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Table of contents INDEX \e "" \c "1" \z "1025" 1. Laboratory Introduction22. Operation Analysis-Flow Process Chart53. Activity Chart (Right/Left Hand Activity Chart)124. String Diagram 165. Motion Study (Therbligs Technique)206. Direct Time Study Method257. Work Sampling Measurement Method308. Learning Curves Theory381. Laboratory Introduction1.1 Introduction XE "1.1 Introduction" This laboratory class aims to provide students with a general knowledge of work study and methods engineering. Also, the laboratory session is an introductory laboratory in which students obtain general knowledge of human factor engineering as well as the nature of experiments and laboratory exercises that are covered throughout the semester. Safety instructions that must be followed during each laboratory session will be explained and discussed with students. Work is an activity in which one exerts physical and mental effort to accomplish a given task or perform a duty. In fact, work study or methods engineering refers to the analysis and design of work methods, including the tooling, equipment, workplace layout, human activity, and environment. Work study aims to analyse a task’s contents to determine the time that should be allowed for a qualified worker to perform the task. Generally, there are several engineering methods to analyse task contents as well as different charts and diagrams to measure task time.Main objectives in methods engineering or work studyare:Increase productivity and efficiencyReduce cycle time Reduce product costReduce labour content Generally, there are six main steps to accomplish methods engineering or work study:Define the problem and objectivesAnalyse the problemFormulate alternativesEvaluate alternatives and select the best solutionImplement the best methodAudit the study (review the success of the method)In general, there are four main types of charts and diagrams that are used to analyse the task and operations: Operation chart: Graphical and symbolic representation of the operations used to produce a product. Process chart: Graphical and symbolic representation of the processing activities performed on something or by somebody. It includes a flow process chart, a worker process chart, and a form process chart.Flow diagram: represents the drawing of the facility layout with the addition of lines that represent the movement of materials or workers within the facility.Activity chart: A listing of the activities of one or more subjects (e.g., workers, machines) plotted against a time scale to indicate graphically how much time is spent on each activityThese charts and diagrams are commonly used to analyse existing operations, sequences of operations, or other work activities to make improvements. The main objectives of charting and diagramming techniques are:Reduce cycle time Eliminate unnecessary steps in an operation Mitigate safety hazardsImprove product qualityPropose new way to complete the operation or design new operations1.2 ObjectivesThe objectives of this laboratory session are as follows:To gain a general background and knowledge about work study definitions, work study methods, and its applications.To gain a wide description regarding to work study laboratory experiments, tools, and equipment that will be used in the experiments. To learn the various types of charts and diagrams used in work study and in this laboratory. 1.3Requirements (Individual lab report)A short laboratory report includes the following(Internet search lab):Work study definitions, objectives, methods, and applicationsThe different types of charts/diagrams that are used in work study to analyse operations and tasks. In brief, provide an explanation of the work measurements and methods (time study). A list of commercially available software tools that are used in the work study field to motion and time study.2. Operation Analysis-Flow Process Chart XE "2. Operation Analysis-Flow Process Chart" 2.1 IntroductionThe Flow Process Chart was developed many years ago as a means of listing out the activities performed by a worker, with quantities, times, and movement distances. In fact, flow Process Chart is chart that uses 5 symbols to analysis and detail the work performed on a material or work part through a sequence of operations and other activities. It uses five symbols to detail the work performed on a material or workpart as it is processed through a sequence of operations and activities (ASME, 1972):Operation (O) – Processing of a material, an object is changed intentionally, assembled or dis-assembled to/from another, or prepared for another process, or information is given or received.Inspection ( ) – Check for quality or quantity, an object is examined for identity, quality, or quantity.Move ( ) – Transport of material to new location, an object is moved from place to place, except as part of an operationDelay (D) – Material waiting to be processed or moved, The next planned step cannot take place immediatelyStorage ( ) – Material kept in protected location, an object is stored under some controlIn addition, the flow process chart is a simple half-text, half-picture method of showing the steps in a process, using symbols to indicate the type of action being taken and text to give details of the action. The Standard form for flow process chart is showed in Figure 1.This exercise plays an important part in forming a critical way of thinking about the design of work, that is, making full use of both hands, eliminating unnecessary tasks and delays, shortening distances, and simplifying the tasks involved. Such experiences aim to make the student critically aware of deficiencies and avoidable effort whenever work designs are examined, and help to develop a consciousness of the need for high productivity. There are five important questions that are used to improve the steps of process and contents of the flow process charts in order to reduce the waste time, effort and cost of the specific process. These questions are: Questions Related to MaterialMake or buy decisions: Should the part be produced in the factory or purchased from an outside vendor?Questions Related to Operations and InspectionsIs the operation time too high?Is the inspection operation necessary?Questions Related to MovesHow can moves be shortened or eliminated by combining or eliminating operations?Can the level of mechanization in material handling be increased?Questions Related to DelaysIs the delay avoidable?What is the reason for the delay? Can the reason be eliminated?Questions Related to StorageIs the storage necessary?Why can’t the material be move immediately to the next operation?Figure 1.Flow Process Chart There are three principal types of process charts:Flow process chart – analysis of a material or workpiece being processedWorker process chart – analysis of a worker performing a taskForm process chart – analysis of the processing of paperwork forms2.2 ObjectivesThe objectives of this laboratory experiment are as follows:To use the flow process chart type of task analysis to describe a two-operation process:First: to describe a simple assembly process task in a laboratory setting which simulates an industrial task process (laboratory experiment).Second: to describe a task process of changing a flat tire, this demonstrates a non-industrial task. This task will be given to a student with a text and video (non-laboratory experiment).32385834390Figure 1: Standard form of flow process chartObtain an improved solution and recommendations through critical questioning of the contents of the chart for the both tasks: assembly and tire change.2.3 InstrumentA wooden plate and two uprights have small wooden plates with 6 bolts for each upright plate and each bolt has nuts and washers (Hand tool dexterity test, model 32521, Lafayette Instrument, US; see Figure 2) for a total of 12 bolts. The device has the following dimensions: 0.76×0.40×0.40 m. The wooden plate simulates the assembly task because this type of task is common in many different factory jobs, particularly in the industrial sector, and the operator can assume an awkward posture to perform this type of task. Two types of hand tools (10-inch Crescent wrench and screwdriver) are used to fix the bolts to the wooden plate (see Figure 2). 2000251470025A digital stopwatch (Dad-7141, China) also records the time to complete a task. The stop watch has these features: 10-500 laps and split memory with 1/100sec memory recall during operation, calendar and time (12/24 hour format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water resistance (See Figure 3). 10477579375Figure 2: Assembly wooden plate, hand tools and bolts with nuts and washers. 199072595885Figure 3: Digital stopwatch. (Dad-7141, Japan)2.4 Experiment Procedures (assembly task)The experiment procedures are as follows (group work):Participants are given a brief introduction to the experiment in order to familiarize themselves with the procedure. They are provided with instructions and advised on how to assemble the wooden plates.Participants devise an assembly procedure in which the work is done largely by the dominant hand, and helped by the other hand. One student in the group assembles all the components supplied (without any arrangements for the bolts, nuts, washers and hand tools). In one plate assembly the student is required to fix 12 complete bolts sets (consisting of bolts, nuts and washers) with different sizes on both upright plates. The students must work at a pace that can be maintained for an 8 hours shift. Assuming that pay is $25 per hour; he needs to complete 75 assembled plates during the shift.A second student records the time to complete each assembly (i.e., the cycle time) as well as the time to affix each bolt as an element times or subgroups of element times. These times are recorded in the flow process chart as illustrated previously in Figure 1.A third student records the order of operations in the flow process chart and any events of note, such as bad parts or a difficult insertion task.As the group repeats the assembly task and similar measurements, they need to arrange the components in individual bins depending on the type and size of bolt and hand tools in a line in front of the student.2.5 Non-industrial process task (Tire change task)In this exercise, the group needs to use the flow process chart to describe the steps of the service task which is changing a flat tire (non-industrial task). The exercise is:A motorist experienced a flat tire on the driver side rear wheel of his car and went through the following procedure to replace the flat tire with the spare. The tire change occurred in the middle of the day in his own driveway about six metres in front of his garage. He first secured the other three wheels of the car with three bricks from his garage to prevent the vehicle from rolling (two trips back and forth to the garage) with a distance of 11.5m. He then took out the jack, crank, and lug nut wrench from the trunk of the car, traveling a distance of 1.5m. He then removed the spare tire from the trunk and placed it near the rear left wheel with a time of 1.04 min. Next, he proceeded to position the jack under the car at the recommended support beam on the car frame with a time of 0.44 min. He then began to turn the crank to elevate the car with a time of 1.09 min. After the left rear portion of the car was lifted a few inches, but before the flat tire was lifted from the driveway surface, he used the lug nut wrench to loosen the five lug nuts securing the tire to the wheel hub with time 0.85 min. He then returned to the task of elevating the car, turning the jack crank until the flat tire was completely off the driveway surface (0.92 min).The next step was to remove the loosened lug nuts, placing them in a nearby position within reach (0.12 min). The flat tire was then removed with time 0.10 min and lifted into the trunk with a distance of 2.5 m. The motorist then moved the spare tire into position with a distance of 2.5 m and lifted it onto the five studs protruding from the wheel hub with a time 0.22 min. He then reached for the five lug nuts, one at a time, placing them onto the studs and rotating them until finger tight (0.60 min). The lug nut wrench was then used to tighten the five nuts with a time of 1.01 min. With the tire secure, he proceeded to lower the car by cranking the jack down slowly until the spare tire supported the car with a time of 1.14 min. For good measure, he again tightened the five lug nuts now that the car was securely on the ground (0.62 min). He then collected the hardware (0.09 min), put it back into the trunk (2.5 m), and removed the bricks from the other three rear right tire, front right tire and front left tire wheels with a distance of 1.5, 3.6 and 1.5, respectively. Then, he put them back into his garage with distance 9 m. Document this tire changing procedure using a worker process chart.2.6 Results of the ExperimentA laboratory report includes the following:Compile a description of the assembly task on the Flow Process Chart (Figure 1). Get the mean time for the cycle; add in the transport distances (if possible) and totals and list all the actions required. Also, you need to add the worker costs for an 8-hours shift.Provide the flow process chart for the new design of the assembly task as mentioned in step 7 (section 2.4). Get the mean time for the cycle; add in the transport distances (if possible) and totals and list all the actions pile a description of the tire change task on the Flow Process Chart (Figure 1). Get the mean time for the cycle; add in the transport distances (if possible) and totals and list all the actions required.3. Activity Chart (Right/Left Hand Activity Chart) XE "3. Activity Chart (Right/Left Hand Activity Chart)" 3.1 IntroductionIn general, the activity chart is a listing of the activities of one or more subjects (e.g., workers, machines) plotted against a time scale to indicate graphically how much time is spent on each activity. There are various types of activity charts and the right/left hand activity chart is one of the common activity charts that are used to describe the manual repetitive task such as manual assembly task. -5048251252855The usual is to provide brief descriptions of the work activities against a vertical time scale. The activities in the activity charts are indicated by vertical lines or bars instead of using symbols for the work activities as in the other charting such as process charts. When the bars are used, they are shaded or colored to indicate the kind of the activity being performed as illustrated in Figure 1. Figure 1: Shading Formats for Activity ChartHowever, the right-hand/left hand activity chart explains the left and right activities during performing a task that is highly repetitive. The chart includes four columns one column for the right hand, second column for the left hand and the other two columns for the time (min) and total task cumulative time (min) as shown in Figure 2 also, represents the Standard Form for right-hand/left hand activity chart. The right-hand/left hand activity chart is also, called Workplace Activity Chart since it is usually describes a repetitive task which is performed at single place such as assembly task in production line. The main objective of this activity chart is to achieve a more even balance of the workload during task performing between the right and left hands.Left hand (activity description)Time (min)Right hand (activity description)Cumulative time (min)Figure 2: Standard Form of Right /left Hands Activity Chart3.2 ObjectivesThe objectives of this laboratory experiment are as follows:To understand and use the activity chart (Right/Left Hand Activity Chart) while performing a task:To describe a simple assembly process task in a laboratory setting that simulates a simple repetitive task, such as a basic assembly task (laboratory experiment) and create an appropriate right/left hand activity chart for the simple repetitive task.Understand how to improve the simple repetitive task's activities and create the proposed right/left hand activity chart for the improved activities. 3.3 InstrumentThe Grooved Pegboard (Simple assembly tool test, model 32025, Lafayette Instrument, US; see Figure 3) is a manipulative dexterity test that consists of 25 holes with randomly positioned slots. the pegs are keyhole-shaped must be rotated to match the hole before they can be inserted, requiring more complex visual-motor coordination. A digital stopwatch (Dad-7141, China) also records the time to complete a task. The stop watch has these features: 10–500 laps and split memory with 1/100sec memory recall during operation, calendar and time (12/24 hour format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water resistance (See Figure 4). 297180016129095250085090Figure 3:Grooved pegboard tool and pegs. 199072595885Figure 4: Digital stopwatch. (Dad-7141, Japan)3.4 Experiment Procedures (simple repetitive assembly task) The experiment procedures are as follows (group work):Participants are given a brief introduction to the experiment in order to familiarize themselves with the procedure. They are provided with instructions and advised on how to insert the pegs inside the holes.In the first part of the experiment (present method), one student in the group needs to hold the board with his left hand and is required to pick up the peg and then insert it into the hole in the board with his right hand.The student needs to insert 25 pegs in order to complete the assembly. A second student records the order of left- and right-hand activities in the right/left hand activity chart form. At the same time a third student records the time for each activity that the subject needs to complete the assembly task.The group then repeats the repetitive assembly task and similar procedures, but in the second part of experiment (proposed method), the student needs to put the board on the table and then put the first 12 pegs near his right hand and the other 13 pegs near his left hand. After that, the subject he needs to pick up the pegs and insert them into the holes with both hands, simultaneously. The other two students are required to record the descriptions of the activities for both hands as well as the time, as mentioned in step 4.3.5 Results of the ExperimentThe laboratory report includes the following:Construct a right-hand/left-hand activity chart for the present method and record the cumulative time of the task.Construct a right-hand/left-hand activity chart for the proposed method and record the cumulative time of the task.State the results summary for both the present and the proposed methods.4. 4. String DiagramIntroductionThe string diagram is a scale plan or model on which a thread is used to trace and measure the path of workers, material or equipment during a specified sequence of events. The string diagram is mostly used for studying workers’ movement.The work study person observes the movement of a worker over enough period of time. The observations may be recorded in a simple movement study sheet. Then, the string diagram can be constructed. The examination of the diagram and the development of the new layout can now proceed with templates being used and the pins and templates being moved around until an arrangement are found by which the same operations can be performed with a minimum movement between them.The string diagram is a useful aid in explaining proposed changes to management, supervisors and workers.4.2 ObjectivesThe objectives of this laboratory experiment are as follows:To understand the concept and the technique of String diagram.To let students practice on the construction of string diagram from data submitted in a movement study sheet. Figure 1: movement study sheet4.3 MaterialsPieces of cork (50cm*50cm) or biggerPinpointsPiece of string Figure 2: Pieces of cork Figure 3: PinpointsFigure 4: Piece of string4.4 Experiment ProceduresEach group has to construct 2 string diagrams using the tools given:Participants are given a brief introduction to the experiment. They are provided with instructions and advised on how to construct a string diagramUsing the data presented in the submitted movement study sheet. The students required to put the pinpoints on the cork as the work layout and make connection between the pinpoint using the string step by step. After that they need to determine the length of the string used in the process.The students will construct another string diagram by using another piece of cork and pin points but they need to make a change in the position of pinpoints to make the string used shorter than before by the same way of connections. In other words, the second diagram shows the proposed improvement in layout. Figure 5: work layout4.5 Requirements Construct a string diagram for the work layout given in the class by using the material described above.Construct a string diagram for the work developed (improved) layout by using similar set of material.Make a comparison between the diagrams and the length of the strings used to show how long moving distance you saved.5. Motion Study (Therbligs Technique) XE "5. Motion Study (Therbligs Technique)" 5.1 IntroductionMotion study is an analysis of the basic hand, arm, and body movements of workers as they perform work. Frank Gilbreth was the first to analyze and classify the basic motion elements. He called each hand motion a therblig. Therbligs is spelled backward except for “th”. Therbligs are Basic building blocks of virtually all manual work performed at a single location (so the primary interest is the hand motions). Therbligs involved 17 letters symbols that are descriped the hands motion (right and left hands motion) of worker while perform a manual task (i.e. hand tasks). The list of 17 therbligs symbols are: Transport empty (TE) – reach for an object with empty hand – today we call it “reach”. Grasp (G) – grasp an object by contacting and closing the fingers until control has been achived. Transport loaded (TL) – move an object with hand and arm – today we call it “move”.Hold (H) – hold an object with one hand. Release load (RL) – release control of an object.Use (U) – manipulate/use a tool.Pre-position (PP) – position object for next operation.Position (P) – position object in defined location.Assemble (A) – join two partsDisassemble (DA) – separate multiple parts that were previously joinedSearch (Sh) – attempt to find an object using eyes or handSelect (St) – choose among several objects in a group (hand-eye coordination is involved) Plan (Pn) – decide on an action (a short pause or hesitation ???? in the motions) Inspect (I) – determine quality of object using the eyes Unavoidable delay (UD) – waiting due to factors beyond worker controlAvoidable delay (AD) – worker waitingRest (R) – resting to overcome fatigue.Ineffective therbligs:Physical Basic Motion Elements: Hold Pre-positionPhysical and Mental Basic Motion Elements: Position Search SelectMental Basic Elements: PlanDelay elements: Unavoidable delay Avoidable delayThe therbligs classified into two main sections; effective therbligs and ineffective therbligs and these classifications are:Effective therbligs:Physical Basic Motion Elements: Transport empty Grasp Transport loaded Release load Use Assemble DisassembleMental BasicElements: InspectDelay Elements: RestIn general, Therbligs include physical elements such as transport, grasp assembly and it refers to any activity that needs physical hands movements. Also, therbligs include mental elements such as position, search and select and it refers to any activity that needs to information process and visual effort rather than physical effort. Micromotion Analysis is analysis of therbligs that make up a repetitive task and the standard form of therbligs showed in Figure 1. The objectives of therbligs analysis are:Eliminate ineffective therbligs if possible; for example, eliminate the need to search for parts or tools by positioning them in a known & fixed location in the workplace.Avoid holding objects with hand – Use workholderCombine therbligs – Perform right-hand and left-hand motions simultaneouslySimplify overall method resequence of therbligs in the cycleReduce time for a motion, e.g., shorten distance of therbligs such as transport loadedSeq. of activitiesLeft handTherbligsRight handCumulative TimeFigure 1: Standard Form of Therblig Analysis Sheet5.2 ObjectivesThe objectives of this laboratory experiment are as follows:To understand and use the therblig analysis technique for hands motion while manual assembly task and create the present therbligs list of right and lift hands while perform a simple assembly task.To learn the various symbols of therbligs that used to analysis the hands motion activities.Understand how can make improve in the therbligs symbols in order to improve the hands motion activities and create the proposed list of therbligs chart for an improved activities of right and left hands activties. 5.3 InstrumentRoeder Board Manipulative Aptitude Test (Model 32026; Lafayette Inst. Company; see Figure 2) is the test that uses to measure hand, arm, finger dexterity, and speed. The board of the roeder board has four receptacles for holding washers, rods, caps, and nuts. The performance board also is comprised of a horizontal T-bar and 40 inserts arranged in a predetermined pattern.5232401228725A digital stopwatch (Dad-7141, China) also records the time to complete a task. The stop watch has these features: 10-500 laps and split memory with 1/100sec memory recall during operation, calendar and time (12/24 hour format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water resistance (See Figure 3). 3086100209550Figure 2: Roeder Board (Model 32026; Lafayette Inst. Company) and four receptacles for holding washers, rods, caps, and nuts. 1990725180975Figure 3: Digital stopwatch. (Dad-7141, Japan)5.4 Experiment Procedures (Cutting saw machine task) The experiment procedures are as follows (group work):1. Participants are given a brief introduction to the experiment in order to familiarize themselves with the procedure. They are provided with instructions and advised on how to insert the pegs inside the holes.In the first part of the experiment (present method), one student in the group needs to assemble all four parts washers, rods, caps, and nuts together and insert into the hole in the board after pick-up these parts from pin that placed in the front of the student. Note: In the current method all the four parts washers, rods, caps, and nuts are placed in one pin together. The student requires to repeat this activity for 8 times which means that he needs to complete 8 assembly tasks and assemble only 8 holes in the board. A second student records the order of hand motions (right and left hands) of the student activities (e.g., reach, search, grasp, transport loaded, position, assemble and etc.) as mentioned previously. At the same time a third student records only the cumulative time of each complete assembly cycle that means he needs to records the cumulative time for 8 cycles. The group need to complete all the hands motions data of both hands as well as the cumulative time in the form of Therblig Analysis Sheet.As the group repeats the assembly task and similar procedures, but in second part of experiment (proposed method) the students need to arrange and separate the four parts washers, rods, caps, and nuts and place each part the identified location on the board and also, they can combine the washers and nut together and put both on the T-bars to reduce the time and effort of search and assemble. 5.5 Results of the ExperimentA laboratory report includes the following:Construct a Therblig analysis sheet chart for the present method and complete the cumulative time of the task.Construct a Therblig analysis sheet chart for the proposed method.6. Direct Time Study Method XE "6. Direct Time Study Method" 6.1 IntroductionDirect Time Study is a direct and continuous observation of a task using a stopwatch or other timekeeping device to record the time taken to accomplish the task. Direct time study is also known as stopwatch time study method. The direct time is one of the most work measurements that uses to determine the standard time of a task. However, while observing and recording the time, an appraisal of the worker’s performance level is made to obtain the normal time for the task. Since, the performance rating in this method is important in order to determine the standard time. The normal time in this method obtain by multiply the observation time of the work element with worker performance rating in percentage. The data are then used to compute a standard time for the task after adding the PFD allowances (personal needs, fatigue and delay allowance time). The direct time study is much more appropriate for repetitive tasks (batch and mass production). In order to implement the direct time study (DTS) the work study engineer should follow the following procedures:Define and document the standard methodDivide the task into work elementsTime the work elements to obtain the observed time TobsEvaluate worker’s pace relative to standard performance to obtain normal time TnCalled performance rating (PR %)Tn = Tobs(PR) (1)Apply allowance factor to compute standard timeTstd = Tn(1 + Apfd) (2)The engineer should be consider the following guidelines while divide task into work elements: Each work element should consist of a logical group of motion elements. Beginning point of one element should be the end point of the preceding element. Each element should have a readily identifiable end point. Work elements should not be too long nor too short (less than 3 sec). Separate irregular elements (non-frequent element) from regular elements. Separate manual elements from machine elements.Separate internal elements (during machine work) from external elements.Figure 1: Standard Form of Therblig Analysis Sheet- There are two important stopwatch timing methods used in direct time study to record the observation time:Snapback timing method Flyback – stopwatch is reset to zero at the start of each work elementContinuous timing method – stopwatch is allowed to run continuously throughout the duration of the work cycle6.2 ObjectivesThe objectives of this laboratory experiment are as follows:To understand the concept and the technique of direct time study method in time measurement. To learn the direct time study in order to determine the normal time and standard time for a task.To learn and understand the calculation of the appropriate number of time readings (i.e., number of time observations) that are need to give an accurate standard time value for a task. 6.3 InstrumentA wooden plate and two uprights have small wooden plates with 6 bolts for each upright plate and each bolt has nuts and washers (Hand tool dexterity test, model 32521, Lafayette Instrument, US; see Figure 2) for a total of 12 bolts. The device has the following dimensions: 0.76×0.40×0.40 m. Two types of hand tools (10-inch Crescent wrench and screwdriver) are used to fix the bolts to the wooden plate (see Figure 1).A digital stopwatch (Dad-7141, China) also records the time to complete a task. The stop watch has these features: 10-500 laps and split memory with 1/100sec memory recall during operation, calendar and time (12/24 hour format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water resistance (See Figure 2). -95251333502800350133350Figure 1: Roeder Board (Model 32026; Lafayette Inst. Company) and four receptacles for holding washers, rods, caps, and nuts. 1628775314325Figure 2: Digital stopwatch. (Dad-7141, Japan)6.4 Experiment Procedures (Cutting saw machine task) The experiment procedures are as follows (group work):1. Participants are given a brief introduction to the experiment in order to familiarize themselves with the procedure. They are provided with instructions and advised on how to assemble the wooden plates.The students need to divide task into work elements. The assembly task includes 12 bolts so; the student should consider each bolt as a one work element (12 work elements). They need to use the Form of Direct Time Study (see Figure 3) to record the observation time and performance rating for the task. Also, they require to write all work elements in the form.One student in the group assembles all the components supplied. In one plate assembly the student is required to fix 12 complete bolts sets (consisting of bolts, nuts and washers) with different sizes on both upright plates. The student needs pick up the small bolts and nuts in order to fix them and he requires to check the tight quality of the assembly. After that he needs to pick up the large bolts and nuts and fix them and also, he needs to check it. Finally, the student to needs to lift the plate (assembled object) and put it in other location. The other students record the observation time to complete each work element (fix one bolt) as well as the performance rating for each work element. The performance rating of the student depends on the speed and the quality of assembly task. Therefore, the students require to check the tight quality of the assembly. The student should assign PR = 100% for the normal performance, greater than 100% for the faster and good accuracy performance and lower 100% for the slower student performance and poor accuracy.Each group have to collect the data of observation time and performance rating for each work element from all other class groups and complete these data in cycle columns as illustrated in the form direct time study.Then the students need to compute the normal time for each work element by using the previous equation (1) in section 6.1. After that, they require to add all normal time for all work elements to determine the total normal time for the task.25400-165100Figure 3: Direct Time Study Form6.5 Results of the ExperimentA laboratory report includes the following:Determine the total normal time (Tn) of the task in min.Determine the standard time (Tstd) of the task if the PFD allowance is 12% (see equation 2 in section 6.1).Determine the number of cycles that should be timed for the assembly task at a 95% confidence level and the actual element time is within ± 11% of the mean.7. Work Sampling Measurement Method XE "7. Work Sampling Measurement Method" 7.1 IntroductionWork sampling is one of the work measurements most used to determine the standard time of a task. In particular, it aims to find the standard task time for different numbers of workers or machines. Work sampling is a statistical technique for determining the proportions of time spent by subjects (e.g., workers, machines) in various defined categories of activity (setting up a machine, producing parts, idling, etc.). Therefore, the work sampling is useful to determine the idle time of machine or worker in a task as well as their work time. In a work sampling study, a large number of observations are made over an extended period of time, and statistical inferences are drawn about the proportion of time spent by subjects (workers/machines) in various defined categories of activity. The following general characteristics of work situations are particularly well-suited for work sampling:Sufficient time should be available to perform the study.Several weeks are usually required for a work-sampling study.Multiple subjects should be used.Work sampling is suited to studies involving more than one subject.Long cycle times should be used for the jobs covered by the study.Nonrepetitive work cycles should be used.Jobs consist of various tasks rather than a single repetitive task.In fact, for highly repetitive jobs with short cycle times performed by one worker, an alternative work measurement method such as a direct-time study, predetermined time system, or standard data system is preferred over work sampling. There are other names used for work sampling, such as activity sampling and ratio delay study.There are various applications for the work-sampling method:Machine utilisation: how much time is spent by machines in various categories of activityPrevious example Worker utilisation: how workers spend their timeAllowances for time standards: assessment of delay components in PFD allowance factorAverage unit time: determining the average time on each work unitTime standards: limited statistical accuracy when standards are set by work samplingDifferent guidelines are used to define categories in a work-sampling study: First, the categories must be defined to be consistent with the objectives of the work-sampling study. Second, they must be immediately recognizable by the observer (mutually exclusive). Third, if output measures are included, then activity categories must correlate with those measures (i.e., the machine idle time is considered the output measure for machine utilisation). Fourth, if there is more than one output measure, then an activity category must be defined for each. Finally, it is helpful to minimize the number of activity categories to reduce the level of confusion for the study observer (work-study engineer). 7.2 ObjectivesThe objectives of this laboratory experiment are as follows:To understand the concept and the technique of the work-sampling study method in time measurement. To use the work-sampling study in order to determine the average time of a task.To use the work-sampling study in order to determine the normal and standard times of a task.To understand the implementation of a work-sampling study in the evaluation of various workers’ utilisation.7.3 Experiment Exercise (First part of the experiment) A work-sampling study was performed on nine workers in the milling production department in a steel factory. The task was divided into four activity categories: ‘worker operates on machine’ (producing units), ‘worker waits for raw materials’, ‘worker talks with advisor and co-workers’, and ‘worker inspects unit’. The below table 1 shows the work-sampling data study form that was used in the study and contained the data collection for the nine workers with randomised time and time of data collection. The factory approved 13% as an allowance factor Apfd. A total of 438 work units were produced during the two weeks. Furthermore, 753 were inspected during the two weeks.7.4 Results of the ExperimentA laboratory exercise report includes the following:Construct a 90% confidence interval for the true proportion of time spent producing units.Construct a 95% confidence interval for the true proportion of time spent inspecting units.Determine the average time per day that each worker spends producing units as well as inspecting unit. Determine the standard time for the ‘worker operates on machine’ category. Determine the total percentage of idle time (delay time) for each worker. Date: 2/5/2011Work Sampling Data Collection FormPage 1 of 1Table 1: Work Sampling Data Form for the StudyPeriod of Study : Two weeksActivity Category (AC) 1. Worker operates on machine (producing units) 2.Worker waiting the raw materials 3.Worker Talking with advisor and coworkers 4. Worker inspects unit Observer: Eng. MarkDepartment: Milling production departmentNotes: all workers have same levels of training and experiences?SubjectsObservation Date and TimeWorker#1Worker#2Worker#3Worker#4Worker#5Worker#6Worker#7Worker#8Worker#9ACPR (%)ACPRACPRACPRACPRACPRACPRACPRACPR2/5/11 (10:05 am)3?3?2?1951933?3?1902?4/5/11 (11:15 am)4953?2?3?3?3?4100410119412/5/11 (4:11 pm)3?3?1922?4983?41024991916/5/11 (4:30 pm)1902?41053?2?1922?41012?3/5/11 (10:44 am)1903?410219519019419341003?2/5/11 (3:10 pm)49941033?2?41003?2?1891934/5/11 (8:20 am)4102410541033?3?3?3?19341042/5/11 (2:14 pm)1923?3?3?19119041004972?9/5/11 (9:30 am)3?2?2?3?1933?1902?410011/5/11 (11:10 am)3?19441091942?2?2?2?1924/5/11 (4:12 pm)190410241003?1902?3?3?49811/5/11 (2:00 pm)41002?41003?3?3?4103410049510/5/11 (11:30 am)41012?2?41021941912?2?1915/5/11 (10:20 am)4981961903?3?191192410141014/5/11 (8:16 am)41052?2?41002?4971892?1903/5/11 (3:45 pm)3?3?2?1922?410041022?41039/5/11 (1:30 pm)4991934992?1894983?41022?12/5/11 (2:50 pm)1893?1931931913?2?3?19111/5/11 (9:38 am)1882?3?2?19049819019241006/5/11 (9:58 am)1922?2?3?1893?19419141007.5 Practical Exercise (Second part of the experiment)For this part, as a group you need to conduct a work sampling study on one of the jobs listed below. Select any one of the listed jobs and implement the study on at least four subjects (i.e. workers OR machines).Any job in an industrial factory (production lines)Barber shop jobs Reception employees at a hospital or hotelBank teller at a bankSupermarket cashier or restaurant cashierWorkshop jobs (woodworking, painting, or forge workshop)Your choice (discussed with me in advance)Each group needs to collect 100 observations as a total in one week. The group must use the work sampling data form to collect the data from the job. In addition, groups must use the scheduling observations technique and pseudo random number generators in Excel (see the class’s slides 22-25, chapter 9) in order to ensure randomization in observation dates, times, and workers.The group must determine the following:Determine the proportion of time spent on each activity categoryDetermine the hours spent on each category by all workers/machinesDetermine the average time that each worker/machine spends on each producing unit (worker/machine activation) activity category.Determine the normal time of worker/machine work activity category (worker/machine activation category)Determine the percentage of utilization of each worker/machineYou may use figures and photos to illustrate your description (if needed).8. Learning Curves Theory XE "8. Learning Curves Theory" 8.1 IntroductionLearning Curve Phenomenon as in term of task time refers to the Reduction in cycle time that occurs in a repetitive work activity as the number of cycles increases. It means that when a worker accomplishes a task over and over, the time required for each successive cycle decreases as he or she learns the task. Learning Curve analysis has been applied for different areas rather than cycle unit time such as estimates the product cost, product quality and occupational safety. According to theory, there is a constant learning rate that applies to a given repetitive task. Learning Rate means that the proportion by which the dependent variable (e.g., task time) is multiplied every time the number of task cycles doubles. The learning curve effect is inherent in any work system that continuous to seek improvement in its operations. There is other alternative term for the learning curves used for organizations learning and technology improvement which is experience curve. Improvement time of task over time during a repetitive task was pointed out by Wright and Crawford those developed a number of equations to express the time improvement mathematically (Grover, 2007). They plotted the results of time against the number of cycles on log-log paper and that gave a straight line. The plotted showed that the time of cycle was significantly decreased while the number of cycles is doubled. There is one important term related to the learning rate which is called improvement rate. It defines as the parentage of improvement in cycle time of the unit (dependent variable) as the number of unit doubles. In fact, the occurring of learning curve related to two important factors which are: workers and organization. The workers can contribute in occurring learning curves with different ways such as: worker becomes familiar with the task - the worker learns the task, worker makes fewer mistakes as the task is repeated, hand and body motions become more efficient, and there is a rhythm and pattern developed and minor adjustments in workplace layout to reduce distances. In contract, the organization can contribute in occurring learning curves with different ways such as: methods improvements by the IE Department (i.e., layout and design methods, process optimization and just-in-time method), technological improvements, development of special tooling, better scheduling, improved logistical support and better motivation of workers. Learning curves can be also useful in showing how differences in work design can have an effect on the rate of learning 8.2 ObjectivesThe objectives of this laboratory experiment are as follows:To learn how to draw learning curve for more than one subject and task. To understand the concept of learning curves theory.To learn how calculate the time of any specific unit in the task as well as the cumulative time of the task.To calculate the learning rate for the subject for different two tasks.8.3 InstrumentThe Grooved Pegboard (Simple assembly tool test, model 32025, Lafayette Instrument, US; see Figure 1) is a manipulative dexterity test consisting of 25 holes with randomly positioned slots. Pegs with a key along one side must be rotated to match the hole before they can be inserted, requiring more complex visual-motor coordination. Roeder Board Manipulative Aptitude Test (Model 32026; Lafayette Inst. Company; see Figure 2) is the test that uses to measure hand, arm, finger dexterity, and speed. The board of the roeder board has four receptacles for holding washers, rods, caps, and nuts. The performance board also is comprised of a horizontal T-bar and 40 inserts arranged in a predetermined pattern.A digital stopwatch (Dad-7141, China) also records the time to complete a task. The stop watch has these features: 10-500 laps and split memory with 1/100sec memory recall during operation, calendar and time (12/24 hour format), 5 daily alarms, countdown and repeat (9h 59m 59s) and water resistance (See Figure 3). 8.4 Experiment Procedures (group work)Each student will perform two different experiments since; the student needs to perform the Grooved Pegboard simple assembly tool test(task no. 1) as well as also, he needs to do other task which is Roeder Board Manipulative Aptitude Test (task no. 2):First of all, the lab section needs to divide into two groups and each group needs to select one student to perform the both tasks. In the first experiment (task no. 1):Participants are given a brief introduction to the experiment in order to familiarize themselves with the procedure. They are provided with instructions and advised on how to insert the pegs inside the holes.One student of the group needs to pick up the peg and insert to the board hole with random orientation (see Figure 1) and uses both hands.The student needs to insert 25 pegs in order to complete the assembly. The students requires to timed 15 cycles. The other members of the group need to record the time for each cycle (i.e., time record for 15 cycles).11620501219203181350121920Figure 1:Grooved Pegboard tool and pegs. In the second experiment (task no. 2):Participants are given a brief introduction to the experiment in order to familiarize themselves with the procedure. They are provided with instructions and advised on how to insert the pegs inside the holes.One student of the group (i.e., same student who performs the first task) needs to assemble all four parts washers, rods, caps, and nuts together and insert into the hole in the board after pick-up these parts from pin that placed in the front of the student see Figure 2. The student requires to complete 25 assembly parts out of 40 which means that he needs to assemble only 25 holes in the board. The students requires to timed 15 cycles.The other members of the group need to record the time for each cycle (i.e., time record for 15 cycles). 288607533591569532531115Figure 2: Roeder Board (Model 32026; Lafayette Inst. Company) and four receptacles for holding washers, rods, caps, and nuts. 8.5 Results of the ExperimentA laboratory exercise report includes the following:Record the times for each task using snapback method.Present the data in a tabular form database.Plot the learning curve for both students and both tasks (i.e., 2 graphs with 4 learning curves). Use simple and log-log graph paper.Determine the learning curve slope (m) via the graph using the following equation:lnTN2– lnTN1m =ln(N2) – ln(N1)Determine the learning rate (%) using the following equation:LR = 2mThe total cumulative time and the average total cumulative time, using the following equation of Crawford model. 304800185420Compare the results of both tasks as well as results of the both students and provide your comments. ................
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