Unit2 Work Study

Work study 2.0

Definitions: Work study is the generic term for the techniques of Method study (motion study) and work measurement (Time study) which are used for finding out the best and most efficient way of using available resources namely men, Material and Machines. Motion study: Work simplification – Developed by Frank Gilbreth & Lillian Gilbreth. Time study : Work measurement – Developed by F W Taylor.

2.1

2.2

2.3

Applications: 1. Production operations, R & D 2. Marketing, Sales and distribution 3. Stores, ware house and offices 4. Material Handling 5. Design Advantages of Work study: 1. Uniform and improved production flow 2. Higher Productive Efficiency 3. Reduced Manufacturing Cost 4. Fast and prompt Delivery 5. Good Industrial Relations

6. Buildings, Roads and other Constructional activities 7. Transport 8. Hospitals 9. Army 10. Agriculture 6. Better service to customers 7. Job satisfaction to employees 8. Improved working conditions 9. Higher wages to workers

Contributions of F W Taylor: 1. 2. 3. 4.

2.4

Developed Time study and established work standards Developed the concepts of Scientific Management Introduced the concepts of Fair day’s task considering the fatigue of workers Developed the Functional organization where the importance of Specialists in various fields is highlighted 5. Suggested a Wage incentive scheme known as Taylor’s Differential Piece Rate Plan Contributions of Frank Gilbreth: 1. 2. 3. 4.

Developed the concepts of Motion study Evolved the Principles of Motion Economy Introduced the use of Process Charts Identified the Fundamental motions involved in doing an activity Known as THERBLIGS 5. Developed Micro-motion study and SIMO chart, Microcrhronometer, Cyclegraph, chronocyclegraph and flow diagrams. 6. Carried out studies on fatigue and its elimination by lighting the load, spacing the work and introducing rest periods.

2.5 2.5.1

Motion Study: Definition: Motion study:

It is the science of eliminating wastefulness resulting from ill directed and inefficient motions.

Method study:

It is a systematic investigation of the existing method of doing a job (process) and developing an easy, rapid, efficient, effective and less fatiguing procedure for doing the job at lower cost. The scope of motion study is enlarged to form the method study. 2.5.2

Objectives of Method study: 1. Elimination of wastage of time and labor 2. Least fatigue to workmen 3. To find the best way of doing a job 4. Better lay out, neat and clean environment and working conditions 5. Effective utilization of resources 6. Better quality of products 7. Efficient material handling 8. Reduced health hazards and safe working conditions 9. Stream lined working procedures

2.5.3

Procedure of method study: Steps: 1. Select the work for study and define objectives 2. Record all the relevant information pertaining to the existing method. Break up the operations of the job. Use (a) Process charts (c) Motion & Film analysis (b) Diagrams (d) Models 3. Critical examination -Question each details of the job. The basic questions are on the following points. 1. Purpose 4. Sequence 2. Place 5. Means 3. Persons 4. Develop the best method 1. Practical & Feasible 2. Economical 2. Safe & Effective 3. Acceptable to other departments Design, Prod. Control, QC, sales 5. Install the best method so devised Stages: 1. Planning 3. Implementing 2. Arranging 6.

Maintain the new method 1. Periodic checks & Verification 2. Views of workmen, supervisors and other persons may be obtained.

2.5.4

Flow process charts: A chart representing the sequence of operations of a process is called the Flow process chart.

2.5.5

Symbols used in process chart: 1. Operation

2. Storage: or Temp. Storage

2.5.6

:

5. Inspection 6. Operation cum Transport

: :

7. Inspection cum operation

:

8. Change point cum operation

: :

:

3. Delay

:

4. Transport

:

Types of flow process charts: 1. Outline process chart:

Gives over all picture of the process giving main events sequence wise.

2. Flow process chart 3. Two handed process chart 4. Multiple activity charts Flow process chart:

A detailed version of outline process chart.

1. Sets out sequence of low 2. Records all he events in sequence using symbols 3. Marks distances traveled and time taken by an event Types: 1. Man type : Records activities of an operator 2. Equipment type: Records the usage of equipment 3. Material type : Records the changes in material in location or condition

S.No.

Activity

1

Casting in foundry

2

Moved to gas cutting m/c

3

Wait- setting m/c

4

Raisers cut

5

Wait for trolley

6

Moved to m/c shop

Operations

Distance moved meters

Time in Minut es

Remarks

10

3

By trolley

5 20 10

7

20

Inspection before machining

6 15

--Material type Flow process chart Bring specimen from Metallurgical Lab Start polishing Sprinkle the etching solution Hold the specimen in hand Load the specimen on polishing Machine Wait for a few seconds Take the specimen to wash Basin Wash the specimen Etch the specimen Wash again Dry the specimen

10 m

2m

Check under microscope Keep the specimen in container Flow process chart (Man type)

By trolley

Left hand

Symbols LH

Right hand

RH

Pick up bolt

Idle

Hold

Pickup nut

Hold

To left hand

Hold

Assemble ( Screw up) Two hand process Chart

Multiple activity charts: It records the simultaneously the activities of all the workers in a team or the activities of a worker and the machines he handles on a common time scale showing their inter relations. Operator’s Activities Starting Setting M/c. 1 Setting M/c. 2 Idle

Time Operato r 0 5 10

Setting M/c. 2 Idle

25 30

Setting M/c. 1 Idle

40 45

Machine 1

Machine 2 Remarks

50 60

Multi activity chart

2.5.7

Flow diagrams: Def: A flow diagram is a drawing or diagram which is drawn to scale showing the relative positions of Prodn. Machinery, Jigs &fixtures, gang way etc. and marks the path followed by men and materials. Steps: 1. Draw to scale the plan of work area. 2. Mark up the positions of m/cs. , benches, stores, racks, inspection booths etc. 3. Observe the operations and draw the path of the materials and men on the drawing showing the directions of movements. 4. Use different colours for different movements. Use symbols. 2

1

1 1

5

Flow diagram 2.5.8

String Diagram: A string diagram is preferred to flow diagram when the movements are very much congested and difficult to trace. It is a lay out drawing on which a length of a string is used to record the extent as well as the pattern of movements of workers and materials.

M2

M1

stores

M4

Stock room

M3

Inspection

String Diagram

String

2.5.9

Operation analysis: Operation analysis is a detailed study of different operations involved in doing a job. 1. Possible ways of improving a process: 1. Eliminations of some undue operations 2. Combining one or more operations. 3. Change of sequence of operations. 2. Questionnaire for effective solutions: Areas of questions: 1. Worker 2. Material 3. Material handling 4. Machine set up

2.5.9.1

5. Operations 6. Tools and fixtures 7. Working conditions

Motion analysis: Analysis of an operation when carried out in terms of individual motions of a worker is known as motion analysis. 1. Steps for carrying out operation analysis: 1. 2. 3. 4. 5. 6. 7. 8.

Select the operation to be studied List and chart various motions performed by operator Identify the productive and idle motions Eliminate unnecessary and non-productive motions Redesign the existing procedure Impart necessary instructions to workers Verify the procedure for improvement and usefulness standardize the procedure

2.5.10 THERBLIGS: Frank Gilbreth developed a set of elementary motions commonly found in manual operations and called them “THERBLIGS” (spelled his name in reverse). Different motions of limbs are divided into fundamental events. Each element is allotted a symbol, a letter abbreviation and a color. S.No THERBLIGS Abbr eviat ion 1 Search SH 2 Hold H 3

Select

SE

4

Grasp

G

5

Release load

RL

6

Transport loaded Transport empty Position Preposition

TL

7 8 9

Sym bol

TE P PP

Color

S.No THERBLIGS

Black Gold ochre Light grey Red

10 11

Assemble Disassemble

Abbr Sym eviat bol ion A DA

12

Use

U

13

Inspect

I

Carmi ne red Green

14

DA

Olive green Blue Pale blue

16

Avoidable delay Unavoidable delay Rest

17 18

Plan Find

15

DA R

Orange

PN F

Brown Grey

A SIMO chart is an extremely detailed left and right hand operation chart. 1. It shows on a common time scale the simultaneous minute motions (THRBLIGS) performed by the two hands. 2. SIMO charts record the duration of micro motions. 3. The time scale is in Winks. ( 1 Wink = 1/2000 min. ) SIMO chart

Operation: Name : Component name: Method: LH Description

Symbol

Date: Film No. : Operation No. :

Grasp chistle To job Position Hold

G TL P H

Time in Winks 0 – 10 20 30 - 40 50

Violet Light violet Purple Burnt ochre Lemon yellow Yellow

2.5.11 SIMULTANEOUS MOTION CYCLE (S I M O) CHART: Def:

Color

Symbol

RH Description

G TL AD U

Grasp hammer To job Idle Use

2.5.12 PRINCIPLES OF MOTION ECONOMY •

PRINCIPLES CONCERNING HUMAN BODY 1. Both Hands for Productive Work. 2. Both hands to Start & Finish at the same time. 3. Both hands should not be idle at the same time. 4. Simultaneous, Symmetrical & Opposite motions. 5. Motions to be Simple & Involve min. Limbs. 6. Momentum can assist self ; Not to be overcome by Muscular effort. 7. Motions should be Smooth & Continuous. 8. Ballistic movements to be preferred. 9. Mechanical Aids to be used. 10. Work movements to be Rhythmic & Automatic if possible.

•

PRINCIPLES CONCERNING WORK PLACE LAYOUT 1. Fixed & easily accessible Location for Tools & materials. 2. Matls., tools etc. should be close to the work place. 3. Use of chute/conveyor/gravity is preferred. 4. Tools & Matls. To be placed in their sequence of use. 5. Good illumination. 6. Proper proportions of heights of chair & table. 7. Seating to be Adjustable & comfortable.

•

PRINCIPLES CONCERNING TOOLS & EQUIPMENT DESIGN 1. Use of Jigs & Fixtures. 2. Tools must be of multi-purpose. 3. Max. surface contact while handling. 4. Equal distribution of load for all the Fingers.

•

PRINCIPLES CONCERNING TIME COSERVATION 1. Ceasing of Work to be discouraged. 2. Machines should not be run idle. 3. Two or more Operations to be carried out simultaneously. 4. Min. No. of Motions for a job.

2.5.13 Work place layout: Comfortable work place keeps the workers more satisfied resulting in more productivity. 1. Ergonomics: It is the science which considers all the factors regarding the work place environment including the knowledge of anatomy, physiology, psychology etc. 2. Design considerations: 1. 2. 3. 4.

Location of tools and materials Cleanliness Proper illumination Noise

1. Actual working area

2. Normal working area Typical work place layout

5. Proper chairs 6. Work bench 7. Use of gravity 8. Proper machine elements

3. Max. Working area

2.6

Time Study • Def.: Time study (Work measurement) is defined as the application of different techniques to measure & establish the time required to complete a job by a qualified worker, at a defined level of performance. • OBJECTIVES: 1. To determine the time required to do a job. 2. To compare & develop alternate methods. 3. Estimation of man power requirement. 4. Requirement of equipments. 5. Effective Prodn. Planning & maintenance. 6. Estimation of delivery dates. 7. Basis for sound and fair incentive schemes. 8. Effective labor control. • STANDARD TIME: It is the amount of time required to complete a unit of work a) under existing working conditions, b) using specified machinery & method, c) by an operator able to work in proper manner , d) at a standard pace. 2.6.1

Stop watch procedure for collecting time study data: Steps involved: 1. Identify the operations to be studied 2. Obtain the improved procedure from method study department 3. Collect the necessary equipments and ensure their accuracy Stop watch, Time study record sheets, time study board etc. 4. Select the worker to be observed 5. Take the worker and supervisor into confidence and explain them the objectives of the study 6. Break the operations into small elements and write them in the proper form 7. Separate the constant time elements from variable time elements ( machine and manual elements) 8. Conduct the observations and record them on the time study sheet 9. Rate the performance of the worker during observing the timings 10. Repeat the steps 8 and 9 for taking more observations 11. Compute the average time from the observations 12. Calculate the Normal time from the observed time using Performance rating factor 13. Obtain the standard time by adding process allowance, rest and personal allowance and special allowances to normal time. Policy allowances are in addition to the standard time. Normal time = Observed time x Performance rating factor Standard time = Normal time + Process allowances + Rest & personal Allowances + Special allowances Types of stop watches: 1. Non-fly back 2. Fly back 3. Split hand

2.6.2

2.6.3

Standard data: Standard data is a catalogue of normal time values for different elements of ajob 1. Standard data (Macro data) 2. Universal standard data (Microdata) Time measuring techniques: 1. Stop watch method 2. Analytical estimating 3. Synthesis 4. PMTS ( Pre determined motion time standards)

2.6.4 Performance rating: Definition: Performance rating is gauging and comparing the performance of a worker against a standard performance level set by the time study engineer. PERFORMANCE RATING FACTOR: It is a factor by which the observed Time is multiplied in order to adjust for differences in operator’s performance. Normal Time = Observed time x (performance level of worker / Std. performance level expected) TYPES OF RATING: 1. Speed rating. NT = OT x (worker’s speed / Std. speed expected) 2. Skill & effort rating. This is suggested by Mr. C.E. Bedaux. Unit of Work is expressed in B’s 60 B’s in an hour is standard B- Points = OT x (B- points earned x Relaxation factor) / 60 R.F varies from 1 to 3 depending on the severity of the job 3. Westing House system. 1. SKILL 2. EFFORT 3.CONDITION 4. CONSISTANCY 1. Super - 0.15 2. excellent - 0.11 3. Good - 0.08 4. Average – 0 5. Fair - -0.05 6. Poor -0.16 4. Synthetic Rating. Rating factor = Time value extracted from Predetermined Motion Time Study / Observed time 5. Objective rating. Job difficulty depending on 1. Body used 2. Foot movement involved 3. Eye – hand coordination 4. Weight lifted 5. Handling Requirements First rating the worker against the standard speed and then gives the allowance as per the difficulty in the job. 6. Physiological evaluation of Performance level. Evaluated by 1. Heart beating 2. Oxygen consumption

2.6.5

2.7

2.7.1

Allowances: 1. Process allowance 2. Personal and rest allowances 1. Personal 2. Fatigue 3. Abnormal posture 4. Visual concentration 5. bad light 6. Atmospheric conditions 3. Special allowances 1. periodic activity 2. interference 4. Policy allowances

7. Noise 8. Special protective dress 9. heat 10. Tediousness 11. Mental strain

Work sampling: Def: It is a technique in which a large number of observations are made over a period of time of one or group of machines, processes or workers. It is also known as activity sampling or ratio delay study. 1. Relies upon statistical theory of sampling and probability theory. 2. Based on normal frequency distribution and confidence level. 3. Each observation records the event happening at that instant and the percentage of observations recorded for that event or delay. Procedure: 1. Determine the main objectives and define each activity to be measured 2. Make sure all the concerned with the study understand the objectives 3. State the desired accuracy limits for the results 4. Conduct pilot study to 1. Estimate the approx. % occurrence of an activity(p) 2. Estimate the required No. of observations for the desired accuracy set. 3. Ensure the workers habituated to the visits of observation 5. Design the actual study Required no. of observations N= 4.p(100-p)/LXL P= % occurrence L= % limit of accuracy

Normal distribution curve