ME1007 – PROCESS PLANNING AND COST ESTIMATION_ UNIT 1

ME1007 – PROCESS PLANNING AND COST ESTIMATION

UNIT – I

WORKSTUDY AND ERGONOMICS

WORK STUDY

• IT AIMS AT ACHIEVING HIGHER EFFCIENCY AND EFFECTIVENESS OF EXISTING FACILITIES THROUGH SYSTEMATIC ANALYSIS.

• ADAPTING THIS WORKSTUDY TECHNIQUES PRODUCTIVE PERFORMANCE CAN BE IMPROVED WITH RELATIVELY SHORT TIME AND WITH VERY LITTLE OR NO EXTRA CAPITAL EXPENDITURE.

• IT IS A STUDY OF HUMAN WORK IN ALL ASPECTS IN ORDER TO INCREASE THE EFFECTIVENESS WITH WHICH THE WORK IS DONE

• A generic term for those techniques, particularly method study and work measurement, which are used in the examination of human work in all its contexts, and which lead systematically to the investigation of all the factors which affect the efficiency and economy of the situation being reviewed, in order to effect improvement.

WORK STUDY TECHNIQUE IS DIVIDED INTO TWO PARTS:

• Method study/motion study is the systematic recording and critical examination of existing and proposed way of doing work, as a means of developing and applying easier and more effective methods and reducing cost.

• Time study/work measurement is the application of techniques designed to establish the time for a specified job at a defined level of performance.

WORK STUDY OBJECTIVES

• The objective of applying work study is to obtain the optimum use of the human and material resources, which are available to it. The benefits may stem from improvements in one ore more of the following:

• 1) increased production and productivity.

• 2) reduced cost- labor, material, overheads.

• 3)Improvement of condition, which involves an element of excessive fatigue or danger.

• 4)Improved quality.

• 5) better control of cost and time

BASIC PROCEDURE: Basic steps in conducting work study can be summarized as: • Select the job or process to be studied. • Observe or record everything by using the appropriate

recording technique. • Examine the recorded facts critically with respect to the

purpose of the activity, where it is performed, sequence in which it is done, the person or the machine which is doing it, the means by which it is done.

• Develop the most economical method by considering everything.

• Measure the output of the method and calculate a standard time for it.

• Define the new method and the related standard time to identify it

• Implement the new method as standard practice. • Maintain the new standard practice by appropriate control

procedure

HISTORY OF WORK STUDY

• FERDERICK W. TAYLOR(1856-1915)

• He is known as the father of scientific management and industrial engineering.

• He is the first person to use a stopwatch to study work content and, as such, the father of time study.

• Thought his professional life, he worked as an apprentice machinist, time keeper, expediter, lathe operator, gang boss, foreman of the machine shop and chief engineer.

Methods study/ method engineering/ methods analysis / work improvement

• Systematic recording of existing and proposed ways of doing work in order to simplify the job

• improvement of procedures

• improvement of layout

• reduction of human fatigue

• improvement in the use of materials, machines, labor

• improvement in physical workplace

• The objectives of Method Study are :

• –Improvement of processes and procedures

• –Improvement in the design of plant and equipment

• –Improvement of plant layout.

• –Improvement in the use of men, materials and

• –Improvement in the flow of production and process.

• –Economy in human effort and the reduction of unnecessary fatigue.

• –Method Standardization

• –Improvement in safety standards.

• –Development of a better physical working environment

The Method Study procedure • The basic procedure was first developed and

articulated by Russell Currie at Imperial Chemical Industries (ICI) and consists of six steps (SREDIM):

• SELECT the work or area to be studied. • RECORD all appropriate and relevant data about

the current situation. • EXAMINE critically, the recorded data. • DEVELOP alternative approaches to making

improvements and choose the most appropriate. • INSTALL the new method, to make the required

changes to the situation. • MAINTAIN that new situation.

• Steps and Procedure to conduct Method • Study : Select: the work to be studied. • Record: all the relevant facts about the present method by

direct observation. • Examine: those facts critically and in an orderly sequence,

using the techniques best suited to the purpose. • Develop: the most practical, economic and effective

method, having due regard to all contingent circumstances. • Define: the new method so that it can always be identified. • Install: that methods as standard practice. • Maintain: that standard practice by regular routine checks. • These are the seven essential stages in the application of

method study ; none can be excluded. Strict adherence to the sequence, as well as to their content, is essential for the success of an investigation. They are shown diagrammatically on the chart

• Factors to be considered in selecting a job for method study: • Economic Consideration. • The cost of the study should be estimated and examined: short-term &

Long-term. • The loss of time due to the investigation. • For any job, if accumulated estimated benefits from the recommended

method outweighs the estimated total cost then we should take-up the job under study – Discounted Cash Flow Technique (DCF)

• Under Preliminary Considerations, the early job choices are: • Bottlenecks: which are holding up other production operations. • Movements of material over long distances: between shops or operations

involving a great deal of manpower or where there is repeated handling of material.

• Operations involving Repeated work: using a great deal of labour liable to run for a long time

• Technical Considerations: Make sure that adequate technical knowledge is available with which to carry out the study.

• Human Reactions: These are the most important factors to be taken into consideration, since mental and emotional reactions to investigation, and change of method have to be anticipated.

Method Study

Man, Machines, Materials, Money, Technology and Time are the main resources required to produce goods and are to be deployed in the most effective manner

We have to select the best available combination of these resources at any point of time.

Method Study helps in analysing the existing methods and develop a more efficient method for future.

Method Study

Method Study is the systematic recording and critical examination of existing and proposed ways of doing work, as a means of developing and applying easier

and more effective methods and reducing costs.

The objectives of Method Study are : – Improvement of processes and procedures – Improvement in the design of plant and equipment – Improvement of plant layout. – Improvement in the use of men, materials and

machines. – Efficient materials handling

Definition And Objective of Method Study

– Improvement in the flow of production and process.

– Economy in human effort and the reduction of unnecessary fatigue.

– Method Standardization

– Improvement in safety standards.

– Development of a better physical working environment

Definition And Objective of Method Study

Good working conditions contribute to improvement in productivity.

The following are a few

–Occupational safety and health conditions

– Fire prevention and protection

– Layout and house keeping (5S)

– Lighting and Ventilation

–Noise and Vibration

– Ergonomics

–Arrangement of working Time

Working Conditions And Influence

The solution of any problem follows the following sequence of phases in that order :

1) Define: The problem. 2) Record: All the facts relevant to the problem. 3) Examine: The facts critically but impartially. 4) Consider: The courses of actions (possible solutions)

and decide which to follow. 5) Implement: The solution. 6) Follow Up: The development.

The basic procedure for the whole of work study, which embraces the procedures of both method study and work measurement. Contd…

Procedure

Steps and Procedure to conduct Method Study : a) Select: the work to be studied. b) Record: all the relevant facts about the present

method by direct observation. c) Examine: those facts critically and in an orderly

sequence, using the techniques best suited to the purpose.

d) Develop: the most practical, economic and effective method, having due regard to all contingent circumstances.

Procedure…

e) Define: the new method so that it can always

be identified.

f) Install: that methods as standard practice.

g) Maintain: that standard practice by regular routine checks.

These are the seven essential stages in the application of method study ; none can be excluded. Strict

adherence to the sequence, as well as to their content, is essential for the success of an

investigation. They are shown diagrammatically on the chart.

Procedure…

Method Study

Record

At Work Place By means of

At Work Place By means of

Examine the facts critically

Two handed ; Simo ; Multiple Activity Charts

Other Means Cycle Graphs ; Chronocycle Graphs ; Film Analysis ; Memotion Photography

Select

Define Scope of Study

Work which can be studied With economic advantage

Charts

Other Means

Outline Process ; Flow Process – Man type , Material type ; Multiple Activity ; Travel

Flow Diagrams ; String Diagrams ; Models

Challenge

PURPOSE – PLACE – SEQUENCE – PERSON - MEANS

Seek Alternatives

Find Pointers

Combine or Change Simplify Eliminate

Develop

A record of an improved method

Re - Examine that record to establish

Method Study to improve

methods of production

The Best Method under Prevailing Circumstances

Planning and Control Materials Handling General Environment and Working Conditions Plant Layout

Mechanical Aids ; Manual Controls and Visual instruments Equipment design ; Jigs and fixtures Local Working Conditions

Define

Install

The Improved method

Plan - Arrange - Implement

Maintain Verify at regular intervals that

The important method as defined is in fact in use

To achieve improved factory and work space layout

Improved design of equipment Better working conditions

Reduction of fatigue Resulting in improved use of material

Plant and equipment manpower

Higher Productivity

Factors o be considered in selecting a job for method study:

Economic Consideration. Technical Consideration. Human Reactions. Economic Consideration. The cost of the study should be estimated and

examined: short-term & Long-term. The loss of time due to the investigation. For any job, if accumulated estimated benefits

from the recommended method outweighs the estimated total cost then we should take-up the job under study – Discounted Cash Flow Technique (DCF) or Pay-back period method may be used for this purpose.

Selection Of Job

Under Preliminary Considerations, the early job choices are:

Bottlenecks: which are holding up other production operations.

Movements of material over long distances: between shops or operations involving a great deal of manpower or where there is repeated handling of material.

Operations involving repetitive work: using a great deal of labour liable to run for a long time.

Selection Of Job…

Technical Considerations: Make sure that adequate technical knowledge is available with which to carry out the study.

Human Reactions: These are the most important factors to be taken into consideration since mental and emotional reactions to investigation, and change of method have to be anticipated.

Selection Of Job…

The Field Of Choice

Types of Jobs Examples Recording Technique

Complete

Sequence of

manufacture

Manufacture of an electric motor

from raw material to dispatch

Transformation of thread into cloth

from preparation to inspection

Receipt, packing and dispatch of

fruit

Outline process chart

Flow process chart

Flow diagram

Factory layout :

movement of

materials

Movements of a diesel engine

cylinder head through all machining

operations.

Movements of grain between milling

operations


Flow process chart–

material type

Flow diagram

Travel chart

Models

The Field Of Choice…


Factory layout

: movement of

workers

Labourers servicing spinning

machine with bobbins

Cooks preparing meals in a

restaurant kitchen

Flow process chart-man

type string diagram

String diagram

Handling of

materials

Putting materials into and taking

them out of stores

Loading lorries with finished

products.

Flow process chart –

material type

Flow diagram

String diagram

Workplace

layout

Light assembly work on a bench

Typesetting by hand

Flow process chart-man

type. Two-handed

process chart. Multiple

activity chart. Simo chart.

Cyclegraph.

Chronocyclegraph.


Gang work or

automatic

machine

operation

Assembly line

Operator looking after semi-

automatic lathe

Multiple activity chart

Flow process chart-

equipment type

Movements of

operatives at

work

Female operatives on short – cycle

repetition work

Operations demanding great

manual dexterity


Flow process chart –

equipment type

Films

Film analysis

Simo chart

Memotion

photography

Micromotion analysis


When selecting a job for method study it will be found helpful to have a standerdised list of

points to be covered as shown below :-

1. Product and operation 2. Person who proposes investigation 3. Reason for proposal 4. Suggested limits of investigation 5. Particulars of the job

a) How much is produced or handled per week?


b) What percentage (roughly) is this of the total produced or handled in the shop or plant?

c) How long will the job continue? d) Will more or less be required in future? e) How many operatives are employed on

the job i. Directly? ii. Indirectly?

f) How many operatives are there in each grade and on each rate of pay?

g) What is the average output per operative (per team) per day?

h) What is the daily output compared with the output over a shorter period? (e.g. an hour)


i) How is payment made? (team-work, piece-work, premium bonus time rate, etc)

j) What is the daily output –

i. Of the best operative?

ii. Of the worst operative?

k) When were production standards set?

l) Has the job any especially unpleasant or injurious features? Is it unpopular

i. With workers ?

ii. With supervisors ?


6. Equipment. a) What is the approximate cost of plant and

equipment? b) What is the present machine utilisation

index? 7. Layout

a) Is the existing space allowed for the job enough?

b) Is extra space available ? 8. Product.

a) Are the frequent design changes causing modifications ?

b) Can the product be altered for easier manufacture ?

c) When and how is product inspected ? d) What quality is demanded ?


9. What savings or increase in productivity may be expected from a method improvement ?

a) Through reduction in the work content of the product or process.

b) Through better machine utilisation. c) Through better use of labour

Contd…


It is important to set clearly defined limits to the scope of the investigation

Method study investigations so often reveal scope for even greater savings that there is a strong temptation to go beyond the immediate objective

This should be resisted, and any jobs shown up as offering scope for big improvements through method study should be noted and tackled separately.

“Do not use a spoon when a steam shovel is needed”


After selecting the work to be studied

Systematic recording of all the existing method and critical examination of these are carried out to eliminate every unnecessary element or operation and to develop the quickest and best method by having an improved sequence of doing the work, omitting the redundant elements, selecting more appropriate person and more suitable place for doing the work.

Is to record all the facts relating to the existing method. The success of the whole procedure depends on the accuracy with which the facts are recorded,

Record, Examine, Develop

because they will provide the basis of both the critical examination and the development of the improved method. It is therefore essential that the record be clear and concise.

The usual way of recording facts is to write them down.

Unfortunately, this method is not suited to the recording of the complicated processes which are so common in modern industry.

To overcome this difficulty other techniques or `tools’ of recording have been developed, so that detailed information may be recorded

Record, Examine, Develop…

precisely and at the same time in a standard form, in order that it may be readily understood by all method study men, in whatever factory or country they may be working.

The most commonly used of these recording techniques are charts and diagrams.

There are several different types of standard charts available, each with its own special purposes.


Two groups of charts :

Those which are used to record a process sequence, i.e., a series of events or happenings in the order in which they occur, but which do not depict the events to scale; and

Those which record events, also in sequence, but on a time scale, so that the interaction of related events may be more easily studied.


The most commonly used method study charts and diagrams

A. Charts Indicating process SEQUENCE

Outline Process Chart

Flow Process Chart – Man Type

Flow Process Chart – Material Type

Flow Process Chart – Equipment Type

Two – Handed Process Chart

B. Charts Using a TIME SCALE

Multiple Activity Chart

Simo Chart

C. Diagrams Indicating movement

Flow Diagram

String Diagram

Cyclegraph

Chromocyclegraph

Travel Chart


The recording of the facts about a job or operation on a process chart is made much easier by the use of a set of standard symbols, which together serve to represent all the different types of activity or event likely to be encountered in any factory or office.

The two principal activities in a process are operation and inspection.

Symbols used in Method Study

Process Chart Symbols…

Indicates the main steps in a process, method or procedure.

Usually the part, material or product concerned is modified or

changed during the operation.

Inspection

Indicates an inspection for quality and / or check for quantity

Operation

Transport

Indicates the movement of workers, materials or equipment from place

to place

Temporary Storage or Delay

Indicates a delay in the sequence of events : for example, work waiting

between consecutive operations, or any object laid aside temporarily without

record until required.

Permanent Storage

Indicates a controlled storage in which material is received into or issued

from a store under some form of authorization; or an item is retained for

reference purposes.

Combined Activities

Indicates a controlled storage in which material is received into or issued

from a store under some form of authorization; or an item is retained for

reference purposes.

Process Chart Symbols…

The Outline Process Chart

The Outline Process Chart

• In an outline process chart, only the principal operations and the inspections carried out are recorded to ensure effectiveness

• While preparing the outline process chart we use Symbols of Operation and Inspection

• A brief note of the nature of each operation is made beside the symbol

An outline process chart is a process chart

giving an overall picture by recording in sequence

only the main operations and inspections.

Example

• Assembling a switch rotor

Switch Rotor Assembly

• The operations and inspections carried out on the spindle made from 10mm Ø steel rod are as follows

O 1 Face, turn, undercut and part off on capstan lathe

(0.025 hrs)

O 2 Face opposite end on the same machine(0.010 hrs). Transport to inspn dept

I 1 Inspect for dimensions and finish (no time fixed). Transport to milling section

O 3 Straddle mill four flats on end on a horizontal miller (0.020 hrs). Transport to work bench

O 4 Remove burrs at the burring bench(0.020 hrs). Transport to inspn dept

I 2 Final inspn of machine (no time)

O5 Degreasing(0.0015 hrs) O6 Cadmium plating(.008 hrs) I3 Final check (no time) O7 Face on both sides, bore the cored hole and ream to

size on a capstan lathe(0.080 hrs) O8 Drill cross-hole and burr on two-spindle drill

press(0.022 hrs) I4 Final check dimensions and finish (no time) Transport to finished parts stores and await with-drawl

for assembly. • Note the numbering of operations and inspections


• In making an outline process chart we start with a vertical line down the right hand side of the page to show the operations and inspections undergone.

• The time allowed per piece is also shown on the left hand side.

FLOW PROCESS CHART

Process activity symbols

–Operation

– Inspection

– Transport

– Temporary storage or Delay

–Permanent storage

Process chart symbols

• Used to represent different types of activities or events.

• Very convenient, widely understood type of short hand, saves a lot of writing and helps in making the sequence of activities clear.

Flow process chart

A FLOW PROCESS CHART records what the worker does.

It is a chart setting out the frequency of flow of a product or procedure by recording all events under review using process chart symbols.

there are different types of flow process charts.

Purpose:

To set out the sequence of the flow of a product or a procedure by recording all the events under review

( Inspection ) using the appropriate process chart symbols.

Activities recorded in the flow chart

• Those where some thing is happening to the work piece.

• Those where the work piece is not touched – (stored or standstill)

Three types of flow process charts

• Man type

– Flow chart which records what the worker does

• Material type

– Flow chart which records how material is handled or treated

• Equipment type

– Flow chart which records how the equipment is used

FLOW PROCESS CHART FOR ENGINE Stripping – Cleaning - Greasing

Critical Examination

The questioning technique is the critical means by which the critical examination is conducted – each activity being subjected in turn to a systematic and progressive series of questions

OPERATIONS

• Make Ready

• Do

• Put Away

• Make ready and put away operations can be represented by transport and inspection symbols

• DO operations can be shown by “O”

CRITICAL EXAMINATION - Primary questions

• The Purpose for which…

• The Place at which…

• The sequence in which…

• The person by which…

• The means by which…

…the activities are undertaken

CRITICAL EXAMINATION - Primary questions

With a view to

• Eliminating

• Combining

• Rearranging

• Simplifying

…those Activities

PRIMARY QUESTIONS

• PURPOSE ELIMINATE

• PLACE COMBINE

• SEQUENCE REARRANGE

• PERSON REARRANGE

• MEANS SIMPLIFY

THE SECONDARY QUESTIONS

• Definition

The secondary questions cover the second stage of the questioning technique, during which the answers to the primary questions are subjected to further query to determine whether possible alternatives to place, sequence, persons and/or means are practicable or preferable as the means of improvement up on the existing method

SECONDARY QUESTIONS…

• During the second stage of questioning, we should address – What else might be done?

– What should be done?

• Purpose

• Place

• Sequence

• Person

• Means

These questions are the

basis for a systematic

method study.

EXAMPLE: ENGINE Stripping – Cleaning - Degreasing

DEVELOP IMPROVED METHOD

After critically examining and sequential questioning we develop the improved method and record the improved method in a flow process chart as shown

1. String diagram

2. Flow Process chart

3. Travel Chart

4. Flow diagram

5. Multiple activity chart

6. Template Models

TOOLS USED FOR PREPARING PLANT LAYOUTS

String diagram

String diagram is a useful tool to record the distance traveled by a worker in the working area. The string diagram is a scale plan or model on which a thread is used to trace and measure the distance traversed which has to be minimum by

•Workers

•Material or

•Equipment

during a specified sequence of events

• Observe the clusters of points, pins, turning points.

• Also observe the grid lines which represent a measure of the distance between the points.

Construction of a String diagram

• Step-1

– Preparing a study chart

• Step-2

– Drawing a scale plan of the working area

• Step-3

– Combining steps 1,2 to construct the final diagram

Step-1: Preparing a study chart

• Worker being studied is followed and all the points along the working areas are noted in a study sheet until a representative picture of the workers is obtained.

• Thus the movements are noted down for enough number of cycles so as to capture the actual work in terms of the journey made by the worker with their respective frequencies.

Step-2: Drawing a scale plan of the working area

• Machines, benches, stores and all other points at which calls are made are drawn to scale together with doorways, pillars etc that effect the path movements.

• Then attachments like soft wood, composition board and pins are driven firmly at every point. Pins are driven also at turning points on the route.

• This ensures a shop floor environment which helps to do the study accurately.

Step-3: Combining the steps 1 and 2

• A measured length of thread is wound from the starting point of the movement of the worker and leading through all the points on the path of the worker in the same order noted in the step-1

• This results in a String diagram.

Example of a String diagram Movement, Transport of tiles from Inspection to Storage

IMPROVED METHOD

Serving dinners in a hospital ward

FPC - Dinners in a hospital ward

Original Flow Diagram Inspn and Marking

Improved FD of Inspection and Marking

Travel chart

• A travel chart is a tabular record for presenting quantitative data about the movements of workers, materials or equipment between any number of places over any given period of time.

Why Travel chart ?

Although the string diagram is a neat and effective way of record the movement of worker or material for critical examination,

o they take long time to construct

o look increasingly like a complex maze with increasing complexity of movement paths

When the movement patterns are complex, the travel chart is quicker and more manageable to record.

More about Travel chart

• Always a square

• A column at (m,n) is checked only when there is a direct movement from station at m to station at n directly.

• The number of times a column at (m,n) is checked over a period of time gives the frequency of movement of a worker or material.

• The matrix is always a symmetrical matrix.

Travel chart

FLOW DIAGRAM • While the flow process chart describes the flow of a product

or process, it is generally supplemented with a flow diagram.

• While the flow process chart records travel distances and time taken for various operations, the flow diagram is a plan , drawn to scale of the work area, correctly indicating the position of machines and working positions. The symbols are also indicated in the flow diagram.

The example shown indicates the flow diagram of receiving, inspection, marking and storing materials.

After recording examining and developing a new method, the improved flow diagram shows the transport operations reduced from a 11 to 6. delays from 7 to 2. and the distance travelled reduced from 56.2 to 32.2

Original Flow Diagram Inspection and Marking

Improved FD of Inspection and Marking

MULTIPLE ACTIVITY CHART

• Multiple activity chart is a useful recording tool for situations where the work involves the interaction of different persons. Such as the operator working on different machines.

• In Mac a time scale is used.

• Mac can be used effectively even if there is no movement of workers involved in the work under consideration.

• Focus on Mac in situations where the operator are moving and to identify the idle time of the worker or the machine


• A MULTIPLE ACTIVIITY chart is a chart in which the activities of more than one subject (worker, machine or item of equipment) are each recorded on a common time scale to show their inter relationship.

• By using separate vertical columns or bars, to represent the activities of different operatives or machines against a common time scale, the chart shows very clearly periods of idleness on the part of any of the subjects during the process.

Inspection of catalyst in a converter

• The following slides show the present method of inspecting catalyst in a convertor where teams of electrician and mate, fitter and mate, rigger and process man are working together.

• In the original method it took 6 mins for the inspn.

• After recording, critically examining and developing a new method, the inspection time is reduced to four minute,ie a 32% saving.

MAC-Inspn of catalyst in a converter-original method

MAC-Inspn of catalyst in a converter-Improved method

TEMPLATE MODELS

• Template models are used to study the layout and the positioning of various machines by pasting templates on the plant layout diagram.

• This can be extended by using the string diagram technique to visualize the flow of the material.

Work measurement

Part II of Work Study

100

Introduction

• Work measurement is the application of techniques designed to establish the time for a qualified worker to carry out specified jobs at a defined level of performance.

• We have seen how total time to manufacture a product is increased by:

adding undesirable features to product,

bad operation of the processes, and

ineffective time added because of worker and management.

• All this leads to decreased productivity.

101

Introduction

• Method study is one of principal techniques by which work content in the product manufacture or process could be decreased.

• It is a systematic method of investigating and critically examining the existing methods, to develop the improved ones.

• Method study is, then, a technique to reduce the work content mainly by eliminating unnecessary movements by workers and/or materials and/or equipments.

• However, even after that, there could be substantial unnecessary time taken for the process because of lack of management control and/or inaction of worker.

102

Introduction

• Work measurement (WM) is concerned with investigating,

reducing and eliminating ineffective time, whatever may be

the cause.

• WM is the means of measuring the time taken in the

performance of an operation or series of operations in such a

way that the ineffective time is shown up and can be separated

out.

• In practice, proving existence of the ineffective time is the

most difficult task.

• After existence is proved, nature and extent is easy to see!

103

Introduction

• WM is also used to set standard times to carry out the work, so

that any ineffective time is not included later.

• Any addition the standard time would show up as excess time

and thus can be brought to attention.

• Since, standard times are set for all the activities through WM,

it has earned bad reputation amongst workers.

• Major reason for that has been the initial focus of the WM

methods, which essentially targeted only the worker

controllable ineffective times.

• Management controllable ineffective times were ignored

traditionally.

104

Introduction

Two critical issues in work study:

1. Method study should precede the work measurement,

always.

2. Elimination of management controllable ineffective time

should precede the elimination of the ineffective time within

the control of the workers.

105

Purpose of WM

• To reveal the nature and extent of ineffective time, from

whatever cause,

• So that action can be taken to eliminate it; and then,

• To set standards of performance that are attainable only if all

avoidable ineffective time is eliminated and work is performed

by the best method available.

106

Uses of WM

• To compare the efficiency of alternative methods. Other conditions being equal, the method which takes the least time will be the best method.

• To balance the work of members of teams, in association with the multiple activity charts, so that, as far as possible, each member has tasks taking an equal time.

• To determine, in association with man and machine multiple activity charts, the number of machines an worker can run.

107

Uses of time standards

• To provide information on which the planning and scheduling

of production can be based, including the plant and labor

requirements for carrying out the program of work and

utilization of resources.

• To provide information on which estimates for tenders, selling

prices and delivery promises can be based.

• To set standards of machine utilization and labor performance

which can be used for incentive scheme.

• To provide information for labor-cost control and to enable

standard costs to be fixed and maintained.

108

Techniques for WM

• Time study

• Activity sampling; and rated activity sampling

• Synthesis from standard data

• Pre-determined motion time system

• Estimating

• Analytical estimating

• Comparative estimating.

109

Time study

A WM technique for

1. Recording the times and rates of working for the elements of

a specified job carried out under specified conditions,

2. Analyzing the data so as to obtain the time necessary for

carrying out the job at a defined level of performance.

110

Selecting a job for time study

• The job in question is a new one not previously carried out.

• A change in material or method of working has been made and

a new time standard is required.

• A complaint has been received about the time standard for an

operation.

• A particular operation appears to be “bottleneck” holding up

the subsequent operations and possibly previous operations.

• Standard times are required prior to the introduction of an

incentive scheme.

111

Selecting a job for time study

• To investigate the utilization of a piece of plant, the output of

which is low, or which appears to be idle for an excessive

time.

• As a preliminary to making a method study, or to compare the

efficiency of two proposed methods.

• When the costs of a particular job appears to be excessive.

112

Qualified worker

• One who is accepted as having the necessary physical

attributes, who possesses the required intelligence, education,

and has acquired the necessary skill and knowledge to carry

out the work in hand to satisfactory standard of safety, quantity

and quality.

• In setting the time standards, specially when they are to be

used for incentives, the standard to aimed at is one which can

be attained by the qualified worker.

• A representative worker is one whose skill and performance is

the average of the group under consideration. (S/)He may not

necessarily be a qualified worker.

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Steps in making a time study

• Obtaining and recording all the information about the job, the

operator and the surrounding conditions, which is likely to

affect the carrying out of the work.

• Recording a complete description of the method, breaking

down the operation into “elements.”

• Examining the detailed breakdown to ensure that the most

effective method and motions are being used.

• Measuring and recording the time taken by the operator to

perform each “element” of the operation.

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Steps in making a time study

• At the same time assessing the effective speed of the working of the operative in relation to the observer’s concept of the rate corresponding to standard rating.

• Extending the observed times to “basic times.”

• Determining the allowances to be made over and above the basic time for operation.

• Determining the “standard time” for the operation.

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Breaking the job into elements

• An element is an distinct part of a specified job selected for

convenience of observation, measurement and analysis.

• A work cycle is the sequence of elements which are required

to perform a job or yield a unit of production. The sequence

may sometimes include occasional elements.

• For each job, a detailed breakdown of the complete job into

elements is necessary. Because….

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Reasons for breakdown of job

• To ensure that productive work (or effective time) is separated from unproductive activity (or ineffective time).

• To permit the rate of working to be assessed more accurately than would be possible if the assessment were made over a complete cycle.

• To enable different types of elements to be identified and distinguished, so that each may be accorded the treatment appropriate.

• To enable elements involving high fatigue to be isolated and to make the allocation of fatigue allowances more accurate.

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Reasons for breakdown of job

• To facilitate checking the method and so that subsequent omission or insertion of elements may be detected quickly.

• To enable a detailed work specification to be prepared.

• The enable time values for frequently recurring elements, such as the operation of machine control or loading and unloading work-pieces from fixtures, to be extracted and used in compilation of the synthetic data.

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Types of elements

• A repetitive element is an element which occurs in every work cycle of the job.

• An occasional element does not occur in each work cycle of the job, but which may occur at regular or irregular intervals. e.g. machine setting.

• For a constant element, the basic time remains constant whenever it is performed. e.g. switch the machine on.

• A variable element is an element for which the basic time varies in relation to some characteristics of the product, equipment or process, e.g. dimensions, weight, quality etc. e.g. push trolley of parts to next shop.

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Types of elements

• A manual element is an element performed by a worker.

• A machine element is automatically performed by a power-

driven machine (or process).

• A governing element occupies a longer time than any of the

other elements which are being performed concurrently. e.g.

boil kettle of water, while setting out teapot and cups.

• A foreign element is observed during a study which, after

analysis, is not found to be necessary part of the job. e.g.

degreasing a part that has still to be machined further.

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Recording time for activities

Cumulative timing

• The watch runs continuously throughout the study.

• At the end of each element the watch reading is recorded.

• The individual element times are obtained by subsequent

subtractions.

• The purpose of this procedure is to ensure that all the time

during which the job is observed is recorded in the study.

• Typically, most work-study persons attain fair degree of

accuracy quickly when using the cumulative method.

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Flyback time

• The hands of the stopwatch is returned to zero at the end of each element and are allowed to start immediately, the time for each element being obtained directly.

• In a comparative study of two methods carried out the Purdue University, the average error in reading the watch using the cumulative method was +0.000097 min per reading and using the flyback method was -0.00082 min per reading.

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Cumulative time recording is preferred, because:

• Trainees achieve reasonable accuracy more quickly.

• It does not matter if element times are occasionally missed by observed; the over-all time of the study will not be affected.

• Foreign elements and interruptions are automatically included since the watch is never stopped.

• Temptation to adjust the element time to rating is less compared to flyback time.

• Workers have greater faith in the fairness as they see that no time can have been omitted.

• Flyback method can have slight delays when the stopwatch is snapped back to zero at the end of each element.

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Differential timing

• The elements are timed in groups, first including and then

excluding each small element.

• Typically used for short element short cycle work, where

elements are so short that there is not enough time for study-

person to look at the watch and make a recording.

• In this process, either the cumulative or the flyback method of

watch manipulation may be used.

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Time study: Rating

• Rating is the assessment of the worker’s rate of working

relative to the observer’s concept of the rate corresponding to

the standard pace.

• It is a comparison of rate of working observed by the work-

study person with a picture of some standard level.

• The standard level is the average rate at which qualified

workers will naturally work at a job, when using the correct

method and when motivated to apply themselves to their work.

• This rate of working is called standard rating.

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Time study: Rating

• If the standard pace is maintained and the appropriate

relaxation is taken, a worker will achieve standard

performance over the working day.

• Standard performance is the rate of output which qualified

workers will naturally achieve without over-exertion as an

average over the working shift provided they know and adhere

to the specified method and, they are motivated to apply

themselves to their work.

• This performance is denoted as 100 on the standard rating and

performance scales.

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Time study: Rating

• It should be noted though that the “standard pace” applies to particular workers (with good physique, physical conditioning) working in appropriate environment.

• In practice, because of the inherent dissimilarities amongst workers, the rate of work is never the same throughout the working day.

• It is not uncommon for workers to work faster at some periods of the day than they do during others. So standard performance is achieved on average over a period of time with in-built standard deviation.

• In fact, working at the standard rate will not always mean moving the limbs with the same speed.

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Time study: Rating

• The purpose of rating is to determine from the time actually

taken by the operator being observed the standard time which

can be maintained by the average qualified worker and which

can be used as a realistic basis for planning, and incentive

schemes.

• Time study is concerned with speed at which operator carries

out the work, in relation to the concept of normal speed.

• “Speed” here means the effective speed of operation.

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Factors affecting rate of working

Factors outside the control of workers include:

• Variation in the quality or other characteristics of the material

used, although they be within the prescribed tolerance limit.

• Changes in the operating efficiency of tools or equipment

within their normal life.

• Minor and unavoidable changes in methods or conditions of

operations.

• Variation in the mental attention for the performance of

elements.

• Changes in the climatic and other conditions.

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Factors affecting rate of working

Factors within worker’s control:

• Acceptable variation in the quality of the process/product.

• Variation due to worker’s ability.

• Variation due to ability of mind, specifically attitude.

Optimum pace at which the worker will work depends on –

• The physical effort demanded by the work.

• The care required on the part of the worker.

• Training and experience.

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Rating factor

• The figure 100 represents standard performance.

• If the operator is apparently performing with less effective

speed, than the assigned factor is less than 100.

• If, on the other hand, the effective rate of working is above

standard, the operator gets a factor above hundred.

• Essential idea being:

Observed time x Rating = Constant

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Rating factor

• This constant is known as the basic time:

• So, depending on the rating assigned for the operator, the

basic time can either be less than or greater than the

observed time.

Time Basic Rating Standard

Rating timeObserved x

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Selected time

• The selected time is the time chosen as being representative of

a group of times for which an element or group of elements.

• These times may be either observed or basic times; and should

be denoted as selected observed or selected basic times.

• Theoretically, the results of all the computations of the basic

time for any single constant element should be same.

• However, because of inherent process variations, it happens

rarely!

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Selected time

• It becomes necessary to select a representative time for each

element from all the basic times which have been entered into

the time study.

• Multiple ways to pick a representative selected time from the

available ones.

• Statistics suggests….. Taking averages!

• There are other ways though!

• Before the selected time is decided, the anomalies in the

sample should be noted.

• Exceptionally high or low points should get some attention.

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Selected time

Constant element

• A very high or short observed time for a given element of job

should be treated with caution.

• An exceptionally high observed time could be due to incorrect

recording, but most common reason is material or environment

variation.

• In such as case, it should be checked whether such a variation

is frequent or rare.

• Excess observed time because of rarely occurring events is

typically not included as a representative.

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Selected time

• The average time calculations should exclude this observation.

But, the excess-over-average time is added to the contingency

allowance.

• Frequent large variations indicate that the element is not a

constant one but a variable element.

• Excessively large time for this element could be detected by

corresponding reduction in time for the immediate element.

• Exceptionally short times could be due to human error.

• A rare reason of observation of such short times could also be

a last-minute-process-improvement. In such as case, the job

should be studied again with more detailed attention.

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Selected time

Variable element

• In general more observations will be necessary of a variable element than of a constant element before reliable representative basic times can be established.

• The analysis of factors affecting the time to complete the element should be closely studied.

• Some relationship should be established between the observed time and the variable factors.

• Multiple factors could be affecting the observed time variation and establishing relationships amongst multiple factors is difficult

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Work content

• The work content of a job or operation is defined as: basic

time+ relaxation allowance+ any allowance for additional

work (e.g. the part of relaxation allowance that is work

related).

• Standard time is the total time in which a job should be

completed at standard performance – i.e. work content,

contingency allowance for delay, unoccupied time and

interference allowance.

• Allowance for unoccupied time and interference may not be

frequently included in the standard time calculations; however,

the relaxation allowance is.

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Standard time constituents

• A contingency allowance is a small allowance of time which

may be included in a standard time to meet legitimate and

expected items of work or delays, precise measurement of

which is uneconomical because of their infrequent or irregular

occurrence.

• Contingency allowance for work should include fatigue

allowance; whereas the allowance for delay should be

dependent on the workers.

• Typically contingency allowances are very small and are

generally expressed as percentage of the total repetitive

minutes of the job.

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• Contingency allowance should not be more than 5%, and

should only be given where the contingencies cannot be

eliminated and are justified.

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• Relaxation allowance is an addition to the basic time intended to provide the worker with the opportunity to recover from the physiological and psychological effects of carrying out specified work under specified conditions and to allow attention to personal needs.

• The amount of the allowance will depend on the nature of the job.

• One of the major additions to the basic time.

• Industrial fatigue allowance, in turn, forms a major portion of the relaxation allowance.

• Relaxation allowances are also given as percentages of the basic times.

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• Typical values of relaxation allowance are 12-20%.

• In addition to including relaxation allowances, short rest

pauses could be added over the period of work for an operator.

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Other allowances

• Start-up / shut-down allowance

• Cleaning allowance

• Tooling allowance

• Set-up / change-over allowance

• Reject / excess production allowance

• Learning / training allowance

• Policy allowance is an increment, other than the bonus

increment, applied to standard time to provide a satisfactory

level of earning for certain level of performances under

exceptional conditions.

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Standard time

• Now, we can add all the constituents to arrive at the standard

time for a job.

Standard time = observed time + rating factor + relaxation

allowance + work related contingency allowance + delay

related contingency allowance.

ME1007 – PROCESS PLANNING AND COST ESTIMATION_ UNIT 1

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Transcript of ME1007 – PROCESS PLANNING AND COST ESTIMATION_ UNIT 1