Industrial egineering
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Industrial egineering Document Transcript

  • 1. WORK MEASURMENTWork Measurement is a term which covers several different ways offinding out how long a job or part of a job should take to complete. It canbe defined as the systematic determination, through the use of varioustechniques, of the amount of effective physical and mental work in termsof work units in a specified task. The work units usually are given instandard minutes or standard hours.Why should we need to know how long a job should take? The answer tothis question lies in the importance of time in our everyday life. We needto know how long it should take to walk to the train station in themorning, one needs to schedule the days work and even when to takeout the dinner from the oven.In the business world these standard times are needed for:1.) planning the work of a workforce,2.) manning jobs, to decide how many workers it would need to complete certain jobs,3.) scheduling the tasks allocated to people4.) costing the work for estimating contract prices and costing the labour content in general5.) calculating the efficiency or productivity of workers - and from this:6.) providing fair returns on possible incentive bonus payment schemes.On what are these standard times set? They are set, not on how long acertain individual would take to complete a task but on how long atrained, experienced worker would take to do the task at a defined levelof pace or performance.
  • 2. Who sets these standard times? Specially trained and qualified observersset these times, using the most appropriate methods or techniques forthe purpose i.e. "horses for courses".How it is done depends on circumstances that obtain. The toolkitavailable to the comprehensively trained observer is described below.Selecting the most appropriate methods of workmeasurementThe method chosen for each individual situation to be measured dependson several factors which include:a.)the length on the job to be measured in time unitsb.)the precision which is appropriate for the type of work in terms of timeunits (i.e. should it be in minutes, hundredths or thousandths of aminute)c.) the general cycle-time of the work, i.e. does it take seconds, minutesor days to completeThe length of time necessary for the completion of the range of jobs canvary from a few seconds in highly repetitive factory work to several weeksor months for large projects such as major shutdown maintenance workon an oil refinery. It is quite clear that using a stop-watch, for example,on the latter work would take several man-years to time to measure!Thus, more "overall" large-scale methods of timing must be employed.The precision is an important factor, too. This can vary from setting timesof the order of "to the nearest thousandth of a minute" (e.g. short cyclefactory work) to the other end of the scale of "to the nearest week" (e.g.for large project work).These are the dominant factors that affect the choice of method ofmeasurement.
  • 3. The ways of work measurementPMTS.At the "precision" end of the scale is a group of methods known aspredetermined motion time systems that use measurement units in tenthousandths (0.0001) of a minute or hundred-thousandths of an hour(0.00001 hour).The resulting standard times can be used directly, for very short-cyclework of around one minute total duration such as small assembly work.However, they often are used to generate regularly used basic tasks suchusing assembling or disassembling nuts and bolts, using a screwdriverand similar. Tasks of this type are filed as standard or synthetic data-banks.Estimating.At the other end of the scale (long-cycle and project work) we needsomething which is quick to use. Such a method is estimating. This canexist in three main forms.a.)Analytical estimating relies on the experience and judgement of theestimator. It is just of case of weighing up the work content and, usingthis experience, stating a probable time for completion, such as "this jobwill take about eight days to complete".b.)Category estimating. This is a form of range estimating and requiresa knowledge of the work. Estimators may not feel comfortable withoverall, analytical estimates upon which may depend the outlay of a greatdeal of money. They often prefer giving a range estimate such as "this jobshould take between 12 weeks and 14 weeks to complete", whichprovides a safety net should things go wrong. Such ranges are not just
  • 4. picked upon at random but are statistically calculated and based onprobability theory.c.)Comparative estimating. This is another example of rangeestimating. Again, estimators rely on experience of the work in order toproduce estimates. This experience can be augmented by the provision ofeach time-range with a few typical, descriptive, jobs that would guideestimators to the most appropriate range. The estimator would comparethe work to be estimated with those in the various ranges until the mostappropriate fit is found.Timing.The intermediate method between the two groups above, is timing thework in some way, usually with a stop-watch or computerised electronicstudy board. This method is retrospective in that the job must be seenin action in order to be timed whereas the other methods areprospective and can be used for timing jobs before they start.The observer times each element of the work and obtains times that theobserved operator takes to do the elements. Each timing is adjusted(rated) by the pace at which the operator was working as assessed by theobserver. This produces basic times for the elements and hence the wholejob, which are independent of the operator and can be used as the timefor a trained, experienced worker to carry out the same elements.Another method of assessing the work is using activity sampling andrated activity sampling. This is a method based on the observer makingsnap observations at random or systematic sample times, observing whatthe operator is (or operators are) doing at the times of those observationsModels:A most useful method for standard or synthetic data-banks of job orelement times is using computer models of the jobs. These are generated
  • 5. as mathematical formulae in which the observed data are inserted tocompile a time for completion of the task or project. It is a useful methodfor recycling time standards for elements of basic work over and overagain, only changing the values of the variables to suit each project ACTIVITY SAMPLINGWhat is it ?Activity Sampling is a statistical technique that can be used asa means for collecting data. It is defined by BS 3138:41008 as:A technique in which a large number of observations are madeover a period of time of one group of machines, processes orworkers. Each observation records what is happening at thatinstant and the percentage of observations recorded for aparticular activity or delay is a measure of the percentage oftime during which that activity or delay occurs.It is normally used for collecting information on thepercentages of time spent on activities, without the need todevote the time that would otherwise be required for anycontinuous observation.One of the great advantages of this technique is that it enableslengthy activities or groups of activities to be studiedeconomically and in a way that produces statistically accuratedata.Fixed and Random Interval SamplingActivity Sampling can be carried out at random intervals orfixed intervals. Random activity sampling is where the intervalsbetween observations are selected at random e.g. from a tableof random numbers. Fixed interval activity sampling is where
  • 6. the same interval exists between observations. A decision willneed to be made on which of these two approaches is to bechosen. A fixed interval is usually chosen where activities areperformed by a person or group of people who have a degreeof control over what they do and when they do it. Randomintervals will normally be used where there are a series ofautomated tasks or activities as part of a process, that arehave to be performed in a pre established regular pattern. Iffixed interval sampling were to be used in this situation there isa danger that the sampling point would continue to occur atthe same point in the activity cycle.Confidence LevelsRemember, that activity sampling is used for assessing thepercentage of time spent on activities.Because activity sampling conforms to the binomial distributionit is possible to use a calculation to determine how manyobservations will be needed to operate within specified limits ofaccuracy.The formula for the number of observations is as follows:= 4 x p x (100 - p) L2Where p is the estimated % time spent on the activityWhere L is the limit of error, expressed as a %Once the above calculation has been completed theobservations can begin and activities are recorded at theagreed time intervals. When they have been completed afurther calculation can be used to determine the error rate, asfollows:
  • 7. Error Rate = ± 2 x √( p x (100 - p) )Number of observationsThis is very much an overview to the topic of activity sampling,with a definition of what it is, its advantage over continuousobservation and the formulae that can be used to establish theconfidence levels that can be obtained. DATA COLLECTIONWhat is/are data?One definition of data is: "known facts or things used as a basisfor inference or reckoning":- The OED.Another is: "facts given from which others may be inferred": -Chambers Dictionary.The term "data" more commonly is another word for "statistics"or numerical facts. The UK Prime minister, Disraeli, is quotedas saying, "There are lies, damned lies and statistics". Indeed,statistical data can be presented to mean what you wish themto mean. ("Data" is a plural word, the singular being datum.However, through American influence it is acceptable to use"data" in the singular form rather than "data are".
  • 8. Forms of dataData can be separated into three categories of data(variables):a.)discrete variables, which are numerical and can only beparticular numbers, such as the number of workers in anorganization (i.e. they are counted in single units)b.)continuous variables, which are dimensions of items inunits of measurement such as metres, litres, volts and otherunits of length, volume, time.c.)attribute variables, which are descriptive e.g. a machine"on" or "off", or an employee absent or present.The main phases in the collection of data using samplingmethods are:1. The purpose or objective for collecting the data,2. identification of the entire "population" from which the dataare to be collected (e.g. a sampling frame).3. decisions on: o method of collection, or how the data are to be collected o sample size (i.e. how many readings to collect), and4. validation of the results, this being a vital part of thecollection/analysis process.SamplingOne important thing to bear in mind is that something in thesystem must be random. This could be the situation which israndom or a sampling method which contains a random
  • 9. element for picking the components of the sample. Some ofthese follow.The choice of sampling method depends on the type of databeing sampled.Random sampling:A common method is simple random sampling or the lotterymethod. One of the most convenient ways is to allocatenumbers to all components of the population to be sampledand obtain the required amount of numbers to constitute thesample size. The ways of obtaining a random sample ofnumbers range from drawing numbers blindly "from a hat", (orthe mechanized version of agitated balls being ejected from adrum), to the use of computer generated numbers.Systematic sampling.Often known as the constant skip method, this form ofsampling is based on taking every nth reading from the randompopulation. For example, in a survey, taking every 9th house ina street, for example, numbers 3, 12, 21, 30, 39 and so on).Care must be taken to avoid bias, so in the UK, taking every10th house means they would all be on the same side of theroad, and this might be significant.Stratified sampling.In order to ensure that all groups in a population are properlyrepresented, this method separates the population into strataand allocates proportional representation to each stratum. Withpeople, the strata may be occupations, or social classes, ages,
  • 10. or income groups for example. Once selected, one of the othertwo methods may be used within the strata.Other methods.These include quota sampling, cluster sampling and multi-stagesampling.ValidationIt is of little use if the sample collected does not represent thewhole population. Clearly no sample can exactly reflect the trueresult had the whole population been surveyed. Therefore,probably there the sample result will differ from the truesituation. What is important is that we are aware of theprobable statistical errors which inevitably arise because thewhole population was not investigated. Provided that thepopulation is relatively large, the magnitude of the statisticalerror depends not on the size of the population but on the sizeof the sample. The error can be calculated (dealt withelsewhere in this Managers-net Web-site) or alternatively, thesample size can be calculated prior to data collection if wedecide on the size of the error which we can tolerate. If thesubsequent error is too large, then a bigger sample size mustbe taken, i.e. a further set of observations to add to theexisting ones. At least, we can be aware of the statistical errorto which our results are subject due to sampling and use thedata appropriately.
  • 11. STATISTICAL PROCESSING CONTROLThe fundamentals of Statistical Process Control (though thatwas not what it was called at the time) and the associated toolof the Control Chart were developed by Dr Walter A Shewhartin the mid-1920’s. His reasoning and approach were practical,sensible and positive. In order to be so, he deliberately avoidedoverdoing mathematical detail. In later years, significantmathematical attributes were assigned to Shewharts thinkingwith the result that this work became better known than thepioneering application that Shewhart had worked up.The crucial difference between Shewhart’s work and theinappropriately-perceived purpose of SPC that emerged, thattypically involved mathematical distortion and tampering, isthat his developments were in context, and with the purpose,of process improvement, as opposed to mere processmonitoring. I.e. they could be described as helping to get theprocess into that “satisfactory state” which one might then becontent to monitor. Note, however, that a true adherent toDeming’s principles would probably never reach that situation,following instead the philosophy and aim of continuousimprovement.Explanation and Illustration:What do “in control” and “out of control” mean?Suppose that we are recording, regularly over time, somemeasurements from a process. The measurements might belengths of steel rods after a cutting operation, or the lengths oftime to service some machine, or your weight as measured onthe bathroom scales each morning, or the percentage ofdefective (or non-conforming) items in batches from a supplier,or measurements of Intelligence Quotient, or times betweensending out invoices and receiving the payment etc., etc..
  • 12. A series of line graphs or histograms can be drawn to representthe data as a statistical distribution. It is a picture of thebehaviour of the variation in the measurement that is beingrecorded. If a process is deemed as “stable” then the conceptis that it is in statistical control. The point is that, if an outsideinfluence impacts upon the process, (e.g., a machine setting isaltered or you go on a diet etc.) then, in effect, the data are ofcourse no longer all coming from the same source. It thereforefollows that no single distribution could possibly serve torepresent them. If the distribution changes unpredictably overtime, then the process is said to be out of control. As ascientist, Shewhart knew that there is always variation inanything that can be measured. The variation may be large, orit may be imperceptibly small, or it may be between these twoextremes; but it is always there.Wheeler and Chambers combine and summarise these twoimportant aspects as follows:  "While every process displays variation, some processes display controlled variation, while others display uncontrolled variation."Why is "in control" and "out of control" important?Shewhart gave us a technical tool to help identify the two typesof variation: the control chart .What is important is the understanding of why correctidentification of the two types of variation is so vital. There areat least three prime reasons.First, when there are irregular large deviations in outputbecause of unexplained special causes, it is impossible toevaluate the effects of changes in design, training, purchasingpolicy etc. which might be made to the system by
  • 13. management. The capability of a process is unknown, whilstthe process is out of statistical control.Second, when special causes have been eliminated, so thatonly common causes remain, improvement then has to dependupon management action. For such variation is due to the waythat the processes and systems have been designed and built –and only management has authority and responsibility to workon systems and processes. As Myron Tribus, Director of theAmerican Quality and Productivity Institute, has often said:  “The people work in a system.  The job of the manager is o To work on the system o To improve it, continuously,  With their help.”Finally, something of great importance, but which has to beunknown to managers who do not have this understanding ofvariation, is that by (in effect) misinterpreting either type ofcause as the other, and acting accordingly, they not only fail toimprove matters – they literally make things worse. Theseimplications, and consequently the whole concept of thestatistical control of processes, had a profound and lastingimpact on Dr Deming. Many aspects of his managementphilosophy emanate from considerations based on just thesenotions.
  • 14. So why SPC?The plain fact is that when a process is within statisticalcontrol, its output is indiscernible from random variation: thekind of variation which one gets from tossing coins, throwingdice, or shuffling cards. Whether or not the process is incontrol, the numbers will go up, the numbers will go down;indeed, occasionally we shall get a number that is the highestor the lowest for some time. Of course we shall: how could itbe otherwise? The question is - do these individual occurrencesmean anything important? When the process is out of control,the answer will sometimes be yes. When the process is incontrol, the answer is no.So the main response to the question Why SPC? is thereforethis: It guides us to the type of action that is appropriate fortrying to improve the functioning of a process. Should we reactto individual results from the process (which is only sensible, ifsuch a result is signalled by a control chart as being due to aspecial cause) or should we instead be going for change to theprocess itself, guided by cumulated evidence from its output(which is only sensible if the process is in control)?Process improvement needs to be carried out in threechronological phases:  Phase 1: Stabilisation of the process by the identification and elimination of special causes:  Phase 2: Active improvement efforts on the process itself, i.e. tackling common causes;  Phase 3: Monitoring the process to ensure the improvements are maintained, and incorporating additional improvements as the opportunity arises.Control charts have an important part to play in each of thesethree Phases. Points beyond control limits (plus other agreedsignals) indicate when special causes should be searched for.
  • 15. The control chart is therefore the prime diagnostic tool in Phase1. All sorts of statistical tools can aid Phase 2, including ParetoAnalysis, Ishikawa Diagrams, flow-charts of various kinds,etc., and recalculated control limits will indicate what kind ofsuccess (particularly in terms of reduced variation) has beenachieved. The control chart will also, as always, show when anyfurther special causes should be attended to. Advocates of theBritish/European approach will consider themselves familiarwith the use of the control chart in Phase 3. However, it isstrongly recommended that they consider the use of aJapanese Control Chart (q.v.) in order to see how much morecan be done even in this Phase than is normal practice in thispart of the world. STATICAL SAMPLING FOR DATA COLLECTIONWhen it is possible to collect all the data for a population, theresults (for example the parameters like average (mean) ordispersion of the data values) will accurately represent thesituation. However, because the sampling frame from whichthe sample is taken usually will be large, it is impossible tomeasure all the data, so a sample must be obtained.Unfortunately, because we cannot measure all of the data thesample parameters when calculated probably will notaccurately represent the whole data field. This gives rise towhat are known as statistical, or sampling, errors.Two important points about sampling are that the sample mustbe (a) representative of the situation and(b) usually random, in order to avoiding the effects of bias. Random sampling isthe most usual methods of obtaining representative sampling.
  • 16. Methods of sampling1. Random samplingAs already mentioned above, when taking a sample somethingwithin the sampling frame must be random in order to avoidthe effects of bias. Either the situation must be random or thesampling must be on a random basis.One of the most common, but not the simplest, is randomsampling as used in lotteries. Random samples may be takenby several methods including thoroughly mixing up the items inthe sampling field and then picking the number of items in thesample size at random e.g. without selecting). Another methodis to number each item in the population of values and thenuse randomly generated numbers to obtain the randomsample. Many are already numbered such as serial numbers onequipment, passports or National Insurance numbers. Randomnumbers may be found in textbooks, statistical tables or ascomputer programs.The following example is not necessarily how it is done inpractice but is one method of sampling to illustrate the methodin general terms.Suppose an electricity supply organisation needs to assess thedegree of corrosion of its main power lines in various areas ofthe country in order to find those areas which are prone to theworst corrosion and hence might need more attention thanother areas. It is an impossibly time-consuming task to inspectevery power line between every tower in every area and,indeed, not necessary. Sampling can provide a sufficiently"accurate" or reliable answer with a known degree of error.Meanwhile, using a map of the grid system the researchercould divide the territory into areas and the areas into smallerlocations. Each power line could be divided into smaller lengths
  • 17. (possibly "between each tower") and each smaller lengthwould be identified in some way (e.g. numbering or coding).In order to decide which of the thousands of lengths of cableare to be examined, first of all the sample size (i.e. how manylengths to be inspected) must be determined. It is the samplesize that eventually determines the degree of error in theresult, when this is applied to the whole network includingthose thousands of lengths which were not checked. Basically,the larger the sample size the smaller is the statistical error.These statistical errors are not to be confused with humanerror nor with measuring equipment error.When the sample size has been calculated (as dealt with in alater Topic) The next stage is to identify which of the lengthsare to be inspected.For this purpose it is necessary to generate random numberseither from tables available in many books on statisticalmethod or from computer spreadsheets (e.g. Lotus 1-2-3, orEXCEL). When the required number of random numbers hasbeen obtained these are used to identify the correspondingnumbers on the grid map as the ones to be inspected.Figure 1 illustrates a very simplified, abridged example ofthis method in diagrammatic form showing only 30 lengths ofcable. These are numbered 1 to 30.A sample size of eight is used in this instance. Randomnumbers, taken from a random number table, are18,28,5,13,16,9,26 and 21. These are indicated in red on the"map" below. These numbered cables would be used as thesample:
  • 18. Cablenumbers 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 31 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0Methods of sampling2.Systematic samplingSystematic sampling (or constant skip method) is not random.Nevertheless, it can be used where the situation is random.For example, suppose the objective of a large organization is toobtain a random selection from the 800 employees to sit asrepresentatives on a management productivity group. Each hasan employee staff identification number issued randomly byPersonnel Department. To collect a sample of 20 names,management could take, for example every 40th name from thestaff register (i.e. 800 divided by 20 equals 40, hence every40th name).Methods of sampling 3. - stratified samplingThis method is useful where the sampling frame has naturalstrata or divisions. For example, to ensure that alloccupations in a company are equally represented theoccupations could be the strata and within each stratum,random or systematic samples could be taken. So, using theexample quoted for systematic sampling, if the employeesconsisted of 64 managers, 200 supervisors and 536 engineers(=800 employees) to obtain a representative proportion fromeach employee grade (or stratum), the proportions would be:
  • 19. for managers, 64 out of 800 total employees = 8%, 200 out of800 = 25% and 536 out of 800 = 67%.Therefore, 8% of the random numbers would be frommanagement names, 25% from supervisors names and therest, 67%, from the engineers names. This ensures arepresentative proportion from each group.Mystery shoppersThe "mystery shoppers" method of sampling is used in marketresearch to determine the quality of goods and services. Withthis method employees or specially engaged agencies acting as"customers" make notes on the service they receive in theenvironment being inspected.This method can be used for testing the "ambience" of areas(e.g. "how pleasant" is the area). For example, some railservices use the method for inspecting their rolling stock andstations for litter, vandalism, malicious damage, graffiti and thegeneral appearance of the environment and "feel" of theirassets. ANALYTICAL SAMPLINGWhat is it ?Analytical estimating is a structured work measurementtechnique. The formal BSI definition (22022) states that it is adevelopment of estimating, in which the time required toperform each constituent part of a task at a defined rate ofworking is estimated from knowledge and practical experienceof the work and/or from synthetic dataAn important feature of this technique, which helps to improveaccuracy, is that a whole job should be broken down intosmaller individual tasks. This is because any errors in the time
  • 20. estimates may be seen as random and will thereforecompensate for each other.How can it be used ?Analytical estimating would normally be used for assessingwork over a reasonably lengthy period of time, where it may bedifficult and more expensive to collect the information requiredusing other measurement techniques. Also, in some workenvironments the presence of an individual carrying out workmeasurement in the work place could be unacceptable. Inthese cases, analytical estimating may be an appropriatemethod to use, assuming someone with experience of the workis available to apply their experienced judgement. ( This maybe work measurement personnel who have previous experienceof this particular work )However, the work content of some jobs cannot be estimatedin advance because one is unclear about what is required untilan assembly operation has been tested or stripped down. Forexample, during the progress of repair unforeseen and nonstandard difficulties can arise. Removing a wooden door fromits frame by unscrewing 8 or 12 screws could take five minutesif the screws were recently inserted, or a great deal longer ifthe screws are rusted and clogged with paint.In summary, the technique is used most commonly in any workenvironment where a lengthy time (and associated high cost) isneeded to collect data.Advantages & DisadvantagesPerhaps the most significant advantage of using anayticalestimating is its speed of application and low cost. Usingtrained and experienced personnel process and measurementdata can be quickly assembled and applied.However, the use of experienced judgement when determiningthe time necessary to perform a task is the techniques most
  • 21. obvious source of weakness when compared with a moreprecise technique such as time study. This is why thetechnique would not normally be used when a more preciseand accurate alternative is a feasible and economic alternative,particularly to highly repetitive, standardised operations.Many jobs, such as craft work in the maintenance field, consistof a group of tasks which are periodically repeated but theprecise nature of each task varies each time in minor respects (see research on Natural & Normal Variation for furtherexplanation). In this example, since it is impractical, in termsof time and cost, to allocate one time study observerpermanently to each craftsman, the alternative is to use atime-study basis plus the experienced judgement of an ex-craftwork-study observer to allow for detailed task variations. BUSINESS PLANNINGBusiness (Corporate) Planning is the process of deciding whattactical action and direction to take, in all areas of businessactivity, in order to secure a financial and market positioncommensurate with the strategic objectives of the organisation.To put it another way, it is the comprehensive planning for thewhole of the business and involves defining the overallobjectives for the organisation, and all the actions that must beadopted in order that those objectives are achieved.Illustration:If only we spent as much time doing our jobs, as we waste inthese budget meetings, we would be a lot better off. Thisplanning stuff is all very well, but has anyone ever worked outhow much it costs? Anyway, all we can ever do is write downwhat we think will happen, then wait until it hasn’t happened,and finally argue about why it didn’t. Sometimes I wonder if itis all worthwhile.
  • 22. Statements like these occur because:  No one has taken the trouble to explain the purpose and benefits of planning;  The planning methods are wrong;  Plans are imposed from above, rather than worked out and agreed with the people who are going to have to carry them out;  So-called planning is often no more than totalling up the various departments’ forecasts, and calling them the company plan.In general it can be assumed that FIVE important features ofCorporate Planning prevail, they are: 1. Objectives and objective setting; 2. Flexibility - the ability to be adaptable within the plan; 3. Growth - anticipating opportunities for new markets; 4. Synergy - the sum of joint efforts being greater than either one; 5. Time span - the critical length of the plan - long termism is increasingly risk managed in today’s business environment.
  • 23. CORPORATE PLANNINGA planning technique that aims to integrate all the planningactivities of an organisation and relate them to the best overallobjectives for the organisation.Explanation:A large number of planning techniques has been extensivelyused in business and commerce for a considerable time.Budgetary control (q.v.) which involves a large amount ofbudgetary planning has been one of the most wide ranging andsuccessful, via its materials, labour, sales, overheads, R&D,capital and cash budgets. A further development of this is thetechnique of profit planning (q.v.), which considers a numberof alternative strategies on capital investment, expansion,diversification for example, before setting a single preferredplan. Corporate planning represents a further widening and, atthe same time, a closer integration of earlier techniques. Asexamples of the widening process, corporate planning wouldnormally include management development and training,environmental and community plans in addition to operatingplans. As an example of closer integration, the technique wouldinvolve all managers and departments in setting objectives anddetermining the means to achieve them, in relation to theoverall company plan.Illustration:The technique has found most favour with larger companies ofmature standing, i.e. those whose days of headlong growth areover, who are subject to strong international competition andwho wish to think out extremely carefully their futureinvestment projects and at the same time to harmonise andintegrate the policies, procedures and plans created in eachcountry, division and operating unit of the company.
  • 24. Predetermined motion time system (PMTS)Definition:PMT Systems are methods of setting basic times for doing basichuman activities necessary for carrying out a job or task.Tables of time data at defined rates of working for classifiedhuman movements and mental activities. Times for anoperation or task are derived using precise conventions.Predetermined motion time data have also been developed forcommon combinations of basic human movements and mentalactivities.BackgroundThe principle of analyzing work into into basic actions was firstpublished by F. Gilbreth in 1920, as his Therbligs. The firstcommercial and internationally recognized system was devisedin the 1930s to circumvent the banning by the government ofthe United States time study and the stop-watch as the meansof measuring work performed on US government contracts. Itwas devised by Quick, Malcolm and Duncan under the titleWork-Factor and appeared in 1938. Other methods followed,the main one, some ten years later, being Methods-TimeMeasurement (MTM). Both systems share basic similarities butare based on different standards of time.Outline description of PMTSThe concept of PMTS is to analyse a job into its fundamentalhuman activities, apply basic times for these from tables andsynthesize them into a basic time for the complete job. Thebasic elements include the following:
  • 25.  reach for an object or a location,  grasp an object , touching it or closing the fingers around it,  move an object a specified distance to a specified place,  regrasp an object in order to locate it in a particular way, usually prior to:  release an object to relinquish control on it,other elements for assembling to, or inserting an object into,its intended location.For each of these actions basic times are tabled. For example,in Work-Factor the time unit is one thousandth of a minute(the Work-Factor Time Unit) whereas in MTM the unit is onehundred-thousandth of an hour (time measurement unit, tmu).The times for basic actions are adjusted for other factors whichtake into account such variables as:  distances moved, in inches or centimetres  difficulty in performing the actions, such as avoiding obstacles during moves, closeness of fit during assembling, weight of the object, all of which increase the times to carry out the basic actions.The above basic motions cover most of the actions performedby humans when carrying out work. Other basic activitiesinclude:  walking to a specified place  bending down and stooping  kneeling on one knee and kneeling on both knees  foot and leg motions  sitting down and standing.
  • 26. Mental activities include times for: See, Inspect, Identify,Nerve Conduct, React, Eye focus, Eye travel times, Memorize,Recall, Compute (calculate) and others, mostly from Work-Factor.Levels of detail in systemsIn order to speed up measurement time the major systems allinclude different levels of detail, such as: 1. most detailed systems: MTM and Detailed Work-Factor 2. Second level systems: MTM-2 and Ready Work-Factor (abridged versions) achieved usually by the four methods of combining, statistically averaging, substituting and/or eliminating certain basic motions. 3. Third level systems: MTM-3 and Abbreviated Work-Factor (even more abridged) 4. "higher level" systems, usually times for complete activities.One example of simplifying in the second level system MTM-2is the combining of MTM elements reach, grasp and release toproduce a new MTM-2 element of "Get".PMTS is often used to generate synthetic data or (standarddata banks) which are overall basic times for more complextasks such as maintenance or overhauling of equipment. This isachieved by synthesizing the hundreds of small jobs measuredusing PMTS into a time for the complete project.Basic times produced by PMTS need to have relaxationallowances and other necessary allowances added to producestandard times.
  • 27. An example of part of a typical analysis in MTM-2 isAn extract from an MTM analysis showing the first sevenelements.MTM Analysis Job description: Analyst: EJH Assemble r.f. transformer to base- Date: 3 May plateEl. Description LH tmus RH Description Move hand to1 Move hand to washer R14C 15.6 R14B transformer Grasp2 Grasp first washer G4B 9.1 G1A transformer Move hand clear of3 M2B --- --- Hold in box container4 Palm washer G2 5.6 --- Ditto5 To second washer R2C 5.9 --- Ditto6 Grasp washer G4B 9.1 --- Ditto Transformer to7 Move washers to area M10B 16.9 M14C plateNotes on descriptions of some of the codes as examples.The codes in the LH and RH columns refer to those in the MTMtime tables. For example: R14C is translated as "Reach 14 in.to an object jumbled with other objects in a group, so that
  • 28. search and select occur" (Class C reach). R14B is translated as"Reach 14 in. to a single object in location which may varyslightly from cycle to cycle." G2 is a grasp Case 2 which is aRegrasp to move the washer into the palm G4B is a Grasp Case4B which is for grasping *object jumbled with other objects sosearch and select occur. Objects within the range 0.25 x 0.25 x0.125 in. to 1 x 1 x 1 inch."One tmu is one hundred-thousandth of an hour. Time studyWhat is it?Time study is a tried and tested method of work measurementfor setting basic times and hence standard times for carryingout specified work. Its roots are back to the period between thetwo World Wars.The aim of time study is to establish a time for a qualifiedworker to perform specified work under stated conditions andat a defined rate of working.This is achieved by a qualified practitioner observing the work,recording what is done and then timing (using a timemeasuring device) and simultaneously rating (assessing) thepace of working.The requirements for taking a time study are quite strict.Conditions:  the practitioner (observer) must be fully qualified to carry out Time Study,  the person performing the task must be fully trained and experienced in the work,
  • 29.  the work must be clearly defined and the method of doing the work must be effective  the working conditions must be clearly definedThere are two main essentials for establishing a basic time forspecified work i.e. rating and timing.Some terminology explainedTimingThe observer records the actual time taken to do the elementor operation. This usually is in centiminutes (0.01 min.) and isrecorded, using a stop-watch or computerized study board.Rating.When someone is doing work his/her way of working will varythroughout the working period and will be different from othersdoing the same work. This is due to differing speeds ofmovement, effort, dexterity and consistency. Thus, the timetaken for one person to do the work may not be the same asthat for others and may or may not be reasonable anyway.The purpose of rating is to adjust the actual time to astandardized basic time that is appropriate and at a definedlevel of performance. Rating is on a scale with 100 as itsstandard rating.ElementsA complete job usually will be too long and variable to time andrate in one go, so it would be analysed into several smallerparts (elements) which, separately, will each be timed andrated.
  • 30. Basic timeThis is the standardised time for carrying out an element ofwork at standard rating.Example: An observer times an element as 30 centiminutes(cm) and because it is performed more slowly than thestandard 100, he rates it as 95. Thus the basic time is 95%of 30 or 28.5 basic cm. The formula is: (actual time xrating)/100.AllowancesExtra time is allowed for various conditions which obtain, themain ones being relaxation allowance for: a. recovery from the effort of carrying out specified work under specified conditions (fatigue allowance) b. attention to personal needs c. adverse environmental conditions, d. others concerned with machine operationsFrequencyThe basic time is the time for a complete cycle to be performedbut as not all elements are repeated in every cycle their timesper average cycle must be pro rata. In the example whichfollows, element 2 only occurs once every eight cycles so itsbasic time is one eighth of the element time, per cycle. Similartreatment for element 7 (one twelfth).Standard time:Basic time + allowances
  • 31. RATINGDefinitionRating is a term used in work measurement to assess thespeed and effort put into a job of work by the worker. TheBritish Standard Institute definition of the verb “to rate” is:To assess the worker‟s rate of working relative to theobserver‟s concept of the rate corresponding to standardrating. The observer may take into account, separatelyor in combination, one or more factors necessary to thecarrying out of the task, e.g. speed of movement, effort,dexterity, consistency.The conceptIn order to determine the time necessary to carry out a task orjob it is not sufficient just to assess this by timing with achronometer a worker carrying out the task or even estimatingit. The worker might be working slowly or “extra quickly”.These are vague terms but neither would be satisfactory forthe purposes of obtaining some sort of “standard time” for thejob. What is needed is a time the “average”, trained, qualifiedworker would take to do the job.This concept of the “average rate” at which the qualified workerwould work is a very subjective one - it is a matter of opinion.In essence, we do not want a time for doing a job quickly orslowly. We need a standard time for the job and not a time forany individual worker.The solution is to assess the time actually taken by a qualifiedworker who knows the job and is properly trained to do it andthen adjust this actual time to what it would have been had
  • 32. that worker been working at the standard rate. Thus, ratingeliminates the need to search for that mythical standard workerand takes out of the equation the need for that worker toadjust his/her pace to the standard rate of working, somethingwhich is difficult to do.So, to quote the BSI standard 3138 “Glossary of Terms used inManagement Services” Term number 22074, standard rating isdefined asThe average rate at which qualified workers will work, providedthey adhere to the specified method, and are motivated, suitedand accustomed to the task.How is it done?So, clearly, rating is highly subjective. To aid raters to conformwith the universally accepted concept of rating there are sets offilms/videos/CDs which demonstrate various jobs with theirrates and have tests for training purposes.Capable observers must be trained in the art of rating, firstrecognizing the standard rating and then, through practising,assessing against this standard other levels of rates of working.Rating scales have been developed. One of the original ones isCharles Bedaux’s, known as the “60/80 scale”. Bedauxconsidered that workers paid on a fixed daywork systemwithout any financial incentive would normally do 60 minutesworth of work in an hour whereas one on a financial bonusscheme would get the work done on average one third faster,doing 80 minutes work in an hour (incentive rate). The rest ofthis “60/80 scale” was pro-rata. So, for example, a workerworking twice as fast as this perceived “normal” 60 ratingwould be assessed as working at 120 rating.This Bedaux scale was later converted to decimal formaccepted by British Standard Institute which allocated a ratingof 75 BS in place of Bedaux 60 and 100 BS rating replacing
  • 33. Bedaux’s 80 rating. The complete BS scale supercedes thecorresponding Bedaux scale pro rata.Incentives:- financial reward systemIntroductionThe concept of schemes for incentive payments is a verycontroversial one. The first thing to make clear is that financialincentives and motivation are diametrically opposed to eachother. Frederick Herzberg in particular would, in his time, beaghast at the mention of the two concepts in the same breath.But this is the subject of another Topic (see below).In the Topic “Scientific Management” you will read about thepioneers of this approach the management. The way to getmore work out of people was to give them some incentivewhich could range from the negative “stick” method to thepositive “carrot” incentive. The “stick” drives people to workmore quickly because the must, while the “carrot” attractsthem to speed up to earn rewards. In a nutshell, better outputis achieved because people are made to work better whilepsychological motivation produces better output becausepeople want to achieve. Both methods are largely effective andsuccessful but for different reasons.In order for financial incentive schemes to be effective theymust be based on targets. Targets, usually, are in terms ofoutput in numerical form reling on the jobs being workmeasured.A typical schemeA typical scheme is the piecework method in which workers arepaid “per unit produced”. The format of the system is chosen(described later). A standard time per unit is set on the jobusing a suitable choice of work measurement. The output islinked to the (usually) variable wages. The proposal is put to
  • 34. the workforce and unions if relevant for their discussion andagreement.There is a minimum safeguard for the worker, or basic payrate, usually set at a 50 BS performance. Workers are neverpaid less than this amount. Above the 50 BS a bonusproportional to the actual performance is paid. 100 BS level isknown as the “incentive” performance and 75 BS,is “normal”performanceA basic scheme is as described above with basic wage is paidup to an actual performance of 50 BS. Above this a bonus ispaid in direct proportion to the actual performance on a one-for-one basic. In all cases the pay performance scale is gearedto actual currency of the country, pro rata.There are many different forms of financial incentives. One ofthe most basic schemes is the “50 + a half” which is similar tothe above but pay performance bonus is at a rate of only halfof the actual performance. The Figure below illustrates the 50+ 1/2 scheme. For example, if the worker produces 90 actualperformance, he/she is paid the wage equivalent to a 70performance i.e. half of the bonus part going to the workerand half to the company.Other variants include the Taylor differential piece-ratescheme, which is similar to the above but has a step or “jump”in the payment as an extra inducement to increase output.Another group uses curved schemes, such as the Rowan“hyperbolic” payment scheme and the Barth Variable Sharingscheme.An example of a „fixed‟ bonus schemeIn the 1960’s the Philips organization, tired of theadministration involved in payment-by-results, devised amethod of individual fixed bonuses in its Premium PaymentPlan (PPP). Basically, workers contracted with the company to
  • 35. work at a certain rate on average for an equivalent fixedbonus. Workers who defaulted on the contract were warnedthat in order to maintain their individual bonuses they mustimprove. Employees could work their way up to higher levels ofbonus through contracting to work at correspondingly higheroutput levels as they became more experienced.