Lecture 7 Layout Strategy
Layout Strategy: Specifies the arrangement of processes, the related equipment
and work areas, including customer service and storage areas: Facilitates the flow of
materials and people within and between areas.
Determines long run efficiency of the plant
Objective is to develop an economic layout that will meet the requirements of
1. Product design and volume
2. Process equipment and capacity
3. Quality of work life
4. Building and site constraints
Arrange the system to operate at peak effectiveness and efficiency
Layout Depends on Types of Production Systems
Job production (Process Focused System)
Involves manufacture of products to meet specific customer requirements of special
orders. The quantity is normally small, usually ‘one off’ and is normally concerned
with special projects, models, prototypes, special machinery to perform specialised
tasks. E.g. boilers, bridge, house, ship
Fixed layout is adopted i.e. the product is fixed and labour moves around it
Batch production system (Product Focussed system)
Involves the manufacture of a number of identical products either to meet a specific
order or to satisfy continuous demand. When production of the batch is finished the
plant is available for the production of similar or other products
The batch may be produced once or at irregular intervals. This type of production is
very common and involves the use of flexible systems.
Continuous production systems
Involves the manufacture of identical products on which the plant is fully engaged.
Two types
Mass production systems where the equipment are not specially designed for one
component alone. After the manufacture of one component for a large quantity,
Prepared by: Dr D.K.Hurreeram
August 04
Lecture 7 Layout Strategy
operations can be switched to another but will require major tooling changes. Eg
Toyota car types)
Flow production systems where the equipment and layout have been primarily
designed to manufacture one component and changes in components are not possible
without substancial changes in plant layout and tooling. E.g sugar, chemicals, petrol,
electricity)
Jobbing
Batch
Line/Mass
Flow
Increased dedication to product
Increased inflexibility
Increased interdependancy on machines
Increased production rate/quantity
Increased need for special tooling
Less and less skillful labour needed
General to special equipment/tooling needed
Process to product type of Layout
Decreased cost per unit
Plant Layout
A good layout requires determining
• Capacity and space requirements
• Material handling equipment
• Environment and aesthetics
• Flow of information
• Cost of moving between the various work areas
Strategies
Fixed position layout (ship building, construction sector)
Process oriented layout (low volume, high variety processes)
Product oriented layout (high volume, low variety, best m/c util.)
Retail/service layout, Warehouse layout
Prepared by: Dr D.K.Hurreeram
August 04
Lecture 7 Layout Strategy
Fixed Position Layout
Mostly for jobbing type of production. Project remains stationary and requires
workers and equipment to come to the one work area.
Layout decided upon on an ad hoc basis
Limitations
1. There is limited space at virtually all sites
2. At different stages of the project, different material is required
3. The volume of material required is dynamic
Alternative
Use of Group Technology for off site manufacturing of components
Process Oriented Layout
Mostly used for batch type of production (low volume, high variety)
Transformation resources or similar functions are grouped together in the same work
centre usually a department, under the management and control of a functional
specialist. E.g engineering production, garage services, film processing etc…
Grinding
Store
Drilling
Painting/Electroplating
lathes
Assembly
Inspection
Shipping
The most common tactic is to arrange departments or work centres in the most
economical locations, minimising material handling costs
Place departments with large interdepartmental flow of parts or people next to one
another.
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August 04
Lecture 7 Layout Strategy
Material handling costs depend on
• The number of loads to be moved during some period of time between two
departments
• The distance related costs between departments
Minimise cost = ∑∑ Xij Cij
For i and j ranging from 1 to n, where,
n
= total number of work centres or departments
i,j
= individual departments
Xij
= number of loads moved from department i to j
Cij
= cost to move a load between department i and department j
Example
Procedure
1. Determine the number of trips between each department and construct a from to
matrix
2. Determine space requirements and distance between each department
3. Develop an initial schematic diagram
4. Determine the cost of this layout (multiply trips by distance)
5. By trial and error try to improve the layout
6. Prepare a detailed plan that evaluates other factors
Advantages of Process oriented Layout
1. It enables changes in quantity and type of products manufactured to be introduced
easily
2. Flexibility in terms of production types and ranges
3. Less duplication of specialised equipment (lower investment)
4. Workers and supervisors can become highly skilled in the operation of a single
type or group of production resources
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August 04
Lecture 7 Layout Strategy
5. Machine breakdown would not normally hold up production as a job could be
switched to another similar machine
6. Machines can be kept busy most of the time and low and medium volume
production costs cab be held down
7. Higher effective machine utilisatiion
Disadvantages
1. Scheduling work in the work centres is usually complex and tedious
2. Production throughput time is usually larger
3. Queues of work build up at some centres while others are underutilised (deliberate
queuing policy)
4. Balancing work load is usually difficult
Arrange departments or work centres in the most economical locations (minimise
material handling costs)
Place departments with large interdepartmental flows of people and/or parts next to
each other (number of loads to be moved, the distance to be travelled).
Minimise Cost = Σ
i=1
Σ j=1 Xij Cij
where n = total number of work centres or departments
i,j = individual departments
Xij = number of loads moved from department i to j
Cij = cost to move a load b/w department i to j
Example
Work Cells (Group Layout – special case of process layout)
New production management philosophy – component thinking rather than
product thinking (Each cell capable of producing a family of components)
Based on the Group Technology philosophy – Achieves some of the advantages of
product layout and the flexibility of process layout strategies. GT – a
manufacturing philosophy in which similar parts are identified and grouped
together to take advantage of their similarities in manufacturing and design.
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August 04
Lecture 7 Layout Strategy
Processing of each member of a given family would be similar, resulting in
manufacturing efficiencies
Arrange production equipment into machine groups or cells to facilitate work flow
Similarities in terms of design attributes or manufacturing attributes
Part family – collection of parts which are similar either because of geometric
shape and size or because similar processing steps are required in their
manufacture
Product Oriented Layout
Organised around a product or a family of similar high volume, low variety products:
Volume adequate for high equipment utilisation
Product demand is stable enough to justify investment in highly specialised
equipment
Product is standardised
Supplies of raw material and components are adequate and of uniform quality
Fabrication or assembly lines
Line balancing (high personnel and facility utilisation and equity between
employees’ work loads
Example of line balancing
1. List the tasks to be accomplished
2. Construct precedence chart and diagram
3. Calculate cycle time (time the product is available at each work station)
Cycle time = Production time available per day / demand per day or production rate
per day
4. Calculate the theoretical minimum number of workstations (total task duration
time divided by cycle time)
= Σ (time for task i) / cycle time (i = 1 to m)
5. Perform the line balancing task
Identify a master list of work elements and separate the available work
elements from the unavailable work elements
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August 04
Lecture 7 Layout Strategy
Eliminate those work elements that have been assigned
Eliminate those work elements whose precedence relationship has not
been satisfied
Eliminate those work elements for which there is inadequate time available
at the workstation
Identify a unit of work that can be assigned, such as the first unit of work in
the list, the last unit of work, the unit of work with the shortest time, with
the longest time, or other criterion
Switch the work elements to find the best balance available
Other Production Concepts
Production: Series of individual steps including processing, assembly operations,
material handling, storage, delays, inspection and other non productive activities.
Operation and non-operation elements (value added and non value added elements:
To :
Time per operation at a given machine or workstation
Tno:
non operation time associated with the same machine
nm:
number of separate machines or operations through which product has to be
routed
Q:
Number of units in a batch
Tsu:
Set up time
Compute:
1. Manufacturing Lead time MLT
2. Production Rate
3. Components of Operation time
4. Capacity
5. Utilisation and Availability
6. Work in progress
See Example
Prepared by: Dr D.K.Hurreeram
August 04