Week-5.2 Time Studyendustri.eskisehir.edu.tr/ipoyraz/ENM 301/icerik/Week-5.2_Time_Study.pdfwithout exertion, using correct method. Some examples • Distributing 52 cards in 0,5 min

END 202END 202Work Analysis and Design

Ti S d‐ Time Study ‐

Sibel ALUMUR ALEVSibel ALUMUR ALEV

February 2011

END 202 – Work analysis and design Time Study

Method engineering steps

1. Select project (Pareto, Fish diagram, Gantt, PERT)2 Get and present data (charts computations)2. Get and present data (charts, computations)3. Analyze data (operation analysis)4 Develop ideal method (motion work equipment4. Develop ideal method (motion, work, equipment

design)5. Present and install method (decision making tools)( g )6. Develop job analysis7. Establish time standards (time study)8. Follow up


Time study

• Time study is a technique for recording times• Time study is a technique for recording times and rates of working for specific job elements

bli h d dto establish standards

• Why do we measure time?– The most meaningful and useful measure of work

is the amount of time it takes to accomplish itp

– Time is objective

– Time is quantifiableTime is quantifiable

– People understand time


Standard time

• Standard Time is the time that a person suited to the job and fully trained in the

ifi d h d ill d f hspecified method will need to perform the job if he/she works at a normal or standard ttempo

• Includes some additional time called f ’allowances to provide for the worker’s

personal needs, fatigue, and unavoidable d ldelays


Standard time can be used…

• To define a “fair day’s work”• To define a fair day s work• To determine manpower requirements and capacity

limitations• To compare alternative methods for accomplishing

the same task• To provide a basis for wage incentives and for

evaluating worker performance• To estimate cost• To estimate cost• To provide time data for production planning and

scheduling, material requirements planning and g q p gother management functions that depend on accurate task time data


Time study

Methods to determine time standards:

• EstimationEstimation

• Historical records

• Time study techniques:– Direct time study (with chronometer)y ( )

– Standard data and formulas

– Predetermined time systems

Engineered standards

Predetermined time systems

– Work sampling


Direct time study

• Involves direct observation of a task using a stopwatch or other chronometric device to record time

• The task is divided into work elements and each work element is timed separately

• Performance rating: The worker’s performance (pace) is evaluated

N l ti i l l t d id i th f• Normal time is calculated considering the performance rating

• Allowance is added to the normal time to determine the• Allowance is added to the normal time to determine the standard time


Standard data and formulas

• Finding normal time values for work elements used in tasks using previously determined standard data or formulas

• Steps:– Identify the work elements that make up the task

together with the values of variables

f f– Access the database to find the normal time for each element or use analytical formulas

– Sum to determine the normal time for the task– Sum to determine the normal time for the task

– Add allowances to determine standard time



• Relies on a database of basic motion elements (therbligs) such as reach, grasp, move

• A i t d ith h ti l t i t f l• Associated with each motion element is a set of normal times depending on distance, weight, etc.

• List of all the basic motion elements, find the normalList of all the basic motion elements, find the normal time for each element from the data base, sum the normal times and add allowances

• Advantages– Performance rating is not required– Can be applied to determine time standard for a task beforeCan be applied to determine time standard for a task before

production


Work sampling

• Purpose is to determine proportions of time spent in different activities using randomized observations

• Examples: to determine machine idle times, to pdetermine operator utilization

• When used to establish time standardsWhen used to establish time standards statistical errors cause the standard times to be less accurate than obtained by other techniquesless accurate than obtained by other techniques

• To be studied later…


Prerequisites

Prerequisites for valid time standardsPrerequisites for valid time standards

• The task is performed by an average worker

• The worker’s pace represents standard performance• The worker s pace represents standard performance

• The worker uses the standard method

• The work is performed on a standard work unit


Direct time study (with chronometer)


Analyst’s responsibility

• The analyst should be trained on this job

• The correct people should be warned (supervisor, worker, etc.)

• Be sure that you have all the equipments with youy q p y

• Be respectful with the worker, avoid to make unnecessary commentsunnecessary comments

• Be honest with the performance of the worker

• Accurately record and note the times taken (time• Accurately record and note the times taken (time study results can influence the firm policy)


Supervisor’s responsibility

Supervisor should

• notify the operator in advancenotify the operator in advance

• see that the proper method is established

l t th b t t t t d h• select the best operator: competent and has adequate experience on the job (not too fast neither too slow)too slow)

• sign the final and original copy of the time study


Operator’s responsibility

Worker should

• cooperate in helping to work

• assist the time study analyst in breaking the job down into elements

• work at a steady, normal pacey, p

• use the exact method prescribed


Time study equipment

• Stop watch– Analog – outdatedAnalog outdated– Electronic

• Split = continuous• Lap = snapback

• Videotape camcorders• Time study board

– Holds time study form and stop watchstop watch

– Left and right handed

• Time study software• Time study software– Available for PC, for palms

• Time study form


Time study form

Time study form


Time study form – zoomed

Performance rating (100% is the standard

For continuous timingperformance of a qualified operator)

CycleR

(Rating)

W (WatchTime)

OT (Observed

Time)

NT (Normal Time)( g) Time) Time) Time)

1 85 5 5 4.252 100 12 7 7 02 100 12 7 7.03 110 23 11 12.14 90 32 9 8 14 90 32 9 8.1

Normal time (NT): OT x R/100



Time study procedures

1 Select the job1. Select the job– To implement wage incentives– To control costsTo control costs– To compare methods/jobs

2 Select the operator2. Select the operator– Qualified (intelligence, education, training, fit)– AverageAverage

• Slow worker: loose standard times (not good for the firm)

• Fast worker: tight standard times (not good for the workers)



3 Record all details about the job3. Record all details about the job– Machines, hand tools, fixtures, working conditions,

d k h f ldepartment, a sketch of layout, …

4. Examine the job and break it down into elements

– Use sight and sound for breakpointsg p

– Relatively fine but not less than 0.04 min (3 sec)

– Keep manual and machine elements separateKeep manual and machine elements separate

– Separate constant elements from variable elements



4. Examine the job and break it down into elementsTypes of elements

• repetitive: occurs each cyclerepetitive: occurs each cycle

• occasional: not every cycle

• foreign: not necessarily part of the jobg y p j

• machine: the time is fixed (no rating)

• manual: depends on worker (rating)

• constant



5. Determine the number of cycles to be timeda) Statistical estimations

2

⎟⎟⎞

⎜⎜⎛ ts

t: t distribution value refer to Table A3 3 App 3 pg 701

⎟⎟⎠

⎜⎜⎝

=μk

n

t: t‐distribution value, refer to Table A3‐3, App. 3, pg 701

s: standard deviation

k: an acceptable fraction for errorp

µ: sample mean value

E l 0 30 0 09 %5 d i d t bl f ti kExample: µ = 0.30, s = 0.09, %5 desired acceptable fraction k,0.05 for 24 degrees of freedom: t = 2.064 (Table A3‐3, App. 3)

N 153 3 154 b i


N = 153.3 ≈ 154 observations


5. Determine the number of cycles to be timedb) Approximate guide (from General Electric Company)

C l ti ( i )Recommended

Cycle time (min)number of cycles

0.10 200 (20 min)

0.25 100 (25 min)0.25 100 (25 min)

0.50 60 (30 min)

0.75 40 (30 min)

1 00 30 (30 min)1.00 30 (30 min)

2.00 20 (40 min)

2.00-5.00 15

5 00 10 00 105.00-10.00 10

10.00-20.00 8

20.00-40.00 5


>40.00 3


6 Measurement R W OT NT6. Measurement– Continuous timing

• Stopwatch is never reset

O5 512 7• Stopwatch is never reset

• You record the cumulative times• At the end you need to subtract

12 723 1132 9At the end you need to subtract

times

– Snapback timing

32 9

R W OT NTp g• Stopwatch is reset each time (each elemental work)

R W OT NT57• Read direct times from zero

– No decimal point

7119


9

Comparison btw continuous and snapback timing

Continuous timingContinuous timing• Better adapted to measure and record very short elements

(3 successive elements of <0.04 min followed by 0.15 min)A l d f h i b i i d• A complete record of the entire observation period

• All delays and foreign elements are recorded• More clerical work is involved

Snapback timing• More suitable for long elements• No need to make successive subtractions• Delays are not recorded• Some individual elements are removed or are studiedSome individual elements are removed or are studied

independently of preceding and succeeding elements• Overall time is obtained by summing: prone to error


Performance rating

Different options for rating the operator

• one rating to entire study (for short cycle)one rating to entire study (for short cycle)

• an average rating for each element

• evaluate the performance of each element as it occurs (for long and diversifiedas it occurs (for long and diversified movements)



Finding standard time

Adding allowancesAdding allowances

• Different interruptions can take place. We must provide extra time to take them into account.– Personal interruptions (trips to the restroom, drinking fountain)drinking fountain)

– Fatigue

d bl d l ( l b k– Unavoidable delays (tool breakage, supervisor interruptions, material variations, etc.)


Finding standard time

Adding allowances to obtain the standard time

ST = NT x (1 + allowance)ST NT x (1 + allowance)

• 15% is the average allowance used for manual elements

• 10% is the average allowance used for machine elements


Time study steps


Time study steps


Performance rating and allowances


Performance rating

Rating of 100%Rating of 100%• Standard (normal) performance = 100% = rate of output achieved by a qualified workerof output achieved by a qualified worker, without exertion, using correct method.

Some examplesSome examples• Distributing 52 cards in 0,5 min• Walking with 5 4 km/hWalking with 5.4 km/hRating can change due to• Environmental conditions fatigue quality of• Environmental conditions, fatigue, quality of raw material, changes in method, …


How to rate the performance?

Rating methods:

1. Speed rating

2 W ti h t2. Westinghouse system

3. Synthetic ratingy g

4. Objective rating


1. Speed rating

• Speed rate considers only the rate of work per unit time• Speed rate considers only the rate of work per unit time

• Measurement of the effectiveness of the operator by the ratio of the observed performance to standardratio of the observed performance to standard performance

• Can be used for elemental, cycle, or overall rating, y , g

• Works needing great precision (aircraft engine parts fabrication) can appear slower than a simple work

• Record the rating in the R column before reading the stopwatch time! Do not rate by the watch!

• Begin by rating only by 10s (80,90,110) then move onto 5s (85,95,105)


1. Speed rating – example

Rating Verbal anchor points Walking speed (mph)

Cards dealt in 0 5 ming p speed (mph) in 0.5 min

0 No activity 0 067 Very slow clumsy 2 3567 Very slow, clumsy 2 35100 Steady, deliberate 3 52133 Brisk businesslike 4 69133 Brisk, businesslike 4 69167 Very fast, high dexterity 5 87200 Upper limit for short period 6 104200 Upper limit for short period 6 104


2. Westinghouse system

• Westinghouse Electric Corporation (Lowry et al. 1940) developed a system of 4 factors in evaluating1940) developed a system of 4 factors in evaluating the performance of the operator:

Skill Th fi i t f ll i i th d– Skill: The proficiency at following a given method

– Effort: Demonstration of the will to work effectively

C di i I l d il i li h i– Conditions: Include temperature, ventilation, light, noise

– Consistency: Evaluated as the study is worked up


2. Westinghouse system


2. Westinghouse system – example

• Once each four factor are rated sum the four values and add 1 to give the performance rating factor

• The Westinghouse System is appropriate for either cycle rating or overall study rating but not for elemental rating


3. Synthetic rating

• Determines a performance factor based on fundamental predetermined motion times (F)fundamental predetermined motion times (F)

FROT

R =

R: Performance or rating factor

F: Fundamental motion time

OT: Observed mean time


3. Synthetic rating – example

Element noObserved time Fundamental Rating factor

Element no.(OT) motion time (F)

g(R)

1 0.08 0.096 123%

2 0.15 – 123%

3 0.05 – 123%

4 0 22 0 278 123%

/ /

4 0.22 0.278 123%

• R1 = F1/OT1 = 0.096/0.08 = 120 %

• R4 = F4/OT4 = 0.278/0.22 = 126 %

Average rating factor is 123%


4. Objective rating

Eli i h diffi l f bli hi d d• Eliminates the difficulty of establishing a standard pace for every type of work

DPR ×=R: Performance or rating factor

P: Pace rating factorg

D: Job difficulty adjustment factor (amount of body used, foot pedals, bimanualness, eye‐hand coordination, handling or sensory requirements, weight handledorresistance encountered)


Rating application and analysis

RatingRating

> 1000.16

= 1000.20

0.25 < 100

• Normal time (NT): OT x R/100

• NT = 0.2 x 100/100 = 0.2

• NT = 0.16 x 125/100 = 0.2

• NT = 0.25 x 80/100 = 0.2


Rating application and analysis

Potential mistakesPotential mistakes

• Subjective rating

• Capacity of working memory

• Cultural norms (UK 100% = 4 mph)• Cultural norms (UK, 100% = 4 mph)

• Training is crucial:– Tight rater = rates below actual, unfair

– Loose rater = rates above actual, easy, y

– Conservative = rates close to mean


Allowances

• Normal time does not include unavoidable delaysNormal time does not include unavoidable delays

• Need to make adjustments to compensate for such lossessuch losses

• Allowances can be applied to 3 parts of the study– The total cycle time

– Machine time only

Manual effort only– Manual effort only

• 2 methods for developing allowances:Direct observation– Direct observation

– Work sampling


Noting allowances


Types of allowances


Types of allowances

• Constant allowancesConstant allowances– Personal needs (≈ 5%): restroom, smoking, drinking, lunch

– Basic fatigue (≈ 4%)– Basic fatigue (≈ 4%)

• Variable fatigue

S i l ll• Special allowances– Unavoidable delays: interruptions from supervisor, material i l iti hi i t firregularities, machine interference

– Avoidable delays: socializing, idleness other than rest

E t ll tt ti ti l i t l i t– Extra allowances: attention time, cleaning, tool maintenance

– Policy allowances: new employees, differently ables, workers on light duty


on light duty

Variable fatigue allowances – 1


Source: International Labour Office (ILO)

Variable fatigue allowances – 2


Source: International Labour Office (ILO)

Revised table of allowances – 1


Revised table of allowances – 2


Applying allowances

( )ST = NT x (1 + allowance)

ST: standard time

NT: normal time

Example:P l d 5 0 %

pPersonal needs 5.0 %

Basic fatigue 4.0 %

Unavoidable delay 1 0 %Unavoidable delay 1.0 %

TOTAL 10.0 %


How to use allowances?

• Generally we use it to take a rest

• 30 min lunch time is included

• 2 times 10 min of rest are included

• For a 8 h of work, 50 min of rest ≈ 10%

F h b k f d• Frequent short breaks are preferred over infrequent, long breaks





• Use standard data tabular or graphical collections of• Use standard data, tabular or graphical collections of normal times, for common work elements

• Use formulas to provide quick and consistent normalUse formulas to provide quick and consistent normal times for variable elements

• When properly applied, standard data permit the rapid establishment of accurate time standards before the job is performed

• A time study formula can establish standards in a• A time study formula can establish standards in a fraction of the time required for direct time study

• Advantage of formulas over standard data is that a less gskilled person can plug data into formulas more quickly than adding standard data elements



Steps:

• Identify the work elements that make up the task y ptogether with the values of variables

• Access the database to find the normal time for each element or use analytical formulas

• Sum to determine the normal time for the task

• Add allowances to determine standard time





• Relies on standard times assigned to the basic elements of work:

– basic motion times: further refinement is both difficult andbasic motion times: further refinement is both difficult and impractical

– synthetic times: often the result of logical combinations of therbligstherbligs

– predetermined times: used to predict standard times for new work

h f d l i diffi l l• These fundamental motions are difficult to evaluate with stopwatch time study

• Associated with each motion element is a set of normalAssociated with each motion element is a set of normal times depending on distance, weight, etc.



AdvantagesAdvantages• They are realized on several workers under controlled conditionscontrolled conditions

• The analyst doesn’t need to determine the performance rating which can be subjectiveperformance rating which can be subjective

• The operation is not interruptedTh l l f l iti f h l t l k• The level of complexities for each elemental work can also be computedTh th 50 t h W k• There are more than 50 systems, such as: Work‐Factor, MTM, MOST, etc.


Methods‐time measurement (MTM‐1)

• Maynard et al., 1948y ,• Results of frame‐by‐frame analyses of motion picture

films• Time values for the fundamental motions are given

Ex: reach, move, turn, grasp• Assigns to each motion a pre‐determined time• Assigns to each motion a pre‐determined time

standard which is determined by the nature of the motion and the conditions under which it is made

• Westinghouse technique of rating is used• Ex. Reaching depends on distance and type of reach.

Reach is divided into five distinct cases and Move intoReach is divided into five distinct cases and Move into 3 cases (see p. 502).

• TMU: Time Measurement Unit = 0,00001 hour


,


Steps of MTM‐1Steps of MTM 1• Determine all left‐hand and right‐hand motions

required to perform the job properlyq p j p p y• Determine the rated times from the methods‐time

data tables in TMU for each motion– Tables I‐X: reach, move, turn and apply pressure, grasp,

position, release, disengage, eye travel time and eye focus, body, leg and foot motions, simultaneous motionsbody, leg and foot motions, simultaneous motions

• Sum the TMU values (consider only limiting values)• Add allowancesAdd allowances

– The tabulated values do not carry any allowances – Some analysts state that no fatigue allowance is needed



• The data are adapted to the operator and areThe data are adapted to the operator and are independent of the workplace or equipment

• Used in work assignments whereUsed in work assignments where– The effort portion of the work cycle is more than 1 min– The cycle is not highly repetitivey g y p– Does not involve a large number of either complex or simultaneous hand motions

• In addition to basic MTM motions, there are combinations of them – GET: reach + grasp + release– PUT: move + position + release





11 classes of actions (categories)( g )• Get (reach‐grasp‐release)• Put (move‐position)

h• Get Weight• Put Weight• Regrasp• Regrasp• Apply Pressure• Eye Actiony• Foot Action• Step

B d d A i• Bend and Arise• Crank



Cases for GET(G) Cases for PUT(P)Cases for GET(G) Cases for PUT(P)



• Principle of Simultaneous Motion: If two hands make the same task simultaneously, more time can be assigned depending on the difficulty

• Principle of Limiting Motion: If two hands makePrinciple of Limiting Motion: If two hands make different tasks at the same time, we consider the slowest oneslowest one

• Principle of Combined Motion: If one hand makes two distinct movements we take the slowesttwo distinct movements, we take the slowest time


Methods‐time measurement (MTM‐?)

• MTM‐3: helpful for works where there is an interest in psaving time at the expense of some accuracy

• MTM‐V: for use in metal cutting operations, to establish set p times for all t pical machine toolsestablish setup times for all typical machine tools

• MTM‐C: widely used in banking and insurance industries, for work tasks such as filing, data entry, andindustries, for work tasks such as filing, data entry, and keyboarding

• MTM‐M: for operator working on a microscope, i i i t f t imicrominiature manufacturing

• MTM‐TE: for electronic tests• MTM MEK: one of a kind and small lot production• MTM‐MEK: one‐of‐a‐kind and small‐lot production• MTM‐UAS: for a process description, batch production


Maynard Operations Sequence Technique (MOST)

• Developed by Zandin in 1967 applied inDeveloped by Zandin in 1967, applied in Sweden

• Simpler than MTM but faster than MTM‐1 andSimpler than MTM, but faster than MTM 1 and MTM‐2 (at least 5 times faster than MTM‐1)

• There are three levels:• There are three levels:– MaxiMOST: analyzes long, infrequent operations (range from 2 min to several hours and occur less(range from 2 min to several hours and occur less than 150 times per week)

– MiniMOST: very short and very frequent (less than 1.6 min in length, more than 1500 times a week)

– BasicMOST: 0.5 min to 3 min of length




Time study

Methods to determine time standards:

• EstimationEstimation

• Historical records

• Time study techniques:– Direct time study (with chronometer)y ( )

– Standard data and formulas

– Predetermined time systems

Engineered standards


– Work sampling


Documents

Week-5.2 Time Studyendustri.eskisehir.edu.tr/ipoyraz/ENM 301/icerik/Week-5.2_Time_Study.pdfwithout exertion, using correct method. Some examples • Distributing 52 cards in 0,5 min