Industrial Engineering is Human Effort Engineering and System Efficiency Engineering.
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An Enduring Quest: The Story of Purdue Industrial Engineers
Ferdinand F. Leimkuhler
Purdue University Press, 2009 - Technology & Engineering - 290 pages
The profession of industrial engineering improves the economic efficiency of the technology that drives industrialization.
This book describes how industrial engineering evolved over the past two centuries developing methods and principles for the redesign of production and service systems to make them more economical and efficient. The story focuses on the growth of the discipline at Purdue University where it helped shape the university itself and made substantial contributions to the industrialization of America and the world. The story includes description of prominent industrial engineers like Frank and Lillian Gilbreth, and Charles B. Going.
Routledge, 18-Oct-2010 - Business & Economics - 384 pages
This volume collects eleven essays written by Japanese experts on various aspects of Japanese business management and is a sequel to the volume Industry and Business in Japan. It examines the mechanisms for Japan’s phenomenal economic growth since the Second World War by analyzing Japanese management, business groups, production systems and business strategy.
Essay by Taichi Ohno on development of Toyota Production System is there in the book as one essay.
Scientific Management: Frederick Winslow Taylor’s Gift to the World?
J.-C. Spender, Hugo Kijne
Springer Science & Business Media, Dec 6, 2012 - 192 pages
Many of those interested in the effect of industry on contemporary life are also interested in Frederick W. Taylor and his work. He was a true character, the stuff of legends, enormously influential and quintessentially American, an award-winning sportsman and mechanical tinkerer as well as a moralizing rationalist and early scientist. But he was also intensely modem, one of the long line of American social reformers exploiting the freedom to present an idiosyncratic version of American democracy, in this case one that began in the industrial workplace. Such as wide net captures an amazing range of critics and questioners as well as supporters. So much is puzzling, ambiguous, unexplained and even secret about Taylor's life that there will be plenty of scope for re-examination, re-interpretation and disagreement for years to come.
There is a surge of fresh interest and new analyses have appeared in recent years (e. g. Wrege, C. & R. Greenwood, 1991 "F. W. Taylor: The father of scientific management", Business One Irwin, Homewood IL; Nelson, D. (Ed. ) 1992 "The mental revolution: Scientific management since Taylor", Ohio State University Press, Columbus OH).
Creativity and Performance in Industrial Organization
Routledge, 216 pages
Tavistock Press was established as a co-operative venture between the Tavistock Institute and Routledge & Kegan Paul (RKP) in the 1950s to produce a series of major contributions across the social sciences.
This volume is part of a 2001 reissue of a selection of those important works which have since gone out of print, or are difficult to locate. Published by Routledge, 112 volumes in total are being brought together under the name The International Behavioural and Social Sciences Library: Classics from the Tavistock Press.
Reproduced here in facsimile, this volume was originally published in 1968 and is available individually.
This book has many topics relevant to the subject introduction to industrial engineering. Value analysis, and optimization are two areas that are to be added.
Work Systems: Pearson New International Edition: The Methods, Measurement and Management of Work
Mikell P. Groover
Pearson Education, Limited, Nov 1, 2013 - 744 pages
For sophomore or junior-level courses in industrial engineering. Divided into two major areas of study - work systems, and work methods, measurement, and management - this guidebook provides up-to-date, quantitative coverage of work systems and how work is analyzed and designed. Thorough, broad-based coverage addresses nearly all of the traditional topics of industrial engineering that relate to work systems and work science. The author's quantitative approach summarizes many aspects of work systems, operations analysis, and work measurement using mathematical equations and quantitative examples. https://books.google.co.in/books/about/Work_Systems_Pearson_New_International_E.html?id=h41MngEACAAJ
Table of Contents
Chapter 1 INTRODUCTION
1.1 The Nature of Work
1.2 Work System Defined
1.3 Types of Occupations
1.5 Organization of the book
Part I Work Systems and How They Work Chapter 2 MANUAL WORK AND WORKER-MACHINE SYSTEMS
2.1 Manual Work Systems
2.2 Worker-Machine Systems
2.3 Automated Work Systems
2.4 Determining Worker and Machine Requirements
2.5 Machine Clusters
Chapter 3 WORK FLOW, BATCH PROCESSING, AND WORK CELLS
3.1 Sequential Operations and Work Flow
3.2 Batch Processing
3.3 Defects in Sequential Operations and Batch Processing
Questions on Tool Equipment. The tool and equipment used to perform the operation needs to analysed logically. The following questions are the sort that will lead to suggested improvements:
1. Is the machine tool best suited to the performance of the operation of all tools available?
2. Would the purchase of a better machine be justified?
3. Can the work be held in the machine by other means to better advantage?
4. Should a vise be used?
5. Should a jig be used?
6. Should clamps be used?
7. Is the jig design good from a motion-economy standpoint?
8. Can the part be inserted and removed quickly from the jig?
9. Would quick-acting cam-actuated tightening mechanisms be desirable on vise, jig, or clamps?
10. Can ejectors for automatically removing part when vise or jig is opened be installed?
11. Is chuck of best type for the purpose?
12. Would special jaws be better?
13. Should a multiple fixture be provided?
14. Should duplicate holding means be provided so that one may be loaded while machine is making a cut on a part held in the other?
15. Are the cutters proper?
16. Should high-seed steel or cemented carbide be used?
17. Are tools properly ground?
18. Is the necessary accuracy readily obtainable with tool and fixture equipment available?
10. Are hand tools pre-positioned ?
20. Are hand tools best suited to purpose?
21. Will ratchet, spiral, or power-driven tools save time?
22. Are all operators provided with the same tools?
23. Can a special tool be made to improve the operation?
24. If accurate work is necessary, are proper gages or other measuring instruments provided?
25. Are gages or other measuring instruments checked for accuracy from time to time?
Because of the wide variety of tools available for different kinds of work, this list could be extended almost indefinitely with specific questions. Foundries, forge shops, processing industries, assembly plants, and so on all have different kinds of tools, and different questions might be asked in each case. The list given above, drawn up principally and by no means completely for machine work, will indicate the kind of searching, suggestive questions that should be asked. A special list might well be drawn up by each individual plant to cover the kind of tools that might be advantageously applied upon its own work.
Tool Design. The matter of tools is one that has received a good deal of attention, because a good tool is necessary to do a good job. Therefore, tools that function properly are found on the majority of operations that the methods efficiency engineer studies. If the tool did not function properly, it would not be used. Of course, in some shops where the matter of tools does not receive the proper attention, operations are encountered on which the operator is turning out passable work in spite of his tools rather than because of them.
For the most part, however, it may be said that the tools do function properly from the standpoint of the finished job. Whether or not they function properly from a motion-economy standpoint is another matter. The tool designer is usually more concerned with making a tool that will do a certain job than he is with the motions that will be required to operate it. Therefore, unless he has made a study of the principles of methods engineering or has had the importance of motion economy impressed upon him in some other way, it is probably safe to say that the motions required to operate the tool are the last thing he thinks of.
As a result, tools are designed and built that require much more time to use than they should. The common machine vise is a good example. The quick-acting vise is far superior. On machining operations where the cutting time is short, it will save 20 to 40 per cent of the total operation time. The jaws of the vise are cam-actuated. They are tightened by moving the two levers in opposite directions which conforms to the principles of motion economy. They hold securely without hammering on the levers. They are adjustable to a variety, of sizes of work. In short, they possess many real advantages over the standard vise.
Suggestions that will improve the quickness of operation of tools should be made to tool designers as they are conceived. If they are presented with a summary of the yearly saving in dollars and cents that they will effect, interest in better tool design from a use-time standpoint will be aroused. This is very desirable, for tool designers as a group are clever arid ingenious, and if the importance of reducing the time required to operate tools Is clearly demonstrated, they will be able to assist materially toward this end by producing more suitable designs.
Hand Tools. There is a tendency to pay too little attention to the hand tools used upon even the more repetitive operations. To many, a screw driver is a screw driver, and if it fits the slot in the screw to be driven, it is considered satisfactory. This is far from being the case, however. Screw drivers vary widely in design, and some are more suitable than others. Screw drivers come in a number of different styles. There are the solid screw drivers, the ratchet screw drivers, the spiral screw drivers, and the various types of power-driven screw driyers. Even the variation among screw drivers of a given type is tremendous. They vary in size, of course, but in addition they vary in about every other way imaginable. The handles vary in diameter, length, cross section, shape, and nature of gripping surface. Points are wide, narrow, blunt, sharp, taper toward the point like a wedge, or are narrower right above the point than at the point. A lately introduced type has a special point to fit a special screwhead which offers many advantages.
When all these factors are considered, the wide variation in even such a simple tool as a screw driver becomes apparent.
There is, of course, one screw driver that is better for a given application than any other. For medium work with the conventional screwhead if a solid screw driver is to be used, the one with the largest cylindrical handle which can be comfortably grasped by the operator should be chosen. The handle should, of course, be fluted to prevent slipping. The diameter of the handle will vary with the size of the operator's hand, but two or three standard sizes are sufficient for most hands. The diameter of the handle should be large, because the larger the handle within the limits of the human hand, the more easily can a given torque be applied. To prevent slipping, the point should not be wedge-shaped but should be slightly larger at the point than just above it. Few screw drivers commonly encountered in industry meet these simple specifications.
If many screws have to be driven, a ratchet, spiral, or power-driven screw driver can often be used to good advantage. If many screws of the same size are to be driven, a piece of hardened tubing slipped over the end of the screw-driver point will make it much easier to locate the screw driver in the slot.
The same sort of searching analysis can be made for every type of hand tool used. Wrenches, hammers, chisels, saws, scissors, knives, pliers, and drills all come in a great variety of styles. Standardization on a limited number of the better styles within a plant will tend to prevent the use of the more inefficient tools. Tests must be made to determine which styles are actually the most efficient, however, for the judgment of the operators cannot be relied upon. A man will prefer a certain tool because of its apparent strength, the color of its handle, its pleasing appearance, or its familiarity. Unbiased tests are much more reliable.
Judgment must be used, of course, in determining the amount of time that can economically be spent in analyzing the tools used on any one job. Unless a job is highly repetitive, it will not pay to try to discover the best screw driver for that particular job. Instead, the whole subject of hand tools including screw drivers may be investigated in a general way, and good tools may be adopted for standard use. The tool supply should be plentiful, for it is not uncommon to see operators not only using the wrong size of tool, but also using a chisel for a hammer or a screw driver for a crude chisel merely because the proper tool is not available. An insufficient supply of proper tools may reduce the amount expended for tools, but it will prove costly in the long run.
The setup or the workplace layout or both must be studied in detail, for they largely determine the methods and motions that must be used to perform the operation. The order in which tools are set up in a turret lathe, for example, will determine the order in which the various machining operations are performed. The position in which material is placed with respect to the point of use will determine the class and the length of the motions required to secure it.
Before any work can be done, certain preliminary or "make- ready" operations must be performed. These include such elements as getting tools and drawings, getting material and instructions, and setting up the machine or laying out material and tools about the workplace. When the operation itself has been completed, certain clean up or " put-away " elements must be done such as putting away tools and drawings, removing finished material, and cleaning up the workplace or machine.
Questions on "Make-ready" and "Put-away" Elements. The procedure followed to perform the " make-ready" and "put- away" elements should be questioned closely, particularly on small-quantity work, for these operations are usually fairly long. Many of them carry the operator away from his workplace. This is undesirable for several reasons, and the necessity for trips to other parts of the department should be minimized. The arrangement of the setup or the workplace layout is of primary importance, and the simple rules governing efficient workplace layouts should be clearly understood.
Typical questions which will lead to suggestions for improvement in this connection are as follows :
1. How is the job assigned to the operator?
2. Is the procedure such that the operator is ever without a job to do?
3. How are instructions imparted to the operator?
4. How is material secured?
5. How are drawings and tools secured?
6. How are the times at which the job is started and finished checked?
7. What possibilities for delays occur at drawing room, tool- room, storeroom, or time clerk's office?
8. If operator makes his own setup, would economies be gained by providing special setup men?
9. Could a supply boy get tools, drawings, and material?
10. Is the layout of the operator J s locker or tool drawer orderly so that no time is lost searching for tools or equipment?
11. Are the tools that the operator uses in making his setup adequate?
12. Is the machine set up properly?
13. Is the machine adjusted for proper feeds and speeds?
14. Is machine in repair, and are belts tight and not slipping?
15. If vises, jigs, or fixtures are used, are they securely clamped to the machine?
16. Is the order in which the elements of the operation are performed correct?
17. Does the workplace layout conform to the principles that govern effective workplace layouts?
18. Is material properly positioned?
19. Are tools prepositioned?
20. Are the first few pieces produced checked for correctness by anyone other than the operator?
21. What must be done to complete operation and put away all equipment used?
22. Can trip to return tools to toolroom be combined with trip to get tools for next job?
23. How thoroughly should workplace be cleaned?
24. What disposal is made of scrap, short ends, or defective parts?
25. If operation is performed continuously, are preliminary operations of a preparatory nature necessary the first thing in the morning?
26. Are adjustments to equipment on a continuous operation made by the operator?
27. How is material supply replenished?
28. If a number of miscellaneous jobs are done, can similar jobs be grouped to eliminate certain setup elements?
29. How are partial setups handled?
30. Is the operator responsible for protecting workplace over- night by covering it or locking up valuable material?
From this list, it may be seen that an analysis of "make-ready " and "put-away" operations covers a rather wide field. The general plant routine with respect to the way jobs are given out is questioned, as is also the manner in which tools, drawings, and materials are secured. Much of this is standard for every job; and after it has been thoroughly analyzed for one job and improved as much as possible, it need not be considered so carefully again. Too often, however, procedures of this sort have been hurriedly set up or were not set up at all. In the older shops which were in operation before the principles of scientific management were evolved, the routine in effect today may be merely bad habits. Therefore, the subject should receive a thorough analysis at least once, and preferably so that irregularities will not be permitted to creep in and become standard practice more often, say at least every 6 months.
Make Ready. The methods followed in giving out jobs differ widely throughout industry. Where the same operation is worked day after day, the problem is not encountered; but on more miscellaneous work, some procedure for telling an operator what job he is to work upon next must be provided.
When the operator has received notification in one way or another of the job he is to do, he must next secure drawings, tools, and material. The way in which this is done also varies widely. In some cases, the operator must hunt everything for himself. In others, he goes to a tool- or drawing-room window and waits while an attendant gets what he requires. In still other cases, everything is brought to him, and he does not have to leave his work station.
The exact procedure that is followed will depend upon existing conditions; but if it is possible to work out an economical system for furnishing the operator with what he needs at his work station, it is desirable to do so. Besides reducing costs, this procedure increases the amount of time the equipment is utilized and thus increases the productive capacity of the plant. Often a low-rated worker can do the errands of the operators and bring tools, drawings, and materials.
Where the group system is used and no supply boy is available, the group leader commonly gets all necessary supplies and tools. By getting the necessary items for several jobs at one time, he is able to effect economies.
If a conveyer system of the type illustrated in the preceding chapter is used, the jobs may be dispatched by the production department in the order wanted, and all material, tools, and drawings can be sent out at the same time on the conveyer. Thus the amount of time spent by the operator in
getting ready to make the setup or workplace layout is reduced to a minimum.
The manner in which instructions are furnished with regard to how the job should be done is worthy of careful consideration. In many cases, no instructions at all are given. The operator is supposed to be familiar enough with the work to know how to do it. If not, he may ask the foreman. When no definite instructions are given or when the foreman gives only brief general advice, the method that the operator follows is likely to be one of his own devising which may or may not be efficient. The fact that in so many cases different operators follow different methods in doing the same operation may be traced directly to insufficient instruction. To secure efficient performance, the best method must first be worked out and then taught.
Some plants employ instructors or demonstrators to perform the teaching function. If these men know the best methods themselves and are good teachers, good results will be secured. Too often, however, the instructor is merely an experienced operator who knows only such methods as he himself used before he was promoted. Even though he was a highly skilled operator, the chances of his knowing and being able to impart a knowledge of the best methods are small, unless he has received additional training himself in the principles of methods engineering. If he is a machine instructor, he is likely to teach feeds and speeds and the best way to grind tools, mentioning only briefly, if at all, the arrangement of the workplace and the motions that should be used.
Feeds, speeds, and the grinding of tools all are important, of course, but they constitute only part of the method. A lathe operator, for example, was engaged in turning shafts in an engine lathe. Each shaft had to be stamped with a number. The operator would remove a finished shaft from his lathe, turn to a bench, stamp the number, set aside the shaft, pick up another, and return to his machine. The turning required a long cut under power feed. A much better method is as follows: While a cut is being taken, the operator gets the next shaft to be machined; he places it on the machine ways in a convenient position; as soon as the cut is taken, he removes the finished shaft and inserts the other; he starts the cut and then while the machine is running, stamps and lays aside the finished shaft. Thus, the machine runs nearly continuously, and idle time on the part of both the operator and the machine is reduced.
The better procedure described will, no doubt, seem obvious to the reader, and it is, of course, standard practice in many plants. At the same time, the other method is encountered frequently in plants that have given little attention to methods and methods instruction. An experienced lathe operator going from a plant where the first method was common practice to one where the second was in effect would find it difficult to make satisfactory earnings in the second plant. If he were the only one doing this operation and so could not learn the better method by observation, he would be likely to feel that the rate was too tight and would become discouraged. Instruction in some manner with regard not only to feeds and speeds but also with regard to the proper motion sequence would be necessary to correct his difficulty.
Instruction sheets can be used to instruct operators and, under certain conditions, their use is not too costly. It gives complete and detailed instructions.
Setup. The setup of the machine and of any tools, jigs, or fixtures used should be studied in detail. The correctness and the adequacy of the setup should first be considered, followed by a brief review of the methods employed to make it. The correct setup is fixed by the nature of the operation, the nature of the part, the requirements of the job, and the mechanical features of the machine. Sometimes, it is possible to do a job in more than one way, and care should be taken to ascertain that the best way is being used.
When the setup is being made, certain tools are usually required. These should be suitable for the purpose. If each operator must make his own setup, he should be provided with the necessary tools. If only one or two wrenches are furnished to a group of 10 operators, for example, the time lost in hunting the wrenches and in waiting for a chance to use them will usually far offset the cost of additional equipment.
If setup men are employed to setup machines ahead of the operators, their setup work is to them fairly repetitive work, because they are performing the same elements day after day. It will therefore be desirable to treat it as such and to furnish the setup men with special-purpose quick-acting tools.
The Workplace Layout. The improvement of the layout of the workplace of the industrial worker is too often overlooked as a means for effecting operating economies. The layout of the workplace partly determines the method the operator must follow in doing a given task, and it almost wholly determines the motions he must employ. Since certain motions are more fatiguing and consume more time than others, it is quite possible to effect worth-while cost reductions merely by rearranging layouts. The rearrangement usually comes about as the result of detailed motion study. If the underlying principles which govern workplace layouts are understood by the analyst, however, a consideration of the workplace layout will show whether detailed motion study is likely to bring about improvement, and it may also suggest obvious improvements that can be put into effect immediately. For this reason, the principles which affect workplace layouts will be discussed briefly.
Two general concepts underlie workplace layouts. The first has to do with the classes of motions that a human being can make. There are five general classes, as follows:
1. Finger motions.
2. Finger and wrist motions.
3. Finger, wrist, and forearm motions.
4. Finger, wrist, forearm, and upper-arm motions.
5. Finger, wrist, forearm, upper-arm, and body motions.
It is usually stated that motions of the lower classes can be made more quickly and with less expenditure of effort than inotions of the higher classes. This, however, is true only when the motions are made under not greater than normal load over paths of approximately equal length. It might be possible by exerting a prodigious effort to lift a heavy object an inch or so with a finger movement; but the same object could be lifted the same distance in less time, and -with far less fatigue, by a finger, wrist, and forearm movement. Similarly, it may be seen that a short fourth-class motion can be made more quickly than a long third-class motion.
In applying the concept of motion classes to actual layouts, the attempt should be made to reduce all motions to the lowest possible class. This, of course, must be interpreted with common sense. In actual practice, with what has been said in the preceding paragraph kept in mind, there is no difficulty in recognizing the lowest practical class of motion that can be employed to accomplish any given task.
The lowest class of motion is the finger motion. If a job can be accomplished by using only finger motions, no further improvement can be made. The use of pure finger motions- only, however, is seldom practicable. In most layouts, the aim will be to eliminate all body movements, to reduce many fourth-class motions to the third class, and to reduce the length of all motion paths.
The second concept underlying workplace layouts is that of normal and maximum working areas. The area in which the worker performs his operation should be kept at a minimum, as this automatically keeps the class of motions which must be used in the lower classifications.
The principles of efficient work areas should be applied to all lines of work, for they are universal. It is customary to think of them in connection with bench operations; but they can and should be applied to the arrangement of tools and materials around machines or on work such as molding, forging, and the like, and to the arrangement of levers, handwheels, and so on, when designing machine-tool equipment. When the imaginary boundary lines that limit the normal and maximum working areas in all planes are clearly visualized, it is quite easy to detect inefficient arrangements of workplaces and to know exactly what steps must be taken to. bring about improvement.
When an analysis is made of a specific operation, one of the most glaring faults commonly encountered lies in the arrangement of containers of raw and finished material. If the placement is left to the operators, a body motion will often be used for getting or laying aside material, because the operator sets the material containers on the floor or the bench or in some other place that is available but not particularly convenient. Figure 71 illustrates a condition of this kind. The operator has placed a box of unfinished material on the floor beside his press. Every time he gets a part, he must bend his body, or in other words, must make a fifth-class motion. If before beginning the operation he were to place a stool beside his press and set the raw material box on it as shown in Fig. 72, he could then get the parts with a fourth-class motion. Thus, the time required for the element "get part" is reduced, and fatigue is partly eliminated.
Put Away. The put-away elements usually consume less time than the make-ready elements. Tools are put away, the setup is torn down, and the workplace is more or less thoroughly cleaned up. Usually, some of the put-away elements can be combined with some of the make-ready elements for the next operation.
Tools for one operation, for example, may be returned to the toolroom when the tools for the next operation are obtained. The procedure that will prove most economical for the put-away elements will depend to a large extent upon the manner in which the make-ready elements are performed.
Where a number of similar operations are performed on a machine, it is sometimes possible to use 'the same or part of the same setup on two or more jobs. A part that is common to several assemblies may be ordered separately for each and appear on several different orders. If these orders are grouped, one setup will care for them all. Again, in milling-machine work, for example, it may be possible to use the same cutter for several different jobs. The elements of "get cutter from toolroom/ ; "place cutter on machine, "remove cutter from machine" and "return cutter to toolroom" will thus be performed but once for the several jobs.
Where possibilities of this sort exist, provision should be made when setting up the make-ready and put-away routine so that the economies will be made. If the operator does not know what job he is to do next, if he must completely tear down his setup before going for another job, and if neither the foreman nor the dispatcher attempts to group similar jobs, advantage cannot be taken of partial setups. This is wasteful, of course, and every attempt should be made to secure the benefit of partial setups. Whether or not the operator is paid for the complete setup or only for that part which he actually makes depends upon the difficulty in controlling setups and upon whether or not the saving is due to the operator's own initiative. In either case, more time is available for productive work which is a distinct gain.
These common possibilities are indicated by principles of motion economy.
A good analysis of efficiency improvement opportunities has to include examining the 10 efficiency aids.
Gravity Delivery Chutes.
Gravity delivery chutes are useful for bringing material close to the point of use, thereby shortening the motions required to obtain the material. The usual arrangement consists of a hopper that will hold a reasonable supply of material with an opening at the bottom through which a few pieces may pass. Material may be removed directly from the opening at the bottom of the hopper. If the workplace is crowded, the hopper may be set out of the way and a chute provided between the bottom of the hopper and the point of use along which the parts may slide by gravity.
If parts are of a suitable shape, special delivery devices may be built that are more effective than the common chute. Small, uniform parts with no projections may be handled in an arrange-ment that delivers the parts at the bottom in predetermined quantities. The coin holders used by street-railway conductors, newsboys, and others who must make change frequently are a well-known example of this sort of delivery device.
Many parts are by no means free from projections or even symmetrical in shape. The design of chutes and hoppers that will handle irregular parts is more difficult, and considerable cutting and trying may be necessary before an arrangement can be devised that will deliver parts uniformly at a given point and will neither jam nor overflow. If the chute is used in conjunction with moving machinery, the delivery problem is much easier. Even the smoothest running machine has a certain amount of vibration, and if the chute Is rigidly attached to some part of the machine, the vibration mill cause the parts to move slowly and uniformly down the chute and even around bends.
Illustration: Chute used in conjunction with a trimming machine for a leather of machine.
As originally designed, the parts tended to jam in the hopper. Removing the key of the jam brought a rush of parts which sometimes overflowed the sides of the chute. The parts did not slide easily, and, therefore, the chute had to be steep. An angle sufficient to overcome starting friction was too steep when the parts were in motion, and the parts shot down so quickly that they were continually falling to the floor. These difficulties were overcome by slight design changes, but principally by attaching the chute to the machine so that the vibration from the machine kept the parts in motion. After this, the parts fed uniformly down the chute and arrived without interruption at a point where they could conveniently be grasped by the operator.
Drop delivery, as the name implies, consists of getting rid of a part by dropping it. It is used when placing finished parts aside. Sometimes, it is possible to arrange a setup In such a way that the finished part falls off into a container or chute as it Is completed, and the operator does not have to handle it after completing work upon it. For example, after completing the trimming operation on the machine, the operator merely opens his fingers, and the finished part falls into a box placed directly beneath the cutter. On operations where the finished part must be carried aside by the operator, drop delivery is still obtained if the part is carried over a container or a chute and is released by opening the fingers as the hand continues on its way to the next point, which is usually the raw-material supply. Not all parts can be dropped, of course. Fragile, brittle, or soft parts would be damaged if dropped with any appreciable jar. Even with parts of this kind, however, drop delivery can sometimes be used if the parts are dropped onto some sort of soft, yielding surface. A canvas chute may be provided, for example, which first breaks the fall of the part and then permits It to slide gently into a container.
When drop delivery is employed, the relative position of the raw- and the finished-material containers is Important. Many times workplace layouts are encountered In which the raw material Is close to the operator and the finished material farther away. This is Incorrect. The finished material should be closer to the operator and the raw material farther away and in the same line. When the operator finishes work on a part, he grasps the part. He moves toward the raw-material container and drops the part in the finished-material container on the way. With a little practice, he can do this without hesitation. Finished material is laid aside and raw material is obtained with two motions, one over to the raw-material container and one back to the work point. If the position of the material containers is reversed, three motions will be required, one to the finished-material container where the part is dropped, one to the raw-material container, and one from the raw-material container to the work point.
In order that parts may be dropped during a motion without hesitation, the object into which they are dropped must be large enough so that there is no danger of missing it. If the container itself is small or if the part must pass through a small hole in the bench, a funnel should be provided to make it easy to drop the part in the desired location.
Drop delivery suggests that the part falls away owing to the force of gravity. The same effect may be obtained by the use of springs that carry the released part aside, usually in an upward direction. The most common application of this arrangement is in the suspension of tools above the workplace. The tools are hung on a "spring. After the tool has been used, it is released by opening the fingers. The spring carries it away without further attention on the part of the operator.
A similar application of this principle may be made to the levers of small hand-operated arbor presses. When the handle of the press is released after the operation has been performed, a spring carries it out of the way and raises the arbor. The hand of the operator at the point of release is thus near the point where it must next go. Instead of some distance away as it would be if the hand had to return the press lever to the aside position.
Methods Used by Two or More Operators.
If no detailed instruction has been given, in at least 95 per cent of all cases observed by the authors, different operators on the same job will use different methods, even if the operation is fairly simple. The methods will all resemble each other, to be sure, but the trained observer will be able to detect many minor differences, and it is these differences that account for variations in production, fatigue, and quality of work.
As a matter of fact, where no specific instruction regarding proper methods has been given, it is not uncommon to see the same operator using two or three different methods on the same operation. Questioning fails to reveal the reason for this. Most operators do not seem to realize that they are using different methods. They have not been taught to regard their job as a series of elemental motions, and therefore an extra motion or two may be made without conscious recognition.
On repetitive work, considerable difference is found in the output of different operators doing the same operation. The usual tendency is to attribute this to differences in skill and perhaps effort. In reality, however, the difference is usually primarily due to a difference in method. The high producers have the best methods. These may have been developed as the result of long experience, or they may have been hit upon the first day on the job. The low producers have poor methods. These operators may be new to the work, or they may be old operators following a poor method from habit.
With proper operator instruction, this condition will not exist. If the best existing method is first recognized and then taught, all operators but the obvious misfits may be raised to the levels of the highest producers.. This can be done by any supervisor who is able to recognize different methods when he sees them and who realizes the difference that minor variations make. If he is sufficiently interested to decide which of several methods is best and to teach that method in detail to each operator in the department, he can raise the performance level of his department within a short time without any outside assistance.
It must be recognized, of course, that it is not always easy to teach operators new methods. Old methods, because of constant repetition, become habitual, and habits are hard to change. Very often, the easiest and best method will seem harder and slower to an operator than his own method. His production will fall off at first, and he will want to return to his own way of doing things. Patience and persistence on the part of both the operator and his instructor will overcome these difficulties, however, and a better performance and higher earnings will eventually result.
Chairs for Industrial Workers.
The subject of chairs for industrial workers has received a good deal of attention, and most progressive concerns have tried to do something along these lines. Interest in the subject is usually not sustained, however, and therefore the analyst often finds room for improvement. Many chairs designed for industrial use have been placed upon the market, some of which are good.
To minimize fatigue, work should be done alternately seated and standing. Although it is less fatiguing to work seated than standing, even the seated position becomes tiring after long periods of time. Therefore, a workplace arrangement that permits the operator to vary his position from time to time is the best from the standpoint of fatigue.
In order to permit the use of the same motions seated or standing, the height of the chair must be such that the elbows of the operator are the same distance from the floor when he is seated as when he stands. The proper height of the workplace should be determined while the operator is standing.
This is the ideal condition, and like many ideals, is difficult to attain under everyday conditions. Operators vary in size which makes adjustable chairs and even adjustable work-station heights necessary- Where two or more shifts use the same equipment, the problem is further complicated. A tall operator may work a given operation on one shift and a short operator on the next. For example, a certain plant operated a large sewing department on a two-shift basis. When the first shift finished work, all the operators were required to leave the department. Then ; after a signal was given, the second-shift operators entered. The first few minutes were occupied by a confused search for suitable chairs. The sewing machines were all the same height from the floor, and so each operator had to search for a chair that was adjusted so that it would enable her to assume a fairly comfortable working position. Considerable time was lost in starting work, and it was not always possible for an operator to find a suitable chair.
Variable conditions of this sort may best be met by providing equipment that is suitable for a certain size range. Chairs may be adjusted for several classes of operators as very short, short, medium, tall, and very taU. If the chairs are marked as to class and the operator is informed of the class to which she belongs, she will have no difficulty in locating a proper chair at the beginning of the shift, provided that a sufficient number of all classes is available.
The height of the workplace is a point that has received too little attention throughout industry. Benches are made to a standard height. Thus, when an operator stands at the bench, if he is short, he stands on a box or a platform if he can get one. If he is tall, he stoops and as a result has an aching back at the end of the day. Conditions of this sort should be corrected wherever found. A slight change in the height of a workplace will often result in more production of a better quality and a more satisfied and less fatigued operator.
An industrial chair, besides being adjustable for height, should have a wide seat from side to side and an adjustable back rest. If, however, the seat is wide from front to back, many operators will sit on the front edge of the chair and will not use the back rest. This apparently is. because, when one is sitting far back on a wide seat, the front edge of the chair presses the underside of the thighs, cutting off circulation from, the feet and legs and causing general discomfort. A tired back seems preferable, and so operators sit on the front edge of their chairs. This condition may be avoided by providing narrow seats not greater than 13 inches from front to back.
Ejectors and Quick-acting Clamps.
The possibility of improving jigs and fixtures and of providing ejectors, quick-acting clamps, and other time-saving devices should have been considered when the tool equipment was analyzed. The point is so important, however, that it is brought up for consideration again under item 7 of the analysis sheet so that it will not be overlooked. Quick-acting clamps, for example, materially reduce the time required to fix a part in a holding device. Ejectors kick the part out of the holding device and make the removal of the part easier.
Any time that an operation can be performed by parts of the body other than the hands, it should be so done, if there is other work that the hands can perform at the same time. In this way, the hands are relieved of performing certain motions, and time is saved. If, however, there is no other work for the hands to do, there is usually no point in transferring operations to the feet.
The foot-operated drill press is a common example of a foot-operated mechanism. The operator works the drill spindle by a foot pedal, leaving both hands free to place drilled parts aside and to get other parts to be drilled. Foot-operated ejectors are sometimes advantageous, as they leave both hands free to grasp the part as it is ejected. Vises may be opened and closed by foot with a considerable saving of time. When chips or cuttings must be removed from a fixture at the end of an operation, an air jet built into the fixture and controlled by a foot-operated valve may be provided. The possibilities for employing foot-operated mechanisms are many, and the analyst should constantly be on the watch for them.
Two-handed setups which permit the use of motions made simultaneously by both arms moving in
opposite directions over symmetrical paths are highly desirable, because they yield far greater output with the same or less expenditure of energy than do setups on which one hand only is able to work effectively.
Although when two-handed setups are once devised they are fairly simple to operate, it requires considerable ingenuity and a thorough understanding of the principles of motion economy to make them correctly. Two-handed-operation setups are usually made only after detailed motion study. The possibility of making such a setup should be considered during the analysis of all operations, however, for throughout the analysis process, the desirability of a subsequent more detailed study must be kept in mind.
Normal Working Area.
The concept of normal and maximum working areas (a principle of motion economy) has been discussed in under the head of "The Workplace Layout." If the arrangement of tools and material was not considered during the analysis of item 6, it should be studied during the analysis of item 7, for the proper arrangement of the workplace is highly important to effective performance.
Layout Changes and Machine Coupling .
(One operator manning multiple machines)
As the result of detailed analysis, the possibility of coupling machines may have occurred. Machine coupling or multiple machine operation is possible when the operator is idle during part of the operation cycle, usually because a machine is doing the work without attention on his part. The idle time can often be utilized in running another machine if the second machine is located near the first.
If no machine is available near by, it may be desirable to change the layout and move one or more machines about. It is usually best to avoid making many minor layout changes separately, for if all factors affecting the department as a whole are not considered, the layout is likely to become inefficient. Unless a change is obviously desirable and easy to make, it is better to accumulate suggestions for change until sufficient are at hand to make a detailed layout study advisable.
The possibilities for machine coupling are brought out by man and machine process charts. (discussed in another chapter). Plant layout is a study in itself. Some of the issues in related to making layout studies are described in another chapter.
Utilization of Improvements Developed for Other Jobs.
Each operation analysis should not be regarded as an entirely new investigation. Many different operations present points of similarity; if a good method has been worked out for one operation, parts of it may often be applied to another.
The handling of material costs money, and therefore it should be eliminated or reduced as much as possible.
The material must be transported to the work station, it must be handled by the operator before and after processing, and finally it must be taken away again. On a punch-press operation, for example, the processing time is the time required for the press to make a single stroke, is extremely small.. All the rest of the labor expended on the part is material handling.
Material handling adds nothing to the value of the part, although it does increase its cost. Therefore, a determined attempt should be made to reduce material handling to an absolute minimum.
The material-handling problem resolves itself into two natural subdivisions, the handling of material to and from the work station and handling at the work station.
Material Handling to and from Work Station. There are a number of different ways of transporting material to and from work stations, and the one which is the most effective and efficient will depend upon such individual conditions as the size of the material to be moved, the amount, the frequency of movement, and the distance transported.
The oldest, and probably even yet the most commonly employed method is movement through human agency. A move man or an operator carries or trucks material from place to place.
In certain instances, this is a proper and efficient method. For example, if a given material is so light and so small that a supply sufficient for 2 hours work can be carried in a container the size of an ordinary bread pan, a mechanical means of transportation would be uneconomical. The handling time during the process of manufacture between operations may be as little as 1 per cent of the total processing time, because of the large number of pieces that may be carried at one time. This could undoubtedly be reduced somewhat by relaying out the work space and arranging the operators so close together that they can pass material from one to the other without getting up. Even this Is not particularly desirable, however, for little if any real saving would be made. The operations performed on such parts are usually rapid and comparatively monotonous. Getting up and going for a fresh supply of material every 2 hours or so breaks the monotony and actually acts as a rest period by providing a change of occupation. If the, handling operation did not provide this interruption and rest, fatigue would cause the operators to seek it anyway by extra trips to the washroom or drinking fountain. Material handling on small parts that provides an occasional break during a monotonous operation is desirable, and no attempt should be made to eliminate it.
Hand Trucks. The larger the parts are, the more effort is required to handle them by hand. Added weight involves added muscular effort, and .added volume means more trips to transport
a given number of pieces. As weight and volume increase, trucks of some sort become increasingly desirable. . Human labor is required to push them from place to place, but they add to the effectiveness of that labor by making it possible to move a large number of parts easily and at one time.
Hand trucks are superior to no trucks at all, but they offer a number of disadvantages. They are bulky, and since they must be pushed through the aisles that are used by anyone who desires to go from one part of the plant to another, with or without material, they cause interference to easy movement and often serious congestion. Where only one aisle is available, empty trucks commonly flow back against the stream of loaded trucks. In addition, the trucks occupy considerable valuable floor space at the various work stations. The replacing of hand trucks by conveyers will often result in worth-while economies.
Electric Trucks. Electric trucks are used for much the same purpose as hand trucks. They require the services of an operator, but usually more material may be handled per trip, and handled faster. Electric trucks are made in a number of different styles, and special trucks are made for special applications.
Tractor-trailer Systems. When miscellaneous material must be transported to a number of different places located over a large area, electric trucks may be replaced to advantage by a
tractor-trailer train. For example, a train replaced eight electric trucks. Before its instal-lation, the electric trucks were used to transport material, some of them being assigned to- specific departments and some operated from a central point. Wherever material had to be moved, the electric trucks were used. The departmental trucks took finished material to other departments and usually returned empty. The other trucks were sent empty to whatever part of the plant they were needed. They did the required moving and then returned to the dispatch station empty. An earnest attempt was made by the dispatcher to route the trucks so that they were loaded as much as possible, but it was a difficult task. In addition, often when a rush call for service was received, all trucks were , and delays were frequent.
The installation of the tractor-trailer system reduced labor and greatly improved service throughout the plant. A route was laid out that took the train past every important material station in the plant. A regular schedule was set up, calling for several complete trips per day. The train moved along its route, drop-ping off trailers at the proper destinations and picking up others bound for different departments. Delays were reduced to a minimum, and each department knew, within a minute or two, the time it would receive incoming material or could ship outgoing material. A few of the old electric trucks were retained at first for emergency service, but the tractor-trailer system functioned so well and gave such rapid service that there was little call for
Conveyers are widely used throughout industry and, where they are properly installed to meet a definite need, will give worth-while economies. Considerable care must be taken to determine if a conveyer will really be an advantage before it is put in, for not all handling problems can be solved by this means. A shop superintendent was once heard to refer contemptuously to an elaborate overhead conveyer system as a "traveling storeroom/ 7 As a matter of fact, this is just what it amounted to. Because there was no real need for a conveyer in this department, it was used principally to keep unwanted material off the floor. Material would sometimes slowly circle the department for a week at a time before it was removed from the conveyer. This was wasteful, of course, and was the direct result of an improper installation.
There is a wide variety of kinds and types of conveyers offered by conveyer manufacturers for industrial use. Since conditions in every plant differ, all installations are in a sense special, but most conveyers designed to handle standard materials such as cartons, boxes, or tote pans are made up of standard sections or units. Gravity conveyers are in general cheaper than power-driven conveyers but, of course, require that the opposite ends of the conveyer be at different levels.
A conveyer does not have to be expensive or even purchased to be effective. Often a homemade arrangement of wooden boards will be as efficient as any conveyer that can be installed. On punch-press work, for example, where a product is made in several operations of approximately equal length, if the punch presses are set side by side, wooden chutes make excellent conveyers. At a given work station, the operator lays aside his finished part in the raised end of a chute. The part rolls or slides to the next operator and arrives in a position convenient for grasping.
Roller conveyers take advantage of the force of gravity to bring about material movement. The rollers run freely on ball bearings ; hence, a comparatively slight drop per foot of travel is necessary. If long distances must be covered, an occasional belt conveyer may be used to boost the material from the low end of one roller conveyer to the high end of the next. .
Other commonly used conveyers are the belt conveyer, , the spiral conveyer which may be either a roller conveyer or - a sheet-metal spiral with a steeper pitch, and the overbad chain conveyer. Many other types are alsQ^Ti|ilable, and special conveyers for almost any sort of specific material-handling problem can be obtained. Information and advice can be obtained from the leading conveyer manufacturers whenever an installation is contemplated. The main point to be decided upon first is the necessity for the conveyer. If a conveyer is desirable, a suitable type can be found.
Conveyers for Miscellaneous Work.
It is commonly felt that conveyers are applicable only where a standard product is manufactured in quantities. Under certain conditions, however, they may be used successfully to handle a miscellaneous variety of work. Figure 61 shows a conveyer running through a storeroom for finished material. A number of miscellaneous products are kept in this storeroom. When an order is received, material is taken from the shelves of the storeroom and is placed on the conveyer which takes it to a checker. When the order has been checked, other conveyers take it to various packing stations for packing and shipping. In spite of the variety of product handled and the number of ways in which orders are packed and shipped, a large saving was made by convey erizing the stores and shipping department.
Another and perhaps even more striking example of the use of conveyers on miscellaneous work occurred in a machine shop doing milling and drilling operations on small quantities of metal parts. Horizontal milling machines, vertical milling machines, and sensitive, radial, and multiple spindle drill presses were used, and there was a total of 51 machines in the department. Because of the small lot sizes, each machine worked on several different jobs each day. The order in which operations were performed was by no means fixed, for some jobs required drilling before milling, others milling before drilling, and others were milled, drilled, and milled again.
The former layout is shown in the upper half of Fig. 62. Material was moved about by laborers. They brought unfinished material to the various work stations and removed finished material. Material was piled about the machines and, besides occupying floor space, was decidedly unsightly. In addition to the material-handling problems, the matter of proper production control presented difficulties. In every shop, there are always certain jobs that are undesirable from the worker's viewpoint. When a number of jobs are available, the operators will choose the most desirable and will put off doing the least desirable as long as possible. Therefore, the production department has to be continually on the alert to prevent jobs being neglected until they become overdue.
A conveyer installation eliminated the move men and overcame production-control difficulties. All material is sent out from the central dispatch station, The dispatcher has a set of records which show when each job is wanted and what the operations are that must be performed. At the proper time,, he places material on the outgoing conveyer and by means of a control apparatus shunts it off on the proper lateral conveyer which takes it to the machines. When the operation has been completed, the material is put on a return conveyer located directly below the outgoing conveyer. The job returns to the dispatcher who sends it out to the next operation. In this way, a definite control of the order in which jobs are to be done is obtained. A definite check on the production of each man is available, and certain phases of the clerical routine are simplified.
Material Handling at the Work Station. When material has been brought to the general neighborhood of the work station, the from that point until the operation Is complete is usually done by the operator. When material is brought by truck f move men, or tractor-trailer train, he usually has to walk a varying .distance to the material and transport it to working position himself. Conveyers or overhead cranes usually bring the material close to the operator.
When the material is at the work station, it must be picked up and moved to the working position. The work is done, after which the material is set aside. When the job is finished, the complete lot of material may be removed from the immediate vicinity of the work station by the operator.
The exact procedure followed "will vary considerably with varying conditions and products; but unless the material is brought directly to the operator by conveyer and the work is done on the part while it is still on the conveyer, there will be a certain amount of material handling at the work station. This should be reduced as much as conditions permit. The initial and final moves can sometimes be shortened by rearranging the layout of the department. Material handling at the workplace can be reduced by detailed motion study.
Questions. The discussion of the material-handling problem given here is of necessity rather brief. No particular mention of such transportation devices as overhead cranes or elevators has been .made, for these are usually provided when necessary and are usually installed and working at the time the operation analysis is begun.
As a matter of fact, the analysis of a single operation seldom leads to the installation of a conveyer system or other expensive handling means unless the operation is highly repetitive. Usually it results in the installation of simple handling devices such as the gravity chutes or the development of special tote pans .or racks, which facilitate the handling of the particular job.
At the same time, the desirability of the more elaborate handling devices should be considered. If several analyses indicate that a conveyer system, for example, offers possibilities, then a more general study of material handling may be undertaken. These greater possibilities should be kept in mind during all analyses.
The Rules of Work: A Practical Engineering Guide to Ergonomics, Second Edition
CRC Press, Oct 23, 2012 - 196 pages
The experience of the past decade since the publication of the first edition of The Rules of Work: A Practical Engineering Guide to Ergonomics proves just how central ergonomics is for effective production. Revised and updated to reflect new insights from workplace developments, the second edition continues the tradition of providing essential tools for implementing good ergonomics in a way that simultaneously improves both productivity and safety.
In beginning the analysis of any industrial operation, the very first point that should be considered is the purpose of the operation. Why is the operation being performed?
In a number of instances where the authors (Maynard) have directed detailed studies of the operations performed on mass-production jobs, they have found that from 10 to 35 per cent of the operations were unnecessary.
In view of this experience, therefore, the logical point at which to begin an operation study lies in a consideration of the purpose of the operation.
Unnecessary Operations in Industry.
The reasons that unnecessary operations are performed in industry are several. In the first place, even the most standardized product at one time passed through the development stage. At the outset, the designer was the only one in all probability who thoroughly understood the product. When manufacture was begun, he had to tell the shop what was wanted through the medium of drawings and written and verbal instructions. This is not easy to do. No matter how clearly information is prepared, there are always questions that arise. Every designer has been called upon again and again to explain points that are clearly portrayed on his drawings. It requires a definite period of cutting and trying and developing before all the so-called "bugs" are worked out.
During this development stage, the operations by which the product is to be made are being devised. The operations are performed on a sort of hand-to-mouth basis; that is, one operation is performed before the next is considered. Even if an attempt is made to lay out in advance the proper sequence of operations on new work in the planning or methods department, difficulties are likely to develop in the shop that make changes necessary. The design may be changed, or the material, or the operations themselves as trouble is encountered.
As a result of this development condition, it is small wonder that the process is finally set up with certain unnecessary operations. These operations may have seemed necessary at one time, but owing to changes or development they are no longer necessary. Nevertheless, they are performed and are likely to continue in effect until, after the process has been reduced to a standard routine, someone with the questioning attitude comes along and begins an investigation.
After the initial-development state has been passed, manufacturing troubles are by no means over. A process may run smoothly for a number of months, and then suddenly a difficulty is encountered. The difficulty, of course, must be corrected immediately, and it is often much quicker to add an extra operation than to investigate the causes of the difficulty. If the operation corrects or seemingly corrects the difficulty, it soon becomes a standard operation, even if the causes of the difficulty disappear or are otherwise eliminated, and thus another unnecessary operation is born.
The difficulties referred to may be several. A shipment of poor or improperly prepared material may cause difficulties that can be eliminated only by extra work. The extra work may develop into a standard operation, even though good material is received in the future. If the product is an assembly, it may suddenly start to function improperly on test. If it is at all complicated, it may be difficult to determine just what the causes of the unsatisfactory performance are. Extra operations are added to overcome this or that supposed difficulty. When the product begins to function again, it is not always clear which operation corrected the difficulty and some or all are retained.
Those who are responsible for setting up manufacturing processes are no more infallible than other men. In the judgment of a certain individual, an operation may seem necessary, and he orders it to be performed. Regardless of the soundness of his judgment, the operation will continue to be performed until someone proves it to be unnecessary.
Again, certain operations are performed because of the snap judgment of someone who has the authority to enforce his decisions. Again and again, operations are discovered that are performed because an executive of the company in walking through the shop saw something of which he did not approve and at once issued orders that were followed ever since. When various department heads meet to consider a customer's complaint that may seem serious at the time, extra work may be insisted upon by the sales department and agreed to by the manufacturing department for reasons of policy. The cases of unnecessary work caused in this way are too numerous to attempt to list completely.
In the final analysis, unnecessary operations are due primarily to a lack of thorough investigation at the time the operations are first set up or to a natural inertia or an oversight that keeps operations in effect after changes have rendered them unnecessary. Detailed, searching analysis is needed to reveal these conditions, and it is this kind of investigation that methods studies bring. about.
It should be recognized, of course, that operations rendered unnecessary by new developments, inventions, improved machinery, and the like, are not being referred to here.
It is important to consider the purpose of the operation, but the mere question "What is the purpose of the operation?", mentally framed, may not be suggestive enough to develop a thorough understanding of the matter. If one approaches the supervisor in charge of the operation and asks the question, one will get an answer, of course, and usually the answer will appear logical on the surface. It is not until one begins to search and probe more deeply that the real answer is obtained. For this reason, questions similar to those contained in the following list should be asked. Further, they should be answered only after mature consideration, if the true answer is to be obtained.
1. What is the purpose of the operation?
2. Is the result accomplished by the operation necessary?
3. If so, what makes it necessary?
4. Was the operation established to correct a difficulty experienced in the final assembly?
5. If so, did it really correct it?
6. Is the operation necessary because of the improper performance of a previous operation?
7. Was the operation established to correct a condition that has since been corrected otherwise?
8. If the operation is done to improve appearance, is the added cost justified by added salability?
9. Can the purpose of the operation be accomplished better in any other way?
10. Can the supplier of the material perform the operation more economically?
In a plant manufacturing frames for automobiles, the last operation before painting consisted of reaming certain holes which had previously been punched in the frame. Two operators equipped with air-driven reamers stood at the end of the assembly line and reamed the holes as the frames passed them on a chain conveyer. It was a full-time job for both men and had been for several months.
During the course of a study of frame-manufacturing methods, the purpose of this operation was questioned. The thought at first was that it might be possible to punch the holes sufficiently closely to size to eliminate the reaming operation. Reference to the drawing, however, showed that the customer demanded reamed holes.
It would have been natural, perhaps, to consider that the question "Is the operation necessary? " was satisfactorily answered by the drawing. One of the methods efficiency engineers in the plant, however, realized the danger of accepting the first answer that came to hand and decided to investigate more thoroughly. He went out on the plant parking lot and located a car of the model that used the frame in question. To find the ultimate purpose of the reaming operation, he crawled underneath the car to see what the holes were used for and discovered that they were not used at all. Obviously, then, not only the reaming but also the punching of the holes was unnecessary.
Subsequent investigation showed that at one time an engineering change in the construction of the frame had been made which eliminated the use of the holes. Through an oversight, the drawing was not changed, and the reaming operation continued until the time of the investigation.
This incident, besides confirming the fact that errors are made in connection with manufacturing information, illustrates two important points. In .the first place, it shows the necessity of constantly questioning the purpose of operations. The reaming operation was performed day after day for a number of months.
It would be entirely natural to assume that the operation was necessary just because it had been done so long. Unless a man is trained to question every factor connected with the manufacturing process he is studying, he is likely to accept familiar operations as necessary and to concentrate upon better tools or methods for doing the operations, rather than to attack them from a more fundamental viewpoint,
In the second place, the case illustrates the necessity of applying the questioning attitude with a real desire to get at the bottom of the matter. The asking of a question will nearly always bring forth an answer. The first answer is quite likely to be superficial, however, and more thorough probing is necessary to learn the real facts. Hence, repeated questioning is necessary.
For example, the first question in the above list is "What is the purpose of the operation?" Asked in connection with the reaming operation, the answer is "To make the holes a certain specific size." This might seem to be an answer , but the trained analyst would follow up with the second question on the list, " Is the result accomplished by the operation necessary? " Reference to the drawing apparently evokes an answer in the affirmative. The .basic reason for performing the operation is still not clear, however, so the analyst asks the third question, "If so, what makes it necessary? " His investigation to determine the answer to this question finally uncovers the fact that the operation is absolutely needless.
For many years, it was the practice to polish the edges of the glass windows that go in the doors of automobiles. The reason given was that a good appearance was desired. It is true that edge polishing improves the appearance of a window glass, but only when it is outside the car. When it is assembled, as it is when the customer sees it, only the top edge shows in most designs of window. Hence, three-quarters of the edge-polishing operation is unnecessary. A smooth edge is required so that the window will not mar the channels in which it runs, but a polished edge is a refinement that is in no way justified. This fact was obvious as soon as it was pointed out, but until that time thousands of dollars were spent unnecessarily by a large manufacturer of automobile glass.
In the manufacture of an electric-clock motor, four small pinion shafts were pressed into a bakelite housing. The first shafts received from the supplier went in nicely. On subsequent shipments, however, difficulty was encountered. The shafts had a small burr on the end formed by the cutting-off tool. In order to use the shafts, it was necessary to add the operation "grind burrs."
This condition was taken up with the supplier by letter, but the supplier said that it was impossible to avoid the burr. There the matter rested until a methods efficiency study was made of the operation. Preliminary questioning brought out the above-mentioned story. The analyst, however, was not convinced that the shaft could not be produced without burrs. As a matter of fact, an investigation showed that a similar shaft used for the rotor of the motor was received from a different supplier without burrs. The first supplier was again asked if he could not furnish shafts without burrs, but he again answered in the negative. The analyst then suggested a change of suppliers. This was made, and shafts free from burrs were received thereafter. The first supplier had been too indifferent to attempt to improve his product. The easiest thing to do was to correct the supplier's shortcomings by adding an extra operation. The correct procedure, however, was to persist until satisfactory material was obtained.
A certain metal article manufactured in large quantities required a label of directions. This label was stuck onto the outside of the article. During the course of a study of the product, it was learned that the label was pasted on with flour paste. Several labels were placed face down on a cloth. Paste was applied with a brush, after which the labels were stuck in place. The analyst questioned the use of paste. He was told that gummed labels had been suggested and undoubtedly would be supplied in the future. He examined the labels being used at the time and found that they were coated with gum. Seven operators were engaged in applying paste to gummed labels.
This case illustrates the strength of habit and inertia. The original labels were ungummed. Therefore, paste had to be used. A suggestion was made that gummed labels be substituted. They w^ere accordingly ordered and when the supply of ungummed labels was exhausted the gummed labels were issued. No one but the operators realized, probably, that the new labels had arrived, and they proceeded to apply paste as before either without thinking or in order to appear busy in a department that was facing part-time operation.
A stamping, was made, was formed in a series of punch-press operations. On a certain order, the first two operations were performed on about 5,000 pieces. A rush order for another part was then worked on. The 5,000 partly completed pieces remained in temporary storage in the punch-press department and during that time picked up considerable dirt, including particles from the rush job which was made of metal screen.
As a result, when the job was put back in work again, considerable difficulty was experienced on the third operation. The operator had to wipe each blank clean with a rag before he could put it in his press and, of course, could not meet the regular time allowance. He complained to the time-study engineer who arranged to have a boy wipe the parts clean. The operator could then go ahead without interruption.
About two months later, the time-study engineer found that the parts were still being wiped off between the second and third operations, although the particular dirty lot had long since been completed. When he asked why the operation was being performed, he was informed that he himself had authorized it. The operation was, of course, absolutely unnecessary on subsequent lots, but so strong is the reluctance to abandon an operation after it has once been performed that it was necessary for the time-study engineer specifically to authorize its discontinuance.
If an operation is necessary, it can sometimes be accomplished better in some other way. The pinions on the previously mentioned electric clock contained burrs which in this case could not be eliminated. They were removed by picking them off with a pointed instrument. Tumbling them in a tumbling barrel removed the burrs equally satisfactorily at but a fraction of the former cost.
Occasionally , a consideration of a better way of accomplishing a certain purpose leads to a major design change. For example, the coils used in large turbo generators are made up of a number of turns of heavy strap copper. These are formed on a bending machine and form rectangles some 30 or 40 feet in perimeter. The last three turns of each coil have to be about -^ inch narrower than the other turns to fulfill insulation requirements. Formerly, it was the practice to remove the J-g inch of metal from the last three turns by hand filing, the equivalent of filing a strip of copper 120 feet long for each large coil. Thousands of hours were consumed on this work in the department making the coils. During the course of a methods study, the question was asked, " Can the purpose of the operation be accomplished better in any other way?" The operation was at length eliminated by a design change. The last three turns were made of narrower strap copper and joined to the heavier turns of the coil by a single brazed joint.
The battery cable discussed in Chap. IV was originally purchased in 200-foot lengths. It was made up into leads 49 inches long, and the first operation consisted of cutting the cable into 49-inch lengths. The operation was necessary, of course, but the suggestion was made that the manufacturer of the wire might have a better cutting-off method than the comparatively crude method then in use. Investigation showed that the wiremaking machine could be set to cut off the wire in 49-inch lengths as easily as in 200-foot lengths. Thus the cutoff operation was eliminated, and the wire was obtained in 49-inch lengths at no additional cost.
The examples just given demonstrate the fact that many industrial operations can be eliminated if proper investigation is made, It is much easier to add an operation, however, than it is to eliminate one. Even after an operation has been shown to be unnecessary, it is not always easy to obtain its discontinuance. Habit is strong, and there is a natural tendency to resist change. If a process is working smoothly, there is a decided reluctance to abandon any part of it. It is common experience that operations that are added, almost one might say on the spur of the moment, can be discontinued only after serious discussion on the part of a group of interested supervisors and usually only after someone in a fairly responsible position gives the order and accepts the responsibility.
Thereafter, for a time, the change is likely to be blamed for any difficulty that crops up whether there is any justification for it or not. This is a peculiar condition, perhaps, but one that any progressive shopman encounters again and again. Its existence should therefore be recognized. Resistance to change should be taken as a matter of course, and those who desire to make a change must be prepared to make an effort to get it adopted probably out of all proportion to the effort that would be required if human beings were not human beings.
At the same time, the man who prides himself upon being progressive must be careful that he does not adopt a similar attitude when changes are suggested in his own work that he himself does not initiate.