February END 202 Work analysis and design

Transcription

1 END 202 Work Analysis and Design SibelALUMUR ALEV February 2011

2 Method engineering steps 1. Select project (Pareto, Fish diagram, Gantt, PERT) 2. Get and present data (charts, computations) 3. Analyze data (operation analysis) 4. Develop ideal method (motion, work, equipment design) 5. Present and install method (decision making tools) 6. Develop job analysis 7. Establish time standards (time study) 8. Follow up

3 Time study Timestudy is a technique for recording times and rates of working for specific job elements to establish standards d Why do we measure time? The most meaningful and useful measure of work is the amount of time it takes to accomplish it Time is objective Time is quantifiable People understand time

4 Standard time Standard Time is the time that a person suited to the job and fully trained in the specified method will need to perform the job if he/she works at a normal or standard tempo Includes some additional time called allowances to provide for the worker s personal needs, fatigue, and unavoidable dl delays

5 Standard time can be used To define a fair day s work To determine manpower requirements and capacity limitations To compare alternative methods for accomplishing the same task To provide a basis for wage incentives and for evaluating worker performance To estimate cost To provide time data for production planning and scheduling, material requirements planning and other management functions that depend on accurate task time data

6 Time study Methods to determine time standards: Estimation Historical records Time study techniques: Direct time study (with chronometer) Standard data and formulas Predetermined time systems Work sampling Engineered standards

7 Direct time study Involves direct observation of a task using a stopwatch or other chronometric device to record time The task is divided into work elements and each work element is timed separately Performance rating: The worker s performance (pace) is evaluated Normal ltime is calculated l considering i the performance rating Allowance is added to the normal timeto to determine the standard time

8 Standard data and formulas Finding normal time values for work elements used in tasks using previously determined standard data or formulas Steps: Identify the work elements that make up the task together with the values of variables Access the database to find the normal time for each element or use analytical formulas Sum to determine the normaltime for the task Add allowances to determine standard time

9 Predetermined time systems Relies on a database of basic motion elements (therbligs) such as reach, grasp, move Associated with each motion element tis a set of normal times depending on distance, weight, etc. List of all the basic motion elements, find the normal time for each element from the data base, sum the normal times and add allowances Advantages Performance rating is not required Can be applied to determine time standard for a task before production

10 Work sampling Purpose is to determine proportions of time spent in different activities using randomized observations Examples: to determine machine idle times, to determine operator utilization When used to establish time standards statistical errors cause the standard times to be lessaccurate than obtained by other techniques To be studied later

11 Prerequisites Prerequisites for valid time standards The task is performed by an average worker The worker s pace represents standard performance The worker uses the standard method The work is performed on a standard work unit

12 Direct time study (with chronometer)

13 Analyst s responsibility The analyst should be trained on this job The correct people should be warned (supervisor, worker, etc.) Be sure that you have all the equipments with you Be respectful with the worker, avoid to make unnecessary comments Be honest with the performance of the worker Accurately record and note the times taken (time study results can influence the firm policy)

14 Supervisor s responsibility Supervisor should notify the operator in advance see that the proper method is established select tthe best operator: competent tand has adequate experience on the job (not too fast neither too slow) sign the final and original copy of the time study

15 Operator s responsibility Worker should cooperate in helping to work assist the time study analyst in breaking the job down into elements work at a steady, normal pace use the exact method prescribed

16 Time study equipment Stop watch Analog outdated Electronic Split = continuous Lap = snapback Videotape camcorders Time study board Holds time study form and stop watch Left and right handed Time study software Available for PC, for palms Time study form

17 Time study form

18 Time study form zoomed Performance rating (100% is the standard performance of a qualified operator) For continuous timing Cycle W OT NT R (Watch (Observed (Normal (Rating) Time) Time) Time) Normal time (NT): OT x R/100

19 Time study procedures 1. Select the job To implement wage incentives To control costs To compare methods/jobs 2. Select the operator Qualified (intelligence, education, training, fit) Average Slow worker: loose standard times (not good for the firm) Fast worker: tight standard times (not good for the workers)

20 Time study procedures 3. Record all details about the job Machines, hand tools, fixtures, working conditions, department, a sketch of layout, 4. Examine the job and break it down into elements Use sight and sound for breakpoints Relatively fine but not less than 0.04 min (3 sec) Keep manual and machine elements separate Separate constant elements from variable elements

21 Time study procedures 4. Examine the job and break it down into elements Types of elements repetitive: occurs each cycle occasional: not every cycle foreign: not necessarily part of the job machine: the time is fixed (no rating) manual: depends on worker (rating) constant

22 Time study procedures 5. Determine the number of cycles to be timed a) Statistical estimations n ts = kμ t: t distribution value, refer to Table A3 3, 3 App. 3, pg 701 s: standard deviation k: an acceptable fraction for error µ: sample mean value Example: µ = , s = 0.09, 009 %5 desired dacceptable tbl fraction k, 0.05 for 24 degrees of freedom: t = (Table A3 3, App. 3) N = observations 2

23 Time study procedures 5. Determine the number of cycles to be timed b) Approximate guide (from General Electric Company) Cycle time (min) Recommended number of cycles (20 min) (25 min) (30 min) (30 min) (30 min) (40 min) >

24 Time study procedures 6. Measurement R W OT NT Continuous timing 5 5 Stopwatchisnever reset You record the cumulative times At the end you need to subtract times Snapback timing Stopwatch is reset each time (each elemental work) Read direct times from zero No decimal point R W OT NT

25 Comparison btw continuous and snapback timing Continuous timing Better adapted to measure and record very short elements (3 successive elements of <0.04 min followed by 0.15 min) A complete record of the entire observation period All delays and foreign elements are recorded More clerical work is involved Snapback timing More suitable for long elements No need to make successive subtractions Delays are not recorded Some individual elements are removed or are studied independently of preceding and succeeding elements Overall time is obtained by summing: prone to error

26 Performance rating Different options for rating the operator one rating to entire study (for short cycle) an average rating for each element evaluate the performance of each element as it occurs (for long and diversified movements) Normal time (NT): OT x R/100

27 Finding standard time Adding allowances Different interruptions can take place. We must provide extra time to take them into account. Personal interruptions (trips to the restroom, drinking fountain) Fatigue Unavoidable dbl delays dl (tool lbreakage, supervisor interruptions, material variations, etc.)

28 Finding standard time Adding allowances to obtain the standard time ST = NT x (1 + allowance) 15% is the average allowance used for manual elements 10% is the average allowance used for machine elements

29 Time study steps

30 Time study steps

31 Performance rating and allowances

32 Performance rating Rating of 100% Standard (normal) performance = 100% = rate of output achieved by a qualifiedworker worker, without exertion, using correct method. Some examples Distributing 52 cards in 0,5 min Walkingwith 5.4 km/h Rating can change due to Environmentalconditions conditions, fatigue, qualityof raw material, changes in method,

33 How to rate the performance? Rating methods: 1. Speed rating 2. Westinghouse system 3. Synthetic rating 4. Objective rating

34 1. Speed rating Speed rate considers only the rate of work per unit time Measurement of the effectiveness of the operator by the ratioof of the observed performance to standard performance Can be used for elemental, cycle, or overall rating Works needing great precision (aircraft engine parts fabrication) can appear slower than a simple work Record the rating in the R column before reading the stopwatch time! Do not rate by the watch! Begin by rating only by 10s (80,90,110) then move onto 5s (85,95,105)

35 1. Speed rating example Rating Verbal anchor points Walking speed (mph) Cards dealt in 0.5 min 0 No activity Very slow, clumsy Steady, deliberate Brisk, businesslike Very fast, high dexterity Upper limit for short period 6 104

36 2. Westinghouse system Westinghouse Electric Corporation (Lowry et al. 1940) developed a system of 4 factors in evaluating the performance of the operator: Skill: The proficiency i at following a given method Effort: Demonstration of the will to work effectively Conditions: i Include temperature, ventilation, i light, noise Consistency: Evaluated as the study is worked up

37 2. Westinghouse system

38 2. Westinghouse system example Once each four factor are rated sum the four values and add 1 to give the performance rating factor The Westinghouse System is appropriate for either cycle rating or overall study rating but not for elemental rating

39 3. Synthetic rating Determines a performance factor based on fundamental predetermined motion times (F) R = F OT R: Performance or rating factor F: Fundamental motion time OT: Observed mean time

40 3. Synthetic rating example Element no. Observed time Fundamental Rating factor (OT) motion time (F) (R) % % % % R 1 = F 1 /OT 1 = 0.096/0.08 = 120 % R 4 = F 4 /OT 4 = 0.278/0.22 = 126 % Average rating factor is 123%

41 4. Objective rating Eliminates i the difficulty of establishing a standard d pace for every type of work R = P D R: Performance or rating factor P: Pace rating factor D: Job difficulty adjustment factor (amount of body used, foot pedals, bimanualness, eye hand coordination, handling or sensory requirements, weight handledor resistance encountered)

42 Rating application and analysis Rating > 100 = < 100 Normal time (NT): OT x R/100 NT = 0.2 x 100/100 = 0.2 NT = 0.16 x 125/100 = 0.2 NT = 0.25 x 80/100 = 0.2

43 Rating application and analysis Potential mistakes Subjective rating Capacity of working memory Cultural norms (UK, 100% = 4 mph) Training is crucial: Tight rater = rates below actual, unfair Loose rater = rates above actual, easy Conservative = rates close to mean

44 Allowances Normal time does not include unavoidable delays Need to make adjustments to compensate for such losses Allowances can be applied to 3 parts of the study The total cycle time Machine time only Manualeffort only 2 methods for developing allowances: Direct observation Work sampling

45 Noting allowances

46 Types of allowances

47 Types of allowances Constant allowances Personal needs ( 5%): restroom, smoking, drinking, lunch Basic fatigue ( 4%) Variable fatigue Special allowances Unavoidable delays: interruptions from supervisor, material irregularities, iti machine interference Avoidable delays: socializing, idleness other than rest Et Extra allowances: attention ti time, cleaning, tool maintenance Policy allowances: new employees, differently ables, workers onlight duty

48 Variable fatigue allowances 1 Source: International Labour Office (ILO)

49 Variable fatigue allowances 2 Source: International Labour Office (ILO)

50 Revised table of allowances 1

51 Revised table of allowances 2

52 Applying allowances ST = NT x (1 + allowance) ST: standard time NT: normal time Example: Personal needs 50% 5.0 Basic fatigue 4.0 % Unavoidable delay 10% 1.0 TOTAL 10.0 %

53 How to use allowances? Generally we use it to take a rest 30 min lunch time is included 2 times 10 min of rest are included For a 8 h of work, 50 min of rest 10% Frequent short breaks are preferred over infrequent, long breaks

54 Standard data and formulas

55 Standard data and formulas Use standard data, tabular or graphical collections of normal times, for common work elements Use formulas to provide quick and consistent normal times for variable elements When properly applied, standard data permit the rapid establishment of accurate time standards before the job is performed A timestudy formula can establish standards in a fraction of the time required for direct time study Advantage of formulas over standard data is that a less skilled person can plug data into formulas more quickly than adding standard data elements

56 Standard data and formulas Steps: Identify the work elements that make up the task together with the values of variables Access the database to find the normal time for each element or use analytical formulas Sum to determine the normal time for the task Add allowances to determine standard time

57 Predetermined time systems

58 Predetermined time systems Relies on standard times assigned to the basic elements of work: basic motiontimes: times: further refinement is bothdifficult and impractical synthetic times: often the result of logical combinations of therbligs predetermined times: used to predict standard times for new work These fundamental motions are difficult to evaluate with stopwatch time study Associated with each motion element is a set of normal times depending on distance, weight, etc.

59 Predetermined time systems Advantages They are realized on several workers under controlled conditions The analyst doesn t need to determine the performance rating which can be subjective The operation is not interrupted The level lof complexities for each elemental lwork can also be computed There are more than 50 systems, such as: Work Factor, MTM, MOST, etc.

60 Methods time measurement (MTM 1) Maynard et al., 1948 Results of frame by frame analyses of motion picture films Time values for the fundamental motions are given Ex: reach, move, turn, grasp Assigns to each motion a pre determined time standard which is determined by the nature of the motion and the conditions under which it is made Westinghouse technique of rating is used Ex. Reaching depends on distance and type of reach. Reach is divided into five distinct cases and Move into 3 cases (see p. 502). TMU: Time Measurement Unit = 0,00001 hour

61 Methods time measurement (MTM 1) Steps of MTM 1 Determine all left hand and right hand motions required to perform the job properly p Determine the rated times from the methods time data tables in TMU for each motion Tables I X: reach, move, turn and apply pressure, grasp, position, release, disengage, eye travel time and eye focus, body, leg andfoot motions, simultaneous motions Sum the TMU values (consider only limiting values) Add allowances The tabulated values do not carry any allowances Some analysts state that no fatigue allowance is needed

62 Methods time measurement (MTM 2) The data are adapted to the operator and are independent of the workplace or equipment Used in work assignments where The effort portion of the work cycle is more than 1 min The cycle is not highly repetitive Does not involve a large number of either complex or simultaneous hand motions In addition to basic MTM motions, there are combinations of them GET: reach + grasp + release PUT: move + position + release

63 Methods time measurement (MTM 2)

64 Methods time measurement (MTM 2) 11 classes of actions (categories) Get (reach grasp release) Put (move position) Get Weight Put Weight Regrasp Apply Pressure Eye Action Foot Action Step Bend and Ai Arise Crank

65 Methods time measurement (MTM 2) Cases for GET(G) Cases for PUT(P)

66 Methods time measurement (MTM 2) Principle of Simultaneous Motion: If two hands make the same task simultaneously, more time can be assigned depending on the difficulty Principle of Limiting Motion: Iftwo hands make different tasks at the same time, we consider the slowest one Principle of Combined Motion: If one hand makes two distinct movements, we take the slowest time

67 Methods time measurement (MTM?) MTM 3: helpful for works where there is an interest in saving time at the expense of some accuracy MTM V: for use in metal cutting operations, to establish setup times for all typical machine tools MTM C: widely used in banking and insurance industries, for work tasks such as filing, data entry, and keyboarding MTM M: for operator working on a microscope, microminiature i i manufacturing MTM TE: for electronic tests MTM MEK: MEK: one of a kind of and small lot lot production MTM UAS: for a process description, batch production

68 Maynard Operations Sequence Technique (MOST) Developed by Zandin in 1967, applied in Sweden Simplerthan MTM, but faster than MTM 1 and MTM 2 (at least 5 times faster than MTM 1) There are three levels: MaxiMOST: analyzes long, infrequent operations (range from 2 min to several hours and occur less than 150 times per week) MiniMOST: very short and very frequent (less than 1.6 min in length, more than 1500 times a week) BasicMOST: 0.5 min to 3 min of length

69 Predetermined time systems

70 Time study Methods to determine time standards: Estimation Historical records Time study techniques: Direct time study (with chronometer) Standard data and formulas Predetermined time systems Work sampling Engineered standards