Machine Work Study - Machines and Tools Related Efficiency/Productivity Analysis
The machines, accessories and tools used to perform the operation needs to analysed logically to identify process improvement opportunities to increase productivity and engineering has to be done to modify the process to use new equipment, accessories, tools and modified equipment, accessories or tools.
_______________
_______________
________________
Some Questions regarding Machines, Tools and Equipment - Introduction
Can a foot device be arranged so that an operation now performed by hand can be done by foot?
Are raw materials properly placed? Are there racks for pans of material and containers for smaller parts? Can the parts be secured without searching and selecting? Are the most frequently
used parts placed in the most convenient location? Are the handling methods and equipment satisfactory? Would a roller or a belt conveyer facilitate handling? Can the parts be placed aside by means of a chute?
Is the design of the apparatus the best from the viewpoint of manufacturing economy? Can the design be changed to facilitate machining or assembly without affecting the quality of the apparatus? Are tools designed so as to insure minimum manipulation time? Can eccentric clamps or ejectors be used?
Is the job on the proper machine? Are the correct feeds and speeds being used? Would a bench of special design be bettor than a standard bench? Is the work area properly laid out?
Such questions examine th emachines, equipment and related aspects.
Relation of Machine Work Study - Industrial Engineering to Quality. Industrial Engineering and a method of it, machine work study focus primarily on eliminating waste and reducing costs. In so doing, it is imperative that nothing should be done to impair the quality of the finished product or
its saleability. F.W. Taylor particularly stated it explicitly and also in product industrial engineering method, value engineering L.D. Miles stated it explicitly. Industrial engineers exist and do their work to enhance the competitive position of his company's products, he quite naturally must take a keen interest in the factor of quality. Products of superior quality outsell products of inferior quality, other things being equal; hence, an improvement in quality is always desirable and efforts to preserve it are made by IEs. Industry engineer is quite likely to discover ways of making the product better. In addition, because he eventually sets up working methods that are easy, efficient methods, and because he trains all operators to follow those methods, a higher and more uniform quality of workmanship results than where each operator is left to develop methods for himself. As a result, therefore, methods study either of machine work or human work tends to raise the quality of the finished product.
Industrial engineers examines every detail in the engineering system or production system, that is likely to affect operating time and cost. Experience leads to the recognition of the points at which the greatest possibilities for improvement lie, and the major part of the study will be made on them.
In a machine shop, the term "setup" is loosely used throughout industry to signify the workplace layout, the adjusted machine tool, or the elemental operations performed to get ready to do the job and to tear down after the job has been done. More exactly, the arrangement of -the material, tools, and supplies that is made preparatory to doing the job may be referred to as the " workplace layout." Any tools, jigs, and fixtures located in a definite position for the purpose of doing a job may be referred to as "being set up' or as "the setup." The operations that precede and follow the performing of the repetitive elements of the job during which the workplace layout or setup is first made and
subsequently cleared away may be called "make-ready" and "put-away" operations. For the sake of clearness, the more exact phraseology will be used throughout this book, although the workplace layout, the setup, and the make-ready and putaway operations are all considered under item 6 on the analysis sheet.
The workplace layout and the setup, or both, are important because they largely determine the method and motions that must be followed to do the job. If the workplace layout is improperly made, longer motions than should be necessary will be required to get materials and supplies. It is not uncommon to find a layout arranged so that it is necessary for the operator to take a step or two every time he needs material, when a slight and entirely practical rearrangement of the workplace layout
would make it possible to reach all material, tools, and supplies from one position. Such obviously energy-wasting layouts are encountered frequently where methods studies have not been made and when encountered serve to emphasize the importance of and the necessity for systematic operation Analysis.
The manner in which the make-ready and put-away operations are performed is worthy of study, particularly if manufacturing quantities are small, necessitating frequent changes hi layouts and setups. On many jobs involving only a few pieces, the time required for the make-ready and put-away operations is greater than the time required to do the actual work. The importance of studying carefully these no-nrepetitive operations is therefore apparent. When it can be arranged, it is often advisable to have certain men perform the make-ready and put-away operations and others do the work. The setup men become skilled at making workplace layouts and setups, just as the other men
become skilled at the more repetitive work. In addition, on machine work it is usually possible to supply them with a standard tool kit for use in making setups, thus eliminating many trips
to the locker or to the toolroom.
The tool equipment used on any operation is most important, and it is worthy of careful study. Repetitive jobs are usually tooled up efficiently, but there are many opportunities for savings
through the use of well-designed tools on small-quantity work which are often overlooked. For example, if a wrench fits a given nut and is strong enough for the work it is to do, usually
little further attention is given to it. There are many kinds of wrenches, however. The list includes monkey wrenches, openend wrenches, self-adjusting wrenches, socket wrenches, ratchet wrenches, and various kinds of power-driven wrenches. The time required to tighten the same nut with each type of wrench is different. The more efficient wrenches cost more, of course, but for each application there is one wrench that can be used with greater over-all economy than any other. Therefore, it pays to study wrench equipment in all classes of work. The same remarks apply to other small tools.
Jigs, fixtures, and other holding devices too often are designed without thought of the motions that will be required to operate them. Unless a job is very active, it may not pay to redesign an inefficient device, but the factors that cause it to be inefficient may be brought to the attention of the tool designer so that future designs will be improved.
Under the head of "Setup," a description is given of the workplace layout and the arrangement of tools, fixtures, and so on. This description may be written if the setup is simple, but a photograph will be found more useful and infinitely clearer if the arrangement is at all complex. It would require several hundred words, for example, to describe the workplace layout pictured in Fig. 44, and even then it would be difficult to visualize the layout in its entirety. The picture tells the story at a glance and shows clearly the arrangement of the workplace at the time of the analysis.
When the machine setup is being considered, the tool equipment also is examined. The tools and the setup are so closely related that it is difficult to separate them, and nothing is gained by attempting to do so. In examining the setup of the milling machine, it is noted at once that a standard vise and a special side cutter are used. A description of these items of tool equipment is therefore recorded. Often, when tool equipment is examined with thoughts of job improvement uppermost in mind,
suggestions for improving the tool equipment will immediately occur to the analyst. These should be recorded as they arise, even though they may reoccur during the consideration of items 7 and 9. It is better to duplicate the small amount of writing involved than to risk the possibility of overlooking a good idea.
More Detailed Questions on Machine, Equipment and Tools
The tools and equipment used to perform the operation needs to analysed logically. The following questions are the sort that will lead to suggested improvements:
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.
Equipment.—A study of existing equipment may suggest changes and improvements or repairs. Machine operations should be those which combine economy with uniformity of standard quality. Standard times and methods are dependent upon standardization of machines within each class (using the best machines for operations), and the maintenance of normal conditions with respect to their upkeep. (https://nraoiekc.blogspot.com/2019/07/operation-study-arthur-g-anderson-1928.html)
Tools: For the most part, it may be said that the tools do function properly from the standpoint of the finished job. But from a productivity angle, industrial engineer has to examine the productivity possible from the existing tool and has to compare it with productivity possible from alternative tools to decide the appropriate alternative. Industrial engineers have to receive information regarding new tools from purchase department, representatives of organizations selling tools, consultants and technical literature being procured by the company. Industrial engineers have to monitor technology and engineering developments on a continuous basis and have to set up libraries for their departments or there have to sections within the company library for industrial engineering materials.
Similarly, whether, the jigs and fixtures etc. function properly from a motion-economy standpoint is subject to evaluation by industrial engineers. 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.
There can be alternative work holding methods that require less time to use. The common machine vise takes a lot of time set up the work piece. 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. Tool designers as a group are clever and 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. Too little attention to the hand tools used upon even the more repetitive operations. There is choice available in even simple hand tool as a screw driver from productivity point of view. 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 drivers. 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 screw head which offers many advantages. When all these factors are considered, the choice of the screw driver is important from efficiency or productivity point of view.
There is a screw driver that is better for a given application. For medium work with the conventional screw-head 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.
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. Time taken for the element is the decision criterion.
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.
Setup - Workplace Layout
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 "putaway" elements may carry the operator away from his workplace and should be questioned closely. In small-quantity lot work, these operations may consume more time than productive operation work. The necessity for trips to other parts of the department should be minimized.
Questions which will lead to suggestions for improvement of "Make-ready" and "Put-away" Elements are:
1. How is the job assigned to the operator (job card or ticket issue to operator)?
2. Is the procedure such that the operator is ever without a job to do (delays in giving job ticket)?
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, toolroom, 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 Js 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 overnight by covering it or locking up valuable material?
It may be seen that an analysis of "make-ready " and "put-away" operations covers a rather wide field. Some are related to operator work also. But they are mentioned here as they form part of set up and make ready the equipment step. Some of the steps are 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. 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 - Allocation of Jobs and Giving Instructions
The methods followed in giving out jobs differ widely throughout industry. Some procedure for telling an operator what job he is to work upon next must be provided. In some cases, material to be processed is placed near the work stations of a number of operators. The operators go to the material and themselves select the jobs they wish to do. This procedure has certain serious disadvantages. Some jobs are more desirable from the operator's standpoint than others. They may be easier or lighter or cleaner, some jobs may carry looser rates than others, thus permitting higher earnings for a given expenditure of effort. If the operators are allowed to pick their own jobs, those who have stronger characters or are physically superior are likely to get the best jobs, and the weaker must take what is left. The least desirable jobs will be slighted altogether as long as there is any other work to do, which causes these jobs to lag and become overdue. There is no assurance that the operators will get the jobs for which they are best suited, considering the group as a whole.
Where the group system is used, these difficulties are minimized, but principally because the group leader assumes a function of management and hands out the work to the members of his group. The group knows that sooner or later it will have to handle all jobs sent to it, and so there is less tendency to slight undesirable work. In the interests of good performance as a group, the skilled men will do the more difficult jobs, leaving the easier tasks to the new or less skilled men. In short, the entire
situation is changed; when the group system is used, the selection of jobs may be left to the workers themselves.
Another common procedure is for the foreman to assign jobs. The foreman knows the work, and he knows his men. Therefore, he is in a good position to distribute the work so that it will be performed most effectively. The chief difficulty with this arrangement is that the modern foreman is so loaded
with duties and responsibilities that he often does not have time to plan his work properly. In moments of rush activity, instead of always having several jobs ahead of each operator, he is likely
to assign jobs only when men run out of work. When a man comes to him for a job, he is likely to glance at the available work and assign the first job he sees that he thinks the operator can do. It may not be the one best suited to the operator; perhaps even more important, it may not be the job that fits most important from a delivery standpoint.
With regard to this last point, in order to get work through the shop on schedule, the planning or production department must work closely with the foreman. Usually, chasers or expediters call to the attention of the foreman the job that is required next. If there are only a few rush jobs, the foreman may be able to have them completed as desired. In times of peak activity, however, when the shop is overloaded, all jobs become rush jobs. Each expediter has a long list of jobs to be completed at once.
Considerable pressure is brought to bear upon the foreman to get out this job and that, and he is likely to find himself devoting time to detailed production activities that could better be spent on taking steps to relieve the congestion.
In most up-to-date plants, the foreman is regarded as a very important man. He is called into conferences and meetings and often participates in educational programs. He is, therefore, away from his department at intervals and, if he has the responsibility of giving out jobs, must give out enough work to last until he returns. If he is called away suddenly or is unexpectedly detained, operators will run out of work. Then they either lose considerable time and hence money which creates dissatisfaction, or they help themselves to another job. If this latter practice is countenanced in a time of emergency, there is a danger that it will soon develop into a standard practice. If men get their own
jobs, the foreman is relieved of a certain amount of work and, if he is otherwise overloaded, may tend to allow operators to select their work with increasing frequency, until all the advantages gained by having the foremen hand out work are lost. The decisions with respect to the order in which jobs are to be put through the shop are made by the planning or production department. Since they know in what order jobs are wanted, it would, therefore, appear that a representative of this department should cooperate closely with the foreman in giving out the work. The foreman may specify the men who are to work on each job when the orders first reach his department, and a dispatch clerk may give the work to the assigned men in the order of its importance from a delivery standpoint. This arrangement is followed in a number of plants.In typical dispatching station system under the control of the production department, time tickets for each operation on each job are made out in a central planning department and are marked with the date the operation should be completed. The dispatcher arranges these time tickets in his dispatch board. Each group of machines within the department is assigned a pocket the dispatch board, and each pocket has three subdivisions.
The time tickets are received considerably in advance of the material. They are first filed in a subdivision of the proper machine pockets called the "work ahead " division. The number of tickets in the "work ahead" divisions at any time gives a rough idea of the load on the shop. When material for a given job enters the department, the dispatcher is notified. He then moves the time ticket for the first operation from the "work ahead" division to the "work ready " division. The time tickets in the latter pocket then show the jobs that are actually ready to be worked upon. When an operator completes one job, he goes to the dispatcher's station and turns in the ticket for that job. The dispatcher then gives him another job by taking the time ticket from the "work ready" division and handing it to him. He selects always the ticket marked with the date nearest to the current date and thus gets the work done in the desired order.
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.
A conveyer system can be employed and 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 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 effective. 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 effective 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. 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.
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.
Many ingenious ways are tried to extend the time for doing a job during the course of a time study. Some changes are done in setup like belts may be loosened so that they slip under load, or a carbon steel cutter may be used in place of a higher speed alloy. In one incident of a time study on a milling-machine operation, the operator loosened the bolts slightly that held the vise to the machine table. When the cut was taken, the vise very slowly slid along the surface of the table, and of course, the time for taking the cut was extended. The time-study engineer, checked the feed and length of cut and found a discrepancy between his data and what the cutting time should be. It was difficult to detect at first where the trouble lay, but the vise eventually reached a point where it was noticeably out of position. Then it was reset it properly, and then restudied the job. Therefore industrial engineers have to examine the setuup and described it adequately in the standard process sheet.
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. 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 in motions of the higher classes.
The arc which bounds the maximum working area is traced by the fingers when the arm, fully extended, is. pivoted about the shoulder.
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, hand wheels, and so on, when designing machine-tool equipment.
In work place layout, 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. Industrial engineers can design an arrangement that minimizes motions and fatigue and thus save time and increase productivity.
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 tool room 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.
Setup - Workplace Layout
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 "putaway" elements may carry the operator away from his workplace and should be questioned closely. In small-quantity lot work, these operations may consume more time than productive operation work. The necessity for trips to other parts of the department should be minimized.
Questions which will lead to suggestions for improvement of "Make-ready" and "Put-away" Elements are:
1. How is the job assigned to the operator (job card or ticket issue to operator)?
2. Is the procedure such that the operator is ever without a job to do (delays in giving job ticket)?
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, toolroom, 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 Js 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 overnight by covering it or locking up valuable material?
It may be seen that an analysis of "make-ready " and "put-away" operations covers a rather wide field. Some are related to operator work also. But they are mentioned here as they form part of set up and make ready the equipment step. Some of the steps are 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. 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 - Allocation of Jobs and Giving Instructions
The methods followed in giving out jobs differ widely throughout industry. Some procedure for telling an operator what job he is to work upon next must be provided. In some cases, material to be processed is placed near the work stations of a number of operators. The operators go to the material and themselves select the jobs they wish to do. This procedure has certain serious disadvantages. Some jobs are more desirable from the operator's standpoint than others. They may be easier or lighter or cleaner, some jobs may carry looser rates than others, thus permitting higher earnings for a given expenditure of effort. If the operators are allowed to pick their own jobs, those who have stronger characters or are physically superior are likely to get the best jobs, and the weaker must take what is left. The least desirable jobs will be slighted altogether as long as there is any other work to do, which causes these jobs to lag and become overdue. There is no assurance that the operators will get the jobs for which they are best suited, considering the group as a whole.
Where the group system is used, these difficulties are minimized, but principally because the group leader assumes a function of management and hands out the work to the members of his group. The group knows that sooner or later it will have to handle all jobs sent to it, and so there is less tendency to slight undesirable work. In the interests of good performance as a group, the skilled men will do the more difficult jobs, leaving the easier tasks to the new or less skilled men. In short, the entire
situation is changed; when the group system is used, the selection of jobs may be left to the workers themselves.
Another common procedure is for the foreman to assign jobs. The foreman knows the work, and he knows his men. Therefore, he is in a good position to distribute the work so that it will be performed most effectively. The chief difficulty with this arrangement is that the modern foreman is so loaded
with duties and responsibilities that he often does not have time to plan his work properly. In moments of rush activity, instead of always having several jobs ahead of each operator, he is likely
to assign jobs only when men run out of work. When a man comes to him for a job, he is likely to glance at the available work and assign the first job he sees that he thinks the operator can do. It may not be the one best suited to the operator; perhaps even more important, it may not be the job that fits most important from a delivery standpoint.
With regard to this last point, in order to get work through the shop on schedule, the planning or production department must work closely with the foreman. Usually, chasers or expediters call to the attention of the foreman the job that is required next. If there are only a few rush jobs, the foreman may be able to have them completed as desired. In times of peak activity, however, when the shop is overloaded, all jobs become rush jobs. Each expediter has a long list of jobs to be completed at once.
Considerable pressure is brought to bear upon the foreman to get out this job and that, and he is likely to find himself devoting time to detailed production activities that could better be spent on taking steps to relieve the congestion.
In most up-to-date plants, the foreman is regarded as a very important man. He is called into conferences and meetings and often participates in educational programs. He is, therefore, away from his department at intervals and, if he has the responsibility of giving out jobs, must give out enough work to last until he returns. If he is called away suddenly or is unexpectedly detained, operators will run out of work. Then they either lose considerable time and hence money which creates dissatisfaction, or they help themselves to another job. If this latter practice is countenanced in a time of emergency, there is a danger that it will soon develop into a standard practice. If men get their own
jobs, the foreman is relieved of a certain amount of work and, if he is otherwise overloaded, may tend to allow operators to select their work with increasing frequency, until all the advantages gained by having the foremen hand out work are lost. The decisions with respect to the order in which jobs are to be put through the shop are made by the planning or production department. Since they know in what order jobs are wanted, it would, therefore, appear that a representative of this department should cooperate closely with the foreman in giving out the work. The foreman may specify the men who are to work on each job when the orders first reach his department, and a dispatch clerk may give the work to the assigned men in the order of its importance from a delivery standpoint. This arrangement is followed in a number of plants.In typical dispatching station system under the control of the production department, time tickets for each operation on each job are made out in a central planning department and are marked with the date the operation should be completed. The dispatcher arranges these time tickets in his dispatch board. Each group of machines within the department is assigned a pocket the dispatch board, and each pocket has three subdivisions.
The time tickets are received considerably in advance of the material. They are first filed in a subdivision of the proper machine pockets called the "work ahead " division. The number of tickets in the "work ahead" divisions at any time gives a rough idea of the load on the shop. When material for a given job enters the department, the dispatcher is notified. He then moves the time ticket for the first operation from the "work ahead" division to the "work ready " division. The time tickets in the latter pocket then show the jobs that are actually ready to be worked upon. When an operator completes one job, he goes to the dispatcher's station and turns in the ticket for that job. The dispatcher then gives him another job by taking the time ticket from the "work ready" division and handing it to him. He selects always the ticket marked with the date nearest to the current date and thus gets the work done in the desired order.
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.
A conveyer system can be employed and 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 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 effective. 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 effective 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. 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.
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.
Many ingenious ways are tried to extend the time for doing a job during the course of a time study. Some changes are done in setup like belts may be loosened so that they slip under load, or a carbon steel cutter may be used in place of a higher speed alloy. In one incident of a time study on a milling-machine operation, the operator loosened the bolts slightly that held the vise to the machine table. When the cut was taken, the vise very slowly slid along the surface of the table, and of course, the time for taking the cut was extended. The time-study engineer, checked the feed and length of cut and found a discrepancy between his data and what the cutting time should be. It was difficult to detect at first where the trouble lay, but the vise eventually reached a point where it was noticeably out of position. Then it was reset it properly, and then restudied the job. Therefore industrial engineers have to examine the setuup and described it adequately in the standard process sheet.
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. 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 in motions of the higher classes.
The arc which bounds the maximum working area is traced by the fingers when the arm, fully extended, is. pivoted about the shoulder.
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, hand wheels, and so on, when designing machine-tool equipment.
In work place layout, 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. Industrial engineers can design an arrangement that minimizes motions and fatigue and thus save time and increase productivity.
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 tool room 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.
Source: Operation Analysis by Maynard & Stegemerten, 1939
Full Knol Book - Method Study: Methods Efficiency Engineering - Knol Book
Modern Developments in Tools
2001
Duraspin Screw Fastening System increases productivity by 31%.
https://www.rsmeans.com/consulting/Senco.pdf
Updated 19 November 2019, 31 July 2019, 5 June 2019, 17 February 2019, 4 July 2015
First published 23 Nov 2011
Thanks for Sharing such imported information with us. I hope you will share some more info about tool related operation analysis. please keep sharing!
ReplyDeleteShape Design and Development Consultancy India
Further modified on 31 July 2019.
ReplyDeleteI read your blog on daily basis. This is really great and informative post. Thanks for sharing.
ReplyDeleteCivil Engineering Services
I Found your article very interesting I learned lot from your content So kind of you to provide us a knowledge of these important things really heplful, Check out our face mask brand Urban Secrets
ReplyDeleteIf you're looking to increase your machines and tools efficiency, you'll want to check out these methods. From improving your workflow to investing in new technology, these tips will help you get the most out of your equipment.
ReplyDeleteNice blog, great information you have shared. Professional static caravan accessories provider offers Caravan Parts, Spares & Accessories supplies at Excellent Prices With Fast Delivery. Visit Static caravan accessories shop in the UK.
ReplyDeletestatic caravan chassis parts