Monday 3 June 2013

PLANT LAYOUT

UNIT – 4
4A. PLANT LAYOUT
4A. 1 LAYOUT
Layout concerns with configuration of departments, work centres and equipments, with specific
emphasis on movement of men and materials through the system. Decision in nay of these four design
areas – plant location, products, capacity planning and plant layout often have impacts on the others. Thus,
both layout and location decisions affect capacity. Conversely, efforts to increase capacity may involve
modifications in layout and changes in location. Moreover, any time a new location is established or
products or services are introduced or changed, layout is affected.
4A. 2 IMPORTANCE AND FUNCTION
Layout decisions are important for three basic reasons:
(1) They require substantial investments of both money and effort.
(2) They involve long-term commitments, which makes mistakes difficult to overcome, and
(3) They have a significant impact on the cost and efficiency of short-term operations.
The need for layout planning can arise as part c the design of new facilities as well as redesign of existing
facilities. In the latter instance, the most common reasons for redesign of layout include the following:
(i) Inefficient operations resulting in high-cost bottlenecks
(ii) Frequent accidents or safety hazards.
(iii) Changes in the design of products or services
(iv) Introduction of new products or services
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(v) Changes in volume of output or product mix
(vi) Changes in environmental or other legal requirements
(vii)Employee morale problem.
(viii) Obsolescence of technology / facilities
(ix) Reduced damage or spoilage of materials
4A. 3 PRINCIPLES OF LAYOUT
The basic principles of plant layout are as follows:
(i) The total movement of material should be minimum. For this, one has to consider the movement
distances between different work areas as well as the number of times such movements occur per
unit period of time.
(ii) The arrangement of the work area should have as much congruence as possible with the flow of
materials within the plant (form the stage of raw materials to the stage of finished goods) By ‘flow’
we do not mean a particular straight – line direction, we mean the different stages through which
the material passes before it becomes a finished product. The stages at which value is added to the
product and the sequence of the work areas should correspond with each other, as much as
possible. In effect, there should be no back-tracking and very little interruption in the flow of the
product from the raw materials stage to the finished product.
(iii) The layout should ensure adequate safety and satisfactory working conditions for the employees.
(iv) A good layout should take into consideration all the three dimensions of space available. In
addition to the floor space, the vertical space available should also be taken into account while
designing the work areas.
(v) The layout should be adaptable or flexible enough to allow for probable changes in the future as all
systems should anticipate changes in the future.
(vi) A good layout has to satisfy, therefore, the availability of space, the size and work area
requirements of machinery and other utilities, the flow direction, type and number of movements
of the materials, the men working in the plant, and also the future anticipated changes. The
principle is one of integrating all these aspects.
4A. 4 TYPES OF LAYOUT PROBLEMS
According to the types of facility under consideration, the layout problem can be classified. For
example:
(1) Production centre or manufacturing plant
(2) Commercial establishments like shops, depart mental stores, offices, banks.
(3) Service facilities like hospitals, post offices.
(4) Residential accommodations like apartments houses.
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(5) Town planning, real estate developing
(6) Recreational facilities or entertainment avenues like theatres, parks.
These layout problems may crop in at various stages in any organization. If the organization may plan to
create a totally new complete facility or plan for expanding the existing capacity in the already existing
plant or rearrangement of existing layout or minor modifications to be carried on the present layout , so as
to maximize the profit of the organization.
4A. 5 FLOW PATTERNS
According to the principle of flow, size and content of the job, use of gravitational foce, the layout
plan arranges the work area for each operation of process so as to have an overall smooth flow through
the production plant. Layout plan arranges the work area for each operation or process, so as to have
overall smooth flow thorough the production facility. The basic flow pattern types that are employed in
designing the layouts are I-Flow, L-Flow, U-Flow, O-Flow, S-Flow.
The specialties of different flows are:
I – Type Separate Receiving and shipping area
L – Type Adopted, when straight line flow could not be accommodated.
U – Type Popular, combination of Receiving and Shipping at one end
O – Type Adopted when it is required to terminal the flow nearer to the origin
S – Type When the production line in long and Zig Zaging on the production
floor is required.
4A. 6 OBJECTIVES OF GOOD PLANT LAYOUT
a. Overall simplification of production process in terms of:
Equipment utlisation
Minimization of delays
Reducing manufacturing time
Better provision for maintenance
b. Overall integration of men, materials, machinery, supporting activities and any other
consideration which may give a better compromise
c. Minimize of material handling cost
Achieved through facilities in the best flow sequences
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d. Floor space saving
Effective space utilization
Less congestion and confusion
e. Increased output and Reduced work-in-progress.
f. Better working environment
g. Better working environment
Reduced Hazards
Safety of employees
h. Workers convenience
Worker / Job satisfaction
Improve morale
i. Waste minimization and higher usage.
j. Avoid unnecessary capital investment
k. Higher flexibility and Adaptability to changing conditions
l. Improved work methods and reduced production cycle time
m. Better product quality
n. Better utilization of cubic space.
4A. 7 FACTORS FOR GOOD LAYOUT
The layout is governed by many factors. The best layout is one, which optimize all the factors.
These factors are grouped under eight categories. They are:
(i) Material Factors
Product Design
Product Variety
Quantity Produced
Necessary Operations of producers
Sequence of Production
(ii) Men Factor
The number of Direct Workers
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Supervision and Service help required
Manpower utilization
Safety of employees
(iii) Machinery Factor
Process of Production
Equipment used for production
Tools and their utilization
(iv) Movement Factor
Inter and Intra Department Transport
Material Handling at various operations
Storage and Inspection
Material Handling Equipments
(v) Waiting Factors
Permanent and Temporary Storage
Delay and their location.
(vi) Service Factors
Related to employee facilities such as, parking lot, lockers, toilets, waiting rooms.
Related to material in terms of quality, production control, scheduled, Dispatching, Waste
control.
Related to machinery such as Maintenance
(vii)Building Factors
Interior and Exterior of the buildings
Utility Distribution and Equipments
(viii) Change Factor
Versality
Flexibility
Expansion
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4A. 8 LAYOUT DESIGN PROCEDURE
The overall layout design procedure has four phases. They are :
Phase I : Location
II : General Overall Layout
III : Detailed layout
IV : Implementation
The systematic procedure involves the following steps:
a. Data input and activities
b. Preparation of flow of materials
c. Activity (Precedence – Succeedence ) relationship
d. Plan of material handling
e. Relationship diagram preparation using steps : a to d
f. Calculation of space requirements
g. Identification of availability of space
h. Space Relationship Diagram preparation, using steps: e. f and g.
i. Modifying consideration
j. Practical Limitations
k. Develop Layout alternative, using steps: h, i and j
l. Evaluation of alternative
m. Selection of the best layout
4A. 9 LAYOUT TYPES
There are three basic types of layouts and these correspond to the three types of processing
systems. Product layouts are most conducive to continuous processing, process layouts are used for
intermittent processing and fixed position layouts are used when projects require layouts. There are
another two types of hybrid layouts. Cellular or group layout is a special type of process ay out. For
example systems, the job shop layout is the solution.
4A. 10 PRODUCT LAYOUT
This type of layout is used to achieve a smooth and rapid flow of large volumes of products or
customers through a system. This is made possible by highly standardized products or services which
require highly standardized, repetitive processing operations. A job is divided into a series of standardized
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tasks, permitting specialization of both labour and equipment. The large volumes handled by these
systems usually make it economical to invest substantial sums of money in equipment and in job design.
Because only one or few very similar items are involved, it is feasible to arrange an entire layout to
correspond to the technological processing requirements of the product or service involved.
This layout is for product focused systems, and are popularly known as ‘Assembly Line”. The work
centres are arranged in the job sequence. The raw materials enters at one end of he line and individual
operations are performed in the pre-fixed sequence and get converted to the final shape. There is one
flow for each product. This follows the I – pattern of flow. The work in-process and the material handling
are minimum.
Following conditions favour the selection of product layout.
High volume of production
Standardization of product
Reasonably stable product demand
Uninterrupted supply of material
Holding up of inventory is possible.
Product layouts achieve a high degree of both labour and equipment utilization, and this offsets the high
equipment costs. the investment in work-in-process is minimum because the items move quickly from
operation to operation. This also reduces congestion and ensures smooth flow of items in the shop floor.
Overall supervision and control are effective.
4A. 11 PROCESS LAYOUT
These layout are designed to facilitate processing items or providing services which present
variations in their processing requirements. The processing units are organized by functions into
departments on the assumption that certain skills and facilities are available in each department. Similar
equipments and operations are grouped together. For example, turning, milling, foundry, heat treatment.
Items which require these operations are frequently moved in batches to the departments in a sequence
dictated by technical considerations. Different products may cal for different processing requirements and
different sequence of operations. Consequently, variable path material handling equipment is needed to
handle variety of routes and items.
These layouts, also known as “Functional Layout’ is process focused systems and are used widely in
manufacturing and service sectors. The use of general purpose machines provides flexibility necessary to
handle a wide range of processing requirements. Workers who operate the equipments are usually skilled
or semi-skilled. The example of process layout includes hospitals, colleges and universities, banks,
airlines and public libraries. For instance, hospitals have many departments like surgery, maternity,
emergency, etc. Similarly universities have separate departments that concentrate on different areas of
study as engineering, business management, mathematics, and physics. In business organization, there
will be departments like accounts, personnel, and systems.
Because process layouts arrange equipments by type rather than according to processing sequence,
the system is much less vulnerable to shutdown caused by either maechanical failure or absenteeism.
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Material handling in inefficient and unit handling costs are generally much higher than in product layouts.
The investment in work-in-process is high and material movements will take a zig-zag route. The
equipment utilization comparatively will be less. Hence, this layout is more suited for low volumes of
production and particularly when the product is not standardized. It is economical when flexibility is the
basic system requirements.
4A. 12 FIXED LAYOUT
In this, the material remains in a fixed position, but machinery, tools handling equipment, workers
are brought to the place the material. This is in contrast to both product and process layouts. Such a
layout may be preferred when the equipment and the machinery is small in number and size, and where
the workmen are highly skilled to perform the various small jobs on the product. Fixed position layouts are
sued in large construction projects, ship building, aircraft manufacturing.
4A. 13 “REL” Chart
This denotes Relations Chart. The chart depicts the relationships between various departments and
their relative importance. The relationship is graded as:
A - Absolutely Essential
E - Essential
I - Important
O - Ordinary
U - Unimportant
X - Undesirable
Assembly
Fabrication
Job planning
Pattern shop
Shipping
Testing
Wiring
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FIGURE 4.3 ‘REL’ CHART
The departments which falls in the “A” relationship has necessarily to be place together, whereas
those falling under “x” relationship can be mutually exclusive. This give scope for the layout designer to
position various departments of he organization for optimum utility.
4A. 14 LINE BALANCING
Many differences exist in the management of production activities in make-to-order and make-to-stock
firms. In make-to-order situations, due dates are important, and hence the sequencing of customer orders
at various machine centres is an essential function. This involves both planning and control of activities.
Make-to-stock products are generally high-volume consumer goods, such as telephones, automobiles,
wrist watches, etc. The manufacture of standardized, high-volume items, which involves flow shops
requires control for effective production.
A flow shop consists of a set of facilities through which work flows in a serial fashion. The same
operations are performed repeatedly in every work station, thus require lower-level skilled workers. The
flow shop generally represents a mass production situation and hence the operations are carried out very
efficiently e.g. when an operator has to install a gear box on an automotive assembly or assembling
cooling system on a washing machine.
In flow shops, items enter the finished goods inventory one after another, often in the same order of the
inputs for these goods, leaving very low in-process inventories. Since the items are mostly make-to-stock,
forecasting is a difficult job, and hence the finished goods levels in terms of anticipation inventories are
very high. For the same reason, raw materials are carried at higher inventory levels. Machines in flow shop
tend to have a special – purpose design, and hence the initial investment level is generally high for heavy
automated plants.
The production control system of continuous production is called flow control. Specialization, high
volume, division of labour and efficiency are built into the design of assembly lines.
The main objective of flow control in flow shops it to balance the assembly line. The assembly line
is represented in the form of a precedence diagram.
4A. 15 OBJECTIVE OF ASSEMBLY LINE BALANCING
The objective of assembly line balancing is to subdivide the network into several sub networks (stations)
without violating the precedence relationships and allocating operations to each station without exceeding
the cycle time, i.e. the sum of the times of operations allocated to each station should not exceed the cycle
time.
While allocating operations to each station, the precedence relationships must be maintained. If these are
followed, then we can ensure production of the specific volume of products ore items using the assembly
line. At an interval equal to the cycle time, a completed assembly will be related from the assembly line.
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4B. PRODUCTION PLANNING AND CONTROL
4B. 1 INTRODUCTION
Production is an organized activity of converting raw material into useful products. Planning and control
are two important components of management process,. Before the commencement of production,
production planning is done in order to anticipate possible difficulties and decide in advance as to how the
production should be carried out in the best and most economical way. Planning involves the
considerations of all input variables to achieve defined output goals. Mere planning is a not sufficient for
this. It has to be implemented strictly and within the standard time the jobs are to be completed. For this
purpose control is essential, which involves the corrective actions taken when the actual out put varies
from the desire one cy bringing the actual output in line with the planned output.
Production planning, in particular, would therefore consist mainly of the evaluation and determination of
production inputs such as manpower, machinery and equipments, material handling equipments and
utilities to achieve the desired goals. The definition of the goal is also a part of production planning
process.
The aim of production control is to produce the pro duties of high quality, in right quantity and at the right
time by using the best and leas expensive methods.
Hence, the production planning and control is defined as the process of planning the production in
advance, setting the exact route of each item, fixing the starting and finishing times for each item, to give
production orders to shop floors and to follow up the progress.
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The planning process can be divided into various stages.
(a) Defining objectives and setting priorities to achieve these goals
(b) Studying the external and internal environments
(c) Determining reliable targets
(d) Gearing up the inputs to achieve these targets.
The main functions of production planning and control are:
(i) Planning function
Planning
Process designing
Routing
Material control
Scheduling
Tool control
Forecasting
Loading
(ii) Control function
Dispatching
Follow up
Inspection
4B. 2 INTEGRATIVE NATURE OF PRODUCTION PLANS
Production planning and control (PPC) is an effort to optimize the process of conversion of raw materials
into finished products required in the market. Since various activities are involved the conversion of raw
materials into finished goods, PPC is and has to be an integrated functions if the organization has to
derive maximum benefit out of planning. The procurement of raw materials, the quality control and
inspection of raw materials, inventory levels of in process and finished goods, the production costs, the
labour available, the machinery and equipments that is : available, the Warehousing capacity avail able tec.,
all have their influence on the planning of production operations which convert the raw material into
finished goods. All the functions have inter-links and the more such inter-links are considered int eh
planning process, the better will be the planning process.
Sometimes production and maintenance are planned separately, leading to conflicts between the
preventive maintenance needs and the production requirements. Such conflicts can be avoided if the
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planning for maintenance is done in co-ordination with planning for production, allowing sufficient
number of days of shut downs of different machines while drawing up the production plan for the year.
The more integrative the PPC, the better will be the planning decisions.
Products are manufactured by the transformation of raw material (into finished goods). This is how
production is achieved. Planning looks ahead, anticipates possible difficulties and decides in advance as F
– to how the production, best, be carried out the control phase makes sure that the programmed
production is constantly maintained.
A production planning and control system has many functions to perform, some, before the arrival
of raw materials and tools and other while the raw material undergoes processing. The various functions
are also sub-divided as follows:
Planning Phase
o Prior Planning
Forecasting
Order Writing
Product Design
o Active Planning
Process Planning and Routing
Material Control
Tool Control
Loading
Scheduling
Action Phase
Dispatching
Control Phase
Progress Reporting
Data Processing
Corrective Action
Expediting
Replanning
The details of various functions are:
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(a) Forecasting: Estimation of type, quantity and quality of future work
(b) Order writing: Giving authority to one or more persons to undertake a particular job.
(c) Product design: Collection of information regarding specifications, bill of materials, drawings, etc.
(d) Process planning and routing: Finding the most economical process of doing a work and (then)
deciding how and where the work will be done
(e) Material control: It involves determining the requirements and control of materials.
(f) Tool control: It involves determining the requirements and control of tools used
(g) Loading: Assignment of work to manpower, machinery etc.
(h) Scheduling: It is the time phase of loading and determines when and in what sequence the work
will be carried out. It fixes the starting as well as the finishing time for the job.
(i) Dispatching: It is the transition from planning to action phase. In this phase the worker is ordered
to start the actual work.
(j) Progress reporting:
a. Data regarding the job progress is collected
b. It is interpreted by comparison with the preset level of performance
(k) Corrective action:
a. Expedition means taking action if the progress reporting indicates a deviation of the plan
from the originally set targets.
b. Replanning – Replanning of the whole affair becomes essential, in case expediting fails to
bring the deviated plan to its actual (right) path.
4B. FORECASTING
a) Forecasting means estimation of type, quantity and quality of future work e.g. sales etc.
b) The survival of a manufacturing enterprise depends on its ability to assess, with reasonable
accuracy, the market trends several years ahead.
c) Forecasters will be able to make use of sales trends, but these must be considered in the light of
expected introduction of new materials, fashion changes, policies of competitors, unseasonable
weather, threat of war and the general economic situation expected in the country and foreign
markets. These circumstances and others necessitate changes in sales forecast from time to time
during the forecast period.
d) Forecast represents a commitment on the part of the sales department and each of is divisions of
expected sales. It becomes a goal against which the effectiveness of the sales department will be
measured.
e) Forecasting plays a crucial role in the development of plans for the future.
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f) Sales budget (estimate) forms the basis for manufacturing budget. It is the sales forecast which
enables to determine production quantities, labour, equipment and raw material requirement (Refer
to Chapter no. 28)
g) A sales forecast should be
a. Accurate
b. Simple and easy to understand and
c. Economical
4B. 4 PURPOSE OF SALES FORECASTING
Sales forecasting is essential because,
(i) It determines the volume of production and the production rate.
(ii) It forms basis for production budget, labour budget, material budget, etc.
(iii) It suggests the need for plant expansion
(iv) It emphasizes the need for product research development
(v) It suggests the need for changes in production methods
(vi) It helps establishing pricing policies
(vii)It helps deciding the extent of advertising, product distribution, etc.
4B. 5 BASIC ELEMENTS OF FORECASTING
- Forecasting means predicting future events by the best possible means
- In any sales forecasting analysis, there are four basic elements of economic data that should be
used
1. Trends
2. Cycles
3. Seasonal variations
4. Irregular variations
- Trends are the long term, long range movements of a series of economic data. They have little
relationship to the month-to-month changes that take place, and they manifest their direction
slowly.
- Cycles are of shorter duration and they are usually featured by alternate periods of expansion and
contraction.
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- Seasonal variations occur within a certain period of year and recur at about the same time and to
approximately the same extent from year to year.
- Irregular variations are the result of unforeseen or non-recurring events that have an economic
influence. A strike in a key industry might cause an irregular variation.
4B. 6 SALES FORECASTING TECHNIQUES
Forecasting is the formal process of predicting future events that will significantly affect the
functioning of the enterprise.
Sales forecasting techniques may be categorized as follows:
(a) Historic estimate
(b) Sales force estimate
(c) Trend line (or Time series analysis) technique
(d) Market survey
(e) Delphi method
(f) Judgmental techniques
(g) Prior knowledge
(h) Forecasting by past average
(i) Forecasting from last period’s sales
(j) Forecasting by Moving average
(k) Forecasting by Weighted Moving average
(l) Forecasting by Exponential Smoothing
(m) Correlation analysis
(n) Linear Regression Analysis
The details of the forecasting techniques are given below:
(a) Historic estimate
This technique makes use of the assumption that what happened in past will happen in future.
For example L. a concern has sold 5000 blankets in winter last year, it will be able to sell the
same quantity in winter this year also.
Historic estimate is useful if the activity is affected by pattern of seasonality.
It is useful for determining model, size and colors distribution.
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It is successful only when pattern of events remains unchanged, i.e., if economy is static. This is
rarely true except for short period of time.
Historic estimate is not scientifically valid and thus it is not an accurate method, the total sales
forecast provided by this method should be modified by other techniques.
(b) Sales force estimate
This technique is based upon the principle – that the persons in contact with the market know
best about the future market tends.
Individual salesmen make sales estimates of their territories and submit it with the District
Sales Manager who analysis it, modified it and sends the same to Factory Sales Manager.
Factory Sales Manager in consultation with other related factory executive formulates the final
estimate of sales.
This technique is useful when an industry is making a limited number of products (e.g.,
commercial power generating equipment) and there are a few large customers.
(c) Trend line technique
Trent line technique is employed when there is an appreciable amount of historical data.
This technique involves plotting historical data, i.e., a diagram (Fig. 7.3) between activity
indicator, e.g. tons of material (say past sales) on Y – axis and time on X – axis.
A single best fitting line (using statistical technique) is drawn and projected to show sales
estimate for future.
This technique is more accurate as it makes use of a large past data and possesses scientific
validity.
However, it is time-consuming, involves long mathematical calculations and assumes an infinite
population of relatively small customers so that the decision of an individual customer cannot
have an appreciable effect on total product demand.
(d) Market Survey, i.e. Market Research Technique
This technique finds application when a concern introduces a new product in the market and is
interested to estimate its sales forecast. For a new product, naturally, no historic or past data
regarding sales will be available.
This technique may be very informal, utilizing the sales force to feel out the potential
customers in order to establish the extent of the market or it maybe a systematically conducted
survey using special mathematical tools.
Generally, the new product is introduced in a relatively small critical trial area, market reaction
is noted and the total sale (country wide) is projected from these results.
(e) Delphi Method
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A panel of experts is interrogated by a sequence of questionnaires in which the response to one
questionnaire is used to produce the next questionnaire. Any set of information available to
some experts and not others is thus passes on to the others, enabling all the experts to have
access to all he information for forecasting. The method solicits and collates from experts to
arrive at a reliable consensus. This technique eliminates the bandwagon effect of majority
opinion.
Delphi method has fair to very good accuracy for short and long term forecasts.
The method is applicable to forecasts of long-range and new-product sales.
(f) Judgmental techniques
Opinions of consumers and customers. Questionnaires related to buying the product may be
sent to a selected group of consumers and to the customers who have already purchased the
product. The information thus received can be very useful in estimating product performance
and its probable demand in future.
Retail and wholesale dealers can provide some insight into the pace of current and future sales.
The opinion of area sales manager can also be quite useful.
(g) Prior knowledge
This us used by ancillary units which are more or less a part of the large organisation. The large
organisation informs each ancillary unit how many components parts to make.
The forecast estimate is needed only to establish the material and tool requirements, etc.
(h) Forecasting by Past average
If our objectives is to forecast or predict the sales of an item for the next sale period, then this
method is used.
(i) Forecasting from last period’s sales
The method eliminates the influence of past (old) data and bases the forecast only upon the
sales of he previous period.
(j) Forecasting by Moving Average
This method represents a compromise between the two above explained methods, in that the
forecast is neither influenced by very old data nor does it solely reflect the figure of the
previous period.
(k) Weighted Moving Average Method for Forecasting
Whereas the simple moving average gave equal effects to each components of the moving
average database, a weighted moving average allows any weights to be placed on each element,
providing, of course, that the sum of all weights equals one.
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The weighted moving average method has a defined advantage in being able to very the effects
of past data, but it also has the disadvantage of remembering the total history for the time
period.
(1) Forecasting by Exponential Smoothing
The main disadvantages of the moving average method are:
The lengthy calculations involved
The need to keep quantities of historical data.
The fact that the normal (or simple) moving average method places equal weight on each of the
historical figures used.
The age of the data, which increase with the number of periods used.
All of these disadvantages are overcome by he exponential smoothing technique. Using this technique it is
necessary only to retain the previous forecast figure and to know the latest actual sales figure. The
technique works by modifying the old forecast in the light of new sales figure.
4B. 7 TOOL CONTROL
Tool control implies (1) determining tool requirements (2) procuring necessary tools and (3)
controlling/maintaining tools once they have been procured.
A tool or process planner must calculate tool requirements prior to the time of production to
ensure that proper tools will be available when needed. Lost time resulting from incomplete
tools planning can be expensive as well as causing work to delay.
In order to facilitate tool control and to limit the investment in tool inventory. It is important to
standardize wherever possible all the tools within an organisation.
Need for tool control: It is very important to ensure:
Against loss through theft or negligence and production delays through misplacement or
non-availability of tools.
That the investment in tool inventories is minimized consistent with proper tool availability.
4B. 8 PROCEDURE OF TOOL CONTROL:
Two methods are commonly used to control the issue and receipt of tools to and from the workers.
(1) The Brass ring system. Brass rings with worker’s identification number marked on them are issued
to every worker when he draws a tool from the crib, he gives one of his, rings to the attendant and
the ring is hung on a peg at the tool bin. When the worker returns the tool, the ring is returned to
him.
This method is very simple and can be used where workers are not much educated. However it
invites dishonesty because of the case with which counterfeit rings can be made. The method also
does not provide any means of determining tool usage.
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(2) The Mc Caskey System
This system is based upon 3-part carbon backed form. The worker fills it out and present it to
the tool crib attendant when he wishes to withdraw a tool. One copy of the form is maintained
under a clip with the worker’s name or his clock number and a second copy under a clip of the
tool number. The third copy is given to the worker for identification of the tool. The copy filed
under tool number provides ready reference that, particular tool is not available when a later
request is made for it.
Periodic checks of the slips under the worker’s clip will indicate if tools are being hoarded or
held for an excessively long time.
When the tool is returned along with the third copy of the form which the worker had kept for
his information (identification of tool), the copy under the worker’s clip is removed and given to
the worker. The copy under the tool number clip is removed and placed behind the tool
inventory card at the back of each clip. Every month, the slips behind the card are counted to
indicate tool usage and the individual slip thrown away.
This system is widely used in manufacturing establishments because of its excellent control
features.
4B. 9 LOADING
Loading means assignment of work to manpower, machinery etc., without specifying when the
work is to be done.
Loading results in a tabulated list or chart showing the planned utilization of he machines or
work stations in the plant.
The objective of the loading function is to be maintain an up-to-date picture of the available
capacity of the plant.
Laoding can be defined as the study of the relationship between load and capacity at the places
where work is done. The information provided by loading is used (1) to ensure the efficient
utilization of the plant and labour in a factory, (2) to help in the setting of reliable delivery
promises, (3) and to assist in the forward planning of the purchase of new plant.
Capacity can be defined as the time available for work at work centres expressed in machine
hours or in man hours.
4B. 10 AIMS OF LOADING
(1) To check the feasibility of production programmes
(2) To assist in the efficient planning of new work.
(3) To assist in balancing the plant to the existing load.
(4) To assist in the fixing of reliable delivery promises.
4B. 11 : SCHEDULING AND CONTROL OF PRODUCTION
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Once the planning (work) to meet sales is complete and a set of decisions have been formulated using
Graphical or Linear programming methods the next step in the implementation of the decisions through
detailed plans and schedules. Schedules are made for the use of facilities like equipment and manpower.
Scheduling and Control of production focus attention on the following:
(a) Knowing the total overall production targets – how to determine the amount of each product be
manufactured if there are products of different types and sizes?
(b) How to decide about and deploy work force (different types of workers and kinds of skills) and
equipment to achieve the target production rate?
(c) How to determine individual work assignments?
(d) What should be the information system to feed back quickly and accurately the actual output duly
compared with the scheduled one?
Scheduling and Control of production have one stage in between them, which is known as
dispatching and it will be discussed under Sec. 7.18. In general, first of all the order is scheduled,
then it is dispatched for necessary operation (on the raw material) and lastly the progress of the
order is tracked, to be certain that the schedule is being met. This (last) phase of tracking the
progress of an order and making corrections (if necessary) is known is control of production.
4B. 12 SCHEDULING
In brief, scheduling means – when and in what sequence the work will be done. It involves deciding
as to when the work will start and in certain duration of time how much work will be finished. Scheduling
deals with orders and machines, i.e. it determines which order will be taken up on which machine and in
which department by which operator. While doing so, the aim is to schedule as large amount of work as
the plant facilities can conveniently handle by maintaining a free flow of materials along the production
line.
Scheduling may be called the time phase of Loading. Loading means the assignment of task or
work to a facility whereas scheduling includes in addition, the specification of time and sequence in which
the order/work will be taken up.
A production schedule is similar to a railway time table and shows which machine is doing what
and when. A production schedule is a statement of target dates for al orders or operations in hand and
reveals their starting and finishing dates. Scheduling finalizes the planning phase of Production Planning
and Control System.
4B. 13 FACTORS AFFECTING SCHEDULING
The following factors affect production scheduling and are considered before establishing the
scheduling plan.
(a) External factors
Customer’s demand,
Customer’s delivery dates, and
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Stock of goods already lying with the dealers and retailers.
(b) Internal Factors
Stock of finished goods with the firm,
Time interval to process finished goods from raw material. In other words—how much time will
be required to manufacture each component, subassembly and then assembly (i.e. the final
product).
Availability of equipment and machinery, their total capacity and specifications.
Availability of materials, their quantity and specifications,
Availability of manpower (number, type and kind of skills)
Additional manufacturing facilities if required, and
Feasibility of economic production runs.
4B. 14 SCHEDULING PROCEDURE AND TECHNIQUES
Scheduling normally starts with the Master Schedule. A master schedule resembles central office
which passes information about all the orders in hand.
4B. 15 ADVANTAGES
1. It is simple and easy to understand,
2. It can be kept running (i.e., current)
3. It involves less cost to make it any maintain,
4. It can be maintained by non-technical staff, and
5. A certain percentage of total weekly capacity can be allocated for such orders.
4B. 16 DISADVANTAGES
1. It provides only overall picture, and
2. It does not give detailed information. Applications
4B. 17 APPLICATIONS
In big firms, for the purpose of loading the entire plant,
In Research and Development organizations, and
For the overall planning in foundries, computer centres, repair shops, etc.
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After framing the overall picture of production requirements through a Master Schedule chart, the
detailed schedules are thought of and made for each component and subassemblies so that all
parts are available at the time of assembly. There are a number of visual aides and techniques,
both in the form of conventional charts and commercially available boards, which aid in detailed
scheduling. The technique to be employed for scheduling purposes depends upon the type of
production (intermitted for scheduling purposes depends upon the type of production (intermitted
or continuous), type and frequency of tasks, demand patters, etc A useful scheduling device
normally portrays planned production, actual performance and heir comparison. Actually, the Gantt
Chart forms the basis of commonly used scheduling techniques.
Some of the techniques (besides master schedule) employed for Loading and Scheduling purposes
are:
Perpetual schedule
Order schedule
Loading by schedule period
Commercial devices
(A) PERPETUAL SCHEDULING:
Like master scheduling, it is also simple and easy to understand, is kept current, involves less cost
and can be maintained by clerical staff. But, the information which is provides is very gross ant at the same

time it is not clear from the chart-when the work will take place.
(B) ORDER SCHEDULING
It is most elaborate technique. Time is marked horizontally and the vertical axis shows the
particular facility (say a machine). The information required to generate an order schedule is, regarding the
number of parts to be manufactured, name of the machines, their Set-up times, total production time and
the date of completion of the order.
The scheduling is started by placing the last operation at the date of completion and then working
backwards.
Advantaged of Order Scheduling
1. it is very detailed.
2. The earliest possible completion dates can be met.
Limitations
1. It is very costly
2. It requires accurate (production) time standards and good communication system.
3. It is difficult to maintain effectively if there are many active orders
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(C) LOADING BY SCHEDULE PERIOD
The task is broken into different operations which will be required to turn raw material into
finished product. A Gantt type of chart is employed for scheduling purposes. The rows, mark different
facilities and each column denotes a time period (TP). There are as many time periods as the number of
operations. The first operation is carried out in the time periods as the number of operations. The first
operation is carried out I the time period-1, second operation, in the time period-2 and soon. It is
however not specified that, within the time period, when the operation will start and finish, but the
operation is very much supposed to be completed during that particular time period. The shop supervisor
does the detailed scheduling within the framework of the specified time period.
This type of scheduling involves a longer in – process (total) time because only one operation is to be
performed in one time period. However, this makes it more flexible as an operation can be taken up at the
most convenient time within the specified time period.
4B. 18 PRODUCTION CONTROL
Scheduling completes the planning phase of Production Planning and control. The next is
‘Dispatching’. After dispatching is the control phase or control of production which consists of two parts (a)
Progress reporting, and (b) Corrective action.
A control system involves four stages namely: (1) observation, (ii) analysis, (iii) Corrective action,
and (iv) Post-operation evaluation. A production control system considers these elements in its different
functions.
The control of production is necessary to be sure that the production schedules are being met and
the job will be delivered as per the pre decided (scheduled) plans. Production control involves an
information feedback mechanism and a system of corrective action. Production control follows up the
schedule plans, comprise the actual output with the planned one, and points out deviation, if any, so that
the same can be corrected through the adjustments of men, materials and machines.
In brief, a production control group:
Receives work progress reports;
Compares them with the scheduled plans;
Removes causes of delays in production;
Modifies the schedules or plant capacities; and
Expedites the work.
4B. 19 DISPATCHING
Dispatch function executes planning function. It is concerned with getting the work started.
Dispatching ensures that the plans are properly implemented. It is the physical handing over of a
manufacturing order to the operating facility (a worker) through the release of orders and instructions in
accordance with a previously developed plan of activity (time and sequence) established by the scheduling
section of the production planning and control department. Dispatcher transmits orders to the various
shops. Dispatch function determines – by whom the job shall be done and it co-ordinates production. It is
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the key point of a production communications system. It creates a direct link between production and
sales.
A dispatcher is familiar with the productive capacity of each equipment. He always keeps an eye
over the progress of orders which move at different speeds on different routes.
Dispatch Procedure. The product is broken into different components and components into
operations.
(a) Store Issue Order: Authorize stores (department) to deliver required raw material.
(b) Tool Order: Authorize tool store to release the necessary tools. The tools can be collected by the
tool room attendant.
(c) Job Order: Instruct the worker to proceed with the operation.
(d) Time Ticket. : it records the beginning and ending time of the operations and forms the basis for
worker’s pay.
(e) Inspection Order: notify the inspectors to carried out necessarily inspections and report the quality
of the component.
(f) Move Order: Authorize the movement of materials and components from one facility (machine) to
another for further operations.
In addition, there are certain other dispatch aspects which have to be taken care of,
All production information should be available before hand.
Various order cards, and specification drawings should be ready.
Equipments should be ready for use.
Progress of various orders should be properly recorded on the Gantt charts or display boards.
All production records should be properly maintained.
4B. 20 CENTRALIZED AND DECENTRALIZED DISPATCHING
Dispatch function may be centralized or decentralized. In a Centralized dispatch system, a central
dispatching department, orders directly to the work station. It maintains a full record of the characteristics
and capacity of each equipment and work lad against each machine. The orders are given to the shop
supervisor, who runs his machines accordingly. In most of the cases, the supervisor can also give
suggestions as regards loading of men and machines under him. A centralized system has the following
advantages:
1. A greater degree of overall control can be achieved.
2. Effective co-ordination between different facilities is possible.
3. It has greater flexibility
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4. Because of urgency of orders, changes in schedules can be affected rapidly without upsetting the
whole system.
5. Progress of orders can be readily assessed at any time because all the information is available at a
central place.
6. There is effective and better utilization of manpower and machinery.
In a Decentralized dispatching system the shop supervisor performs the dispatch factions. He decides
the sequence of handling different orders. He dispatches the orders and materials to each equipment
and worker, and is required to complete the work within the prescribed duration. In case he suspects
delay, with due reasons of the same, he informs the production control department. A decentralized
dispatching system has the following advantages.
1. Much of the red tape is minimized
2. Shop supervisor knows best about his shop, therefore, the work can be accomplished by the most
appropriate worker and the machine.
3. Elaborate reports and duplication of postings can be avoided
4. Communication gap is reduced
5. It is easy to solve day-to-day problems
6. It keeps the natural urge of a section to be self-sufficient.
The advantages of a centralized system, more or less give an idea about the disadvantages of the
decentralized system and vice versa.
4B. 21 ROUTING
Routing lays down the flow of work in the plant. It determines what work is to be done and where
and how it will be done. Taking from raw material to the finished product, routing decides the path and
sequence of operations to be performed on the job from one machine to another. The purpose is to
establish the optimum sequence of operations. Routing is related to considerations of layout, temporary
storage of in-process inventory and material handling.
Routing in continuous industries does not present any problem because of the product type of
layout, where the equipment is laid as per the sequence of operations required to be performed on the
components (from raw material to the finished products).
In open job shops, since, every time the job is new, though operation sheets (sometimes) may
serve the purpose, but the route sheets will have to be revise and this involves a greater amount of work
and expertise.
4B. 22 ROUTING PROCEDURE
Various procedural steps are as follows:
(a) The finished product is analyzed from the manufacturing standpoint in order to decide how many
components can be made in the plant and how many others will be purchased (Make/Buy decision)
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from outside through vendors, by subcontracting, etc. Make/Buy decision depends upon the work
load in the plant, availability of equipment and personnel to manufacture all components, and the
economy associated with making all components within the plant itself.
(b) A parts list and a bill of materials is prepared showing name of the part, quantity, material
specifications, amount of materials required, etc. The necessary materials thus can be procured.
(c) From production, standards – machine capacities, machine characteristics and the operations which
must be performed at each stage of manufacture are established and listed in proper sequence on
an operation and route sheet. The place where these operations will be performed is also decided.
Actually, operation sheet and route sheet are separate. An operation sheet shows every thing about the
operations, i.e., operation description, their sequence, type of machinery, tools, set up and operation
times, whereas a route sheet besides the sequence of operations and relation between operation and
machine, also details the section (department) and the machines to whom the work will flow.
The difference between an operation sheet and a route sheet is that an operation sheet remains same
for the components if the order is repeated but the route sheet may have to be revised if certain
machines are already committed to other orders (jobs) on hand. Except this small difference, both the
sheets contain practically the same information and thus are generally combined into one sheet known
as ‘operation and route sheet’.
(d) the next step is to determine the lot size or the number of components to be manufactured in one
lot or batch. In the case of an order from a particular customer, it is generally equal to a number
within 10% of the order quantity. In other cases the principle of economic batch quantity can be
applied (refer Chapter 24)10 determine the batch size.
(e) Standard scrap factors (single or cumulative) and the places (i.e., after a particular operation or
assembly) where scrap is very likely to occur are identified. The actual scrap in each batch can be
recorded on the control chart. Causes for points out of control limits are explored and corrected.
The variables like workers, machinery and schedules may also be adjusted to minimize scrap.
(f) The cost of the component is analyzed and estimated through the information obtained in steps (a)
to (e) above. The cost consists of material and labour charges, and other specific and general
indirect expenses.
4B. 23 PROGRESS CONTROL
Once the actual production has started, it becomes essential to keep an eye at the progress of the
work so that, if required, timely corrective action can be taken. Progress control means – trying to achieve
the standards set, i.e., a certain level of efficiency or a certain volume of production in a specified duration.
The system of progress control should be such that it furnishes timely, adequate and accurate information
about the progress made, delay and under-or-over-loading.
4B. 24 STEPS INVOLVED IN PROGRESS CONTROL
(a) Setting up a system to watch and record the progress of the operating facility (production section).
(b) Making a report of the work progress or work accomplishment.
Control group for necessary control action, and
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Accounting group for recording material and labour expenditures.
(c) Interpretation of the information contained in the progress report by the control group
(d) Taking corrective action, if necessary.
4B. 25 CHARTS FOR THE WORK ACCOMPLISHMENT
Progress charts are normally employed for this purpose. They compare the work progress against a
prescribed target, and point out the failure to achieve the same, thus progress charts draw attention for an
action or investigation.
The chart construction may have the following four forms
1. The Bar Chart
2. The Curve chart
3. The Gantt Chart and
4. Mechanical chart
1. The Bar Chart consists of a number of bars. Each bar ahs its length proportional to the activity
duration. A bar chart is generally used to point out and analyze interrelated data which otherwise is
difficult to read.
2. A Curve Chart is a graph between two variables (like, number of days and number of items
produced) marked along the X and Y axes. As the days pass, the number of items being produced
is marked over the graph. When all such points are joined they indicate the production trend.
Both the bar and curve charts show the past data. They are not readily adaptable to current or
future action.
3. The Gantt Chart was developed by Henry L. Gantt. It is frequently used to keep track of multiple
machine schedules. Gantt chart is actually a modified bar chart, wherein load is marked against a
time scale with one horizontal bar or line allocated to each machine. A Gantt chart displays the
following.
1. Plans for future.
2. Progress on present operations
3. Past achievements till date,
4. Relationship among several variables
5. It focuses attention on situations threatening delays
6. It tells whether a plan has fallen short and if the delivery dates can e met, and
7. A cursor attracted to the Gantt chart (See fig. 7.30) can be moved across the chart to know the
work progress till any particular day.
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4B. 26 FOLLOW UP OR EXPEDITING
The manufacturing activity of a factory is said to be in control when the actual performance is as
per the planned performance. Follow up or expediting regulates the progress of materials and the
components through the production process. Follow up serves as a catalytic agent to fuse the various
separate and unrelated production activities into the unified whole that means progress. Follow up is
concerned with the reporting of production date and the investigating of any deviation from the
predetermined production (or time) schedules. Follow up ensures that the promise (i.e. of delivery dates) is
backed up by performance.
The work within the organisation can be expedited by the following two principles:
(i) the exception principle, and
(ii) the fathering principle
in exception principle, the scheduling group (on the basis of progress reports), explores the jobs
behind the schedule. The expediting group takes up such jobs, procures necessary materials, tools, etc.
i.e., (expediting group) solves all problems related to these jobs and intimates the scheduling group to
reschedule them.
According to fathering principle each expeditor is made responsible for a job or a group of jobs for
which he arranges the tools, materials, equipment, etc. Such a system works very well for controlling
large projects.
4B. 27 LINE BALANCING
The assembly line should be balanced. Each work station should have the same operation time and
the various operations should be sequenced properly. There should be perfect balance between the output
rates of the parts and the subassemblies. However, it is not always possible that the parts reach in a
steady stream immediately before subassembly. This may be because of the limitations as regards
materials, men and equipments or it may be economical to manufacture and supply parts in batches. The
flow control section has to cope with such situations and thus carry big inventories and arrange facilities
for storage.
4B. 28 ROUTING AND SCHEDULING
A combination route and schedule chart showing the fabrication of parts subassemblies and final
assembly in proper sequence, upon a time scale proves to be very advantageous, especially, when there is
smooth flow of work.
4B. 29 LINE OF BALANCE (LOB)
LOB is a manual planning and scheduling technique similar in nature to MRP (material resource
planning)
This method was developed by the U.S. Navy during World War II. It is most appropriate for
assembly operations involving a number of distinct components. In essence, it employs the
principle of management – by – exception through a comparison of progress of individual
components with the time schedule for completed assemblies. Regular progress checks reveal
the future effect of any current delays and indicate the degree of urgency for corrective action.
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It complements Gantt technique in determining production status.
While the Gantt chart/technique primarily relates information on the effective and efficient utilization of
resources (e.g., machine loading, man loading), LOB is more product – oriented.
LOB is not directly concerned with the resources expended but is utilized in determining
production progress in terms of per cent of task completion. Major bottlenecks in the production process
are emphasized.
LOB technique can be regarded as a slightly more sophisticated form of the Gantt chart, the
objective being to study the progress of jobs at regular intervals, to compare progress on each operation
with the progress necessary to satisfy the eventual delivery requirements, and to identify those operations
in which progress is unsatisfactory.
LOB technique is an example of management-by-exception since it deals only with the important
or crucial (exceptional) operations in a job, establishes a schedule (or plan) for them and attracts attention
to those which do not conform to this schedule. It is particularly useful where large batches of fairly
complex items, requiring many operations, are to be completed / delivered over a period of time.
4B. 30 LOB TECHNIQUE
LOB technique consists of five main stages, all utilizing graphic aids:
1. A graphical representations of the delivery objective.
2. A chat of the production program showing the sequence and duration of all activities required to
produce a product.
3. A progress cart of the current status of component completion.
4. A line-of-balance drawn to show the relationship of component progress to the output needed to
meet the delivery schedule.
5. Analysis of progress
FIGURE: 4.5 ‘LOB’ DIAGRAM
The objective chart shows the expected schedule of products (i.e. scheduled deliveries) and the actual
completion rate (i.e. actual deliveries made by a date)
PRODUCTION AND OPERATIONS MANAGEMENT

A dip in actual deliveries line below the scheduled deliveries line is an obvious cause for alarm.
(2) Program Plan
A chart of the operations required to complete one unit of the finished product is called the
program plan.
Each major row of activities is associated with one component of the final assembly
The final completion date is zero and the time scale runs from right left.
The completed chart serves as a reference to the amount of lead time by which each event must
precede final completion. Events must be completed by their respective lead times to maintain
anticipated output.
Objective chart and Program plan are prerequisites for use of the LOB technique. They need to be
constructed only once for any job, unlike the following documents which must be constructed each
time the schedule and progress is examined.
(3) Progress Chart
FIGURE : 4.6 ‘LOB’ – CUMULATIVE DELIVERY AND PROGRESS CHART
Progress chart shows the number of items which have been finished at each of the critical or important
operations at a given date.
The results can then be depicted by means of a histogram.
(4) Line of Balance
Since the object of the exercise is to compare actual progress with scheduled progress, the information
given in progress chart must be compared to required progress. This is done by constructing a line on the
progress chart which shows the requisite number of items which should have been finished at each
operations at the time of review.
This line-the Line-of-Balance-can be constructed analytically or graphically, the latter method
being perhaps the more convenient. The L.O.B., shows the total number of items which should have been
finished at each operation.
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(5) Analysis of Progress
In comparing required progress with actual progress it is again convenient to work backwards,
beginning with the last operation.
If shortage occurs, we must obviously attempt to ascertain the reasons. If operations other than those
considered as critical are the cause of shortages, then those operations must be included in
subsequent versions of the progress and line-of-balance chart.
4B. 31 ADVANTAGES
The L.O.B. is a simple and useful planning and control technique, its main advantages being:
Like network analysis, it formalizes and enforces a planning discipline
Which itself is useful
It is a simple but powerful procedure, which relies on several assumptions.
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