.

This example could be multiplied over and over. The key element was the labor expended. Manufacturing was indeed labor intensive.

When, as noted above, power was introduced to manufacturing, it was possible to introduce machines to perform the work formerly done manually. The power plant was expensive, and the machines which used the power and performed the work were expensive. It is obvious that there was no need for power until there were machines that could use it, and no incentive to build machines until there was power to operate them. They came together, in a slow step-by-step evolutionary mode. For example, in shoemaking, soles for many centuries had been attached to the shoe by driving wooden pegs through the outersole and the innersole. An apprentice whittled the wooden pegs by hand, while the master drove them into the shoe. A peg driving machine was an obvious possibility, but it was difficult to design a machine that could drive hand-whittled pegs. However when someone invented a peg-making machine (about 1850) that made uniform pegs, it was not long before someone else developed a powered peg-driving machine.

Throughout industry, machine followed machine, and in the course of the nineteenth century, manufacturing evolved into a process using many machines and their related power sources. All of these machines and engines were expensive. The key element in manufacturing became the capital equipment. Manufacturing was then a capital intensive industry. It is still largely so today.

We are now, in the 1980s, entering a third and new mode of manufacturing operation. It is characterized by the fact that every one of the many acts of manufacture, and every bit of the managerial control of those acts, can be represented by data. Data are generated, transformed, and transmitted. In the ultimate analysis, all of manufacturing may be seen as a continuum of data processing. It provides the one base to which all the parts of the process...