1. WORK STUDY WORK MEASUREMENT PART II TECHNIQUES

3. 3 TECHNIQUES OF WORK MEASUREMENT WORK SAMPLING Work sampling is the process of randomly observing working people or machinery to  Work sampling is the process of randomly observing working people or machinery to determine how they spend their time. determine how they spend their time.  Everyone who has worked with others, has performed work sampling at one time or another. Our personal attitudes developed in time about the “work ethics of fellow eployees” or about their “productivity” are based on random observations. Supervisors are work sampling their employess all the time.  In order to obtain a complete and accurate picture of the productive time and idle time of the machines in a specific production area, it would be necessary to observe them continuously and record when and why any of the machines were stopped. This would be practically infeasible since we would need a large number of people dedicated for this task only.  For this reason, we have to find out a better method: We can make tours of the factory at random intervals (hours) and record which machines are working and which are not by noting the reason of each idle case.  However, if it were possible to see the state of every machine in the factory at a glance, for example, it might be observed that 80% of them are working and 20% of them are idle. If we repeat this observation at 20 different times of the day and get the same result each time, then with some confidence level it will be possible to say “at any time always 80% of the machines are working”. But, generally this is not possible to do either.

4. 4 TECHNIQUES OF WORK MEASUREMENT  Work sampling obeys the theories and laws of probability. So, even in using this method, we must be sure about specific factors such as; “required number of observations” and their “randomness” and the “accuracy” of the result at a specified “conficence level”.  Now the question is what do we mean by all the above mentioned terms such as; sampling, probability, number of observations, accuracy of the result, and randomness of observations. Few Words on Sampling  As previously mentioned, since it is impractical to use method of “continuous observation”, we prefer to use a “sample” of observations which is likely to represent the result which we would have obtained by continuous observation.  Thus, we can say that, such a “sampling” is based on probability rules. Here, “probability” is defined as “the extent to which an event is likely to occur”. We can illustrate this by reviewing the classical example of “tossing a coin”. When we toss a coin, there are two possibilities. The result will be either “heads” or “tails”. The law of probability tells us that, we are likely to have 50 heads and 50 tails in every 100 tosses of the coin. Note that, we use the term “likely to have”. In fact we might have a score of 55-45, or 48-52, or some other ratio. But it has been proved that,

5. 5 TECHNIQUES OF WORK MEASUREMENT The law becomes increasingly accurate as the number of tosses increase. In other words, the greater the number of tosses, the more chance for having 50 heads to 50 tails. This suggests that the larger the size of the sample, the more accurate or representative it becomes with respect to the original “population”, or group of items under consideration.  We can therefore visualise a scale where, at one end we can have the complete accuracy achieved by continuous observation, and at the other hand doubtful results derived from only a few observations.  Therefore the size of the sample is important and by using a certain “confidence level”, we can express our confidence in whether the sample is representative of the reality or not. Establishing Confidence Levels  Let’s go back to example of tossing the coins. Assume that our operation which we are observing involves tossing 5 coins at a time. That is, we toss the 5 coins and record how many times we get heads and how many times we get tails. Then repeat this operation 100 times. The results which are likely to be observed can be presented as in following table or graphically as in following figure.

6. 6 TECHNIQUES OF WORK MEASUREMENT Combination Number of combinations Heads (p) Tails (q) 503 4117 3230 2330 1417 053 Total number of combinations 100 Proportional Distribution of “Heads” & “Tails (100 tosses of 5 coins at a time)

7. 7 TECHNIQUES OF WORK MEASUREMENT  What happens if we considerably increase the number of tosses in each case (in other words increase the sample size)? If in each case we toss 100 coins instead of 5, we can obtain a smoother curve as shown below. Distribution curve showing probabilities of combinations when large samples are used.  The above curve is called the “curve of normal distribution”. Basically, this curve tells us that, in majority of the cases, the tendency is having equal number of heads and tails in any one series of tosses. You can see a more descriptive curve of normal distribution on the next page.

8. 8 TECHNIQUES OF WORK MEASUREMENT  Curves of normal distribution may have many “bell” type shapes. Some may be flatter and some maybe more rounded. These curves are described by two attributes :, is the average or measure of central dispersion; and б, is the deviation (standard deviation) from the average. In our case, since we are dealing with a percentage value (proportion or ratio), we use б p to denote standard deviation of a percentage. Curve of Normal Distribution  The area under the normal distribution curve can be calculated. In the above figure; one б p on both sides of gives an area of 68,27 % of the total area. Similarly, two б p on both sides of

9. 9 TECHNIQUES OF WORK MEASUREMENT Some Selected Confidence Levels gives an area of 95,45 % of the total area, and three б p on both sides of gives an area of 99,73 % of the total area.  In other words, we can say that, 95.45 % of all our observations will fall within ± 2 б p and 99.73 % of all our observations will fall within ± 3 б p.  In fact, this is the LEVEL OF CONFIDENCE we have in our observations. Some selected confidence levels are given in the following table. Area under the normal distribution curve The number of required standard deviations for a specific confidence level. Most commonly used confidence level is 95%  For example, if we take a large sample at random we can be confident that, in 95% of the cases our observations will fall within ± 1.96 б p.

10. 10 TECHNIQUES OF WORK MEASUREMENT  Say that we are observing the occurrance of an event such as idleness of our machines in our shop. After an observation period we will come up with a result and, for examle, say that at any time 10% of our machines are idle. Accuracy measures the closeness of this percentage value to the true percentage of idleness. Accuracy of the results we obtain  For the above example, if we had set our goal to have ± 5% accuracy, it means that the true percentage value of idleness is within the range of 9.5% - 10.5%.  Most commonly used accuracy level is ± 5%. But, we have to keep in mind that, the level of desired accuracy will effect the cost of work sampling process. Determination of sample size (number of observations)  When conducting a work sampling application, we must be able to say that, “we are confident that at 95% (or 99% or some other confidence level) of the time this particular observation is correct within ± 5% (or some other accuracy level)”.  In order to be able to say the above statement, our sample size or the number of observations should support the desired confidence and accuracy levels. That, is we must be able to determine the number of observations which will satisfy the results of the study at a given confidence level and within a given accuracy value.

11. 11  In order to find out what will be the required number of observations (or sample size) we make use of some statistical formulas. Our first formula is; TECHNIQUES OF WORK MEASUREMENT б p = √ (pq/n) = √ [p(1-p)] / n Where, б p = standard deviation of a percentage p = true percentage occurrance of the element being sought, expressed as a decimal. q = probability of absent occurrence, expressed as a decimal. n = total number of observations upon which p is based. And we have another formula which is for “A”, acceptable limit of error at a specified confidence level; A = Z cl б p = Z cl √ (pq/n) When we solve this equation for n ; n = (Z 2 pq) / A 2 = [Z 2 p(1-p)] / A 2 Where, Z = The number of required standard deviations for a specific confidence level.  Before using the above formulas, we need to have an idea of the values of p and q. The first step is therefore to carry out a preliminary study which involves a number of random observations in the working area.

12. 12 Let’s go back to the very fist example in this section where we were trying to determine the percent idleness of our machines in our shop. Let’s say that we have performed 100 random observations as a preliminary study and the result says that machines are to be idle in 25% of the cases while working in 75% of the cases. TECHNIQUES OF WORK MEASUREMENT EXAMPLE 1 : SOLUTION : At this point, we know that, p = 25%, q = 75%, desired confidence level = 95% and desired accuracy (A) = ± 10% If we apply our formula with a Z value of 1.96 (due to confidence level of 95%), n = (Z 2 pq) / A 2 = [(1.96) 2 x (0.25 x 0.75)] / (0.10) 2 = [(3,8416) x (0.1875)] / (0.01) = 72,03 = 72 Therefore, we have already made more than enough number of observations (n=100). What should be the number of observations if we want to be confident at 95% that our estimated percent idleness is ± 10% of the real value?

13. 13 What should be the number of observations if we want to be confident at 95% that our estimated percent idleness is ± 5% of the real value? TECHNIQUES OF WORK MEASUREMENT Solution : At this point, we know that,p = 25%, q = 75%, desired confidence level = 95% and desired accuracy (A) = ± 5% We apply our formula with a Z value of 1.96 (due to confidence level of 95%), n = (Z 2 pq) / A 2 = [(1.96) 2 x (0.25 x 0.75)] / (0.05) 2 = [(3,8416) x (0.1875)] / (0.0025) = 288,12 = 289 Therefore, we have to make (289-100 =) 189 additional observations.

14. 14 A = Z cl б p = Z cl √ (pq/n) = (1.96) √ [(0.08)(0.92)]/500 = ± 2.37% TECHNIQUES OF WORK MEASUREMENT EXAMPLE 2 : Assume that we are interested in the proportion of “personal and unavoidable idle time” within our insurance company. Also, suppose that, the true proportion of “personal and avoidable idle time” is between 6%-10%. What should be the number of observations if we want to be confident at 95% if our expected “personal and unavoidable idle time” is 8% ? n = (Z 2 pq) / A 2 = [(1.96) 2 x (0.08 x 0.92)] / (0.02) 2 = [(3,8416) x (0.0736)] / (0.0004) = 706.85 = 707 Solution : At this point, we know that,p = 8%, q = 92%, desired confidence level = 95% and accuracy (A) = ± 2% What happens to “A” if you can make only 500 observations? Solution :

15. 15 TECHNIQUES OF WORK MEASUREMENT EXAMPLE 3 : A pilot study of 25 observations at a machine shop which has 10 machining centers showed that proportion of downtime occurrance is 4%. What should we do if we wish to find greater accuracy for our estimate within ± 1% of the true value with 99% confidence? n = (Z 2 pq) / A 2 = [(2.575) 2 x (0.04 x 0.96)] / (0.01) 2 = [(6.6306) x (0.0384)] / (0.0001) = 2546 Solution : p = 4%, q = 96%, desired confidence level = 99% and accuracy (A) = ± 1%

16. 16 TECHNIQUES OF WORK MEASUREMENT Making Random Observations All of our previous conclusions are valid provided that we perform the required  All of our previous conclusions are valid provided that we perform the required number of observations at RANDOM. number of observations at RANDOM.  Randomness is a requirement of sampling. The exact time of an observation must be completely random (based on chance only), or study’s accuracy and confidence will be destroyed.  The opposite of randomness is routine, which means predicability and both destroy the study. If we need to take 10 trips through the department today, we use the random numbers to select the starting time of each trip. If we are sampling all day long, we vary our path to introduce randomness. It is important not to build predictability into our study. One way to ensure randomness of our observations is to use a random number table an example of which is given onthe following page.  One way to ensure randomness of our observations is to use a random number table an example of which is given onthe following page. EXAMPLE : How to use a random number table In our case let us assume that we shall carry out our observations during a day shift of 8 hours, from 7 a.m. to 3 p.m. An eight hour day is 480 minutes. These may be divided into 48 10-minute periods.

17. 17 TECHNIQUES OF WORK MEASUREMENT We can start by choosing any number from the table at random. For example, by closing our eyes and placing a pencil point somewhere on the table. Assume that, by mere chance, we have pick the number 11 which is in the second block, fourth column, fourth row. Now we choose any number between 1 and 10. Assume we choose the number 2. Starting from 11, we go down the column and pick every second number and write it down until we have 10 numbers in all. Result will be as follows; 11, 38, 45, 87, 68, 20, 11, 26, 49, 05. Looking at these numbers, we find that we have to discard 87, 68 and 49 (since we have 48 ten-minute periods). The second 11 also must be discarded since we had already picked it. Random Number Table

18. 18 TECHNIQUES OF WORK MEASUREMENT We therefore have to continue with our readingsto replace the four numbers we have discarded. Using the same method, that is, choosing every second number after the last one (05) we get; These four numbers are within the desired range and have not appeared before. Now we can arrange these numbers in numeric order and and associate the times of observations throught the eight-hour day shift (see the below table). 14, 15, 47, 22 Determining the Sequence of Times For Random Observations

19. 19 TECHNIQUES OF WORK MEASUREMENT Until now, within this chapter, we have discussed about the basics of the work sampling as a procedure. From here on we will discuss about some applications where work sampling is proved to be useful. These areas of application can be given as follows; USES OF WORK SAMPLING 1. Elemental Ratio Studies 2. Performance Sampling Studies 3. Time Standard Development Studies 4. Process Effectiveness Studies 1.ELEMENTAL RATIO STUDIES Here, the word “element” refers to an activity within a complete job cycle where subject activity is distinguished from the other activities by its nature and/or type. An example of a list of elements for a machine operator’s job and the estimated elemental ratios can be given as follows;

20. 20 TECHNIQUES OF WORK MEASUREMENT An “elemental ratio study” may be for a person, for a department of many people, or for a whole plant. It makes no difference how many people are covered in the study. Only, the number of total observations is important. The element with the smallest percentage (in the above table: material handling with 4%) will determine the total number of observations required for a specific confidence level and accuracy. This is because elements with larger percentages will require fewer samples. for an “elemental ratio study” will have the following steps; THE PROCEDURE for an “elemental ratio study” will have the following steps; 1. Identify the subject. 2. Establish the purpose and goal of the study. 3. Identify the elements. 4. Estimate the ratio percent of the elements. 5. Determine the level of accuracy and confidence. 6. Determine the number of observations needed to achieve the quality goals. 7. Schedule the observations. 8. Talk with everyone involved. 9. Collect the data. 10. Summarize and state conclusions.

21. 21 TECHNIQUES OF WORK MEASUREMENT An “elemental ratio study” may be for a person, for a department of many people, or for a whole plant. It makes no difference how many people are covered in the study. Only, the number of total observations is important. The element with the smallest percentage (in the above table: material handling with 4%) will determine the total number of observations required for a specific confidence level and accuracy. This is because elements with larger percentages will require fewer samples. EXAMPLE – Elementary Ratio Study : A busy fork truck and driver The subject (1) is a fork truck that seems to be overloaded. The supervisor has asked management to purchase another truck. Good management requires hard data before making such an expensive decision. They have asked for your help. The goal (2) is to see how busy the fork truck and driver are. We need to see how the fork truck and driver spend the day. The elements (3) of this study will be “driving loaded”, “driving empty”, and “idle”. We estimate the ratios to be 40%, 40% and 20% respectively. With an “accuracy” (4) of ±5% and a “confidence level” (5) of 95%, we look up the “number of observations” (6). n = (Z 2 pq) / A 2 = [(1,96) 2 x (0.2 x 0.8)] / (0.05) 2 = [(3.8416) x (0.16)] / (0.0025) = 245.86 = 246 observations required

22. 22 TECHNIQUES OF WORK MEASUREMENT We have a work sampler who can do 50 observations a day. An observation is seeing the truck and driver once. With one observer, collecting 50 samples per day, our study will take 5 days. We will “schedule the random observations” (7) by using the random numbers table as we have seen earlier in this chapter. At the end of the fourth day our “data collection” (9) results may be seen as in the following table. The pencil marks in the above table are called tallies. Each tally is for one observation. Until the end of fourth day, we have collected 192 observations. Each day we have added that day’s totals to the previous totals and keep a running ratio accounting. As we progress, the volatility of changing ratios should lessen until the fluctiations are less than 5%. In conclusion (10), if the final ratios look anything like our first day’s data,the supervisor will not hire a new driver. Instead, we should look at how we can reduce the “transporting empty” element by scheduling the existing driver with back hauling of return material, trash or scrap.

23. 23 TECHNIQUES OF WORK MEASUREMENT Performance sampling requires rating the operator when observing him or her. Rating is a major subject of stop watch time study, and that is exactly what must be done in performance sampling. The observance of an operator happens in a moment, and in that moment the observer must judge the speed and tempo of the operator. 2.PERFORMANCE SAMPLING STUDIES Operator speed and tempo vary from person to person. At the same time for an individual operator, speed and tempo can vary from minute to minute. For work sampling, performance sampling fine tunes the ratios, making them more accurate. EXAMPLE – Performance Sampling Study : Bag packing operation In a bag-packing operation there are five independent work stations. From an elemental ratio study, the operation is divided into four elements as shown in the following table.

24. 24 TECHNIQUES OF WORK MEASUREMENT Elements 1 & 2 are productive and can be rated (*) (leveled / normalized) by placing a tally mark under proper % heading. Elements 3& 4 are nonproductive and therefore can not be rated. The data for this bag-packing example is summarized in the below table. The question is “how many hours were spent on each element of the job?”. Assume that during the one month study of these five bag-packing stations, 825 hours of labor is used (see the table on following page). The question is “how many hours were spent on each element of the job?”. (*)Rating is the process of adjusting the time taken by an individual operator to what could be expected from a “normal” operator. Rating, leveling, and normalizing all mean the same thing. It includes four factors: skill, consistency, working conditions, and effort. Average Time x (rating/100)=Normal Time (7.2 / 6) x 100 = 120% Efficiency loss = (7.5/122)x100=6.1%

25. 25 TECHNIQUES OF WORK MEASUREMENT What if during this 825 hours of bag packing, the operators packed 35392 bags? Hours spent on each job element [Hours Used / Bags Packed] = [(507.38+84.56)hours / (35392 bags)] = 0.01673 hours/bag Adding 10% allowance => 0.01673 + 0.00167 = 0.01840 hours/bag Bags/hour = 1/0.01840 = 54

26. 26 TECHNIQUES OF WORK MEASUREMENT 3.TIME STANDARD DEVELOPMENT STUDIES Work sampling can be used to develop time standards accurately and quickly. Time standard development studies pull together all the techniques of work sampling, and it is the ultimate use of work sampling. The step by step procedure is exactly the same as for the elemental ratio study (see page 19 of this chapter) and the performance sampling study. The additional data needed for a time standard development study are;  Quantity of units produced during the study period, and  Allowances. The time standard development system starts after the other two techniques (elemental ratio study and performance sampling) are completed. EXAMPLE – Time Standard Development Study : Activities of a maintenance department A maintenance department was work sampled according to 95% confidence level and ± 5% accuracy based on the elemental job with the smallest percentage of occurrance. The goal of of the study is setting time standards. Resulting data is summarized in the following table.

27. 27 TECHNIQUES OF WORK MEASUREMENT If 40% of the maintenance time is “Millwright” (mekanik işçiliği), then the maintenance department spent (40% x 3840 hrs =) 1536 hours working on millwright jobs. This is pure 100% work, no idle time). Results of one-month work sampling (includes elemental ratio & performance sampling studies) At this point, elemental ratio studies and performance sampling studies would leave us. Now the production counts and allowances are to be added. Table on the following page shows how we extend the obtained data to create time standards.

28. 28 TECHNIQUES OF WORK MEASUREMENT In the above table; How Do We Extend the Obtained Data to Create Time Standards 1) Element numbers refer to the elements given in the previous table. Only the productive elements have time standards. 2) Hours were calculated in the previous table. 3) Work order counts were collected and given to the work sampling specialist by the maintenance supervisor. 4) Hours per work order are calculated by dividing hours (2) by work orders (3). 5) Plus 15% allowance. A management decision is made to include 5% of 8% walking ratio plus 10% personal and fatigue time resulting in 15% of personal, fatigue and delay allowance. Thus, 115% times the hours per work order (4) equals standard time (5). 6) Work orders per hour is the 1/x of standard hours (5). For example, for element 1, millwright, work orders per hour is (1 / 2.14=) 0.47.

29. 29 TECHNIQUES OF WORK MEASUREMENT The entire plant can be work sampled and time standards can be set in one month. The size of the plant will determine the number of observers, but no other system or technique can develop a total plantwide time standard system faster than work sampling. Following table shows an example of the “daily data collection sheet” of such a study. Example Work Sampling Data Collection Sheet : Work sampling observations

30. 30 TECHNIQUES OF WORK MEASUREMENT After the completion of a one-month plantwide work sampling study, the summary of the study is given as in the following table. Summary of Work Sampling Data After One Month and Time Standards THIS IS THE ULTIMATE USE OF WORK SAMPLING Note that time standards are developed for all jobs (operations) and totals have the “labor hour total” for labor costing. THIS IS THE ULTIMATE USE OF WORK SAMPLING.

31. 31

32. 32 TECHNIQUES OF WORK MEASUREMENT STOPWATCH TIME STUDY : General Notes  A time study technician is under pressure from both labor and management. There is both humor and truth in the following statement; Stopwatch time study is the most common technique for setting time standards in  Stopwatch time study is the most common technique for setting time standards in manufacturing area. It is often the only method acceptable to both management manufacturing area. It is often the only method acceptable to both management and labor. and labor. “If time study tehnicians set time standards too tight, labor is mad at them. If they set time standards too loose, management is mad at them. If time standards are perfect, everyone is mad at them.”  The modern practitioner of time study has often been an alert person promoted out of the shop and trained in the time study technique.

33. 33 TECHNIQUES OF WORK MEASUREMENT TOOLS OF STOPWATCH TIME STUDY It is important to know the tools of stop watch time study before getting into the details of the technique itself. These tools, which we will review are as follows; 1. Stopwatches a. Continuous mechanical stopwatch b. Snapback mechanical stopwatch c. Three-watch time study technique d. Methods time measurement stopwatch e. Digital stopwatches and electronic timers f. Computer 2. Boards for holding watches and paper. 3. Video recorders 4. Tachometers 5. Calculators 6. Forms

34. 34 TECHNIQUES OF WORK MEASUREMENT Continuous Mechanical Stopwatch Continuous stopwatch has two dials Continuous stopwatch has two dials : The large dial The large dial is divided into hundredths of a minute (0.01), and one revolution of the sweep hand is one minute. The small dial The small dial records minutes up to 30. The crown of the watch The crown of the watch, when depressed, stops the watch. Depressing the crown second time resets the watch, and the third depression is needed to restart the watch. Three depressions is time consuming and should be done only once per study. The continuous stopwatch is used in the application of continuous time study technique. When it is used and what is “Continuous Time Study Technique”? : Continuous Mechanical Stopwatch STOPWATCHES & TIME STUDY TECHNIQUES

35. 35 TECHNIQUES OF WORK MEASUREMENT Although this technique can be accomplished by using any type of stopwatch, continuous stopwatch is specifically designed for this purpose. The continuous time study technique calls for starting the stopwatch when the operator finishes an element of a job and allowing the stopwatch to run continually until the study is complete. While the watch is running, the time study person reads the watch at the end of each element and records this time on the continuous time study form. For this reason, the continuous time study technique is said to have integrity. The time and nature of all foreign elements are recorded during the study period, and a decision will be made to include or exclude these elements. We can’t hide anything, because all the time must be accounted for. When conducting a continuous time study, it must be extended when the readings are complete. Since, only the element endings have been recorded, every reading must be subtracted from the previous reading in order to calculate the elemental times. This subtracting is time consuming and is the most undesirable part of the continuous time study.

36. 36 TECHNIQUES OF WORK MEASUREMENT Snapback Mechanical Stopwatch Snapback stopwatch has also two dials : The large dial The large dial is divided into hundredths of a minute (0.01), and one revolution of the sweep hand is one minute. The small dial The small dial records minutes up to 30. The crown of the watch The crown of the watch, resets the watch every time when it is depressed. The second of the two basic time study techniques is the snapback time study technique. The snapback mechanical stopwatch is specifically designed for this technique. When it is used and what is “Snapback Time Study Technique”? : Snapback Mechanical Stopwatch The side shifter lever The side shifter lever, turns the watch off and on (or pauses). This is a useful device when interruptions occur. The time study specialist can pause the watch until the operator goes back to work. But, then there is the chance of error or controversy.

37. 37 TECHNIQUES OF WORK MEASUREMENT The snapback watch can be used for the continuous time study technique, but continuous stopwatch can not be used for a snapback time study because it needs to be reset using three depressions of the crown. The snapback time study technique is faster and easier than continuous time study. Each time when an element ends, the time study specialist reads the watch and immediately snaps it back to zero. Thus, the watch restarts automatically timing the next element. When the next element is being timed, the specialist can record the reading which he or she obtained for the previous element. The advantage of the snapback technique is that each recorded reading is the elemental time.

38. 38 TECHNIQUES OF WORK MEASUREMENT Three-Stopwatch Set Three continuous stopwatches are used on one board. The three-watch time study technique is the best of both the continuous and snapback techniques. As previously indicated on the three-watch board, there are three continuous stopwatches each of which is at one of three different stages. When it is used and what is “Three-Watch Time Study Technique”? : Three-watch set For continuous stopwatches, remember that, first push of the crown stops the watch, the second push resets the watch and the third push starts the watch. common lever There is a common lever on the board which depresses the crowns of all three stopwatches simultaneously when pulled.

39. 39 TECHNIQUES OF WORK MEASUREMENT When the operator finishes an element of work, the time study specialist pulls the common lever that depresses all three crowns at a time. One watch is stopped, so reding can be made, the second watch started timing the current element, and the third watch is reset to zero and waiting to time the next element. Major advantages of three-watch time study technique are higher quality readings and lack of subtraction to calculate elemental times. resetstopstart 1 st push: stop 2 nd push: reset 3 rd push: start reset stop start reset stop start stopresetstart initial adjustment first pull of lever second pull of lever third pull of lever resetstartstop fourth pull of lever

40. 40 TECHNIQUES OF WORK MEASUREMENT Methods Time Measurement Stopwatch The MTM Stopwatch measures time in one hundred-thousndths of an hour (0.00001) or one TMU (time-measured unit). This stopwatch is used to reduce the math required in MTM technique. It is efficient, but few people understand what is happening. So, it creates mistrust of industrial engineering and technologists. When it is used and what is “MTM Time Study Technique”? : Methods Time Measurement Stopwatch It reads in TMUs. The hand of the watch The hand of the watch makes one revolution in 0.001 hours (0,06 minutes or 3.6 seconds). This is the same unit of time as in the MTM system.

41. 41 TECHNIQUES OF WORK MEASUREMENT Methods Time Measurement (MTM) time study technique is used where selected “predetermined time stadard system” is MTM (a copyrighted system). MTM-1 has 10 elements of micromotion. These are, Reach, Move, Turn, Apply Pressure, Grasp, Position, Release, Disengage, Eye Movements and Body Movements. Each element is assigned a number of time-measured units (TMUs), which are 0.00001 hours (one hundred thousandths of an hour). Thus, one minute equals 1667 TMUs. The MTM-2 and MTM-3 systems are faster but less accurate than MTM-1. Each of these systems has considerably fewer variables, and a standard that would take a week to set by MTM-1 would take a day in MTM-3. There is a complete package for computerizing the MTM analysis which is calld 4M. MTM system was developed by Maynard, Stegemarten and Schwab in 1948, and is probably the best known predetermined times system in use today. There are distances, cases, and classes that modify the table values, so that there are about 1700 different values to apply. There is also a way of determining which motions can be performed simultaneously. It requires over 80 hours to become proficient in using MTM-1. After completing the line of course, the student must pass an exam to be sertified as an MTM practitioner (the famous blue card).

42. 42 TECHNIQUES OF WORK MEASUREMENT Digital Stopwatches and Electronic Timers Digital stopwatches and/or electronic stopwatches come in every style and type, and most of them have multiple study technique abilities. A memory ability is available in some of the models. From left to right : Nine-memory Decimal Timer, 500-memory Decimal Timer, Digital Timer

43. 43 TECHNIQUES OF WORK MEASUREMENT Above are examples of digital watches built into time study boards. All digital and/or electronic watches need to be recharged. The maintenance of charge is important. These watches can also be used in both continuous and snapback time studies. Digital Stopwatches

44. 44 TECHNIQUES OF WORK MEASUREMENT Computers Computers can be programmed to perform the calculation side of time study yielding more accurate time standards. Hand-held Data Collectors

45. 45 TECHNIQUES OF WORK MEASUREMENT The hand-held data collectors ( ) The hand-held data collectors ( which infact either may be a portable terminal or a data storage unit ) are taken to the shop floor where the time study is performed. Once ending elements are defined and the time study is started, the time study specialist needs only to push a botton on the collector to record the time. Accuracy is much improved in this way. After data collection is complete, data collector is connected to a computer terminal for extending the time study. The math is totally automatic. Such automated systems will lower the cost of time study and increase the quality of time standards.

46. 46 TECHNIQUES OF WORK MEASUREMENT Three-watch boards are designed to hold three watches and a common lever for depressing all three crowns at the same time. They also have clips for paperwork. But, left-handed boards must be specially ordered. Time study boards vary from cheap clipboards to multiwatch digital boards and they have one goal : to hold equipment for ease of use. Continuous and snapback time study boards will have one watch holder and a clip for paperwork. The watch holder may be reversible for left-handed people. BOARDS FOR HOLDING WATCHES & PAPER Digital boards have built in watches. Two watch displays are common. They are very expensive.

47. 47 TECHNIQUES OF WORK MEASUREMENT A tachometer is used for determining the speeds of machines or conveyors. A center point attachment is placed on the tachometer and then placed against the center of a turning shaft, chuck, or arbor. The number of revolutions per minute (RPM) is recorded on the time study form as part of the operation description. Also center point attachment can be replaced by a wheel to convert RPM into FPM (feet per min) or MPM (meters per min). One of the newest and best tools for studying and recording the method and time standard is video cameras. These cameras may be recording on a tape or digitally on a hard disk. VIDEO RECORDERS, DIGITAL CAMERAS We can record an operation on a tape or hard disk and review it for the purpose of method study. Also we can use the recording device as a stopwatch. Many video recording devices have built in timer functionality. Thus, the beginning time of an operation element can be subtracted from the ending time resulting in elemental time or cycle time. TACHOMETER

48. 48 TECHNIQUES OF WORK MEASUREMENT Time study involves alot of math, and the accuracy can not be overemphasized. The calculator will speed up the process and make the results more accurate. CALCULATOR One special feature of the calculator is recommended for time study : 1/x function (for example, hours/unit and units/hour are 1/x of each other). FORMS Time study forms are generally printed forms of standard size, so that, they can be filed neatly for reference as required by a well conducted time study. The number of different designs of time study forms is probably not less than the number of work study departments in the world. Most experienced work study men have their own ideas on the ideal layout of respective forms. The principal forms used in time study generally falls into two groups : those used at the point of observation while actually making the time study, and which should therefore be of a size to fit on the study board; and those which are used in the office after the observations are completed.

49. 49 TECHNIQUES OF WORK MEASUREMENT FORMS USED ON STUDY BOARD Time Study Top Sheet : It is the top and introductory sheet of a study on which;  all the essential information about the study is recorded,  the elements of the operation which is being studied are shown,  break points of the elemental breakdown are indicated and,  readings of first few cycles are recorded. The sketch of the work place or station or the work piece being studied is drawn on the back side of the top sheet.

50. 50 TECHNIQUES OF WORK MEASUREMENT Time Study Continuation Sheet Time Study Continuation Sheet : It is used for the further cycles of the study. This form consists of only the columns and space for the study and sheet number. On the back side, heading is not necessary. “Time study top sheet” and “time study continuation sheet” are the one most generally used. They are adequate for most of the general time study work. However, for recording the short cycle repetetive work, it is more convenient to use a specially designed form as described in the following page.

51. 51 TECHNIQUES OF WORK MEASUREMENT Short Cycle Study Form Short Cycle Study Form : As told before, when the job to be studied is a short cycle repetetive job, we use a “short cycle study form” for its convenience. Short cycle study form (Simple design) Here, two different designs of short cycle forms are given as examples to this type. First of them has a simple design and the second has a little bit more complicated design. The international standard A4 size paper is a good one to use for the above mentioned forms since it is the biggest standard size which will fit conveniently on a study board. For the simple design, the sketch of the work place or station or the work piece being studied is drawn on the back side. And if required, a continuation sheet of similar design can be used.

52. 52 TECHNIQUES OF WORK MEASUREMENT Short cycle study form (Complicated design - front)

53. 53 TECHNIQUES OF WORK MEASUREMENT Short cycle study form (Complicated design - back)

54. 54 TECHNIQUES OF WORK MEASUREMENT FORMS USED IN THE STUDY OFFICE Working Sheet : It is used for analysing the readings recorded during the study and obtaining representative times for each element of the operation. One example of a “working sheet” is given on the left. Since there are various ways by which the analysis may be performed, each working sheet will have different rules to follow. Example Working Sheet

55. 55 TECHNIQUES OF WORK MEASUREMENT Study Summary Sheet : The selected or derived times for all the elements of the job together with the frequency of their occurrance are transferred to the summary sheet. This sheet neatly summarises all the information which has been obtained during the course of the study. Summary Sheet The completed study summary sheet is clipped on top of all the other study sheets and thus filed with them.

56. 56 TECHNIQUES OF WORK MEASUREMENT “Analysis of Studies” Sheet : The results obtained in different studies of a specific operation which are given on “summary sheet” of each respective study are recorded on this sheet. It does not matter whether when or Example of “Analysis of Studies” Sheet

57. 57 TECHNIQUES OF WORK MEASUREMENT by whom those studies were made. This sheet is used for final compilation of “basic times” for the elements of the operation. Analysis of studies sheet is often much larger than the ordinary study forms (it may have a standard size of A3 paper). Example of “Analysis of Studies” Sheet

58. 58 TECHNIQUES OF WORK MEASUREMENT Tables for strain allocation according to various strain types and a point conversion table are frequently used tools for calculation of “Relaxation Allowances” which are to be added to “basic times”. Points Allocated for Various Strains (summary) Guidelines for Calculation of “Relaxation Allowances” : Points Conversion Table

59. 59 TECHNIQUES OF WORK MEASUREMENT STOPWATCH TIME STUDY : Procedure The time study procedure is a ten step procedure as given below; 1. Select the job to study. 2. Obtain and record information about the job. 3. Divide the job into elements. 4. Determine the number of cycles to be timed. 5. Do the actual time study. 6. At the same time, rate the operators performance. 7. Extend the observed times to basic times. 8. Apply allowances. 9. Check for logic. 10. Publish the time standard. Now, let’s go over each step in order to get a clear understanding of what it covers.

60. 60 TECHNIQUES OF WORK MEASUREMENT There may be various reasons for a time study; 1. Unions can question time standards and request a restudy. 2. Supervisors, who are judged partly on the performance of their subordinates can request a restudy. 3. The job could change requiring a new standard. 4. New jobs may have been added to the plant. 5. New products can be added requiring many new time standards. 6. Anyone can improve a method requiring a new time standard. 7. Cost reduction programs can require new standards in relation with new machinery, tools, materials, methods ect. Once the reason for studying a job has been determined, the question is “which person do you time study?”. The person selected for time study; 1.Select the job to study 1. SHOULD NOT BE the FASTEST person on the job. The other employees may think you are going to require them to keep up. You don’t want to create employee relations problem.

61. 61 TECHNIQUES OF WORK MEASUREMENT 2. SHOULD NOT BE the SLOWEST person on the job. No matter how you rate the job and no matter how good the time standard is, employees will wonder how you come up with that standard. 3. SHOULD NOT BE a person with NEGATIVE ATTITUDES. Such an attitude will effect his/her performance while being studied. 4. The person or persons to be time studied should have sufficient experience on the job to be a qualified and well trained worker. 2.Obtain and record information about the job Recording of all relevant information about the job is very important if the subject time study is to be used as a reference in future. An incomplete information may make a study practically useless a few months after it has been made. The information we are talking about can be grouped as follows; A. Information which will enable us to find the study and identify it quickly when we need it.

62. 62 TECHNIQUES OF WORK MEASUREMENT B. Information needed for the accurate identification of product or part being processed. Study number Sheet number and number of sheets Name or initials of the study man making the study Date of the study Name of the person approving the study Name of product or part Drawing or specification number Part number (if different from drawing number) Material Quality requirements (quality standard specification number) C. Information needed for the accurate identification of process, method or machine being used. Department or location where the operation is taking place Description of the operation or the activity Method study or standard practice sheet numbers (if they exist) Plant or machine (brand name, type, size or capacity) Tools, jigs, fixtures and gauges used

63. 63 TECHNIQUES OF WORK MEASUREMENT D. Information needed for the identification of the operator being studied. Sketch of the work place layout, machine setup or part showing the surfaces worked (may be either on the back side of time study top sheet or on a separate sheet attached to it) Machine speeds and feeds or other setting information governing the rate of production by the machine or process Name of the operator / worker Clock number (in order to have an idea of operator’s experience E. Information about the duration of the study The start of the study (time “on”) The finish of the study (time “off”) Elapsed time F. Information about the working conditions Temperature, humidity, adequecy of lighting etc (recorded as a supplement information on the sketch of the work place layout.

64. 64 TECHNIQUES OF WORK MEASUREMENT 3.Divide the job into elements When we are talking about the “elements” of a “one cycle” of the specified job, it is belived that, recalling the definitions for these two terms will be beneficial; “An element of a specified job/operation refers to an activity within a complete job/operation cycle where subject activity is distinguished from the other activities by its nature and/or type”. Thus, we understand that an “element” is a distinct part of a job, and selected for convenience of observation, measurement and analysis. “A job /operation cycle is the sequence of elements which are required to perform the respective job for one unit of production”. A work cycle starts at the beginning of the first element of the job/operation and continues to the same point in a repetition of the operation, that is, to the start of second cycle.

65. 65 TECHNIQUES OF WORK MEASUREMENT 1. It makes the job easier to describe. 2. Different parts of the job has different tempos/paces. It is required to rate the operator accordingly. An operator may be more or less proficient at different parts of the job. Machine controlled elements will be constant and normally at 100% tempo. 3. Breaking the job into elements allows for moving a part of the job from operator to operator. This is called line or work station balancing. 4. Standard data can be more accurately and universally extracted with smaller elements and applied in other studies. All jobs are made up of common elements. One cycle of an operation element 1element 2element 3element 4element 5element 6 Start of the cycle End of the cycle yields one unit of production Reasons for elemental breakdown :

66. 66 TECHNIQUES OF WORK MEASUREMENT 5. Elemental breakdown enables a work study specialist to see different types of elements, so that he/she can treat them according to their type (we will talk about type of elements a little bit later). 6. Elemental breakdown enables a work study specialist to distinguish and isolate elements involving high degree of fatigue and to assign fatigue allowances more accurately. Different types of elements : “Glossary of terms in work study” There are eight different types of elements which we can distinguish from each other. The definition of each, as stated in British Standards Intitution’s “Glossary of terms in work study” is given as follows; 1. A repetetive element : 1. A repetetive element : Is an element which occurs in every cycle of job / operation. Examples : Examples : the element of picking up a part prior to an assembly operation; the element of placing a work piece in a holding device such as fixture; the element of putting aside a finished component or assembly.

67. 67 TECHNIQUES OF WORK MEASUREMENT 2. An occasional element : 2. An occasional element : Is an element which does not occur in every cycle of job / operation, but which may occur at regular or irregular intervals. Examples : Examples : adjusting the tension or machine setting; receiving instructions from the foreman. The occasional element is useful work and a part of the job. It will be incorporated in the final standard time for the job. 3. An constant element : 3. An constant element : Is an element for which the basic time remains constant whenever it is performed. Examples : Examples : switch-on the machine; gauge diameter; tighten nut; insert a particular cutting tool into machine. 4. An variable element : 4. An variable element : Is an element for which the basic time varies in relation to some characteristics of the product/equipment/process such as, dimensions, weight, quality etc. Examples : Examples : saw logs with handsaw (time varies with hardness and diameter); sweep floor (time varies with area); push trolley of parts to next shop (time varies with weight and distance).

68. 68 TECHNIQUES OF WORK MEASUREMENT 5. An manual element : 5. An manual element : Is an element performed by a worker. 6. A machine element : 6. A machine element : Is an element automatically performed by a power driven machine or process. Examples : Examples : anneal tubes; form glass bottles; press car body shell to shape; most actual cutting elements on machine tools. 7. A governing element : 7. A governing element : Is an element occupying a longer time than any other element which is being performed concurrently. Examples : Examples : turn diameter on a lathe while gauging from time to time; boil cattle of water while preparing tea glasses for service; developing fotographic negative while agitating the solution occasionally. 8. A foreign element : 8. A foreign element : Is an element observed during a study which, after analysis, is not found to be a necessary part of the job. Examples : Examples : in furniture manufacture, snding the edge of the board before plaining has been completed; degrease a part which is still to be machined further.

69. 69 TECHNIQUES OF WORK MEASUREMENT As can be seen clearly the element categories as described above are not “mutually exclusive”. That is; a repetetive element may also be a constant element or a variable one, a constant element may also be a repetetive or occasional element an occasioınal element may be a constant or variable element and so on. Principles of Elemental Breakdown : 1. Elements should be easily identifiable, with definite beginnings and endings. Thus, once established, they can be repeatedly recognized. These beginnings and endings can often be recognized by a sound (the stopping of a machine, unlocking a catch of a jig, putting down a tool) or by a change in the direction of hand or arm. They are known as “break points” and should be clearly described on the study sheet. A break point is thus athe instant at which one element in a work cycle ends and another begins.

70. 70 TECHNIQUES OF WORK MEASUREMENT 2. Elements should be as short as possible, but can be conveniently timed by a trained observer.The smallest practical element is generally considered to be 0.04 min (2.4 sec). For an avarage observer it may be 0.07 to 0.10 min. 3. Natural breaking points are best. For example, let’s consider the action of reaching for a wrench, moving it to the work and positioning it to tighten a nut. It is possible to identify the respective elements as, reaching, grasping, moving to the work piece, shifting the wrench in the hand to the position giving the best grip for turning it and positioning. The worker will probably perform all these as one natural set of motions rather than a series of independent acts. It is better to treat the group as a whole and define the element as “get and position wrench”. 4. Machine-controlled elements should be separated from operator-controlled elements so that the pace/tempo can be differentiated. Machine time with automatic feeds or fixed speeds can be calculated and used as a check on the stopwatch data. Hand time is normally and complately within the control of operator.

71. 71 TECHNIQUES OF WORK MEASUREMENT 5. Constant elements should be separated from variable elements to show a truer time. 6. Elements which do not occur in every cycle, that is, foreign and occasional elements, should be timed separately from those that do. 7. Elemental breakdown enables a work study specialist to distinguish and isolate elements involving high degree of fatigue and to assign fatigue allovances more accurately. 4.Determine the number of cycles to be timed (Sample Size) representative average value for each element Much of what we have discussed in “work sampling” such as, confidence levels and application of random number tables also applies here. But there is one major difference. In this case we are not concerned with a proportion (percent occurrance), but, finding out the “ representative average value for each element ”. The accuracy of time study depends on the number of cycles timed : The accuracy of time study depends on the number of cycles timed : the more cycles studuied, the more accurate the study.

72. 72 TECHNIQUES OF WORK MEASUREMENT Almost all time study work is aimed at an accuracy of ±5% with a 95% confidence level, so the question is “How many cycles should be studied to achieve this accuracy?”. Here, again, we can apply a statistical method for determining the number of cycles to be timed. In this method, first we have to make a number of preliminary observations by which we get preliminary readings ( n´) and then we apply the following equation for 95.45 confidence level with an accuracy of ±5%; n = 40 √ n´ ∑ x 2 – (∑ x) 2 (∑ x) Where, n = number of cycles to be timed (sample size we wish to determine). n´ = number of readings taken in the preliminary study. x = value of readings. NOTE THAT ; if we choose a different confidence level and accuracy margin, the above formula changes as well. However, most commonly used confidence level is 95% or 95.45%.

73. 73 TECHNIQUES OF WORK MEASUREMENT Let’s assume that our goal is to have 95.45% confidence level and precision ±5%. Readings of preliminary study are; 0.08, 0.07, 0.10, 0.06, 0.11 What should be the number of cycles to be studied ( n )? EXAMPLE – Number of cycles to be timed Solution : n´ = 8 ∑x = 0.42 ∑ x 2 = 0.0064+0.0049+0.01+0.0036+0.0121=0.037 n = 40 √ n´ ∑ x 2 – (∑ x) 2 (∑ x) 40 √ 8 (0.037) – (0.42) 2 (0.42) = = 32.9 = 33 cycles We have to increase our sample size. However, we can not simply say that we need 28 observations more. When we add the values obtained from these 28 additional observations, the values of x and x 2 will change effecting the value of n.

74. 74 TECHNIQUES OF WORK MEASUREMENT The statistical method can cumbersome since one cycle of a given job may be composed of several elements. As the sample size will vary with the readings for each element, we can arrive at different sample sizes for each element within a given cycle. In such a situation, we may calculate the sample size for the cumulative timing of all elements by basing it on the element which will call for the largest sample size. Some authors and companies such as General electric, adopted a conventional guide for the number of cycles to be timed, based on the total number of minutes per cycle (see below table). Minutes per cycle To 0.10 To 0.25 To 0.50 To 0.75 To 1.00 To 2.00 To 5.00 To 10.0 To 20.0 To 40.0 Over 40.0 Recommend ed number of cycles (to be observed) 200100604030201510853 Source: A.E.Shaw: “Stop-watch time study” in H.B. Maynard: “Industrial Engineering Handbook” Recommended Number of Cycles to be Observed for Time Study

75. 75 TECHNIQUES OF WORK MEASUREMENT After the elements have been identified and written down on the appropriate time study form, timing can start. Stopwatch time study techiques were described in the section titled “STOPWATCHES & TIME STUDY TECHNIQUES” (page:34 of this document). For this reason we will not repeat the detailes of the subject techniques here. However, in summary, we can say that various stopwatch time study techniques use either one of the two principal methods of timing with stopwatch; Continuous timing (also called as cumulative timing) Snapback timing (also called as flyback timing) 5.Do the actual time study : Stopwatch procedure 6.Rating the operator’s performance Rating and “allowances” are the two most controversial aspects of time study. They are largely matters of judgement and therefore each is a subject of bargaining between management and labor. Previously, it has already been said that, as far as possible, time studies should be made on a number of qualified workers. Also, it had been indicated that, very fast or very slow workers should be avoided at least while making the first few studies of an operation.

76. 76 TECHNIQUES OF WORK MEASUREMENT The qualified worker Previously, it has already been said that, as far as possible, time studies should be made on a number of qualified workers. Also, it had been indicated that, very fast or very slow workers should be avoided at least while making the first few studies of an operation. Different jobs require different human abilities (mental alertness, concentration, visual acuity, physical strength, some acquired skill or knowledge etc.). Not all workers have the same abilities because each person is unique. Knowing these, one can ask the question of “who is the qualified worker?”. The definition is given as follows; “A qualified worker is the one who is accepted as having the necessary physical attributes, who posseses the required intelligence and education, and who has acquired the necessary skill and knowledge to carry out the work in hand to satisfactory standards of safety, quantity and quality.” It would be ideal if the time study specialist could be sure that, he would find properly qualified workers for the job he had selected to study. Let’s suppose that, there are several representative qualified workers for the respective job. This time, work study specialist should be looking for the “average qualified worker” to study which is not as easy as it might seem. Thus, we can say that, according to the concept of standard time, it is a time

77. 77 TECHNIQUES OF WORK MEASUREMENT The average worker for a job or operation which should normally be attained by the “average qualified worker”. The truly “average worker” is an idea. It does not exist. It is the invention of statisticians. We are all individuals and no two of us are exactly alike. However, among a large number of people from the same country or area, variations in measurable characteristics such as height and weight tend to form a pattern which is defined as normal distribution. This is exactly same in regard to the performance of the operators and can be shown by the figure given in the following page. If 500 qualified workers, in a given factory were to do the same operation by the same method and under the same conditions, the times spent to perform the operation would be distributed as in the figure. To simplify the figure, the times have been divided into groups at intervals of 4 seconds. When the time groups are examined, it is seen that, 32.4% of the times are less than 46 seconds and 34.8% of the times are greater than 50 seconds.The largest single group of times (32.8%) lies between 46 and 50 seconds. Therefore, we can say that, for this group of 500 workers average time to perform the operation is between 46 and 50 seconds, say

78. 78 TECHNIQUES OF WORK MEASUREMENT Distribution of Times Spent by Workers to Perform a Given Job

79. 79 TECHNIQUES OF WORK MEASUREMENT 48 seconds. Then we can also call 48 seconds as the time spent by an average qualified worker. At this point it must be noted that, 48 seconds may not be good for another factory where the same operation is performed. In a factory where pay and working conditions are better the corresponding time may be 44 seconds and in a factory where poor management is operating it may be 56 second. Rating and normal performance Then comes the question; “if, this is the true picture of what is being actually happening in real world, how can we set a fair standard pace of performing a job?”. The work study specialist must have some means of assessing the rate of working of the operator he is observing and relating it to normal pace/performance.

80. 80 TECHNIQUES OF WORK MEASUREMENT The definitions of “rating” and “normal performance” are given as follows; “Rating is the assesment of the worker’s rate of working relative to the observer’s concept of the rate which corresponds to normal/standard pace.” “Normal performance is the rate of output which qualified workers naturally achieve without overexertion as an average over the working day or shift, provided that they know and adhere to the specified method and that they are motivated to commit themselves to their work. On the standard rating and performance scales, normal performance is denoted by 100%.” How is it possible accurately comparing the observed rate of working with the theoritical standard (normal rate)? “By long practice” is the only answer. Confidence in the accuracy of one’s rating can be acquired only through long experience and practice on many types of operation. Comparing “observed rate of working” with “normal rate”

81. 81 TECHNIQUES OF WORK MEASUREMENT Variations in actual times of a particular element may occur due to factors either inside or outside the control of the worker. We can summarize the factors which are outside the control of worker as follows; Factors effecting the rate of working Variations in the quality or other characteristics of the material used, Changes in the operating efficiency of tools or equipment within their useful life, Minor or unavoidable changes in methods or conditions of operation, Variations in the mental attention necessary for the performance of the operation, Changes in climatic and other surrounding conditions such as light, temperature, etc. Factors inside the control of worker can be given as; Acceptable variations in the quality of the product, Variations due to his/her ability, Variations due to his/her attitude of mind.

82. 82 TECHNIQUES OF WORK MEASUREMENT The optimum pace at which the worker will work depends on; The physical effort demanded by the work, The care required on the part of the worker, His/her training and experience. The time study specialist should be careful not to rate highly when; The worker is worried or looks hurried, The worker is obviously over-careful, The job looks difficult to the time study specialist, The time study specialist himself is working very fast, as when recording a short- element study. Conversely, there is a danger of rating too low when; The worker makes the job look easy, The worker is using smooth, rythmic movements, The worker does not pause to think when the time study specialist expects him to do so, The worker is performing heavy manual work, The time study specialist himself is tired.

83. 83 TECHNIQUES OF WORK MEASUREMENT Scales of rating In order to be able to effectively compare the “observed rate of working” against the “normal rate”, it is necessary to have a numerical scale against which this assesment is to be made. The rating then can be used as a factor by which the “observed time” can be multiplied to give the “basic/normal time”, which is the time for a qualified worker to carry out the element at “normal rating”. On the next page some rating scales are given as an example. Among the given scales, “0-100” scale is a British Standard and is important in this respect. In the “0-100” scale, 0 represents no activity and 100 represents the “normal” rate of working of the motivated qualified worker.

84. 84 TECHNIQUES OF WORK MEASUREMENT Examples of Various Rates of Working on the Principal Rating Scales

85. 85 TECHNIQUES OF WORK MEASUREMENT How the rating factor is used? The figure 100 represents normal (standard) performance. If the time study specialist decides that the operation he is observing is being performed with less effective speed than the concept of “normal”, he will use a factor of less than hundred, say 90 or 75 according to his/her assesment. If on the other hand, he/she decides that effective rate of working is above “normal”, he/she gives it a factor greater than 100, say, 110, 115 or 120. If the time study specialist’s time measurement and rating is dependably consistent, no matter how many cycles he/she repeats the time measurement and associated rating, multiplication of the two figures will yield a constant value. For clarification of this situation we can give the following example; Cycle Observed time (decimal minutes) RatingConstant 1 0.20 x 100% 0.20 2 0.16 x 125% 0.20 3 0.25 x 80% 0.20

86. 86 TECHNIQUES OF WORK MEASUREMENT The product of “observed time” and “rating” (as a percent of normal rate) is called the “basic time” (or normal time). Observed Time x Rating100 = Basic Time In the following example, where; Observed time (decimal minutes) Rating Basic Time 0.16 x 125% 0.20 the basic time, 0.20 minutes, is the time the element would take to perform, if the operator were working at the normal rate instead of the faster one which was actually observed. 7.Extending observed time to basic time

87. 87 TECHNIQUES OF WORK MEASUREMENT The effect of extending an observed time for an element to the basic time is shown graphically as follows; Effect of Extention on the time of an element

88. 88 TECHNIQUES OF WORK MEASUREMENT It is not very easy to precisely determine the allowances needed for a given job. The difficulty in preparing a universally accepted set of precise allowances which can be applied to any working situation is due to various reasons which can be summarized as follows; 8.Apply allowances 1. Factors related to the individual :  Let’s consider each worker individually in a particular working area. It may be found out that, slim, active, and alert workers who are at the peak of their physical condition require a smaller allowance to recover from fatigue than an obese and inapt worker.  Similarly, each worker has a unique learning curve which can affect the manner in which he works.  There may be some ethnic variations in response to the degree of fatigue experienced by workers (such as when engaged on heavy manual work).

89. 89 TECHNIQUES OF WORK MEASUREMENT 2. Factors related to the nature of work itself :  Every working situation has its own attributes which may effect the degree of fatigue experienced by the worker. Posture during work, requirement for exertion of force, causing eye or mental strain are examples of such factors.  Other factors inherent in the job can also contribute to the need for allowances. For example, when productive clothing or gloves must be worn, or when there is constant danger, or when there is a risk of spoiling or damaging the product. 3. Factors related to the evironment :  In particular, relaxation allowances have to be determined in regard to various environmental factors such as; heat, humidity, noise, dirt, vibration, light intensity, dust, wet conditions and so on. Each of these will affect the amount of relaxation allowances.  Environmental factors may also be seasonal especially for people who work in open air, such as in construction work.

90. 90 TECHNIQUES OF WORK MEASUREMENT TYPES & DEFINITIONS OF ALLOWANCES The basic model for the calculation of allowances is shown in below figure. From the given model, it is clearly seen that, relaxation allowances form the essential part of the time added to the basic/normal time. Allowances

91. 91 TECHNIQUES OF WORK MEASUREMENT Other allowances, that is, contingency, policy and special allowances are applied only under certain conditions. 1. Relaxation allowances : “Relaxation allowance is an addition to the basic (normal) time to provide the worker with opportunity to recover from physiological and psychological effects (fatigue) of the specified work.” Allowances for relaxation (fatigue) are normally added to the basic time of each element within a specified job cycle. Relaxation allowances have two major components; a) Fixed allowances : These allowances are “allowances for personal needs” and “allowances for basic fatigue”. Allowances for personal needs are assigned for needs such as; washing, getting a drink, going to lavatory etc. Allowances for basic fatigue are given for compansating the energy expended and for diminishing the effects of monotony.

92. 92 TECHNIQUES OF WORK MEASUREMENT 2. Contingency allowances : Contingency allowances are always very small and it is usual to express them as a percentage of the total repetetive basic minutes in the job. Contingency allowances should not be greater than 5%, and should only be given in cases where the time study specialist is absolutely satisfied that the contingencies can not be eliminated and that they are justified. b) Variable allowances : These allowances are added to fixed allowances when working conditions markedly differ from the ones stated above. For example, such an allowance may be assigned for added stress and strain because of poor environmental conditions which can not be improved. “A contingency allowance is a small allowance of time which may be included in a standard time to meet legitimate and expected items of work or delays, the precise measurement of which is uneconomical because of their infrequent or irregular occurrance.”

93. 93 TECHNIQUES OF WORK MEASUREMENT 3. Policy allowances : Policy allowances are not a genuine part of time study and should be used with the utmost caution and only in clearly defined circumstances. They should always be dealt quite separately from basic times, and, if used at all, should preferably be arranged as an addition to standard times, so as not to interfere withthe time standards set by time study. “A policy allowance is an increment, applied to standard time (or to some constituent part of it, e. g. work content) to provide a satisfactory level of earnings for a specified level of performance under exceptional circumstances.” 4. Special allowances : Special allowances may be assigned to any of the activities which are not normally part of the operation cycle but which are essential for the satisfactory performance of the work. Such allowances may be temporary or permenant, care should be taken to specify which.

94. 94 TECHNIQUES OF WORK MEASUREMENT Examples to this kind of allowances are given as follows; Start-up allowance (at the start of the shift) Shut-down allowance (end of work day or shift) Tool allowance Set-up allowance (per batch) Dismantling allowance, Change over allowance (to compensate for waiting time) Reject allowance (when defective products are inherent) Learning allowances (to inexperienced workers) Training allowance (to experienced workers) Implementation allowance (for implementation of new method or process) Small batch allowance

95. 95 TECHNIQUES OF WORK MEASUREMENT 8.The standard time Standard Time for a Simple Manual Job “Standard time is the total time in which a job should be completed at standard (normal) performance.”