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INEN 416 Facility Location, Layout, and Material Handling
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Computerized Layout Planning
Focus on how computers can aid the facility layout process.
Designer must interact with multiple design databases and provide the integration between them to translate information and ensure consistency.
We will concentrate on decision aids for block layout planning.
Information required Common elements Classical layout programs
Craft, Corelap, Aldep, and Planet Newer layout programs
M-Craft, LayOpt, FactoryPlan
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Computerized Layout Planning
Information in layout planning Numeric information
Space required for an activity Total flow between two activities
Logic information Preferences of the designer, i.e., activity relationship
chart Graphical information
Drawing of the block plan
Key element of computerized layout planning is the representation and manipulation of these three types of information.
Graphical representation is most challenging. A method suitable for display is not suitable for manipulation and vice-versa.
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Computerized Layout Planning
Graphical Representation Points and lines representation is not convenient
for analysis
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Computerized Layout Planning
Graphical Representation (cont.) Most procedures employ a unit area square
representation as an approximation Space available and space required for each activity
are expressed as an integer multiple of the unit area.
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Computerized Layout Planning
Graphical Representation (cont.) Unit Square Area approximation can also be
represented by a two dimensional array or matrix of numbers
Easy to manipulate (e.g., determine adjacency) but difficult to visually interpret
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Computerized Layout Planning
Layout Evaluation Algorithm needs to distinguish between good
layouts and bad ones Develop scoring model, s = g(X) Adjacency-based scoring
Based on on the relationship chart and diagram
Aldep uses A=64, E=16, I=4, O=1, U=0, and X=-1024 Scoring model has intuitive appeal; the ranking of
layouts is sensitive to the weight values. Layout B may be preferred to C with certain weights but not with others.
Therefore, correct specification of the weights is very important -- but how do you do that?
s w Xi ii
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Computerized Layout Planning
Layout Evaluation (cont.) Distance-based scoring
Approximate the cost of flow between activities Requires explicit evaluation of the flow volumes and costs
cij covers both the i to j and the j to i material flows Dij can be determined with any appropriate distance metric
Often the rectilinear distance between department centroids Assumes that the material flow system has already been
specified Assumes that the variable flow cost is proportional to
distance Distance often depends on the aisle layout and material
handling equipment
s c Dij ijj i
m
i
m=
= +=
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Computerized Layout Planning
Layout Evaluation -- Distance-based scoring Example
A B
C D
From/To A B C DA - 2 4 4B 1 - 1 3C 2 1 - 2D 4 1 0 -
From/To A B C DA - 40 25 55B 40 - 65 25C 25 65 - 40D 55 25 40 -
From/To A B C D TotalA - 80 100 220 400B 40 - 65 75 180C 50 65 - 80 195D 220 25 0 - 245
Total 310 170 165 375 1020
Initial Layout Flow Data
Distance Data
Total Cost
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Computerized Layout Planning
Layout Evaluation (cont.) Distance-based scoring Impact of aisle layout and direction of travel
A B
C D
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Computerized Layout Planning
Layout Evaluation (cont.) Distance-Weighted Adjacency-Based Scoring
A smaller score is better As before, the scoring model is sensitive to the
adjacency class weights, wij More Complex Scoring Methods
Could employ simulation to determine material handling equipment utilization, etc.
Would probably better reflect the preferences of the layout planner
Certainly more difficult to compute and could effect the number of alternatives considered
s w Xij ijji
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Computerized Layout Planning
Layout Generation Construction Algorithms
Start with basic SLP data and build a block layout by iteratively adding activities to a partial layout until all activities have been placed.
Improvement Algorithms Require an initial block layout which they then
attempt to improve.
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Computerized Layout Planning
Construction Algorithms For i = 1 to n
SELECT an activity to be placedPLACE the selected activity in the layout
End For Selection rules
Choose the next activity having the largest number of A (E, I, etc.) relationships with the activities already in the layout. Break ties randomly.
Supplement above procedure with TCR for choosing first department and breaking ties.
Consider flow cost chart and user specified placement priorities.
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Computerized Layout Planning
Construction Algorithms Placement Rules
Contiguity Rule If an activity is represented by more than one unit area
square, every unit area square representing the activity must share at least one edge with at least one other unit area square representing the activity.
Connectedness Rule The perimeter of an activity must be a single closed
loop that is always in contact with some edge of some unit area square representing the activity.
The following are infeasible shapes for activities.
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Construction Algorithms (cont.) Placement Rules (cont.)
Five basic shapes for an activity represented by 4 unit area squares.
Determining possible shapes becomes nontrivial for activities with more than 5 unit area squares, and some of the shapes have bizarre configurations.
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Computerized Layout Planning
Construction Algorithms (cont.) Placement Rules (cont.)
Therefore, additional rules are often used. Enclosed Voids Rule
No activity shape shall contain an enclosed void. Shape Ratio Rule
The ratio of a feasible shapes greatest length to its greatest width shall be constrained to lie between specified limits.
Corner Count Rule The number of corners for a feasible shape may not
exceed a specified maximum. Given an activitys shape there are a large number of
alternative placements for it in a layout, including different locations and mirror images and rotations.
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Computerized Layout Planning
Construction Algorithms (cont.) Bounded placement procedures
Accept a specified facility configuration and fit the activities into the facility.
May not be able to enforce all of the activity shape rules.
E.g., ALDEP Free placement procedures
Create a layout without regard to the resulting facility configuration.
May produce layouts requiring considerable adjustment to conform to conventional building configurations.
E.g., CORELAP
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Computerized Layout Planning
Improvement Algorithms Moves activities around within the block plan,
much like a jigsaw puzzle except that the shapes of the pieces are not fixed.
Too many degrees of freedom to devise a good method for modifying the block plan.
Most all improvement algorithms limit the kinds of changes that are permitted.
Basic procedure CHOOSE a pair (or triple) of activities
ESTIMATE the effect of exchanging themEXCHANGE if the effect is to reduce the total costCHECK to be sure the new layout is betterRepeat Until no more improvements are possible.
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Improvement Algorithms (cont.) To CHOOSE a pair of activities
Activities that have the same area, or Activities that share a common boundary.
There are many possibilities for EXCHANGE when the areas are not equal.
Generally, the shape ratio and corner count rules are violated, therefore, manual adjustment is sometimes required.
ESTIMATE the value of the exchange by comparing the cost if the two centroids are switched.
However, this estimate will not necessarily be correct for unequal area activities.
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Computer-aided layout techniques are classified by
Method of recording flows between departments Quantitatively in a from-to chart Qualitatively in a relationship chart
Method of generating layouts Construction of a layout Improvement of an existing layout
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Computer-Aided Layout
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Computer-Aided LayoutTechniques
Construction Routine Improvement Routine
Quantitative Input PLANET CRAFT
COFAD
CORELAPQualitative Input ALDEP
PLANET
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Attempts to minimize transportation cost, where
Transportation cost = flow * distance * unit cost Requires the assumptions that:
Move costs are independent of the equipment utilization.
Move costs are linearly related to the length of the move.
Distance metric used is the rectilinear distance between department centroids.
CRAFT
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Procedure1. Determine department centroids.2. Calculate rectilinear distance between centroids.3. Calculate transportation cost for the layout.4. Consider department exchanges of either equal
area departments or departments sharing a common border.
5. Determine transportation cost of each departmental interchange.
6. Select and implement the departmental interchange that offers the greatest reduction in transportation cost.
7. Repeat the procedure for the new layout until no interchange is able to reduce the transportation cost.
CRAFT
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CRAFT is a path-oriented method so the finallayout is dependent on the initial layout.
Therefore, a number of different initial layouts should be used as input to the CRAFT procedure.
CRAFT allows the use of dummy departments to represent fixed areas in the layout.
CRAFT
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CRAFT Example
Initial Layout
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 181 A A A A A A A A A A G G G G G G G G2 A A G G Shipping3 A A A A A A A A A A G G G G Department4 B B B B B C C C C C E E G G G G G G5 B B C C E E E E E E E E6 B B C C C C C E E E E E E E E7 B B B B B D D D D F F F F F F F E E8 D D D D D D D F F F9 D D F F F F F F10 D D D D D D D D H H H H H F F F F F
Dummy Department
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CRAFT Example
Distance Matrix
Cost MatrixA B C D E F G H Total
A 270 75 150 130 80 705B 180 275 210 665C 35 100 135D 120 420 540E 195 140 335F 70 75 455 600G 0H 0
2980
A B C D E F G HA 6 5 6 13 16B 6 11 14C 7 10D 6 12E 3 4F 14 3 7GH
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CRAFT Example
Trial Distance Matrix
Trial Cost Matrix
A B C D E F G HA 6 5 6 16 13B 6 14 11C 10 7D 6 9E 3 7F 11 3 4GH
A B C D E F G H TotalA 270 75 150 160 65 720B 180 350 165 695C 50 70 120D 120 315 435E 195 245 440F 55 75 260 390G 0H 0
2800
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CRAFT Example
New Layout
Final Layout
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 181 A A A A A A A A A A G G G G G G G G2 A A G G3 A A A A A A A A A A G G G G4 B B B B B C C C C C F F G G G G G G5 B B C C F F F F F F F F6 B B C C C C C F F F F F F F7 B B B B B D D D D E E E E E E F F8 D D D D D D D E E F F9 D D E E E E E E F F10 D D D D D D D D H H H H H E E F F F
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 181 A A A A A A A A A A G G G G G G G G2 A A G G3 A A A A A A A A A A G G G G4 C C C B B B B B B B F F G G G G G G5 C C C B B F F F F F F F F6 C C B B B B B B F F F F F F F7 C C C C B D D D D E E E E E E F F8 D D D D D D D E E F F9 D D E E E E E E F F10 D D D D D D D D H H H H H E E F F F
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COFAD
A modification of CRAFT to allow for a variety of material handling equipment alternatives.
It attempts to select both the layout and the material handling system.
A special version, COFAD-F, allows the evaluation of varying the product volumes and mixes to analyze the flexibility of the design.
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PLANET is a construction routine with the same basic input requirements as CRAFT.
Material Flow Input Methods Specify a route or production sequence for each
part. From-to Chart. Penalty Matrix -- quantitative representation of a
relationship chart. Construction Algorithm Selection Methods
Choose based on individual flow-between costs. Choose based on the sum of the flow-between
costs with previously placed departments. Choose based on the sum of the flow-between
costs with all other departments.
PLANET
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CORELAP
Constructs a layout for a facility by calculating the total closeness rating (TCR) for each department.
The total closeness rating is the sum of numerical values assigned to the closeness relationships from the relationship chart.
A = 6, E = 5, I = 4, O = 3, U = 2, X = 1 Procedure (similar to one of the procedures for
relationship diagramming) Place department with the highest TCR in the center of
the layout. Scan the relationship chart for a department with an A (if
none, then E, I, and so on) relationship with the selected department. Highest TCR is tie-breaker.
Continue until all departments are in the layout.
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Same basic input requirements and objectives as CORELAP.
Selection Procedure Randomly select first department in the layout. Scan the relationship chart for an A (then E, etc.)
relationship with the selected department. Break ties randomly.
Repeat procedure until all departments are selected. Placement Procedure
Place first department in upper left corner and extend it downward. Width of the extension is determined by the sweep width.
Next department begins where the previous department ended and follows the serpentine sweep pattern.
ALDEP
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ALDEP
Sweep Pattern
Can accommodate a variety of building shapes and irregularities.
Scoring Mechanism: Adjacency Score ALDEP rates the layouts by determining an
adjacency score by assigning values to the relationships among adjacent departments.
A = 64, E = 16, I = 4, O = 1, U = 0, X = -1024
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ALDEP Example
Layout Construction4 44 44 44 44 44 4 4 44 4 4 44 4 4 44 4 4 44 4 4 4
4 4 2 2 2 24 4 2 2 2 24 4 2 2 2 24 4 2 2 2 24 4 2 2 2 24 4 4 44 4 4 44 4 4 44 4 4 44 4 4 4
4 4 2 2 2 2 1 14 4 2 2 2 2 1 14 4 2 2 2 2 1 14 4 2 2 2 2 1 14 4 2 2 2 2 1 14 4 4 4 1 1 1 14 4 4 4 1 1 1 14 4 4 4 1 1 1 14 4 4 4 1 1 1 14 4 4 4 1 1 1 1
4 4 2 2 2 2 1 1 6 6 5 5 5 5 7 7 3 34 4 2 2 2 2 1 1 6 6 5 5 5 5 7 7 3 34 4 2 2 2 2 1 1 6 6 5 5 5 5 7 7 3 34 4 2 2 2 2 1 1 6 6 5 5 5 5 7 7 3 34 4 2 2 2 2 1 1 6 6 5 5 5 5 7 7 3 34 4 4 4 1 1 1 1 6 6 6 6 7 7 7 7 3 34 4 4 4 1 1 1 1 6 6 6 6 7 7 7 7 3 34 4 4 4 1 1 1 1 6 6 6 6 7 7 7 7 3 04 4 4 4 1 1 1 1 6 6 6 6 7 7 7 7 0 04 4 4 4 1 1 1 1 6 6 6 6 7 7 7 7 0 0
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ALDEP Example
Scoring ProcedureAdjacent
Departments Relationship Value Rating4-2 and 2-4 E 16 324-1 and 1-4 I 4 82-1 and 1-2 E 16 321-6 and 6-1 U 0 06-5 and 5-6 A 64 1286-7 and 7-6 E 16 325-7 and 7-5 I 4 87-3 and 3-7 U 0 0
Total 240
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Spiral
Graph based algorithm which attempts to create a structured adjacency graph.
The objective is to maximize the adjacency score. The selection and location decisions are made
simultaneously, using a greedy approach on a hexagonal grid.
Procedure Convert the flow matrix to a symmetric matrix. Sort the pairwise relationships by decreasing value. Place the first two departments in the layout. Add the departments by order in the list from step 2,
such that the adjacency with already placed departments is maximized. Use a random tie breaker.
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Input Data Asymmetrical Flow Matrix
Symmetrical Flow Matrix
Spiral Example
Dept 1 2 3 4 5 6 71 - 45 15 25 10 52 - 30 25 153 - 5 104 20 - 355 - 65 356 5 25 - 657 -
Dept 1 2 3 4 5 6 71 - 45 15 25 10 52 - 50 25 203 - 5 104 - 355 - 90 356 - 657 -
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Spiral Example
Sorted Flow ListDept Dept Flow
5 6 906 7 652 4 501 2 454 5 355 7 351 4 252 5 252 6 201 3 151 5 103 6 101 6 53 5 5
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Spiral Example
Graph Construction
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Spiral Example
Graph Evaluation Adjacency Matrix * Symmetrical Flow Matrix
Score is 385 Maximum score is 435 Efficiency is 385/435 = 88%
Dept 1 2 3 4 5 6 71 - 45 15 25 10 52 - 50 25 203 - 5 104 - 355 - 90 356 - 657 -
Dept 1 2 3 4 5 6 71 - 1 1 1 0 0 02 - 0 1 1 0 13 - 1 0 0 04 - 1 0 05 - 1 16 - 17 -
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Spiral Example
Alternative Adjacency Graph
Score is 405 Efficiency is 93%
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Spiral
Creating a Layout Can use a sweep pattern similar to ALDEP to sweep
through the adjacency graph and create a block layout
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Excel Layout Tool
Uses CRAFT-type flow*distance objective Layout is specified by a department sequence
User-specified and random sequences can be used ALDEP placement procedure based on a vertical
sweep pattern is used to place departments in layout Sweep width parameter can be changed Grid size and facility shape can also be adjusted
Pairwise exchange is performed on the sequence position of departments
Not restricted to adjacent or equal size departments Due to using the sweep method to create a layout
Additional add-ins to generate and improve sequences are available
Software also solves traditional CRAFT
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M-Craft
Layout is specified by a sequence of departments
Horizontal sweep patterns are used to place departments in layout
Number of bays controls sweep width Pairwise exchange is performed on the
sequence position of departments Not restricted to adjacent or equal size departments
Due to using the sweep method to create a layout
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MULTIPLE / LayOpt
Layout is specified by a sequence of departments
Sweep patterns are used to place departments in layout
Sweep pattern is based on space filling curve (SFC) concept
Many alternative SFCs can be created Pairwise exchange is performed on the
sequence position of departments Not restricted to adjacent or equal size departments
Due to using the sweep method to create a layout
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Factory CAD/Flow/Plan
AutoCAD based add-on Has multiple applications
CAD: drawing templates FLOW: evaluation of material flow; manual SLP-
type manipulation PLAN: layout alternative generation
FactoryPLAN Uses Spiral-type algorithm to generate alternative
layout options
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Computerized Layout Planning
Conclusion Does not provide an absolute best model for
finding the optimal layout. Does provide algorithms for evaluating a
large number of alternative layouts.
It is important to understand the underlying assumptions and scoring models of each procedure in order to correctly interpret the results.