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PLANT LAYOUT
BBA-6
Lecture conducted by Apoorva Srivastava, ABS, AMITY, Lucknow
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LAYOUT
1.Define the meaning of layout planning the questions it addresses,
2.Describe the basic layout types and when each is best used,
3.Identify the types of performance criteria that are important inevaluating layouts.
4.Explain how cells can help create hybrid layouts,5.Recommend a step-by-step approach in designing process layouts.
6.Calculate load-distance scores for a process layout and explain howthis capability helps managers find a good solution.
7.Discuss different strategies in the layout of warehouses and offices.8. Describe how to balance lines in a product layout and evaluatedifferent solutions.
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What is Layout Planning ?
1.What centers should the layout include ?
2.How much space and capacity does each center need ?
3.How should each center space be configured ?
4.Where should each center be located ?
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IDENTICAL RELATIVE LOCATIONS AND DIFFERENT ABSOLTE
LOCATIONS
FROZEN
FOODS
BREAD
DRY GROCERIES
MEATS
VEGETABLES
ORIGINAL LAYOUT
DRY GROCERIES
FROZEN
FOODS
BREADVEGETABLES
MEATS
REVISED LAYOUT
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HOW SHOULD LAYOUT REFLECT
COMPETITIVE PRIORITIES ?
A Layout ought to reflect the following-
1.Facilitating the flow of materials and information.
2.Increasing the efficient utilization of labor and
equipment,3.Increasing customer convenience and sales at a
retail store,
4.Reducing hazards to workers,5.Improving employee morale,
6.Improving communications.
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VISHAL MEGA
MART
COLORFUL AND HIGH
ENERGY ATMOSPHERE
GLASS COLOR
MOSAICS,FULL
SPECTRUM DIGITAL
LIGHTING, LED SYSTEM
WALL MART
WIDE AISLES, LESS-CRAMPED
RACKS, SITTING AREAS FOR
CUSTOMERS, ATTRACTIVEDISPLAYS,
BARGAIN BASEMENT PRICES
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TYPES OF LAYOUT
PROCESS LAYOUT- with a job process, which is thebest for low volume, high variety production, theoperations manager must organize resources (employeesand equipment) around the process. A process layout,
which groups workstations or departments according tofunction, accompalish this purpose.
The process layout is most common when the sameoperation must intermittently produce many different
products or serve many different customers.
Demand levels are too low or unpredictable for managementto set aside human and capital resources exclusively for a
particular product line or type of customer.
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ADVANTAGES OF A PROCESS
LAYOUT OVER A PRODUCT
LAYOUT1.Resources are relatively general purpose and less capitalintensive.
2.The process layout is less vulnerable to changes in productmix or new marketing strategies and is therefore more
flexible.3.Equipment utilization is higher. When volumes are low,
dedicating resources to each product or service( as is donewith a product layout) would require more equipmentthan pooling the requirements for all product costs.
4.Employee supervision can be more specialized, animportant factor when job content requires a good deal oftechnical knowledge.
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DISADVANTAGES
1.Processing rates tend to be lower,
2.Productive time is lost in changing from one product or serviceto another,
3.More space and capital are tied up in inventory, which helps
workstations to work independently despite their variableoutput rates,
4.The time lags between job starts and end points are relativelylong,
5.Materials handling tends to be costly,6.Diversity in routings and jumbled flows necessitate the use of
variable path devices, such as carts rather than conveyors.
7.Production of planning and control is more difficult.
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PRODUCT LAYOUT
1.Processing rates tend to be slower.
2.Production time is lost in changing from one product or serviceto another,
3.More space and capital are tied up in inventory, which helps
workstations to work independently despite their variableoutput rates,
4.The time lags between job starts and end points are relativelylong,
5.Materials handling tends to be costly,6.Diversity in routings and jumbled flows necessitate the use of
variable path devices, such as carts rather than conveyors,
7.Production planning and control is more difficult.
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PRODUCT LAYOUT
1. With line or continuous processes, which are best for repetitiveor continuous production, the operations manager dedicatesresources to individual products or tasks. This strategy isachieved by Product Layout.
2. Resources are arranged around the products route, rather thanshared across many products.
3.Product Layouts are common in high-volume types ofoperations. Although product layouts often follow a straightline, a straight line is not always best, and layouts may take anL,O,S or U shape. A product layout often is called a production
line or an assembly line. The difference between the two is thatan assembly line is limited to assembly processes, whereas a
production line can be used to perform other processes such asprocesses such as machining.
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4.Product layouts often rely heavily on specialized,
capital intensive resources. When volumes are high,
the advantages of product layouts over process
layouts include-a).Faster processing rates,
b).Lower inventories,
c).Less unproductive time lost to changeovers andmaterials handling.
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There is less need to decouple one operation from the next,allowing management to cut inventories. The Japaneserefer to a line process as overlapped operations, wherebymaterials move directly from one operation to the next
without waiting in queues. The disadvantages of productlayouts include-
1.Greater risk of layout redesign for products or serviceswith short or uncertain lives,
2.Less flexibility,3.Low resource utilization for low volume products and
services.
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the challenge of product layout is to group activities into
workstations and achieve the desired output rate with
the least resources.
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HYBRID LAYOUT
1. More often than not, the process combines elements of both aproduct and portions of the facility are arranged in a process layoutand others are arranged in a product layout.
2. Hybrid layouts are used in facilities having both types of layout werein same building.
3. Fabrication operations- in which components are made from rawmaterials- have a jumbled flow, whereas assembly operations- inwhich components are assembled into finished products-have a lineflow.
4. Operations mangers also create hybrid layouts when introducingcells and flexible automation, such as Flexible ManufacturingSystem (FMS).
5. A cell is two or more dissimilar workstations located close togetherthrough which a limted number of parts or models are processedwith line flows.
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6.Two special types of Cells- Group Technology andOne Worker, Multiple Machines cells
7.An FMS is group of computer controlled workstations
at which materials are automatically handled andmachined loaded.
8.These technologies help achieve repeatability, even,when product volumes are too low to justify
dedicating a single line to one product, by bringingtogether all resources needed to make a family ofparts in one center. The rest of the facility represents aProcess Layout.
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A retail store is an example of a hybrid layout in a non-
manufacturing setting.
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FIXED POSITION LAYOUT
1.The product is fixed in place, workers, along with their tools
and equipment, come to the product to work on it.
2.Many project processes have this arrangement. This type of
layout makes sense when the product is particularly massiveor difficult to move, as in shipbuilding, assembling
locomotives , making huge pressure vessels, building dams,
or repairing home furnaces.
3.A fixed-position layout minimizes the number of times that
the product must be moved and often is the only feasible
solution.
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PERFORMANCE CRITERIA
1.level of capital investment,
2.Requirements for material handling,
3.Easy stockpiling,
4.Work environment and atmosphere,
5.Ease of equipment maintenance,
6.Employee attitudes,
7.Amount of flexibility needed,
8.Customer convenience and level of sales.
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CREATING HYBRID LAYOUTS
1.ONE WORKER MULTIPE MACHINES,
2.GROUP TECHNOLOGY.
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ONE WORKER, MULTIPLE MACHINES
1. The machines for production encircle the worker,
2. The operator would move around the cricle to perform tasks,that have not been automated.
3. An OWMM arrangement reduces both inventory and labor
requirements. Inventory is cut because, rather than piling upin queues, materials move directly into the next operation.
4. Different products or parts can be produced in an OWMMcell by consuming for one part, management can add aduplicate machine to the cell for use whenever that part is
being produced.
5. An OWMM arrangement both inventory and laborrequirements.
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6.Inventory is cut because, rather than piling up in queues,
materials move directly into the next operation. Labor is
cut because more work is automated.
7.The addition of 7 low cost automated devices canmaximize the number of machines included in an
OWMM arrangement: automatic tool changers, loaders
and unloaders, start and stop devices, and fail-safe
devices that detect defective parts or products. Japanesemanufacturers are applying the OWMM concept widely
because of their desire to achieve low inventories.
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MACHINE 1
MACHINE 2
MACHINE 3 MACHINE 4
MACHINE 5
MACHINE 6
ONE WORKER MULTIPLE MACHINES
CELL
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GROUP TECHNOLOGY
1.A second volume for achieving product layouts with
low volume processes is group technology(GT). This
manufacturing technique creates cells not limited to
just one worker or has a unique way of selecting workdone by the cell.
2.The GT Method group parts or products with similar
characteristics into families and set aside groups of
machines for their production. Families may be basedon size, shape, manufacturing or routing requirments,
or demand.
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3.The goal is to identify a set of products with similarprocessing requirements, or demand.
4. The goal is to identify a set of products with similarprocessing requirements and minimize machine
changeover or setup.5.Once parts have been grouped into families, the next
step is to organize the machine tools needed toperform the basic processes on these parts intoseparate cells.
6.The machines in each cell require only minoradjustments to accommodate product changeoversfrom one part to the next in the same family.
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7.By simplifying product routing, GT cells reduce
time a job is in shop. Queues of materials
waiting to be worked on are shortened or
eliminated.
8.Frequently, materials handling is automated so
that, after loading raw materials into the cell,
a worker does not handle machined partsuntil the job has been completed.
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RECEIVING AND SHIPPING
L
L
L
L
L
L
L
L
LATHING MILLING
M M
M M
M M
M M
DRILLING
D D
D D
G
GG
G
G G
GRINDING
ASSEMBLY
A A
A A
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DESIGNING PROCESS LAYOUT
The essence of designing a layout depends on whether aprocess layout or product layout has been chosen. Afixed-position format basically eliminate the layout
problem, whereas the design of the hybrid layout
partially uses the process-layout principles and partiallyuses product layout principles.
Process layout involves three basic steps, whether thedesign is for a new layout or for revising an existingone:
1.Gather information,2.Develop a block plan,
3.Design a detailed layout.
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Gather information
1.Space requirements by center- the layout designer must tie
space requirements to capacity plans, calculate the specific
equipment and space needs for each center, and allow
circulation space such as aisles and the like.
Block Plan- a plan that allocates space and indicates placement
of each department.
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Available Space
2.A Block Plan allocates space and indicates placement of eachdepartment. To describe a new facility layout, the plan need
only provide the facilitys dimensions and space allocations.
When an existing facility layout is being modified, the current
block plan is also needed.
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Closeness Factors
The layout designer must also know which centers need to be
located close to one another. Location is based on the number
of trips between centers and qualitative factors.
Trip Matrix- a matrix that gives the number of trips( or some
other measure of materials movement) between each pair of
the departments per day.
The designer estimates the number of trips between centers by
using routings and orderings frequencies for typical items made atthe plant, by carrying out statistical sampling, or by polling
supervisors and materials handlers. Only the right hand portion of
the matrix, which shows the number of trips in both directions, is
used.
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DEPARTMENT 1 2 3 4 5 6
1.Burr and
Grind
- 20 20 80
2.NC
Equipment
- 10 75
3.Shipping
and Receiving
- 15 90
4.Lathes and
drills
- 70
5.Tolls andcribs
-
6.Inspection -
TRIP MATRIX
TRIPS BETWEEN DEPARTMENTS
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Rel Chart
A chart that reflects the qualitative judgements of managers and
employees and that can be used in place of a Trip Matrix.
Rel is short for Relationships.
One advantage of of a REL chart is that the manager can account
for multiple performance criteria when selecting closeness
ratings, whereas, a trip matrix focuses solely on materials
handlings or stockpiling costs.
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RATING DEFINITION
A ABSOLUTELY NECESSARY
E ESPECIALLY IMPORTANT
I IMPORTANT
O ORDINARY CLOSENESS
U UNIMPORTANT
X UNDESIRABLE
CLOSENESS RATINGS
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CODE MEANING
1 MATERIALS HANDLING
2 SHARED PERSONAL
3 EASE OF SUPERVISION
4 SPACE UTILIZATION
5 NOISE
6 EMPLOYEE ATTITUDE
EXPLANATION CODES
Noise levels and management preference are potential sources ofperformance criteria that depend on absolute location. A REL chart
or Trip Matrix cannot reflect these criteria, because it reflects only
relative location considerations. The layout designer must list them
separately.
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DEPARTMENT 1 2 3 4 5 6
1.Burr and Grind - E(3,1)
U I(2,1)
U A(1)
2.NC Equipment - 0
(1)
U E
(1)
I
(6)
3.Shipping and receiving - O
(1)
U A
(1)4.Lathes and drills - E
(1)
X
(5)
5.Tool crib - U
6.Inspection -
CLOSENESS RATING BETWEEN DEPARTMENTS
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Step 2: Develop a Block Plan
The second step in layout design is to develop a block plan that
best satisfies performance criteria and area requirements. The
most elementary way to do so is by trial and error.
Because success depends on the designers ability to spot patterns
in the data, this approach does not guarantee the selection of
the best or even a nearly best solution. When supplemented by
the use of the a computer to evaluate solution, however, such
an approach often compares quite favorably with more
sophisticated computerized techniques.
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DEVELOPING A BLOCK PLAN
The goal is to minimize the materials handling costs.
Solution-
5 4 3
2 1 6
When relative locations are a primary concern, such as for effective
materials handling, stockpiling, and communication, the load-distancemethod can be used to compare alternative block plans. Here, Loads
are just the numbers in the Trip Matrix. Each Load goes between two
centers. The distance between two of them is calculated from the
block plan being evaluated. Of course, the loads need not be trips, anynumerical closeness measure related to distance would do.
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Calculating a Total Desirability Score
1.How much better, in terms of the ld score, is the proposed block plan? Use the Rectilinear Distance measure.
The accompanying table lists each pair of departments that has anonzero closeness factor in the trip matrix.
For the third column, calculate the rectilinear distance between the
departments in the current layout.Departments 1 and 2 are in the southeast and northwest blocks of the
plant, respectively.
The distance between the centers of these blocks is 3 units(twohorizontally and one vertically). For the fourth column, we multiplythe loads of distances and then add the results for a total of ld scoreof 785 for the current plan. Similar calculations for the proposed
plan produce and ld score of only 400. For example, betweendepartments 1 and 2 is just 1 unit of distance( one horizontally andone vertically).
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DEPARTME
NT PAIR
CLOSENESS
FACTOR,I
DISTANCE
d
LOAD-
DISTANCE
SOCRE,ld
DISTANCE
d
LOAD-DISTANCE
SCORE,ld
1,2 20 3 60 1 20
1,4 20 2 40 1 20
1,6 80 2 160 1 80
2,3 10 2 20 3 30
2,5 75 2 150 1 75
3,4 15 1 15 1 15
3,6 90 3 270 1 90
4,5 70 1 70 1 70ld = 785 ld = 400
CURRENT PLAN PROPOSED PLAN
To be exact, we could multiply the two ld scores by 30 because each unit of distance
represents 30 feet. However, relative differences between the two totals remains
unchanged.
SOLVER PROCESS LAYOUT
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DEPARTMENT PAIR
CLOSENESS FACTOR
DISTANCE SCORE
3,6 90 3 270
1,6 80 2 160
2,5 75 2 150
4,5 70 1 70
1,2 20 3 60
1,4 20 2 40
3,4 15 1 15
2,3 10 2 20
BUILD TABLE
SOLVER-PROCESS LAYOUT
RECTILINEAR EUCLIDEAN
2 4 1
6 5 3
TOTAL 785
SOLVER PROCESS LAYOUT
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DEPARMENT CLOSENESS
FACTOR
DISTANCE SCORE
3,6 90 2 180
1,6 80 1 80
2,5 75 1 75
4,5 70 2 140
1,2 20 3 60
1,4 20 2 40
3,4 15 1 15
2,3 10 2 20
TOTAL 610
SOLVER PROCESS LAYOUT
BUILD TABLE
RECTILINEAR DISTANCE
EUCLIDEAN DISTANCE
2 4 3
5 6 1
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DESIGN A DETAILED LAYOUT
After finding a satisfactory block plan, the layout designer into a
detailed representation, showing the exact size and shape of
each center, the arrangements of elements( e.g. desks,
machines, and storage areas), and the location of aisles,
stairways, and other service space. These visual representationcan be two-dimensional drawings, three-dimensional models,
or computer-aided graphics. This step helps decision makers
discuss the proposal and problems that might otherwise be
overlooked.
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AIDS FOR PROCESS LAYOUT
DECISIONSFinding an acceptable block plan actually is a complex process. A company
with 20 departments has 2.43*1018 possible layouts if each of the 20departments can be assigned to any of the 20 locations. Fortunately, severalcomputationally feasible aids are now available for helping managers make
process layout decisions.
ALDEP-Automated Layout Design Program- is a computer software packagethat uses REL chart information to construct a good layout. Being a heuristicmethod, it generally provides good, but not necessarily the best- solutions.ALDEP constructs a layout from scratch, adding one department at a time.The program picks the first department randomly. The second departmentmust have a strong REL rating with a department randomly. The second
department must have a strong rating with the second, and so on. When nodepartment has a strong rating with the department just added, the systemagain randomly selects the next department. The program computes a score(somewhat different from the ld score used earlier) for each solutiongenerated and print out the layouts having best scores for the managersconsideration.
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COMPUTERIZED RELATIVE ALLOCATION OF FACILITIES
TECHNIQUE- is a heuristic method that uses a Trip Matrix,
including materials flow rates, transportation costs, and an
initial block layout. Working from an initial block plan (or
starting solution), CRAFT evaluates all possible pairedexchanges of departments. The exchange that causes the
greatest reduction in the total ld score is incorporated into a
starting solution. The process continues until no other
exchanges can be found to reduce the ld score. The startingsolution at this point is also the final solution and is printed out
with the ld score.
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WAREHOUSE LAYOUTS
Warehouses are similar to manufacturing plants in that materialsare moved between activity centers.
LAYOUT SOLUTION- the decision rule is as follows-
1.Equal Areas- if all departments require the same space, simply
place one generating the most trips closest to the dock, the onegenerating the most trips closest to the dock, the onegenerating the next largest number of trips next closest to thedock, and so on.
2.Unequal Areas- if some departments need more space than
others, give the location closest to the dock to the departmentwith the largest ratio of the trip frequency to block location,and so on.
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Computer Software Systems
1.Computerised Relative Allocation of Facilities,
2.Computerised Facilities Design
3.Computerised Relationship Layout Planning
4.Automated Layout Design Program5.Plant Layout Analysis Evaluation Technique
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Performance Ratios
Storage Space Usage Ratio(SSUR)
= (Storage Space actually Occupied by materials
already used) / (Total square feet storage space
in facility)
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Inventory Turnover Ratio = (Annual sales in dollars)/
Average Inventory
Distance Travel Ratio = (total distance in feet orders
traveled during a specific planning horizon)/ (total
number of orders processed during the planning
horizon)
Damaged Goods Ratio = (number of damaged loads
moved during a specific planning horizon) / total
number of loads moved during the planning horizon
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Job Tardiness Ratio = (Number of jobs late during aspecific planning process) / total number of jobs
processed during the planning horizon
Order-Line Picking Ratio = (Number of lines( a line
represents an item) on orders picked during aspecific planning horizon) / (number of hoursworked by department personnel per day)
Receiving/ Shipping Ratio = Number of pounds( orpallets) shipped per day / Number of hours workedby department personnel per day
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Uses of Ratios
1.To see if layout performance can be improved by making
design changes and observing the results of the ratios.
2.To monitor layout performance to observe shifts in ongoing
operations.
3.To establish performance criteria that can be used as goals to
motivate improved performance.
USING TENG BLACK EXPERT
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USING TENG BLACK EXPERT
SYSTEM
The Teng Black Expert System or Delivery System comprises
three components: a knowledge base ( a set of rules in this
case to deal with known cellular problems), a working
memory ( a dynamic set of rules that shall change the
knowledge base a new problems are encountered in the cellsand solved), and the Inference Engine(a set of rules that
allows the system to reason, infer problems, and draw
conclusions on the control of cell behavior).
Electronics cells are positioned in the cells to provide feedbackon its operation against known or stated system parameters.
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Use of the Teng Black System
1. To control and monitor the cell operations,
2. To solve problems existing during the cells operation,
3. To communicate with higher-level human controllers( the cell
supervisor or plant manager)
STRUCTURE OF TENG-BLACK EXPERT SYSTEM
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MANAGEMENT
INTERFACINGLAYER
SIMULATIO
N
MODULE
HIGHER LEVELCONTROL UNITS
CELL
SUPERVISOR
PROBLEM
HANDLINGLAYER WORKING
MEMORY
KNOWLEDGE
BASE
INTERFACEENGINE
ROUTINE CELL
CONTROL LAYER
CELL
FLOW OF INFORMATION IN TENG BLACK EXPERT SYSTEM
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HIGH-LEVEL CONTROL
SYSTEM
CALL
CONTROL
SYSTEM
SIMULATION MODULE
SUPERVISOR
FLOW OF INFORMATION IN TENG BLACK EXPERT SYSTEM
SYSTEM
PARAMETERSSCHEDULE OF
FINAL
ASSEMBLY
CELL
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PRECEDENCE DIAGRAM
A diagram that allows one to visualize immediate predecessors
better; work elements are denoted by circles, with the time
required to perform the work shown below each circle.
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Desired Output Rate
The goal of the line balancing is to match the output rate to theproduction plan. For example, if the production plan calls for4,000 units per week and the line operates 80 hours per week,the desired output rate ideally would be 50 units (4000/80) perhour.
Matching output to demand ensures on-time delivery andprevents build-up of unwanted inventory.
However, managers should avoid rebalancing a line toofrequently, because each time a line is rebalanced, many
workers jobs on the line must be redesigned, temporarilyhurting productivity and sometimes even requiring a newdetailed layout for some stations.
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Desired Output Rate
Some automobile plants avoid frequent changes by eliminating a
shift entirely when demand falls and inventory becomes
excessive, rather than gradually scaling back the output rate.
Managers can also add shifts to increase equipment utilization,
which is crucial for capital-intensive facilties. However, higherpay rates or low demand may make multiple shifts undesirable
or unnecessary.
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Cycle Time
After determining a desired output rate for a line, the analyst cancalculate the lines cycle time.
A lines Cycle Time is the maximum time allowed for work on a unit ateach station. If the time required for work elements at a station
exceeds the lines cycle time, the station shall be the bottleneck,preventing the line from reaching its desired output rate. The targetcycle is the reciprocal of the desired hourly output rate- c = 1/ r
Where,
c= cycle time in hours per unit
r= desired output rate in units per hour
For example, if the lines desired output rate is 60 units per hour, thecycle time is c= 1/60 hour per unit , or 1 minute.
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Theoretical Minimum
To achieve the desired output rate, managers use line balancing to assign
every work element to a station, making sure to satisfy all precedence
requirements and to minimize the number of stations, n, formed.
If each station is operated by a different worker, minimizing n also
maximizes worker productivity.
Perfect Balance is achieved when the sum of the work-element times at
each station equals the cycle time, c, and no station has any idle time.
Although perfect balance usually is achievable in practice, owing to the
unevenness of work-element time and the inflexibility of precedencerequirements, it sets a benchmark, or goal, for the smallest number of
stations possible.
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The THEORETICAL MINIMUM( TM) for the number of stations is
TM = t / c
t = total time required to assemble each unit( the sum of all work-
element standard times)
C= cycle time.
For example, if the sum of the work element times is 15 minutes and thecycle time is 1 minute, TM=15/1, or 15 stations. Any fractional values
obtained for TM are rounded up because fractional stations are
impossible.
Idle Time Efficiency and Balance
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Idle Time, Efficiency, and Balance
Delay
Minimizing n automatically ensures (1) minimal idle time, (2)
maximal efficiency, and (3) minimal balance delay.
Idle time is the total unproductive time for all stations in the
assembly of each unit:
Where,
Idle time = nc -t
Where,
n = number of stations
c = cycle time
t= Total Standard Time Required to assemble each unit.
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Efficiency is the ratio of productive time to total time, expressed
as a percent:
Efficiency(percent) = t / nc(100)
Balance Delay is the amount by which efficiency falls short of
100 percent:
Balance delay(percent) = 100efficiency
As long as c is fixed, we can optimize all three goals by
minimizing n.
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CASE LET