Chart Using a Time Scale:
1. Multiple Activity Chart
2. Simo Chart
3. P.M.T.S Chart
Multiple Activity Chart:
A Chart in which the activities of more than one item are recorded on a
common time scale to show their interrelationship. The Man machine chart is the
type of multiple activity charts.
Multiple activity charts are used to show the interrelationships of
individuals in teams of workers, or the relationships between workers and
equipment, usually during the record stage of method study. Multiple Activity
Charts are the process charts using a time scale. It usually comes in a picture
when a work study man wants to record the activities of one subject with
respect to others on a single chart. Here Subject may be the worker, machine or
equipment.
In Multiple Activity Chart Work Load is evenly distributed among the
workers or machines by this the idle time of worker or machine is reduced. The
Multiple activity chart is very useful in planning team work in production or
maintenance and determining the staffing pattern.
Multiple Activity Charts are very useful tool for understanding the
flow of work in a cyclic process and as a consequence, understanding which
resource is controlling the overall progress of the work.
Multiple activity chart brings out the comparative utilization of men
and machines very clearly and helps to synchronize the various activities and
improve the situation.
The multiple activity charts show up clearly the periods of ineffective
time and by rearrangement of work it becomes possible to eliminate or reduce
the ineffective time.
The tool can be used to model different scenarios to determine the
optimum mix of resources for the work.
Activities of the machines are recorded in relation to that of the
operator, the chart is sometimes called as the man machine chart: This is only
a special variant of the multiple activity chart.
Types:
Man-machine Chart: One man handling one job or one machine.
Man-multi machine chart: One man handling a number of machines.
Machine Multi-man chart: A group or gang doing collectively one job as
in riveting.
Multi-man-machine chart: A number of persons working on a computer
system.
Purpose of Multiple Activity
Chart:
1.
To detect the idle time on machine and workers.
2.
To optimize work distribution between workers and machines.
3.
To decide no. of workers in a group.
4.
To balance the work team.
5.
To examine the activities.
6.
It is used for recording the complex movements of material or men.
7.
Used to find out the most economical route.
Application of Multiple
Activity Chart:
1. Plant repair &
maintenance.
2. Job construction.
3. Planning team work.
4. It is used to check whether
the work station is correctly located.
SIMO Chart:
A basic motion-time chart
used to show the simultaneous nature of motions. The SIMO chart is the
micro-motion form of the man type flow process chart. Because SIMO charts are
used primarily for operations of short duration, often performed with extreme
rapidity. Micro motion study is the study of fundamental element or subdivision
of an operation by means of a motion picture camera and a timing device which
accurately indicates the time interval on motion picture film.
Micro motion study provides
a valuable technique for making minute analysis of those operations that are
short in cycle contain rapid movement and involve high production over a long
period of time. For example, Sewing of garment, assembly of small parts.
i. Applicable for operations with very short cycles which are repeated
thousands of times.
ii. Goes into greater details to determine where movements and efforts can
be saved and to develop the best possible patterns of movements.
iii. Enables operations to perform the operation repeatedly with minimum
effort and fatigue.
iv. The technique used for this typically involves filming the operation
and hence is known as micro-motion study.
v. Examples of operators studied could be cashier in the bank routine job
of taking payment slips from customer and issuing cash!
vi. Based on the idea that human activity can be divided into movements or
group of movements according to the purpose for which they are made.
vii. The therbligs cover movements or the reasons for the absence of
movement.
viii.
Each therblig has specific color, symbol and letter for recording
purposes.
ix. Therbligs refer primarily to motions of the human body at the workplace
and to the mental activities associated with them.
x. They permit a much more précis and detailed description of the work
than any other method described.
xi. Considerable practice is required in identification of therbligs before
they can be used for analysis with confidence.
Use of films in micro motion study:
Main Advantages of films over visual methods are:
1.
Permit greater detailing than eye observation.
2.
Provide greater accuracy than pencil, paper ad stop watch.
3.
More convenient.
4.
Provide a positive record
5.
Help in the development of the work study person.
Objective of Micro Motion Study:
1.
To find the most efficient way of doing work.
2.
Helps to study repetitive short cycle operation which cannot be studied
by ordinary method.
3.
To train operator regarding motion economy.
4.
It is a permanent means of keeping records of method
5.
It assists In a research project in the field of work study.
6.
It helps to study complex activities of short duration performed with
extreme rapidity.
Procedure/Step in micro
motion study:
1.
Filming the operation to be studied.
2.
Analyzing the film.
3.
Charting he result of analysis.
4.
Developing and improving the method.
Filming:
The filming speed is 16 frames per second with a 16 mm movie camera.
Film Analysis:
1.
A projector is used for analysis purpose.
2.
Projector runs the films very slowly and film can be stopped and
reversed whenever required.
Cycle-graph:
i.
A record of path of movements, usually traced by a continuous source of
a light on a photograph.
ii. The path of movement of a hand, may be recorded on a photograph by
putting a ring carrying small light on worker’s hand.
iii. A path of light resembling a white wire is seen.
iv. Later it is used with a stereoscopic camera to show the path in three
dimensions.
Chronocyclograph:
i. This is a development of the cycle graph by interrupting the flow of
current so as to obtain, in the resulting sequence of flashes, a record of the
time and direction of the motions under observation. The resulting image was a
chronocyclograph.
ii. The path of light appears as a series of pear-shaped dots, the movement
being in the direction and deceleration.
iii. The space between the dots indicate the speed of movement and show
acceleration and deceleration.
iv. This is done by using a tuning fork, which is vibrating t a known
speed, and connected with a “make and break” contact.
Diagrams:
The Diagram gives illustrated view of the layout of workplace on which
location of different equipment, machines etc. are indicated.
The movement of the subject (man
or machine) is then indicated on the diagram by a line or a string.
The diagram are valuable in highlighting the movement so the analyst
can take steps to simplify or reduce it so as to obtain saving in time.
The most commonly used method study diagrams are:
i. Flow diagram.
ii. String diagram.
iii. Travel chart.
iv. Cyclegraph and Chronocyclegraph
Flow Diagram:
A flow diagram is a chart constructed on a scale plan of the workplace
indicating where each activity takes place. It’s a top view of the work area
correctly indicating the positions of machining and other locations affecting
the movement of the subject.
There it gives “on-the-spot observation” of the paths of movement of
product sometimes using symbols of the process.
It is the use of symbols for flow process charts, superimposed on
drawings and the “descriptions” are not necessary.
String Diagram:
String diagram is used for solving movement problems since it shows
congestions and excessive distances. String diagram is one of the useful and
simplest techniques of method study. The definition of String diagram is a
scale model on which a thread is used to trace the path or movements of man and
materials during a specified sequence of events.
String diagram in a special form
of flow diagram. A thread is used to measure distance.
Necessary that the string diagram be drawn correctly to scale, whereas
the regular flow diagram can be drawn only approximately to scale. Thus string
diagram and flow chart can give the clearest possible picture of what is
actually being done.
String diagram can be used to plot the movements of material to know
how far the materials travel.
Most commonly, the string diagram is used for plotting the movements of
workers.
A brief procedure for the construction of string diagram in given as
follows:
(i) Study and record the complete information about the movement of
various resources.
(ii) Draw a scale layout of the shop area and mark various features
such as machinery, work benches, stores etc.
(iii) Mark and insert panel pins at all workstations between which the
journeys are made. More pegs/pins may be stretched in between the facilities to
trace more or less the actual path followed by men and materials.
(iv) A continuous colored unstretchable string, taken from the first to
last warned to trace the path followed by operators or materials. Use strings/
threads of different colors if the movement of more subjects is being shown so
that their movements are easily recognized and distinguished.
(v) Remove the string to measure their lengths which approximately
gives distances traveled by a worker or a machine or the material.
A string diagram is a useful
tool for the following purposes:
(1) It represents the record of an existing set of conditions and thus
helps the method engineer in visualizing the actual situation.
(2) It indicates complex movements, back tracking, congestion,
bottlenecks and over and under utilized paths on the shop floor.
(3) It is an aid for comparison between different layouts or methods of
doing a job as far as the distances moved are involved.
(4) It helps in tracing existing paths of movement for incorporating
necessary modifications, if any.
(5) It is prefixed when movements are not regular as far as frequency
and distance moved are concerned.
(6) Indicates the pattern of movements and thus helps in deciding the
most economical routes to perform a particular operation.
Travel Chart:
A travel chart is a tabular record of data concerning the movement of
people, material or equipment between any number of places over a given period
of time.
String diagram is good to explain movements and critical examination
but
i. It takes longer time to get constructed and
ii.
Many movements along complex paths may lead to a diagram with a maze of
crisscrossing line.
When movements are very complex travel chart is quick and more
effectively managable recording technique.
Working Procedure:
1.
A travel chart is a tabular record for pressing quantitative data about
the movements of subject between any numbers of places over a given period of time.
2.
This chart is a square table and each square within table represents a
station.
3.
It has number of rows and columns equal to the number of stations that
can be visited by the subject.
Edited By:
Md. Farid Ahmed
IE Officer
Fakir Apparels Ltd.
BSCIC Industrial Area, Enayet Nagar,
Fatulla, Narayangonj, Bangladesh.
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