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.
Full Knol Book - Method Study: Methods Efficiency Engineering - Knol Book
Updated 4 July 2015
First posted 23 November 2013