IE Chapter 2 Unit 1

Unit 1 Method StudyThe Definition and Content of Method StudyIn this unit we will discuss the method study mainly. We can define method study as the systematic recoding and critical examination of ways of doing things in order to make improvements. From the Figure 2.1, we can see that the main contents of the method study include process analysis,operation analysis and motion analysis.Steps of Method StudySelecting----the work to be studies & boundaries to be defined. Method study focuses on certain key operational types of work that should be targeted: such as bottlenecks, poor use of materials, poor layout, inconsistencies on quality, highly fatiguing tasks, high levels of unexplained employee complaints.Recoding----the relevant facts of the job to bt recorded. The main recoding techniques are by charts: including operations process chart, flow process chart, flow diagram, man-machine process chart, gang process chat and two-hand process chart.Examining and developing----the way the job to be performed. Inthis stage researchers should analyze the original system and design new methods to suit needs and abilities of operators, and these methods should be the most practical, economic, andeffective for that job.Six questioning techniques.Six questioning techniques are the primary tools, by which the critical examination is conducted. In the Table 2.1,we list the details of the six questioning techniques.Analysis with “ECRS” principles. When we design new methods for the current work or sistem, we should use the following principles flexibly:•Eliminate: when we could not find the satisfied answers through questioning “What has been down?”“Why is this operation necessary?”“Why is this operation performed in this manner?” these operation belong to unnecessary parts so they should be eliminated.•Combine: We should try to combine theseoperations or motions that could not be cancelled.•Rearrange: By the elimination and conbination, we can rearrange the work according the three quesstions “who,where and when” to get the greatest order and elininate the repetitions.•Simplify: The last idea is simplification. The simplest method and facilities are used to save the manpower, time and money after the above three necessary steps.Setup ----Setting up new standard work methods.Maintaining ----New method is maintained until it becomes the accepted norm.The Classificaions of Method StudyThere are three main classes of method study: process analysis, opeeration analysis and motion analysis.Process AnalysisProcess analysis is one of the main contents of method study, by which researcherscan comlietely observe and record the whole production processes and carry out integrated analysis from a macroscopic viewpoint.Operation Process ChartAn operation process chart is a process chart giving the general flow of all components in a product with symbols and inspections. The chart in itself is an ideal plant layout since each step is shown in its proper chronological sequence. It can record the sequence of operations and inspections, activity times and description of each activity and indicate the main activites involved in tasks. Using this chart people can gain understanding of tasks, eliminate unnecessary tasks or combine tasks. The convention of operation process chart is illustrated in the Figure 2.2.Flow Process ChartThere are five symbols that present flow process chart, as shown in the Table 2.2.They are also called ASME symbols.A flow process chart is a process chart setting out the sequence of flow of a product or a procedure by recording all events under review with appropriate process chart symbols. This chart expands the version of operation process chart with with all five ASME symbols.There are three types of flow process charts:•Worker type----records what the operator does.•Material type----records how material is moved or treated.•Equipment type----records how equipment is used.Flow process charts are used by the following six steps:1. SelectingSelecting a job is analyzed, possibly identified from operation process charts,.2. RecordingInspection, operations, delays, transports, storage, times, distances and sequence of activities are recorded on a flow process chart.3. ExaminingThe critical examination techniques are used to elimitate or combine operations or reorganize the sequence of operations.The additional techniques are possibly dicided to use, for example, flow diagrams are used to indicate the more information.4. DevelopingThe information and knowledge gained during recording and examining stages are used to develop a new sequence of operations.A flow process chart of the new sequence is produced.5. InstallingThe new flow process charts are used to explain proposed changees to managers, supervisors and operators----one of old sequence is compared with one of news.6. MaintianingNew flow process chart is keeping on working, new problems are found and a new turn inprovement is done.Example: one material type of flow process chart (shown as in the Figure 2.3).In addition to the symbols, descriptions aand distance are shown on the chart, the followinginformation should be included:Job: Machining of the shroud ang cooling holes of turbine blade, AX611.Chart begins: Unmachined blade in forge blade stores.Chart ends: Machined blade in finish part stores.Summary:: Operations 2Inspections 2Transports 4Storages 2Delays 2Flow DiagramA diagram or model, substantially to scale, shows the location of specific activities carries out and the routes followed by workers, materials or equipment in there execution. In the flow diagram, layout of work area and movements are recorded, ang the excessive distances, convoluted routes and non-value-added activities are indicated. Then the rearrangement of work area can be done to reduce the traveling distances and non-value-added activities.Operation AnalysisOperation analysis is used to study all productive and nonproductive activites within one operation at one place. Through studying elements of an operation, its purposes are to increase productivity per suit of time and reduce unit costs while maintaining or inproving quality. The difference between process analysis and operation analysis is that process analysis studies the whole production process and the end point is one activity within the operation. Operation analysis can be classified man-machine operaton analysis, gang process analysis and two-hand operation analysis.Primary Demand of Operation Analysis1. Reducing the quantities of operations to the lowest, arranging the processes with reasonable sequence and making every operation easiest by using the principles of ECRS.2. Exerting the function of two hands, balancing the burthen of two hands and avoiding holding work piece for along time and making use of tools to the utmost extent.3. Letting the machines do the most work.4. Reducing the operational cycles and frequencies, decreasing the transportation and transfer times of materials and cutting down the distance of transportation and moving, making the moving and transportation easily.5. Eliminating the unreasonable space and giving the worker enough workspace.6. Eliminating the unreasonable idleness time and realizing the synchronization work of the machine and operator.In a word, the objective of operation analysis is to arrange the reasonable work configuration, to reduce the labor strength of operators and to decrease the work time.Man-machine Operation AnalysisThe man-machine operation analysis is used to investigate, analyze the relationship of worker and machine in the operation cycle. These facts can lead to a fuller utilization of both worker ang machine time, and a better balance of the work cycle.Man-machine operation analysis uses the man and machine chart to show the exact time relationship between the working cycle of the operator and the operating cycle of the machine. So through analyzing the chart we can get new methods to reduce the idle time of worker and machine and to enhance the efficiency of the man-machine system.The relationship between workers and machines is usually one of three types: synchronous servicing, completely random servicing and a combination of synchronous and random servicing.Construction of time Man-machine ChartThe chart is composed of two parts. One part can be called the chart title such as man-machine process chart and other information including part number, drawing number, operation descripton, persent or proposed method, date and name of researcher in the top of the chart.And the other part can be divided into two sides. The left side shows the operations and time for the worker and the right shows the working time and the idle time of the machine or machines.Gang Process AnalysisIn the workplace, there’re always two or more than two workers operating with one machine or job, and then this operation is called gang process analysis. The gang process chart shows the exact relationship between the idle and operating cycle of the machine and the idle and operating time per cycle of the works who serves that machine. This chart presents the possibilities for improvement by reducing both idle operator and machine time.Two-hand Process AnalysisIn the workplace, worker’s two hands finish many concrete motions. Recording and studying these motions of two hands are called two-hang process analysis. The two hand process chart in which the motions of the worker’s hand (or limbs ) are recorded in an operating cycle to show the exact relationship between two hands’ movement. The purpose of the two-hand process chart is to present a given operation in sufficient detail that the operation can be analyzed and improved. In this part there is an example of two-hand process chart study. With this example you can learn to draw this chart and to master the analysis approach.Selecting: a task has been selected because it seems to be takeing too long time for such a relatively sinple activity.Recording: seen in Figure 2.4.Examining: the following are pickups with the critical examination technique: Question:1.Why is it necessary to hold the tube in the jig.2.Why should we cannot the tube be notched while it is being rotated instead of the righthand having to wait.3.Why does the tube have to be taken out the jig to break it.4.Why should we pick up and put down the file at the end of each cycle? Can’t in be held? Answers:1.The tube will always have to be held because the length supported by the jig is shortcompared with the total length of the tube.2.There is no reason why the tube cannot be rotated and notched at the same time.3.The tube has to be taken out of the jig to be taken because if the tube were broken bybending against the fase of the jig, the short end would then have to be picked out----an awkward opeation if very little were sticking out; if the jig were so designed that short end would fall out when broken, it would not then be necessary to withdraw the tube.4.Both hands are needed to break the tube by using the old method. This might not benecessary if a new jig could be devised.Figure 2.5 Two-hand Operation Chart ( Updated )Motion AnalysisMotion analysis regards one activity as target to analyze the motion in details. The main principle of motions analysis is to analyze, campare and research the motion of the operator’s hands, eyes and the other part of body, and then to eliminate the otiose motions, rearrange the necessary and effective motions to a standard set of motions with reasonable tools and layout.ThrebligsF.B. Gilbreth, the creator of motion study, divided the operations of main into 17 smallest units----threlligs ( to see the Table 2.3 ).Principles of Motion EconomyⅠPrinciples related to the use of human body1．The two hands should begin and complate their movements at the same time.2．The two hands should not be idle at the same time except during periods of rest.3．The motons of the arms should be symmetrical and in opposite directions and should be made simultaneously.4．Hand and body motions should be made at the lowest level of classifications at which it is possiable to work satisfactorily.5．Momentum of objects should be made use of to the most extent to help the worker.Whenthe muscle strength is required it should be reduced to the minimum extent.6．Continuous curved movements are to be preferred compared with straight-line motions involving sudden and sharp changes direction,7．“Ballistic”(i.e. free swinging) movements are faster, easier and more accurate than restricted or controlled movements².8．Rhythm is essential to the smoth and automatic performance of a repetitive operation.The work should be arranged to permit easy and natural with them whenever possiable.9．Work should be arranged so that eye movements are confined to a comfortable area, without the need for frequent changes of focus.ⅡPrinciples related to the arrangement of work place1.Definite and fixed stations should be provided for all tools and materials.2.Tools and materials should be pre-positioned to reduce searching time.3.Gravity feed, bins and containers should be used to deliver materials are close to thepoint of use as possiable.4.Tools,materials and controls should be located within the maximum working area and asnear to the works as possiable.5.Materials and tools should be arranged to operate the best sequence of motions.6.“Drop deliveries”or ejectors should be used wherever possiable, so that the operatordoes not use his or her hands to dispose the finished goods.7.Workplace should have adequate lighting and the type and height of a chair makeoperator have good posture and feel comfortable. The height of working-table or of a chair should be adjusted to suit alternate standing and sitting.8.The colors in the workplace should harmonize with that kind of the work and thus eyefatigue is reduced and operators feel comfortable.ⅢPrinciples related to tools and equipment1.The hands should be relieved of all work of “holding” the work piece where work canbe done by a jig, fixture or foot operated device.2.Two or more tools should be combined wherever possible.3.Where each finger performs some specific movement, as in typewriting, the loadshould be distributed in accordance with the inherent capacities of the fingers.4.Handles, such as cranks and large screwdrivers, should be designed by this way thatmuch of the suface of the handle can be contated by hands. This isespeciallynecessary when considerable force has to be put on the handle.5.Levers, crossbars and hand wheels on machinery should be placed in such positions inorder that operatorcan use them with the least change of body position and can makeuse of the greatest “mechanical capabilities”.Notes1. The work study is a integrative technology of engineering and management which canincrease the ratio of output without investment or with little investment, so it has been paidthe general attention of the industaial cirale for a long time.句意：方法研究是一项集工程与管理于一体的技术，其目的是寻求在不投资或少投资的情况下来提高生产效率，因而多年来在工业界一直受到普遍的关注。