Part 6 Determining the time -...

Islamic University, Gaza - Palestine

Part 6

Determining the time


Time Studies

• Used to determine the time required by a qualified and well-trained person working at a normal pace to do a specified task.

• T.S. involves measurement; motion studies involve design.• T.S. involves measurement; motion studies involve design.


Uses for Time Studies

• Determining standard costs and as an aid in preparing budgets.

• Determining schedules and planning work.

• Estimating the cost of a product before mfg.

• Determining machine effectiveness.• Determining machine effectiveness.

• Determining wage incentives for direct and indirect labor.


Let’s Look at the Three Work Analysis Tools

Work Measurement

1. Time Studies – Chapter 28

2. Motion Analysis or Predetermined Time Systems (MODAPTS) – Chapter 29


How do the Three Work Analysis Tools Compare?

• Time Studies – segmental measurement of actual work done by direct, continuous observation

• Motion Analysis – segmental calculation of actual or planned work from predetermined times associated with planned work from predetermined times associated with standard motions

• Occurrence Sampling – periodic sampling of work activities to create work estimate


Non-engineered Time Studies

• These are TEMPORARY estimates known as Type IIestimates.

• Should be set to expire automatically after no more than 60 days.60 days.

• Expressed as DID TAKE (x units of time/unit), as opposed to SHOULD TAKE


Sources of Type II Estimates

• Historical records - production rate/ # employees

• Expert opinion - get supervisor opinion of rate

• Time logs - Records of time allocation

– may omit small jobs– may omit small jobs

– may be modified to add to 8 hr/day

– may be deliberately biased

• Occurrence Sampling - data gathered over time with allowance added in with work times.


Is the Job Ready for a Time Study?

• Need correct method

• Materials in specification

• Correct machine speed

• All other conditions of work in standard settings• All other conditions of work in standard settings

• Lastly, would a motion study bring about improvements?


During the Time Study

The time analyst should ask (for each phase):– Can the speed or feed be increased w/o hurting quality?

– Can changes in tooling decrease cycle time?

– Can materials be moved closer to work area?

– Is equipment operating correctly, and a quality product being produced?

– Is the operation being performed safely?


Overview of Time Study (Type I)

1. Secure and record information about the operation and operator being studied.

2. Orient the supervisor and the workers.

3. Improve the work methods.

4. Break the task into elements and record.4. Break the task into elements and record.

5. Observe and record the time taken by the operator.

6. Determine the number of cycles to be timed.

7. Rate the operator’s performance.


Overview (cont.)

8. Check to make certain that a sufficient number of cycles have been recorded.

9. Determine the allowances.

10. Determine the time standard for the operation.10. Determine the time standard for the operation.

11. Check and debug the standards with audits.

12. Implement with recall review in one month.


Reasons for Element Breakdown

• Data is more readily reusable when each element is described separately, esp. beginning and ending points.

• Standard (estimated) time values may be determined.

• Individual elements may be excessively short (e.g., inspection), or too long. These can be picked out more easily in element or too long. These can be picked out more easily in element form.

• This allows for separate performance ratings for each.


Dividing an Operation into Elements

1. The elements should be as short in duration as can be accurately timed. (Not in individual hand motions, which are too short to time.)

2. Handling time should be separated from machine time.

3. Constant elements should be separated from var-iable 3. Constant elements should be separated from var-iable elements (i.e., those that are size dependent).

4. Regular elements are recorded first, then all others.


Taking and Recording of Data

• Continuous timing - records readings at the end of each element as watch runs

• Repetitive timing - after recording, watch is snapped back to zero at the end of each element

• Multiple watches - connected by a lever; one runs, another is • Multiple watches - connected by a lever; one runs, another is stopped, another set to go

• Electronic watch - may continue in “split” mode


Advantages and Disadvantages of Work Sampling

Advantages (of Work Sampling vs. Time Study):

1. Many operations or activities, which are impractical or costly to measure by time study, can readily be measured by work sampling.measure by time study, can readily be measured by work sampling.

2. A simultaneous work sampling study of several operators or machines may be made by a single observer. Ordinarily an analyst is needed for each operator or machine when continuous time studies are made.


Advantages (cont.)

3. It usually requires fewer man-hours and costs less to make a work sampling study than it does to make a continuous time study. The cost may be as little as 5 to 50 percent of the cost of continuous time study.

4. Observations may be taken over a period of days or weeks, thus decreasing the chance of day-to-day or week-to-week variations affecting the results.


Advantages (cont.)

5. It is not necessary to use trained time study analysts as observers for work sampling studies unless performance sampling is required. If a time standard or a performance index is to be established, however, then an experienced time study analyst must be used.

6. A work sampling study may be interrupted at any time without affecting the results.

7. Work sampling measurements may be made with a preassigned degree of reliability. Thus, the results are more meaningful to those not conversant with the methods used in collecting the information.


Advantages (cont.)

8. With work sampling the analyst makes an instantaneous observation of the operator at random intervals during the working day, thus making prolonged time studies unnecessary.

9. Work sampling studies are less fatiguing and less tedious to make on the part of the observer.


Advantages (cont.)

10. Work sampling studies are preferred to continuous time studies by the operators being studied. Some people do not like to be observed continuously for long periods of time.

11. A stop watch is not needed for work sampling studies. If an electronic data collector is used the results are shown on a computer printout.


Advantages and Disadvantages of Work Sampling

Disadvantages (of Work Sampling vs. Time Study)

1. Ordinarily work sampling is not economical for studying a single operator or machine, or for studying operators or machines located over wide areas. The observer spends too much time located over wide areas. The observer spends too much time walking to and from the work place or walking from one work place to another. Also, time study, standard data, or predetermined time data are preferred for establishing time standards for short-cycle repetitive operations.


Disadvantages

2. Time study permits a finer breakdown of activities and delays than is possible with work sampling. Work sampling cannot provide as much detailed information as one can get from time study.

3. The operator may change his or her work pattern upon sight of the 3. The operator may change his or her work pattern upon sight of the observer. If this occurs, the results of such a work sampling study may be of little value.


Disadvantages

4. A work sampling study made of a group obviously presents average results, and there is no information as to the magnitude of the individual differences.

5. Management and workers may not understand statistical work sampling as readily as they do time study.

6. In certain kinds of work sampling studies, no record is made of the method used by the operator. Therefore, an entirely new study must be made when a method change occurs in any element.


Disadvantages

7. There is a tendency on the part of some observers to minimize the importance of following the fundamental principles of work sampling, such as the proper sample size for a given degree of accuracy, randomness in making the observations, instantaneous accuracy, randomness in making the observations, instantaneous observation at the pre-assigned location, and careful definition of the elements or subdivisions or work or delay before the study is started.


Additional Tips

• Is made easier -if end of element is accompanied by a sound (e.g., dropped a shaft into a jig)

• Foreign elements - should be timed and recorded. They’ll be included if logical to do so. Examples include: putting oil on a included if logical to do so. Examples include: putting oil on a tight screw in a jig, accidentally dropping a wrench, etc.


Number of Observations

• Take at least 10 good readings for cycles of 2 minutes or less; take at least 5 good reading for cycles greater than 2 minutes

• Determine this sub-sample standard deviation to assist in determining number of actual samples needed


Chapter 28 : Stopwatch Time Study

Stopwatch Time study should be preceded by a methods analysis so the resulting standard is a“should take” time not a “did take” time.


OVERVIEW

Stopwatch time study is one of the twomethods to establish a type I time standard.

The analyst observes one or more operators continuously and records the time taken tocontinuously and records the time taken toaccomplish a task. This is called Observed Time

Observed Time x Rating = Normal Time


OVERVIEW

Standard time = (Normal time) * (100/{100 – pct Allowances})

Example:

Observed time = .01 hr./unit

Rating = 120 %

Normal time = .012 hr./unit

Allowances = 10%

Standard time = (.012 hr./unit * 100/90) =.0133hr./unit


PREPARATION

There are basically two steps involved in Preparation

1. Methods Analysis

2. Operator Selection2. Operator Selection


METHODS ANALYSIS

From a productivity standpoint, supervisors of industrial engineering department have to do job design.

•The primary reason for doing a methods analysis before doing a •The primary reason for doing a methods analysis before doing a time study is to establish a safe, productive job.

•The secondary reason is to leave a permanent record of the methods for future audits and improvements.


The typical items that are recorded are :

Date of observation (Improvement curve)Person observed (Skilled…..)Person observing (Viewpoint)

METHODS ANALYSIS

Person observing (Viewpoint)Machine used (Improvement curve)Tools used (Improvement curve)Part no. processed etc..


METHODS ANALYSIS

After a good method has been established (using checklists), the job should be broken into Elements


METHODS ANALYSIS

Five Reasons to divide the tasks into elements:

•Elements make it possible to reuse the data

•Elements permit different ratings for different elements(Machine time and manual time)time and manual time)

•Elements permit consistency checks, within the study and between studies

•Elements improve methods descriptions

•Data collection is flexible


METHODS ANALYSIS

•After the task is broken into elements, we write the element description on the time study form with a description of its EP (End points ) or also called TP (Termination point)(Termination point)

(Example)


OPERATOR SELECTION

It is very important to select the right operator for performing the time study

There are two reasons:

•Rating Accuracy(average worker)•Rating Accuracy(average worker)

•Worker Acceptance( do the study at different times)


TIMING

Timing Techniques (example):

•Videotape

•One watch, continuous

•One watch, snapback

•Three watch system

•Electronic watches


TIMING

Videotape:

•The primary advantage is having a permanent record of the method.

•Videotaping is less intrusive so there might not be any discrepancies.

•The tape counter does not give very accurate data as it gives continuous timing; use a stopwatch.

•The elements can also be performance rated

•If any dispute occurs then the tape can also be replayed


TIMING

One watch, continuous

•The stop watch does not stop, it is continuously run (Example)

•As the clock never stops, there is no time omitted and workers like thatthat

•The disadvantage is that the observer does not know how individual elements vary and the observer tries to read a moving target.


TIMING

One watch, Snapback

•As the element ends, the time is noted and the stop is reset (set back to zero).

•The advantage is that no subtraction to be done and the observer •The advantage is that no subtraction to be done and the observer is able to see the pattern.

•If the observer is confused then he might stop the watch.

•Continuous is preferred over snapback.


TIMING

Three-watch system

As in the title there are three watches and it is a combination of snap back and continuous type

Initially the hands of the first watch are moving, the second’s are stopped at some value, and the third’s are stopped at zero.

The only disadvantage is that there are three watches.


TIMING

. Electronic watches

•These watches can be used either the snapback or the continues modemode

•The key feature is that, when the user depresses the button, the display time is frozen while the clock continues timing.

•Electronic watches with a computer built into the board, generally have replaced the traditional mechanical stop watch.


NUMBER OF OBSERVATIONS

There are two approaches to determining the number of bservations

•Statistical

•Importance of Decision



Statistical

A time study of sequential observations is a sample from a population of times. The goal is to estimate the population mean from the sample mean. from the sample mean.

To minimize the differences between the sample and population means, increasing the sample size is one of the answers….


The number of sample size depends on three factors

•Accuracy Desired (absolute or relative)

•Confidence Desired (based on Z score)

•Data Variability (use subsample to determine)•Data Variability (use subsample to determine)

Calculation formula: (See Box 28.1)

-Westinghouse/ General Electric and Niebel’s approaches are in Tables 28.2 and 28.3



Irregular and Foreign Observations

•Irregular element (exp. Breakdown)

•Foreign element (exp. Customized part)



Recording Techniques

•Missed Readings

•Omitted Readings•Omitted Readings

•Element out of order

•Unexpected element


RATING

Normal Pace

During the time study, the observer will rate the worker, that is, determine the adjustment to convert the observed time to a time that a normal, experienced worker would take a normal, experienced worker would take

APL = MPL - Expectancy


RATING

MPL (Motivated productivity level) :

The work pace of a motivated worker possessing sufficient skill and effort to do the job, physically fit to do the job after adjustment to it, and working at an incentive pace that can be maintained day after day without harmful effect.


RATING

Acceptable productivity level (APL): The work pace established by management or jointly by management and labor at a level that is considered satisfactory; it is established at a given relationship to motivated productivity level.

Expectancy is the expected level of productivity, it is also related to allowance, if allowance is low expectancy discount tends to be high and vice-versa.


RATING TECHNIQUES

•There cannot be a set method to rate as different tasks within an activity requires different levels of skills and ways

•All tasks cannot be rated at a same scale

(example)


RATING TECHNIQUES

Pace Rating:

The observer estimates the speed and concentrate on dynamic micromotions such as reach or move rather then stationary like position and grasp.

Objective Rating: (three steps) (example)

•The observer rates the speed

•Observer estimates the task difficulty

•task difficulty factor is multiplied with speed to get actual pace.


RATING PROCEDURES

•Divide the elements and take multiple readings

•Categorize mental, fine manipulative and muscular jobs

•Categorize skilled, unskilled and semi skilled labor

•Categorize time of the day

•Rating is a very specialized task and enough training via videotapes, practice tests, different paces etc should be carried out before actual assignment


RATING TECHNIQUESE

stim

ated

Pac

e

120

100

80Cte Error

Actual pace

Est

imat

ed P

ace

0 20 40 60 80 100 120 140

80

60

40

20

0 Identity Line

Cte Error

Flat Rating

Consistency


Predetermined Time Systems Using MTM

• MTM = Methods-Time Measurement– MTM-1 // MTM-2 // MTM-3

• Developed by the Gilbreths

• Occurs in 2 steps– Break work down into its therblig elements

– Assign time values to each element

• Each element is independent and additive


MTM-1

• Most detailed system• Motions are broken into

10 categories• Times are found in

MTM Categories– Reach– Move– Turn • Times are found in

Tables 29.1-29.11• Distance, complexity,

and/or weights are taken into consideration

– Turn – Apply Pressure– Grasp– Position– Release– Disengage– Body Motions– Eye Motions


Methods Analysis and Time:

Reference: Karger, D. & Bayha, F. “ Engineered Work Measurement”, 4th edition. New York, Ind. Press 1987.

•Time is given in time measurement units (TMUs)

1 TMU = 0.000 010 h = 0.000 600 min = 0.036 s-Or-1 s = 27.78 TMUs1 min = 1,667 TMUs1 h = 100,000 TMUs


MTM-2 and MTM-3

• Fewer types of motions than MTM-1 therefore are easier to use

• Fewer cycles needed in order to study the process– MTM-1 – requires 250 cycle times– MTM-1 – requires 250 cycle times

– MTM-2 – requires 100 cycle times

– MTM-3 – requires 35 times


Same rules as MODAPTS

MODAPTS: Modular Arrangement of Predetermined Time Standards

• Need experienced operator and experienced practitioner

• Allowances are applied separately

• Will need to measure certain number of cycles in order to get statistically significant sample


Plus some additional rules

• Must be repetitive work, not occasional

• Distances (or degrees or other qualifying codes) determine time elements

• Tables must be present in order to get correct time per • Tables must be present in order to get correct time per element

• Additional weight (or symmetry or other “penalties”) may be applied


MODAPTS: Modular Arrangement of Predetermined Time Standards

• Predetermined time systems

• Steps

• How to be used

• Classes of motions

• Allowances• Allowances

• Exercises

(From: International MODAPTS Association, Inc. Kalamazoo, MI)


Predetermined Time Systems

• Techniques for studying work methods

• Work is divided into micro elements that are standard in any activity

• These micro elements are represented by symbols.• These micro elements are represented by symbols.

• Note that in MTM system these symbols are called therbligs.


Steps

• Determine all the symbols in a work process

• Assign standard time values to each micro movement

• Total up the times to find total time/task(Assuming additivity and independence)(Assuming additivity and independence)


How to be used

• Determine an efficient work method

• Determine the time/unit for an efficient work method

• MODAPTS uses modules (MOD) to express units of human physical work (“normal” time- done by qualified, thoroughly experienced employee)experienced employee)

– 1 MOD = .129 sec. 1 sec. = 7.75 MOD

– 1 MOD = .00215 min. 1 min. = 465 MOD

– 1 MOD = .000036 hr. 1 hr. = 27933 MOD

(Standard time with no allowances)

• MODAPTS codes

– Type of activity + Time to complete

– M3P2,W5, etc.


MODAPTS Classes of Motions

• Movement

– Done by the finger-hand-arm-shoulder trunk system

– Required to position a part of the arm to perform the Terminal activities

• Terminal Activities (GET and PUT)• Terminal Activities (GET and PUT)

– Done at the end of a movement

– In close proximity to the things being worked on

• Auxiliary Activities

– Walking, bending, inspection, deciding, etc.


Movement

• Movements and terminal activities take place in pairs.• Movement first then terminal activities

– Move to get, move to put– Examples: M3GO (move to touch)

• Movement activities are classified by:– Distance moved– Distance moved– Body part required to perform the move

• Light/small objects vs. heavy/large objects– Large objects : 16” x 16” x 16”– Heavy objects : over 18 lbs.

• Award the lowest category that is possible to successfully complete the activity


Movement (cont.)

Finger1 MOD

Hand2 MODs

1”

2”

Forearm3

MODsArm

4MODs Extended

Arm5 MODs

6”

12”

18”


Moves with Small/Light Objects

Type Movement MODs Distances

Finger (M1) Knuckle 1 1”

Hand (M2) Wrist 2 2”

Forearm (M3) Elbow 3 6”

Whole Arm Shoulder directly 4 12”Whole Arm

(M4)

Shoulder directly forward, perhaps body

assistance

4 12”

Extended Arm (M5)

Shoulder fully left, right, or across the body

5 18”

Trunk (M7) Shoulder involving the body trunk

7 30”

Note: Body assistance means to require the body to bend slightly (simultaneously with Move). It increases distances not time.


Examples

• M1 Movements– Rub your thumb and index finger together– Depressing keys – M1P0– Squeezing trigger – M1P0

• M2 Movements– Following a body move: 5 x W5, M2G1– Following a body move: 5 x W5, M2G1– Positioning of a washer: M4G3 M2P5

• M3 Movements– Turning over the page– Draw a free hand line approximately 6 inches long

• How about half an inch long?• M4 Movements

– An imaginary 45 degree cone– Move forward 18” (inside the cone)


Examples (cont.)

• M5 Movements

– Outside imaginary 45 degree cone

– Reaching up to an object from a high shelf – M5P2

– Moving an object across the body – M5P0– Moving an object across the body – M5P0

• M7 Movements

– Fully up, down, or across the body (hinged at the waist)

– Picking up objects from the floor M7G1 M7P0


Exercises

• Hand moves are typically______inches

• Whole arm move forward 15”_______

• Hand turns a nut down______

• Reach to the floor while standing______

• Using a pen or pencil perform the following and provide the • Using a pen or pencil perform the following and provide the correct code:

– Carry the object from I-10 to J-10_______

– Turn your wrist to view the bottom of the object________

– Carry the object to imaginary point H-20_______

– Return the object to G-16_______

– Carry the object to K-1_______


Moves with Large/Heavy Objects

Weight Limit

Maximum Distance

For Large Object Only

2” 6” 12” 18” 24” 35” 39”

ONE 0-2 lb M2 M3 M4 M5 M7 M7 M7

HAND 2-9 lb M3 M3 M4 M5 M7 M7 M7

9-18 lb M4 M4 M4 M5 M7 M7 M7

TWO 18-35 lb M4 M4 M4 M4 M4 M5 M7

HAND 35-136 lb M7 M7 M7 M7 M7 M7 M7


Exercises

• One hand

– Move a 14 lb. box 14” ________

– Move a 18 lb. box 3” _________

• Two hands• Two hands

– Move a 100 lb. box 6” _________

– Move a 40 lb. box 34” _________

– Move a 30 lb. box 10” _________


Terminal Activities

• PUT and GET must be joined to a move

• Influenced by:

What is done at the end of move?

– Muscular control: precision

– Visual control: eye action

– Mental control: mental decision

• Low conscious control (G0, G1, P0)

– Automatic response

– Little muscular control, no visual or mental control

• High conscious control (P2, P5, G3)


Terminal Activities (cont.)Type Conscious Control Description

High* Low

G0 X Touch only

G1 X Pick up easy object

P0 X No consciousP0 X No conscious

G3 X Pick up flat object,or objects in a bin, hard to pick up object

P2 X Requires one feedback** (information)

P5 X Requires two feedbacks

*Employees are required to follow an activity through the end, using their eyes**Provided by the employee’s eyes


Terminal Activities (cont.)

• For each activity below, is it high or low conscious?

– Pick up a pencil from an uncluttered desk. ________

– Pick up a straight pin from an uncluttered desk. ________

– Pick up a match from a matchbox. _______– Pick up a match from a matchbox. _______

– Put your pencil point exactly on the period at this sentence end. _________

– Put your pencil anywhere on this page. _________


Simultaneous Activities

• Always use an M2 to precede the second high conscious control activity

– Left hand -----movement--High control activity at end

Right hand----simo-movement---wait----M2 moveHigh control activity at endcontrol activity at end

• Both low conscious control: record the highest total MOD

• One low , one high conscious control: record on the total high conscious control activity MOD value

• Both high conscious control: sum of MOD values from both hands


Example

Left Hand Right Hand Total MODs

1 Independent

Simultaneous

M3P2

M3P2

M3P5

M2P513

12

2 Independent

Simultaneous

M4G3 M4P2

M4G3 M4P2

M4G3 M4P2

M2G3 M2P226

22

3 Independent

Simultaneous

M4G1 M4P2

M4G1 M4P2

M4G3 M4P5

M4G3 M2P527

25


GET with Small/Light Objects

• G0: Contact get (touching)– Counting small change lying on the counter– Depress button- M4G0 M1P0– Push box – M4G0 M4P0

• G1: Simple grasp get (closing fingers around objects)– Pick up raised object – M4G1– Grasp drawer handle

• G3:Get with feedback (sensory or visual feedback involved)– Pick up small or flat or jumbled object – M4G3


GET with Large/Heavy Objects

• G2: One hand engagement – Picking up a suitcase

• G4: Two hand engagements – Unobstructed object, free standing, unimpeded by

othersothers– Bend over, grasps an object with two hands and returns

to a standing position- M7G4 M7P0

• G8: Three hand engagements – Slightly impeded by others– One hand- pull the box away, two hands –pick it up


PUT with Small/Light Objects

• P0: Simple put (general or indefinite location)– Sliding an object against a stop– Picking up a small object and placing it in the other hand –

M4G3 M4P0– Tossing object into box –M3P0

• P2: Put with feedback (definite location)• P2: Put with feedback (definite location)– Requiring only one feedback form one or more of senses

(usually eyes)– Locate Phillips screwdriver in slot –M3P2

• P5: Put with feedbacks (exact location)– More than one correcting motion, and more than one change

in direction– Putting a screwdriver blade into a slotted screw head- M4P5– Placing nut on bolt- M4P5


PUT with Large/Heavy Objects

• P0: General location (no orderliness) – Hand does not touch object again– Place 40 lb. box on table ______

• P2: With orderliness • P2: With orderliness – Hand do not touch object again– Place 40 lb. box to table edge _____

• P5: One new contact (exact location) – Using one additional hand engagement once the object is

placed down– Moderately heavy box placed exactly in line with others


Exercises

• Lean over, pick up a carton, and return to a standing position before walking _______

• Place a pencil point where two lines cross ______• Begin with hands in the printed area

– Pick up a pencil at C-14, put point on F-9 _______– Pick up a pin at C-14, put point on E-10 _______– Pick up a pin at C-14, put point on E-10 _______– Pick up a washer at I-9, put in other hand _______– Slide a washer from H-9 off the table into the lap _______– With both hands, slide the ruler up to line F _______ – Pick up the pencil near the sharp end with the left hand, from B-4.

Pick up the washer with the right hand from B-13. While carrying these to the print area, put the washer on the pencil. Slide the washer along to the end of the pencil. ___________

– Pick up a washer from B-14 and then one from B-9 with the right hand. Return to rest in the approximate starting position. ___________


Auxiliary Activities

• J2: Juggle

– Two criteria

• The object is already in the control of the operator and better control is required

• All other activity must stop• All other activity must stop

– Place a nut on a screw while there are several nuts in the palm – rolling the nut out from the palm_______

• X4: Apply extra force

– All other motion stops, and then the body braces itself

• B17: Bend and arise (if hand goes below the knee)

• S30: Sit and stand (up and down movement)

• W5: Walk

Part 6 Determining the time -...

Documents

Transcript of Part 6 Determining the time -...