Chapter 10 Methods Engineering

Transcription

1 Chapter 10 Methods Engineering Areas of Application The application of methods engineering may be required in a variety of circumstances. It ranges from the design of a new plant, to the design of a new product, to the design of a new process, to the improvement of an existing process, to the improvement of an existing workplace. Wherever work is being done, methods engineering is a desirable function to ensure that the work is being done in the easiest, safest, and most productive way. Origin of Methods Engineering Methods engineering grew out of the pioneering developments of the Gilbreths (Frank B, and his wife, Lillian M.) who developed many of the tools of motion study as a part of formulation a systematic approach to the analysis of work methods. Frank B Gilbreth first become interested in methods analysis as an outgrowth of his observations of brick-lying. Gilbreth, who in 1885 was employed as an apprentice bricklayer, soon observed that a journeyman bricklayer used one set of motions when laying bricks slowly, another set when working at average speed, and still a different set when working at rapid speed. As a result of his observations, he invented an adjustable scaffold and developed a set of motions that greatly increased the number of bricks that could be laid in a day. Organization for Methods Engineering As indicated previously, methods engineering is a necessary function to ensure that the most efficient methods are being used. This activity is most frequently performed by industrial engineers; however, all engineers should be concerned with work methods. The engineers may be assigned to a central methods engineering or industrial engineering department or may be assigned on a decentralized basis to specific operating departments. Some multiplant companies maintain both a central industrial engineering group to work on problems common to many plants and also assign engineers to each plant to work on projects pertinent only to that plant.

2 Approach to Methods Design Charles E. Geisel States that in order to design a system (method) thoroughly, eight elements must be considered. 1. Purpose: The function, mission, aim or need for the system. 2. Input: The physical items, people, and/or information that enter the system to be processed into the output. 3. Output: That which the system produces to accomplish its purpose, such as finished steel, assembled toasters, boxes, and so forth. 4. Sequence: The steps required to convert, transform, or process the input to the output. 5. Environment: The condition under which the system operates, including physical, attitudinal, organizational, contractual, cultural, political, and legal environment. 6. Human agents: The people who aid in the steps of the sequence without becoming a part of the output. 7. Physical catalysts: The equipment and physical resources that aid in the steps of the sequence without becoming part of the output. 8. Information aids: Knowledge and information resources that aid in the steps of the sequence without becoming part of the output. To ensure that the optimum method is found, a systematic approach to methods design, superior to the use of a hit or miss method, is used. Stated in simplest form, this approach consists of the following steps: 1. Analyze the problem: Identify the problem and then secure all known information about it through the use of appropriate analysis techniques. 2. Question are present method. If a method presently exists, question the details of the known information to determine the principles violated. 3. Synthesize a proposed method: Formulate a proposed method for performing the work, embodying all the principles of sound methods engineering. 4. Apply the proposed method: Standardize and apply the new method.

3 Tools for Methods Analysis Name of Chart Flow Process Operation right and lefthand Simo- simultaneous motion chart Multiple activity worker and machine or crew Where Used Macro analysis; shows big picture of a production process operation by operation; may be performed by visual observation. Micro analysis: Shows steps performed by a worker within an operation; may be performed by visual observation. Fine micro analysis; uses threbligs for a very detailed analysis of human motions; usually makes use of videotape or motion pictures. Macro; may involve machines or several workers and time is of significance, may be performed by visual observation and/or videotape. Process Chart A flow process chart is a graphic symbolic representation of the work performed or to be performed on a product as it passes through some or all of the stages of a process. Typically, the information included in the charts is quantity, distance moved, type of work done by symbol with explanation, and equipment used. Work times may also be included. Right and Left Hand Operation Chart Symbol Name Activities Represented Operation Modification of object at one workplace. Object may be changed in any of its physical or chemical characteristics, assembled or disassembled, or arranged for another operation, transportation, inspection, or storage. Transportation Change in location of object from one place to another Inspection Delay Storage Examination of object to check on quality or quantity characteristics Retention of object in a location awaiting next activity. Not authorization is required to perform the next activity. Retention of object in location in which it is protected against unauthorized removal. Multiple Activity Chart

4 In those operations involving the combination of a person and a machine, a person and several machines, or any combination of people and machines where delays are prevalent, the multiple activity chart provides a convenient technique for analyzing the combined activity. Very often the objectives of this type of analysis are to attain the maximum utilization of a machine, to attain the optimum person to machine relationship, or to bring about the best balance of crew activity. For this reason, the time factor is an important consideration and necessitates the use of a graphical representation involving time. Use of Videotape In the past, the experienced methods engineer found that one of the most important aids was the use of motion pictures. There are many situations in which it is difficult to observe all of the action taking place because of the high speed of activities or the complexity of the operation. Having observed slow-motion motion pictures, we are familiar with the fact that one can take motion pictures at high speed and then, by projecting them at normal speed, slow the action down. By the same token, we can take the pictures at slow speed and project them at what appears to be high speed. In using motion pictures, methods engineers may have had several objectives in mind. First and foremost, they may have wanted a permanent record of the work as it was being performed. Or they may have wished to use the film for analysis purposes, commonly referred to as micromotion or memomotion studies, discussed in some detail in sections that follow. Micromotion Study Micromotion study, which was originated by Frank B. Gilbreth, is one of the most exacting forms of work analysis available for job improvement. It is an analysis technique making use of motion pictures (or videotape) taken at a constant and known speed. The film becomes a permanent record of both the method being used and the time consumed in doing the work. Although micromotion study formerly made use of motion pictures, very few companies today are using them. As indicated earlier, videotape equipment has been developed so extensively that it has virtually supplanted the use of the motion picture camera. Further it is so cheap and easy to use that it makes the older approach archaic. Micromotion study provides a valuable technique for making minute analyses of those operations that are short in cycle, contain rapid movements, and involve high production over a long period of time. Thus it is very useful in analyzing operations such as the sewing of garments, assembly of small parts and similar activities.

5 Memomotion Study Before leaving the general area of micromotion study, let us touch briefly on memomotion study. Memomotion study, which was originated by M.E. Mundel, is a special form of micromotion study in which the motion pictures or videotape are taken at slow speeds. Sixty and one hundred frames per minutes are most common. Memomotion study has been used to study the flow and handling of materials, crew activities, multiperson and machine relationships, stockroom activities, department store clerks, and a variety of other jobs. It is particularly valuable on long-cycle jobs or jobs involving many interrelationships. In addition to having all of the advantages of micromotion study, it can be used at relatively low film or tape cost (about 6% of the cost at normal camera speeds) and permits rapid visual review of long sequence of activities. Principles of Motion Economy Through the pioneer work of Gilbreth, Ralph M. Barnes and other investigators, certain rules for motion economy and efficiency have been developed. Some of the more important of these principles are the following: 1. The movements of the two hands should be balanced and the two hands should begin and end their motions simultaneously. 2. The hands should be doing productive work and should not be idle at the same time except during rest periods. 3. Motions of the hands should be made in opposite and symmetrical direction and at the same time. 4. The work should be arranged to permit it to be performed with an easy and natural rhythm. 5. Momentum and ballistic-type movements should be employed wherever possible in order to reduce muscular effort. 6. There should be a definite location for all tools and materials, and they should be located in front of and close to the worker. 7. Bins or other devices should be used to deliver the materials close to the point of use. 8. The workplace should be designed to ensure adequate illumination, proper workplace height, and provision for alternate standing and sitting by the operator. 9. Wherever possible, jigs, fixtures, or other mechanical devices should be used to relieve the hands of unnecessary work. 10. Tools should be prepositioned wherever possible in order to facilitate grasping them. 11. Object should be handled, and information recorded. Only once.

6 Job Enlargement and Enrichment This has led to the contention of a number of social scientists that hobs need to be enlarged or enriched. Feedrick Herzberg, one proponent of job enrichment, feels that the purpose of job enrichment should be to eliminate the undesirable characteristics of highly repetitive, specialized work by enlarging it to include: 1. Greater variety of knowledge and skill 2. Giving a person a complete natural unit of work (module, division, area, etc.) 3. More complex utilization of the important cognitive and motor abilities possessed by the worker. 4. More freedom and responsibility in the performance of the tasks at hand. Among the principles that commonly are applied in job enrichment programs, the following are attended to by one large company. 1. Ensure that there is variety in the job content. 2. Include in the work situation an opportunity for the worker to grow and learn. 3. Provide an opportunity for each worker to have knowledge of the part that his or her job plays in the total manufacturing process required to produce the product. 4. Design the work so that it has meaning to the worker and provides pride in performance to the worker. 5. Ensure that the work is reasonably demanding and functionally inclusive. Provide for self-direction of the work and for the checking of quality of output. Value Analysis As a part of the approach to methods improvement, the methods engineer should question the impact of the design of the parts, the materials used, and the equipment used on the productivity of operations. That is, the methods engineer should be thoroughly familiar with value analysis, an activity that is closely both to the methods improvement programs and to purchasing and that is being used extensively in industry and the government. Value analysis is an objective study of every item of cost in every component part, subassembly, or piece of equipment. This includes a study of the design, the material, and the process in a continual search for other possible materials and new processes. Value analysis involves the evaluation of an items function and relates its effect to the end product. The purpose is to attempt to ensure that every element of cost contributes proportionately to the function of the item.

7 Social and Economic Effects of method Study As pointed out at the beginning of this chapter, modern industry is constantly searching for better methods. When a business ceases to move forward, it will lost ground and may eventually fail. It is for this reason that the major companies have organized industrial engineering groups, work simplification and value analysis programs, suggestion systems, quality circles, and other methods of achieving reduced costs of manufacturing their products. One of the consequences of these programs has been increased mechanization, which, in turn, has led to the production of more and more goods per work hour. Among the long-range benefits derived from this increased output have been higher real wages, an improved standard of living, a shorter work week, and a reaction of the physical rigors of the job.