1. Computerized Block Layout Algorithms: ALDEP, CRAFT, MCRAFT
Facility Layout 4
Computerized Block Layout Algorithms:
ALDEP, CRAFT, MCRAFT

2. Tarea:
Para la próxima clase, por favor resuelvan en parejas los siguientes problemas:
6.13
6.18
6.28
Para entregar.

3. Computer-Aided Layout Methods
Disadvantages:
Lack human judgment
Lack qualitative
aspects of Layout
Advantages:
Rapid What-if Analysis
Evaluate large number
of alternatives

4. Automated Layout Design Program (ALDEP)
Purpose: Generate many layouts
Derived from CORELAP
Dummy departments
Separate Multiple Floor Capability

5. ALDEP data requirements
Area of Departments
REL Chart with A,E,I,O,U,X rankings
Sweep width
Minimum Closeness Rating (MCR)
A, E, I, O, U
Ranking values:
A = O = 1
E = U= 0
I = X = -1024

6. ALDEP Facility Representation
Discrete
Representation
Sweep Method

7. ALDEP Facility Representation
Dept. size = 8 squares
Facility width = 6 squares
Sweep width = 1 square
Dept. size = 14 squares
Facility width = 6 squares
Sweep width = 2 squares

8. ALDEP Facility Representation
Dept. size = 8 squares
Facility width = 6 squares
Sweep width = 3 squares

9. ALDEP Procedure Set MCR and sweep width.
Choose first department randomly, add it to the first position of the Department Entry Order (DEO).
Choose next department:
Choose department that has A REL with the last department in DEO.
If none, choose department that has E REL with last department in DEO.
Continue until MCR REL.
If none, choose department randomly
Repeat Step 3 until all depts. are in the DEO.
Place departments in layout with DEO and sweep method, do not split if possible.
Score layout with A-based objective.

10. ALDEP Example Step 1: MCR = ‘E’ Sweep Width = 2 DEO: 5, 1
Step 2: Select first department
Randomly choose 5
Step 3: Select 2nd Department
No A’s with 5
1,3, and 6 have E with 5: randomly choose 1

11. ALDEP Example Step 3b: Select 3rd dept. 2 has A with 1, select 2
Step 3c: Select 4th dept
No A’s or E’s with 2
Randomly choose 3
Step 3d: Select 5th dept
No A’s or E’s with 3
Randomly choose 4
DEO:
5, 1, 2, 3, 4, 6
Step 3e: Select 6th dept
Last dept, choose 6

12. ALDEP Example
Dept.
DEO:
5, 1, 2, 3, 4, 6
Sweep Width = 2

13. ALDEP Analysis 6 1 2 3 4 5
Random selection does not produce the “best” layouts
Developed for Layout generation on mainframes and has become the basis for future algorithms.

14. Computerized Relative Allocation of Facilities Technique (CRAFT)
Improvement Algorithm
Discrete Representation
From-To Matrix
Input Data: From-To Matrix
Based on pairwise exchange
Layout “cost” is measured by the distance based objective function
Departments are not restricted to rectangular shapes, Why?
Discrete Representation
CRAFT is an improvement type layout algorithm, therefore the initial starting layout could be:
The actual existing layout of the facility
Layout developed by another algorithm
Distance-Based Objective
Pairwise Exchange

15. CRAFT Algorithm Determine the department centroids.
Calculate the inter department rectilinear distances.
Calculate the initial cost of the layout by multiplying the from-to matrix with the cost matrix.
CRAFT then considers all the possible two-way or three-way department exchanges and identifies the best “exchange”.
Update the layout and calculate the new department centroids.
The above procedure is repeated until no further reduction in the cost can be obtained.

16. CRAFT Example Find Centroids 1 2 4 3 5 7 8 6 Initial Layout Centroid
Dept X Y 1 2 4 3 5 7 8 6

17. Cost of the initial Layout
dist 1 2 3 4 5 6 7 8
18.5
8.5
16.5
14.5 11
4.5 10
Find Distances
Cost = Distance x Reward
20* *
1* *
1* *
1* *
5* * 8 =
= 678.5
FxC 1 2 3 4 5 6 7 8 20 10
Reward Matrix

18. Only equal areas or adjacent depts. are feasible exchanges
Centroid
Dept X Y .
“Exchange 1-3”
Centroid
Dept X Y .
“Exchange 1-4”
Centroid
Dept X Y .
Infeasible Exchange
… and so on…

19. CRAFT exchanges centroids first
Then calculates a new table of distances
And then new layout costs
All possible exchanges are evaluated
The one with the most savings is selected
And the centroids, distances and actual layout are updated

20. Exchange depts. 1 and 4 gives the most savings
Centroids
Dept X Y .
Updated
Centroids
Dept X Y .

21. Let’s calculate the cost of the layout after exchanging depts. 1 and 4
Cost = Distance x Reward
20* *
1* *
1* *
1* *
10* * = =
678.5 –
Savings = = 47.56%
678.5

22. 3 iterations take us to the final layout
Exchange 1 and 4 4 7 8 5 2 1 6 3
Exchange 5 and 7
Exchange 5 and 8
Final cost =

23. CRAFT Pros Evaluates MANY exchanges very quickly
Initial layout can be captured accurately
CRAFT Allows:
Flexible Department Shapes
Dummy depts.
Fixed Departments
Non-rectangular buildings
Dummy
CRAFT only considers exchanging departments that are either adjacent (i.e. they share a border) or equal in area.
This is because it cannot shift other departments if the above criterion were not true.
Therefore adjacency is a necessary but not sufficient condition for exchange.
There is a likelihood that CRAFT will terminate at “local optima” while searching for a solution because:
It follows a “steepest descent” procedure.
It does not “look back” or “look forward” during the search.
CRAFT is flexible with department shapes as long as they are not split.
It can be used with “non-rectangular” buildings through the use of “dummy” departments.
CRAFT allows the user to “fix” the location of any department.
One of CRAFT’s weaknesses is that it rarely generates departments that result in a straight, uninterrupted aisles.
Layout generated by the computer needs to be “molded” into a practical layout.

24. CRAFT Cons 4 Results in Odd Department Shapes Limited exchange options
Greedy Algorithm => Local Optima
CRAFT only considers exchanging departments that are either adjacent (i.e. they share a border) or equal in area.
This is because it cannot shift other departments if the above criterion were not true.
Therefore adjacency is a necessary but not sufficient condition for exchange.
There is a likelihood that CRAFT will terminate at “local optima” while searching for a solution because:
It follows a “steepest descent” procedure.
It does not “look back” or “look forward” during the search.
CRAFT is flexible with department shapes as long as they are not split.
It can be used with “non-rectangular” buildings through the use of “dummy” departments.
CRAFT allows the user to “fix” the location of any department.
One of CRAFT’s weaknesses is that it rarely generates departments that result in a straight, uninterrupted aisles.
Layout generated by the computer needs to be “molded” into a practical layout.
CRAFT is path dependent: The starting layout makes a difference

25. MCRAFT (Micro-CRAFT) – PC Implementation
Similar to CRAFT, except it can exchange two non-adjacent departments
Layout formation technique that allows easy shifting of departments
Facility divided into bands
Layout formed by starting at the upper-left-hand corner of the building and sweeping the bands in serpentine fashion
Two way exchanges formed until no further improvement is achieved.

26. MCRAFT Limitations
May be hard to fit the existing factory layout into bands
Band width assumed to be same for all bands
A fixed department may “float” when certain non-equal area departments are exchanged. 1 7 2 3 5 4 8 6