Process Selection
and Facility Layout
- Process selection
- Deciding on the way production
of goods or services will be organized
- Major implications
- Capacity planning
- Layout of facilities
- Equipment
- Design of work systems
Introduction
Forecasting
Product and
Service Design
Technological
Change
Capacity
Planning
Process
Selection
Facilities and
Equipment
Layout
Work
Design
Process Selection and
System Design
Inputs
Outputs
Key aspects of process strategy
- Capital intensive – equipment/labor
- Process flexibility
- Adjust to changes
Process Strategy
- Variety
- Flexibility
- Volume
Job Shop
Batch
Repetitive
Continuous
Process Selection
Process types
- Job shop
- Small scale, wide variety
of goods
- Batch
- Moderate volume, flexible
- Repetitive or assembly line
- High volumes of standardized
goods or services
- Continuous
- Very high volumes of non-discrete
goods
- Projects
- Non-routine
work, unique set ob objectives, limited timeframe and resources
Process types and volume
Product – Process
Matrix
The diagonal of the
matrix represents the ideal choice of processing system for a given
set of circumstances.
Functions/activities
affected by process choice
Job
variety, process flexibility, unit cost
Volume
Limited
(not ongoing)
Some examples
(find the process type of each)
Movie production
Bakery
Restaurant
(non fast food)
University
Car repairing
(car mechanic shop)
Oil mining
Producing office tools
Veterinarian
Project
Batch
Batch
Batch
Job shop
Continuous
Repetitive
Job shop
Product and service
life cycles
- Alongside the life cycle
the sales and with it the production volume can change.
- Thus managers must be aware
of the change in the optimal processing system.
(the necessity of change is highly dependent on the particular good
or service)
Example
- Computer building shop in
a garage (working for order only, one computer at a time for given purposes)
- The shop hires some workers
and producing some dozens of computers for one customer at a time
- Computer factory is established,
creating large number of computer series
- The R&D function of the
firm invents a new computer prototype
Job shop
Batch
Repetitive
Project
Product/Service Profiling
- Linking key product or service
requirements to process capabilities.
- Design the process with
taking into consideration the following:
- Range of products/services
- Expected order size
- Pricing
- Expected frequency of changes
in schedules etc.
- Order-winning requirements
- …
Sustainable production
- Non-polluting
- Conserving natural resources
& energy
- Economically efficient
- Safe and healthful for workers,
communities and consumers
- Socially and creaqtively
rewarding for workers
- Automation:
Machinery that has sensing and control devices that enables it to operate
- Fixed automation
- Programmable automation
Automation of production
and services
Advantages of automation
- Low variability in performance
and quality
- Machines do not
- get bored or distracted
- go out on strike or ask
for higher wages
- lower variable costs
Disadvantages
- Higher initial (investment)
cost and
- Higher fixed costs
- Lower felxibility
- Higher skills needed
- Lower morale of human workforce
- Need for standardisation
- Products
- Processes
- Equipment and materials
etc.
- Computer-aided design and
manufacturing systems (CAD/CAM)
- Numerically controlled
(NC) machines
- Computerized numerical control
(CNC)
- Direct numerical control
(DNC)
- Robot: mechanical
arm + power supply + controller
- Manufacturing cell
- Flexible manufacturing
systems (FMS)
- Computer-integrated manufacturing
(CIM)
Automation
- Layout: the
configuration of departments, work centers, and equipment, with particular
emphasis on movement of work
(customers or materials) through the system
Facilities Layout
- Requires substantial investments
of money and effort
- Involves long-term commitments
- Has significant impact
on cost and efficiency of short-term operations
Importance of Layout
Decisions
The Need for Layout
Decisions
- Inefficient operations
- High (variable) cost
- Bottlenecks
- Changes in the design of
products or services
- The introduction of new
products or services
- Safety
- Changes in environmental
or other legal requirements
- Changes in volume of output
or mix of products
- Changes in methods and
equipment
- Morale problems
Objectives of facility
layout
Main: smooth flow
of work, material and information
Supporting objectives:
- Product layouts
- Process layouts
- Fixed-Position layout
- Combination layouts:
- Cellular layout (& group
technology)
- Flexible manufacturing systems
Basic Layout Types
- Product layout
- Layout that uses standardized
processing operations to achieve smooth, rapid, high-volume flow
- Process layout
- Layout that can handle varied
processing requirements
- Fixed Position layout
- Layout in which the product
or project remains stationary, and workers, materials, and equipment
are moved as needed
Basic Layout Types
Used for Repetitive
or Continuous Processing
Product Layout
- High rate of output
- Low unit cost
- Labor specialization
- Low material handling cost
- High utilization of labor
and equipment
- Established routing and
scheduling
- Routing accounting and
purchasing
Advantages of Product
Layout
- Creates dull, repetitive
jobs
- Poorly skilled workers
may not maintain equipment or quality of output
- Fairly inflexible to changes
in volume
- Highly susceptible to shutdowns
- Needs preventive maintenance
- Individual incentive plans
are impractical
Disadvantages of Product
Layout
A U-Shaped Production
Line
Advantages/disadvantages
of
U-shaped lines
- Shorter distances for workers
& machines
- Permits communication thus
facilitates teamwork
- More flexible work assignments
- Optimal if the facility
has the same entry and exit point
- If lines are highly automated,
there is no need for communication and travel
- If entry points are on
the opposite side as exit points
- Noise and contamination
factors are increased in the U-shape
Dept. A
Dept. B
Dept. D
Dept. C
Dept. F
Dept. E
Used for Intermittent
processing
Job Shop or
Batch
Process Layout
(functional)
Process Layout
- Can handle a variety of
processing requirements
- Not particularly vulnerable
to equipment failures
- Equipment used is less
costly
- Possible to use individual
incentive plans
Advantages of Process
Layouts
- In-process inventory costs
can be high
- Challenging routing and
scheduling
- Equipment utilization rates
are low
- Material handling slow
and inefficient
- Complexities often reduce
span of supervision
- Special attention for each
product or customer
- Accounting and purchasing
are more involved
Disadvantages of
Process Layouts
Fixed-position layouts
- The product or project
remains stationary and workers, materials, and equipment are moved as
needed.
- If weight, size, bulk,
or some other factor makes it undesirable or extremely difficult to
move the product.
- E.g. firefighting, road-building,
home-building, drilling for oil etc.
- Cellular Production
- Layout in which machines
are grouped into a cell that can process items that have similar processing
requirements
- Group Technology
- The grouping into part families
of items with similar design or manufacturing characteristics
- Makes cellular production
much more effective
Cellular Layouts
Traditional process layout
Cellular layout
Dimension
Functional
Cellular
Number of moves between departments
many
few
Travel distances
longer
shorter
Travel paths
variable
fixed
Job waiting times
greater
shorter
Throughput time
higher
lower
Amount of work in process
higher
lower
Supervision difficulty
higher
lower
Scheduling complexity
higher
lower
Equipment utilization
lower
higher
Functional vs. Cellular
Layouts
Flexible manufacturing
systems
- FMS: a group of machnies
designed to handle intermittent processing requirements and produce
a variety of similar products.
- CIM (Computer Integrated
Manufacturing): a system of linking a broad range of manufacturing activities
through an integrating computer system
- Warehouse and storage layouts
- Minimizing movement &
picking time and cost
- Retail layouts
- Presence & influence
of customers
- Office layouts:
- Information is computerized,
image of openness
Service Layouts
Design Product Layouts:
Line Balancing
Line Balancing is the process of assigning
tasks to workstations in such a way
that the workstations have approximately equal time requirements.
This way the idle time will be minimized,
utilization will be maximized.
Specialization: dividing work
into elemental tasks that can be performed quickly and routinely.
Cycle Time
Cycle time is
the maximum time allowed at each workstation to complete its set of
tasks on a unit.
tmax <
Cycle time < ∑t
Determine the Minimum
Number
of Workstations Required
Theoretical Nmin
is not necessarily will be the Nactual. The latter
is affected by other technical and practical considerations, too.
Nmin ≤ Nactual
(rounded up to the next
integer)
A diagram that shows elemental tasks
and their precedence requirements.
A simplified precedence
diagram
a
b
c
d
e
0.1 min.
0.7 min.
1.0 min.
0.5 min.
0.2 min.
Precedence Diagram
Assume that the desired output is 480
units per day. The facility is working 8 hours a day. The elemental
tasks and their connections are shown on the previous slide.
- Calculate the cycle time.
- Calculate the minimum number
of workstations.
- Arrange the tasks to these
workstations in the order of the greatest number of following tasks.
Example 1: Assembly
Line Balancing
Workstation
Time
Remaining
Eligible
Assign
Task
Revised
Time
Remaining
Station
Idle Time
1
1.0
0.9
0.2
a, c *
c **
none***
a
c
-
0.9
0.2
0.2
2
1.0
b
b
0.0
0.0
3
1.0
0.5
0.3
d
e
-
d
e
-
0.5
0.3
0.3
Total: 0.5
Example 1 Solution
* Tasks
that have no predecessors.
** b is not eligible,
because it needs more time than than the remaining.
*** Every available task needs
more time than 0.2.
Efficiency %= 100 x (1 –
Percentage of idle time)
Calculate Percent Idle
Time and efficiency
Line balancing procedure
- Assign tasks in order of
most following tasks.
- Count the number of tasks
that follow
- Assign tasks in order of
task time.
- Assign tasks in order of
greatest positional weight.
- Positional weight is the
sum of each task’s
time plus the times of all following tasks.
Line Balancing Heuristics
Example 2
Working day is 8 hours and the desired
output rate is 400 units per day.
Draw the precedence diagram.
Compute the cycle time & the minimum
theoretical number of workstations required.
Assign tasks to workstations according
to the greatest number of following tasks. Tiebreaker: longest processing
time goes first.
Calculate Percent idle time & efficiency.
Solution 2
CT = (8*60)/400= 1.2; Nmin
= ∑ti
/ CT = 3.17 → 4
a
b
e
c
f
d
h
g
Work station
Tasks assigned
Idle time
WS1
a,c,b
0
WS2
d,e
0.3
WS3
f
0.2
WS4
g,h
0.5
Percentage idle time
= 1.0 / (4*1.2) = 20.83%
Efficiency = 100 – 20.83
= 79.17%
Other approaches
- Paralell workstations
- Cross-train workers (dynamic
line balancing)
- Mixed model line
(more product on the same line)
1 min.
2 min.
1 min.
1 min.
30/hr.
30/hr.
30/hr.
30/hr.
1 min.
1 min.
on average
1 min.
1 min.
60/hr.
30/hr.
30/hr.
60/hr.
30/hr.
30/hr.
Bottleneck
Parallel Workstations
Parallel Workstations
2 min.
2 min.
Thank you for your attention
