Method Study

7

METHODS STUDY FOR MANUFACTURING

SYSTEMS

7.1 INTRODUCTION

Modern industry is constantly searching for better methods. When a

business ceases to move forward it will lose ground and may eventually

fail. It is for this reason that major companies are now organizing

industrial engineering groups, work simplification, value analysis,

suggestion systems, and other methods for analysis of present and

proposed work systems to develop an optimal transformation of input to

output.

7.2 HISTORICAL DEVELOPMENT

Methods design and work measurement actually grew out of the

pioneering developments of the Gilbreths (Frank B, and his wife Lillian

M) and Taylor in the late 19th

and early 20th

century.

Gilbreths developed many of the tools of “motion study” as a part of

formulating a systematic approach to the analysis of work methods.

Gilbreth has originally introduced his ideas and philosophies into brick

layler‟s trade where he was employed. After introducing methods

improvements through motion study and operator training, he was able to

increase the average number of bricks laid to 350 per man per hour. Prior

to Gilbreth‟s studies, 120 bricks per man per hour was considered as a

satisfactory rate of performance. Gilbreth eventually became so engrossed

in motion study that he gave up his job in order to concentrate his full

attention on the development of motion study along with his wife Lillian

Gilbreth, who was a psychologist, and they developed many of the

analysis technique in common use to-day.

7.3 FIELD OF APPLICATION

The application of methods design may be utilized to find a preferred way

of doing the work and assist in effectively managing or controlling the

activity. It fits equally well when applied to heavy or light factory, office,

production, maintenance, staff or supervisory work. It is equally

applicable to farm work, housework, cafeteria work, department store or

hotel work, the whole range of government activities, or any other human

108 INDUSTRIAL ENGINEERING AND MANAGEMENT

activity since requisite human efforts are in all cases composed of the

same basic acts, and the information relating to the economical use of

human effort is universally applicable.

Method study has its application also in the decision making process

in the cycle of managerial control. For instance the problems of designing

or selecting the tools, equipment, workplaces, and methods may be solved

by various methods design techniques.

7.4 METHODS ANALYSIS PHILOSOPHY

Methods analysis, or methods function, has evolved, as already said, from

the initial efforts of people such as Fredrick W Taylor and Frank Gilbreth.

Today the problem solving approaches, techniques and efforts are being

applied to all functions of the enterprises because the products become

more complex and higher order of mechanization and increased in output

became the pre-requisite for the survival of the companies. The basic

philosophies of methods analysis are the following:

1. Increased productivity and developing man power, facilities and

effectiveness are the objectives for studying systems.

2. Methods analysis is concerned with all phases of system design,

development, installation, operation, control and maintenance.

3. The design and planning of systems should consider alternatives from

models of automation to integrated man-machine systems.

4. All aspects of the system under study regardless of the extent of scope

should be considered in methods analysis.

5. The design or analysis of systems is enhanced through recognition of

people and their abilities and talents as an integral part of the process.

.

Methods design is the systematic study of existing as well as proposed

methods of performing a job with purpose of :

1. developing and applying an easier and effective method called a

preferred method usually the one with lowest cost; and

2. standardizing this method.

Methods design consists of a wide variety of procedures for the

description, systematic analysis and improvement of work methods,

considering:

1. The design of the outputs.

2. The process or method of work.

3. The raw materials.

4. The tools, equipment and work place for each step in the process and

5. The human activity used to perform each step.

METHODS STUDY FOR MANUFACTURING SYSTEMS 109

The aim is to determine or design a preferable work method, the

criterion of preference being usually economy of money, time and effort.

7.5 METHODS IMPROVEMENT: ANALYTICAL TECHNIQUE

A problem-solving approach for the purpose of improving methods design

is described below. In fact, the seven steps that are listed and explained

hereunder may be used in solving almost any problem.

1. Problem definition: It means statement of purpose, goal or objective.

At the outset it is best to define the problem broadly. In many cases,

it is not easy to identify just what the real problem is. However, the

problem must be understood, isolated and brought to light and

carefully studied to accomplish the objective.

2. Analysis of problem: The analysis of problem implied that once the

problem is identified it becomes necessary to sort out the facts

relating to the function of the components involved and try to

determine their interactions.

3. Search for possible solutions : The basic objective of this step is to

find the preferred solution that will meet the criteria and

specifications that have already been gathered through the first two

steps. A normal tendency is to consider-one-method, whereas many

alternatives should be evaluated. A better or best solution can not be

determined unless the alternatives are available.

4. Evaluation of alternative: In the evaluation of solutions or

alternatives economy and practicability of (a) manpower, (b)

facilities, (c) product, and (d) materials are considered. Also quality

and quantity specifications should not be overlooked in the

evaluation process.

5. Recommendation for action: The recommendations presented by the

analyst provide management with technical data necessary for

decisions. Three suggested factors such as: (1) benefits, (2) cost, and

(3) savings are generally mentioned in the recommendation.

6. Follow-up to ensure action: This step is to ensure that the design or

improvement of alternatives is detailed and complete. Decisions must

first be made to proceed on the design and then the responsibility

should be assigned to other aspects and finally to installation.

7. Validation of results: In addition to achieving the proper functioning

of the design, it is always wise to again check the benefits, costs and

savings predicted in the recommendation and recheck the problem

definition and objectives with the purpose of finding further

possibilities for improvement.


In addition to the aforesaid steps, abilities of observing, questioning,

recording, analysis, reasoning and synthesizing are important in

application of problem-solving approach.

7.5.1 Approach to Developing Preferred Method

In practice there is no „perfect method‟ and there are always opportunities

to improve methods and processes. In designing a method for an existing

activity, one usually does not have enough freedom as more constraints or

restrictions are imposed on it simply because the activity is an on-going

one. On the other hand, in designing a method for a new activity there is,

of course, lesser restriction and greater freedom, but the added cost to

make the change must be considered.

However, the following cost-elimination approaches provide possible

solutions in developing a better or more appropriately called preferred

method particularly suitable for a new activity.

1. Eliminate all unnecessary work.

2. Combine operations or elements.

3. Change the sequence of operations.

4. Simplify the necessary operations.

Eliminate all unnecessary work: It is suggested that the factor

contributing major cost should be selected first. If the factor eliminated, ,

there will be elimination of many smaller operations and/or unnecessary

work.

Combine operations or elements : It is customary to break down or

sub-divide a process into too many operations. It is therefore necessary to

make the job easier by simply combining two or more than two

operations or by making some changes in the method which permits

operations to be combined for the purpose of reducing costs.( use of turret

lathe, for example)

Change the sequence of operations: It is sometimes desirable to

change the order in which the various operations are performed. When a

new product first goes into production, the experimentation should be

carried out in this respect. The process chart and flow diagram reveal the

desirability of changing the sequence in minimizing cost.

Simplify the necessary operations: In this step, each operations in the

process is analyzed with the object of simplifying or improving it. The

smaller details are examined after the overall picture is studied and major

changes are made.


7.6 METHODS IMPROVEMENT : QUESTIONING TECHNIQUE

One of the best ways to approach the problem of methods improvement is

to question everything about the job – the way the job is being done now,

the materials that are being used, the tools and equipments, the working

condition and the design of the product itself.

The questioning technique consists of two sets of detailed questions:

the primary questions to indicate the facts and the reasons underlying

them, and the secondary questions to indicate the alternatives as a means

of improvement upon the existing method.

Primary questions : The following are the primary questions

under their respective headings:

1. Purpose. What is achieved? Why is it necessary?

2. Place. Where is it done? Why there?

3. Sequence. When is it done? Why then?

4. Person. Who does it? Why that person?

5. Means. How is it done? Why that way?

The primary questions clearly indicate any part of the work which is

unnecessary or inefficient in respect of place, sequence, person or means.

Secondary questions. The following are the secondary questions

under their respective heading. These secondary questions are asked only

when the answers to the primary questions are subjected to further query

to establish alternatives to existing or previously proposed methods.

1. Purpose. What else might be done? What should be done?

2. Place. Where else might it be done? Where should it be done?

3. Sequence. When might it be done? When should it be done?

4. Person. Who else might do it? Who should do it?

5. Means. How else might it be done? How should it be done?

When the (two) primary questions and (two) secondary questions

under each of the headings are combined, it forms a complete list, which

sets out the questioning technique in full.

The activities under the questioning techniques are undertaken with a

view: (1) eliminating, (2) combining, (3) rearranging, or (4) simplifying,

these activities as given hereunder:

1. Eliminate unnecessary part : Purpose 2. Combine wherever possible : Place and sequence 3. Rearrange the sequence of operations for more effective result : Place, sequence and person


4. Simplify the operation : Means

The questioning pattern ensures that every aspect of the activity is

examined and that all alternatives are fully considered with the result that

an improved method may be developed.

7.7 TOOLS FOR METHODS IMPROVEMENT

Whether methods work is being used to design a new work or to improve

one already in operation, it is helpful to present in clear and logical form

the factual information related to the process. Pertinent information – such

as the quantity to be produced, delivery schedules, operational times,

facilities, machine capacities, special materials and special tools – may

have an important bearing on the solution of the problem. Visual

observations, calculations or photographic techniques prove useful. That is

why methods analysis is carried out by a series of process charts and

diagrams prepared for both existing as well as proposed methods. These

are:

1. Charts indicating process sequence

(a) Outline process chart

(b) Flow process chart– man, material and equipment

(c) Gang process chart

(d) Two handed process chart

2. Charts using a time scale

(a) Multiple activity chart

(b) Man and machine chart

(c) Simo chart

(d) Memo chart

3. Diagrams indicating movements

(a) Flow diagram

(b) String diagram

(c) Cyclegraphs and chronocyclegraphs.

7.7.1 Process Chart Symbols

The symbols used for recording the nature of activities are:

Operation : Indicates the main steps (operations) in a process,

method or procedure.

Transport : Indicates the movement of workers, material or

equipment from place to place.

Storage : Indicates a controlled storage in which the material is

held, kept or retained for reference purpose.


Temporary storage or delay : D Indicates a delay in the sequence of

operation.

Inspection : Indicates an inspection for quality and/or a check for

quantity.

Combined activities : Combined activities can be shown by super

imposing their respective symbols so that the outer symbol represent the

major activity, e.g. the circle within the square represent a combined

operation and inspection.

These standard symbols serve as a very convenient, widely

understood type of shorthand, saving a lot of writing and helping to show

clearly just what is happening in the sequence being recorded.

7.8 PROCESS CHARTS

The process chart in general is a sequential listing of brief descriptions of

each of the steps in a system. In comparison, the flow-process chart is a

graphical illustration of a system. The process chart is often developed in

conjunction with the flow-process chart to provide for a thorough analysis

of a system for improvement. Several rules should be adhered to in the

completion of the process chart form:

1. The heading and outline inform action of the form should be

completed.

2. The symbols should be outlined or highlighted.

3. The chart should start and end with a store.

4. Numbers should be entered in the symbols independently.

5. Diagonal lines should be drawn joining the symbols to indicate flow.

6. Additional information such as distance moved, operation,

description, type of equipment, etc may be incorporated.

7. The summary section must be completed either at the top or bottom

of the form.

7.8.1 Outline Process Chart

The outline process chart or the operation process chart, as it is

sometimes called, shows the chronological sequence of all operations,

inspections, time allowances and materials to the packaging of the finished

product.

The chart does not show where work takes place or who performs it,

and because it is concerned only with operations and inspections, only the

symbols for “operation” and “inspection” are necessary.


The charts are often used to assist in the layout of plant, and in the design

of the product or of the machinery for making that product. The outline

process chart effectively states the problem and indicates the areas which

require improvement. A typical outline process chart is shown in Fig. 7.1.

Figure 7.1 Operations process chart


7.8.2 Flow Process Chart

The flow process chart is an amplification of the outline process chart, in

that it shows transports, delays and storage as well as operations and

inspection. It is used primarily on one component of an assembly or a

system at a time to effect maximum savings in manufacturing or in the

procedures applicable to a particular component or sequence of work. The

chart is especially valuable in recording hidden costs such as distance

traveled, delays and temporary storages.

Figure 7.2 Flow process chart


Flow process charts recording simultaneous activities of two or more

subjects can be presented alongside each other on the same sheet of paper

to indicate more clearly their interdependence. It is essential, however, that

the activities of a particular subject to which it refers, either man, material

or equipment are recorded on any single chart. A typical example of flow

process chart is shown in Fig. 7.2

7.8.3 Gang Process Chart

The gang process chart is an aid in studying the activities of a group of

people working together. The chart is a composite of individual member

flow process charts, arranged to permit thorough analysis. Those

operations which are performed simultaneously by gang members are

indicated side by side. The basic purpose of the chart is to analyze the

activities of the group and then compose the group-so as to reduce to a

minimum all waiting time and delays. A typical gang process chart is

shown in Fig. 7.3

7.8.4 Two-handed Process Chart

A two-handed process chart, sometimes referred to as a left and right hand

process chart is, in effect, a tool of motion study. The chart shows all

movements and delays made by both the right and the left hand. This is an

effective tool to:

1. Balance the motion of both hands and reduce fatigue.

2. Eliminate and / or reduce non-productive motions.

3. Shorten the duration of productive motions.

4. Train new operators in the ideal method.

A two-handed process chart is made up to two columns in which are

recorded the symbols representing the activities of the left hand and the

right hand respectively. They are interrelated by aligning the symbols on

the chart so that simultaneous movements by both hands appear opposite

to each other. In some cases where micro motion analysis is justified,

detailed movements of hands and arms are shown by their respective

symbols.

Movements of the two feet can be recorded by making two additional

columns.

A typical two-handed process chart is shown in Fig. 7.4.


7.8.5 Multiple Activity Chart

A multiple activity chart is a chart on 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 interrelationships.

Figure 7.3 Gang process chart


By using separate vertical columns or bars to represent the activities

of different operators 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.

The multiple activity chart is extremely useful in organizing operating

teams on mass production work and also on maintenance work when

Figure 7.4 Left hand right hand chart


expensive plant cannot be allowed to remain idle than is absolutely

necessary. It can also be used to determine the number of machines which

an operator or operators should be able to look after. In making a chart the

activities of the different operators and machines are recorded in terms of

working time and idle time. Fig. 7.5 shows a typical multiple activity

chart.

7.8.6 Man and Machine Chart.

The man and machine chart is a common form of multiple activity chart

where man and

machine

relationship is

shown. The man

and machine

work

intermittently on

some types of

work. That is , the

machine is idle

while the worker

loads it or

removed the

finished work

from the machine.

Again, the worker

is idle when the

machine is in

operation. It is

desirable to

eliminate the idle

time of the

worker and at the

same time to see

that the machine be kept operating as near capacity as possible without

remaining idle at any time during the working hours.

The first step in eliminating unnecessary waiting time for the worker

and for the machine is to record exactly what each works and what each

does. Many operations consists of three main stages:

1. Make ready required to prepare the material or workpiece and set it, in

position ready to be worked on the machine.

2. Do operation (doing the work) in which the change is made in the

shape such as turning, and

Figure 7.5 Multiple activity chart


3. Put away or clear up, such as removing the finished piece from the

machine.

The chart shows the exact relationship on a common time scale

between the working cycle of the person and the operating cycle of the

machine. That is the completed man and machine process chart clearly

shows the areas in which both idle machine time and man time occur.

These areas are generally a good place to start effecting improvements.

A typical man and machine chart is presented in Fig. 7.6.

7.9 MOTION STUDY

Motion study is the careful analysis of the various body motions employed

in doing a job. Its purpose is to eliminate or reduce ineffective movements

and to facilitate and speed up effective movements. Gilbreths pioneered

the study of manual motion and developed basic laws of motion economy

that are still considered fundamental.

Motion study, in the broad sense, covers two degrees of refinement

that have wide industrial application. These are visual motion study and

micromotion study.

Visual motion study involves a careful observation of the operation

and construction of a two-handed process chart, and an analysis of the

chart, considering the laws of motion economy.

Micromotion study provides a technique for recording and timing an

activity. It consists of taking motion pictures of the operation with a clock

in the picture of with a motion picture camera or video camera operating at

a constant and known speed. The film becomes a permanent record of both

methods and time and may be re-examined whenever necessary. As the

implementation is costly it is usually utilized only on extremely active

jobs which are repeated thousands of times such as packing of food cans

into cartons. In such cases, it is worthwhile going into much greater detail

to determine where movements and effort can be saved and to develop the

best possible method of movements. This enables the worker to perform

the operation repeatedly with a minimum of effort and fatigue.


Figure 7.6 Man machine chart


7.10 FUNDAMENTAL MOTIONS

Most work is done with the two hands and all manual work consists of a

relatively few fundamental motions that are performed repeatedly. Frank

B. Gilbreth, the founder of motion study, developed 17 elementary

subdivisions of a cycle of motion which he called therblig (Gilbreth

spelled backwards) and concluded that any and all operations are made up

of a series of these 17 basic divisions. Therbligs comprise a system for

analyzing the motions involved in performing a task. The identification of

individual motions, as well as moments of delay in the process, was

designed to find unnecessary or inefficient motions and to utilize or

eliminate even split-seconds of wasted time. Frank and Lillian Gilbreth

invented and refined this system, roughly between 1908 and 1924.

The 17 fundamental motion or hand motions as they are sometimes

called, modified somewhat from Gilbreth‟s summary and their symbols

and colour designations are shown in Table 7.1.

Table 7.1 Therblig-symbol and colour

THERBLIG Name Symbol Colour

Designation

Picture Symbol

Search S Black

Select SE Gray, Light

Grasp G Lake red

Reach RE Olive green

Move M Green

Hold H Gold ocher

Release RL Carmine red

Position P Blue

Preposition PP Sky Blue

Inspect I Burnt Ocher

Assemble A Violet, Heavy

Disassemble DA Violet Light

Use U Purple

Unavoidable delay UD Purple

Avoidable delay AD Lemon Yellow

Plan PL Brown

Rest to over come

fatigue

R Orange


7.10.1 Description of Fundamental Motions

The definitions of the various therbligs are given hereunder:

1. SEARCH. The Search motion starts when the eyes and/or hand start

to seek the object needed and ends just as the object is located. The

Gilbreths stated that in a search, "....the time and attention

required...varies with the number of dimensions in which the search

is performed." A one-dimensional search might be locating a piece of

paper on a desktop. A two dimensional search might be finding a

light switch on a wall and the three dimensional search would be

locating a hanging pull-chain for a light or fan. The Gilbreths also

recognized that contrasting colors, shapes or embossed symbols

could reduce the search function. This science has been expanded by

the modern study of Human Factors Engineering. However, the

classic example of the Gilbreths reducing Search was by arranging

tools and parts in a physical sequence of use through the Packet

Principle.

Example : Trying to find or pick a part from a pile. The original list

of Gilbreth motions contained the therblig find. Since it is a mental

reaction rather than a physical movement, it is seldom used in micro

motion analysis work.

2. SELECT. It occurs when one object is being picked from among

several.

Example : Locating a particular bolt from among several.

3. GRASP. It consists of taking hold on an object.

Example : Closing the fingers around a pencil.

4. HOLD. It refers to the retention of an object in a fixed location.

Example: Retaining a fountain pen barrel in one hand while

assembling the cap to it with the other.

5. TRANSPORT LOADED. It refers to moving an object from one place

to another.

Example : Carrying a desk pen from the holder to the paper.

6. POSITION. It consists of aligning or orienting an object preparatory

to fitting it into some location.

Example : Aligning a plug preparatory to inserting it into an electrical

outlet.

7. ASSEMBLE. It consists of combining one object with another.

Example : Assembling a nut on a bolt.

8. USE. It consists of causing a device for the purpose for which it is

intended.

Example : Tightening a bolt with a slide wrench.


9. DISASSEMBLE. It consists of separating two objects which were

combined.

Example : Removing a nut from a bolt.

10. INSPECT. It refers to examination of an object to determine some

quality such as size, shape or colour.

Example : Visual examination of finish of a desk.

11. PRE-POSITION. It consists of placing an object in a predetermined

manner and in the correct position for some subsequent motion.

Example : Lining up a desk pen for inserting into its holder.

12. RELEASE LOAD. It occurs when the hand lets go of an object.

Example: Letting go of a desk pen when it is placed in a holder.

13. TRANSPORT EMPTY. It refers to moving the empty hand while

reaching for something.

Example : Reaching for a desk pen.

14. REST . It occurs when a worker pauses to overcome the fatigue from

the previous work.

Example : An operator pauses to rest after having lifted several heavy

weights into a truck.

15. UNAVIODABLE DELAY. It refers to a delay by body member which

is beyond the control of the operator.

Example : Right hand pauses during the operation of assembling a job

while the left hand keeps aside a completed job.

16. AVOIDABLE DELAY. It refers to a delay by body member which is

within the control of the operator.

Example : An operator pauses or deviates from the normal motion

pattern.

17. PLAN. It refers to a delay in a motion pattern while the operator

decides how to proceed. It is therefore a mental process before taking

action.

Example : An operator fixing a tool on tool post pauses to decide

which part should be cut next.

7.10.2 Classification of Therblig1

The 17 basic divisions can be classified as either effective or ineffective

therbligs. Effective therbligs are those that directly advance the progress of

the work. Infective therbligs do not advance the progress of the work and

should be eliminated by applying the principles of operation analysis and

motion study.

A further classification breaks the therbligs into physical, semi mental

or mental, objective, and delay groups. Ideally, a work center should

comprise only physical and objective therbligs.

1 Niebel B.W., Motion and Time Study, Richard D Irwin, Illinois


A. Effective.

1. Physical basic divisions.

(a) Reach

(b) Move

(c) Grasp

(d) Release

(e) Pre-position

2. Objective basic division

(a) Use

(b) Assemble

(c) Disassemble

B. Ineffective.

1. Mental or semi mental basic divisions

(a) Search

(b) Select

(c) Position

(d) Inspect

(e) Plan

2. Delay

(a) Unavoidable delay

(b) Avoidable delay

(c) Rest to overcome fatigue

(d) Hold

7.11 PRINCIPLES OF MOTION ECONOMY

Through the pioneering work of Gilbreth and other investigators, notably

Ralph M. Barnes, certain rules for motion economy have been developed.

These principles apply to visual motion study as well as to the

micromotion study and broken into three basic sub divisions:

(A) The use of the human body,

(B) The arrangement and conditions of the workplace, and

(C) The design of the tools and equipment.

The inefficiencies in the methods may be detected by careful

observation of the workplace and the operations. These basic principles

under their respective divisions are as follows2 :

2 Barnes R.M., Motion and Time Study, Wiley & Sons, New York


A. The use of the human body.

1. Both hands should begin and end their motions at the same time

and should not be idle at the same instant, except during rest

periods.

2. The motions made by the hands should be made symmetrically

and simultaneously away from and toward the center of the body.

3. Momentum should be employed to assist the worker wherever

possible and it should be reduced to a minimum if it must be

overcome by muscular effort.

4. Continuous curved motions are preferable to straight-line

motions involving sudden and sharp changes in direction.

5. The least number of basic divisions should be used, and these

should be confined to the lowest practicable classifications. These

classifications, summarised in ascending order of the time and

fatigue expended in their performance, are :

(a) Finger motions

(b) Finger and wrist motion

(c) Finger, wrist, and lower arm motions.

(d) Finger, wrist, lower arm, and upper arm motions.

(e) Finger, wrist, lower arm, upper arm, body motions.

6. Work that can be done by the feet should be arranged so that it is

done simultaneously with work being done by the hands. It

should recognize, however, that it is difficult to move the hand

and foot simultaneously.

7. The middle finger and the thumb are the strongest working

fingers. The index finger, fourth finger, and little finger are not

capable of handling heavy loads over extended periods.

8. The feet are not capable of efficiently operating pedals when the

operator is in a standing position.

9. Twisting motions should be performed with the elbows bent.

10. To grip tools, the segments of the fingers closest to the palm of

the hand should be used.

B. The arrangement and conditions of the workplace.

1. Fixed locations should be provided for all tools and materials so

as to permit the best sequence and to eliminate or reduce the

therbligs; search and select.


2. Gravity bins and drop delivery should be used to reduce reach

and move times; also, wherever possible, ejectors to remove

finished parts automatically should be provided.

3. All materials and tools should be located within the normal

working area in both the vertical and the horizontal planes.

4. A Comfortable chair should be provided for the operator and the

height so arranged that the work can be efficiently performed by

the operator alternately standing and sitting.

5. Proper illumination, ventilation, and temperature should be

provided.

6. The visual requirements of the workplace should be considered

so that eye fixation demands are minimized.

7. Rhythm is essential to the smooth and automatic performance of

an operation, and the work should be arranged to permit an easy

and natural rhythm wherever possible.

C. The design of tools and equipment.

1. Multiple cuts should be taken whenever possible by combining

two or more tools in one, or by arranging simultaneous cuts from

feeding devices, if available (cross slide and hexagonal turret).

2. All levers, handles, wheels, and other control devices should be

readily accessible to the operator and should be designed so as to

give the best possible mechanical advantage and to utilize the

strongest available muscle group.

3. Parts should be held in position by fixtures.

4. The possibility of using powered or semiautomatic tools, such as

power nut and screwdrivers and speed wrenches, should always

be investigated.

7.12 MICROMOTION STUDY The micromotion study is used to make a detailed motion study employing

either videotapes or motion pictures operating at a constant and known

speed. Here each space occupied by a single picture, known as a frame, is

projected and studied independently, and then collectively with successive

frames :

Micromotion study may now be used for the following purposes :

1. As an aid in studying the interrelationships among the members of a

work group.

2. As an aid in studying the relationship between an operator and his

machine.

3. As an aid in obtaining motion time data for time standards.


4. As a permanent record of the methods and time of activities of the

operator and the machine.

Micromotion study provides a valuable technique for making minute

analysis, of these operations that are short in cycle and highly repetitive or

largely manual in character, contain rapid movements, and involve high

production over a long period of time. Thus it is very useful in analyzing

operation such as assembling small parts, and similar activities. But it has

the disadvantages that it is expensive, time consuming, and frequently

meets with union resistance.

7.12.1 Micro-motion Equipment The following equipment is recommended where a fairly extensive

programme is to be carried on :

1. Motion picture cameras

2. Metal striped with tilting and panoramic head

3. Exposure meter

4. Three or four lamps with reflectors

5. Two tripods for lamps

6. Micro chronometer

7. Motion picture projector

8. Portable screen

Motion picture cameras are equipped with spring drive, or with

electric motor drive and there are others with both of these drives. The 16-

mm camera is more widely used for micro motion study. At the normal

speed of 16 exposures per second a 30-m (100ft) roll of film will last

approximately 4 minutes. The most common speed for electric motor

driven camera is 1000 frames per minute.

Microchronometer is a clock driven by small synchronous motor. It

has 100 divisions on the dial. The large hand makes 20 revolutions per

minute and the small hand 2 revolutions per minute. Therefore, time is

indicated directly 1/2000 of a minute by the large hand. This time interval

of 1/2000 of a minute was called “wink” by Gilbreth.

Motion picture projector is indispensable for analyzing film because

the film must be studied frame by frame in minute detail. It is available in

16-mm and 8-mm models and is equipped with digital electronic reset able

frame counter that adds and subtracts. It may be operated at from 800 to

1800 frames per minute with an indicator showing the speed in frames per

minute

.Exposure meter is used during film making to indicate variables so

that the image correctly reproduces the subject in true-to-life tones and


colors. Since film exposure is controlled by the camera‟s shutter and

aperture settings, it is essential to know what those settings should be in

order to take a picture that is properly exposed. A photographer must

measure the amount of light to know how much of it should be allowed to

strike the film

Figure 7.7 Simo chart


7.12.2 Film Analysis Before analyzing the film or tape, it is customary for the analyst to run the

films through the projector several times in order to determine the cycle

that represents the best performance. The shortest cycle is usually the best

one to study.

Once the cycle that is to be studied has been determined, the analyst

can begin the frame by frame analysis. Although the study can be made at

any point in the cycle, it is customary to start the analysis at the beginning

of a cycle. Sometimes it is best to begin the analysis at a point where both

the right and left hands begin or end their therbligs together.

In reviewing the film in tape, the analyst carefully observes the motion

class being used while performing the basic division and records this

information on his data sheet or film analysis sheet. The motions of the

left hand of the operator are usually analysed first. Motion pictures and

videos viewed in slow-motion and stop-motion, while they would seem to

be a wealth of information in the study of motion, are often frustrating.

Material not created specifically for motion study is often flawed with the

distortion of telephoto photography, framing that crops out lower limbs, or

the confusion caused by such natural obstructions as normal in

manufacturing shops.

7.13 SIMO CHART The simultaneous motion cycle or simo chart is used to record

simultaneously on a common time scale the activities of two hands, or

other parts of the workers body during the performance of a single cycle of

the operation being investigated. This chart may be constructed from data

collected with a stopwatch, from analysis of a motion film of the

operations, or from pre-determined motion time data (PMT).

The simo chart is the micromotion form of the man type flow process

chart. It is commonly used on fairly short cycle operations when the

machine process time is relatively short and the worker is operating only

on machines. Since it is often performed with extreme rapidity, it is

generally compiled from film analysis. A simo chart is illustrated in fig.

7.7. The therblig description, symbol, colour, and relative position in the

cycle all appear on the chart. The time required for each motion is drawn

to scale in the vertical column and coloured to represent the particular

motion. Every attempt should be made to find a better way of doing the

work, to eliminate those therbligs that are non-productive (hold, avoidable

delay, unavoidable delay, plan, rest, select, search), as well as to shorten

those that are productive. Thus the simo chart aids one in grouping a

picture of the complete cycle in all its details, and assists in working out

better combinations of the most desirable motions. It is often found that


the sequence of motions in one kind of work may be used in other kinds

and a simo chart suggests in doing that work.

7.14 MEMOMOTION STUDY Memomotion study developed by Marvin Mundel is also a motion study

technique that gives more detail than visual motion study and less than

micromotion study, and has application under certain conditions.

This is, in fact, a special form of micromotion study in which the

motion pictures are taken at slow speeds. Sixty frames per minute or one

hundred frames per minute are most common.

Memomotion study has been used frequently to study the flow and

handling of materials, crew activities, multi-man-and-machine

relationships, stock room activities, department store clerks, and variety of

other jobs. It is particularly valuable on long cycle jobs or jobs involving

interrelationship.

Another important use of memomotion camera is in preparing work

sampling study. By using memomotion equipment, unbiased work

sampling studies may be made. To the typical memomotion camera is

attached a timer that permits taking random observations observing the

eight-hour day.

The major advantage of slow-speed picture over those made at

normal speed is the great savings in film cost and in the time required for

film analysis. With the film exposed at 60 frames per minute instead of

960, film cost is only about 6 percent as great.

7.15 IMPOVEMENT OF PATH OF MOVEMENT Process charting helps to show the sequence of activities or events in

situation, and it does not show the path (s) of movement that men,

materials, and tools have to follow when a job is being done. In the paths

of movement there are often undesirable features such as backtracking,

traffic congestion, and unnecessary long movements which are the causes

of many forms of expense. If these expenses are to be optimized Some

recording techniques are essential. These techniques such as flow diagram

string diagram, cyclegraph, and chronocyclegraph are particularly useful

when problems of plant layout and design are considered. They can also

be used effective to demonstrate proposed improvements both to

management and workers.

7.15.1 Flow Diagrams

The flow diagram is the simplest of all the devices in this class of

technique. It is a drawing, substantially to scale, of the working area,

showing the location of the various activities identified by their numbered


symbols, and is associated with a particular flow process chart, either man

or material or

equipment type.

The routes

followed in

transport are

shown by

joining the

symbols in

sequence by a

line which

represents as

nearly as

possible the

paths of

movement of

the subject

concerned.

Numbers

transport

symbols which

form part of the

flow line show

direction of

movement.

When there are

more than one

component

going through the plant simultaneously, each one should be coloured

differently to distinguish between their individual path of flow. The

essential difference between the flow diagram and flow process chart lies

in the fact that the distance moved in between the operations can be

measured and direction ascertained easily in a flow diagram. A typical

example of flow it illustrated in fig. 7.8 .

7.15.2 String Diagrams

The string diagram is a special form of flow diagram in which a string or

thread is used in place lines to measure distance. Like the flow diagram, it

is most often used to supplement a flow process chart the two together

giving the clearest picture of what is actually being done.

Most string diagrams consist of a scale plan mounted on a soft board,

with pins stuck in the relevant work stations. The path of movement of

workers, materials or equipment during a specified sequence of events is

Figure 7.8 Flow diagram


represented by continuous coloured thread stretched between the pins.

Other pins guide the thread over the path it has to take. Threads of

different colours can represent the various factors of production being

moved.

7.15.3 Cyclegraphs

A Cyclegraph is a record of path of movement, usually traced by a

continuous source of light on a photograph. It is produced by attaching a

small pea bulb to the workers wrists or whatever member it is desired to

observe and making a time exposure on a small lens stop while a single

cycle or portion of a cycle is performed. The camera shutter is then closed

after which a normal instantaneous exposure is made on the same film.

The technique was originated by Gilbreth to enable comparatively

short-motion pattern or movements (that is too fast for the eye to follow)

to be recorded on a photograph of the workplace itself.

One of the defects of the cyclegraph is that it does not indicate speed

or direction of movements. To remedy, Gilbreth arranged to flash at a

convenient rate per second by a flash bulb instead of a pea bulb.

7.15.4 Chronocyclegraphs

The chronocyclegraph is a special form of cyclegraph in which the light

source is suitably interrupted so that the path appears as a series of pear-

shaped dots. The pointed end of the dots indicates the direction of

movement and space between them indicates the speed of movement. This

is achieved in the following way :

1. The interruption of the light source is arranged to take place at

carefully controlled regular intervals, usually 10,20, or 30 times per

second.

2. The method of interruption is such that when the light is being

recorded on the film, the movement of the subject results in a pear-

shaped dot being produced, distinctly tapering off at one end.

When the frequency of the interruptions is known, the speed and

direction of movement at any point along the path can be easily calculated

from the number and shape of dots recorded.

In comparison with other techniques or methods outlined in this

chapter, the cyclegraph and chronocylegraph are of limited applications,

but there are occasions on which photographic traces of this sort can be

useful.

REVIEW QUESTIONS


1. What is methods study ? Why is it a prerequisite to work measurement?

2. Write briefly the contribution of Taylor and Gilbreth in standardizing the

methods.

3. Briefly describe the field of application of methods design.

4. List the basic philosophies of methods analysis.

5. List the tools and techniques of methods improvement.

6. What are the various symbols of process chart? Write and explain briefly.

7. Write short notes on

(a) Flow process chart, (b) Flow diagram, (c) Operations process chart and,

(d) Simo chart.

8. State and explain principles of motion economy as related to the use of the

human body. How these are used in job design.

9. (a) What sort of analytical tool might be used to show working relationship

between a worker and machine he is using. What information is necessary for

the development of such a tool ? (b) Under what conditions would micro

motion analysis be justified?.

Method Study

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