GROUP NO. 5

Layout Planning Models and Design Algorithms

Alfiler, Ronna C.Balagon, Bea B.Valencia, Ronald Ron R.

Table of Contents

IntroductionBasic Layout Types1. Fixed material location departments2. Production line departments3. Product family departments4. Process departmentsLayout Procedures Apples Plant Layout Procedure Reeds Plant Layout Procedure Muthers Systematic Layout Planning (SLP) ProcedureAlgorithmic Approaches Algorithmic Classifications Pairwise Exchange Method Graph-Based Method CRAFT (Computerized Relative Allocation of Facilities Technique) BLOCPLAN MIP (Mixed Integer Programming) LOGIC (Layout Optimization with Guillotine Induced Cuts) MULTIPLE (Multifloor Plant Layout Evaluation)Department Shapes and Main AislesSimulated Annealing and Genetic AlgorithmsCommercial Facility Layout PackagesThe Impact of ChangeAdapting To Change and Planning For Facility ReorganizationDeveloping Layout Alternatives

The generation of layout alternatives is a critical step in the facilities planning process, since the layout selected will serve to establish the physical relationships between activities. Block Layout- shows the location, shape, and size of each planning department concerned primarily with the macro flows in the facility Detailed Layout shows the exact location of all equipment, work benches, and storage areas within each department. often concerned with the micro flows

For the facility layout to be complete and effective, both the block layout and the detailed layout need to be developed and evaluated carefully.1. Which comes first, the material handling system or the facility layout? Centralized versus decentralized storage of work in process (WIP), tooling, and supplies Fixed path versus variable path handling The degree of automation used in handling The type of level of inventory control, physical control, and computer control of materials.2. Which comes first, the block layout or the detailed layout?

BASIC LAYOUT TYPES1. Fixed material location department It involves the sequencing and placement of workstations around the material or product. It is used in aircraft assembly, shipbuilding, and most construction projects (e.g., buildings, dams, and electric or nuclear power plants), shipbuilding, aircraft, aerospace, farming, drilling for oil, home repair, and automated car washes.

Figure 1. Fixed materials location product departmentsTable 1. Advantages and Limitations of Fixed Product LayoutAdvantagesLimitations

1. Material movement is reduced.1. Personal and equipment movement is increased.

2. When a team approach is used, continuity of operations and responsibility results.2. May result in duplicate equipment.

3. Provides job enrichment opportunities.3. Requires greater skill for personnel.

4. Promotes pride and quality because an individual can complete the whole job.4. Requires general supervision.

5. Highly flexible; can accommodate changes in product design, product mix, and production volume.5. May result in increased space and greater work-in-process.

6. Requires close control and coordination in scheduling production.

2. Production line departments The layout for a production line department is based on the processing sequence for the part(s) being produced on the line. Materials typically flow from one workstation directly to the next adjacent one. Generally used in systems where a product has to be manufactured or assembled in large quantities. The machinery and auxiliary services are located according to the processing sequence of the product without any buffer storage w/in the line itself.

Figure 2. Production line product departmentsTable 2. Advantages and Limitations of Product LayoutAdvantagesLimitations

1. Smooth, simple, logical, and direct flow lines result.1. Machine stoppages stops the line.

2. Small work-in-process inventories should result.2. Product design changes cause the layout to become obsolete.

3. Total production time per unit is short.3. Slowest station process the line.

4. Material handling requirements are reduced.4. General supervision is required.

5. Less skill is required for personnel.5. Higher equipment investment usually results.

6. Simple production control is possible.

7. Special-purpose equipment can be used.

3. Product family departments Based on the grouping of parts to form product/part families. The cells become in effect miniature versions of product layouts. Used when various products have to be produced in medium to large quantities. Non-identical parts may be grouped into families based on common processing sequences, shapes, material composition, tooling requirements, handling/storage/control requirements, and so on.

Figure 3. Product family product departments

Table 3. Advantages and Limitations of Group LayoutAdvantagesLimitations

1. By grouping products, higher machine utilization can result.1. General supervision required.

2. Smoother flow lines and shorter travel distances are expected than for process layouts.2. Greater labor skills required for team members to be skilled on all operations.

3. Team atmosphere and job enlargement benefits often result.3. Critically dependent on production control balancing the flows through the individual cells.

4. Has some of the benefits of product layouts and process layouts; it is a compromise between the two.4. If flow is not balanced in each cell, buffers and work-in-process storage are required in the cell to eliminate the need for added material handling to and from the cell.

5. Encourages consideration of general-purpose equipment.5. Has some of the disadvantages of product layouts and process layouts; it is a compromise between the two.

6. Decreased the opportunity to use special-purpose equipment.

4.Process departments The layout for a process department is obtained by grouping like processes together and placing individual process departments relative to one another based on flow between the departments. Also referred as a job shop layout. A manufacturing example is a machine shop. Also quite common in non-manufacturing environments. Examples includes hospitals, colleges, banks, auto repair shops, and public libraries.

Figure 4. Process departmentsTable 4. Advantages and Limitations of Process LayoutAdvantagesLimitations

1. Increased machine utilization.1. Increased material handling requirements.

2. General-purpose equipment can be used.2. More complicated production control required.

3. Highly flexible on allocating personnel and equipment.3. Increased work-in-process.

4. Diversity of tasks for personnel.4. Longer production lines.

5. Specialized supervision is possible.5. Higher skills required to accommodate diversity of tasks required.

LAYOUT PROCEDURES Construction layout methods basically involve developing a new layout from scratch Improvement procedures generate layout alternatives by seeking improvements in an existing layout

Apples Plant Layout Procedure detailed sequence of steps in producing a plant layout1. Procure the basic data.2. Analyze the basic data.3. Design the productive process.4. Plan the material flow pattern.5. Consider the general material handling plan.6. Calculate equipment requirements.7. Plan individual workstations.8. Select specific material handling equipment.9. Coordinate groups of related operations.10. Design activity interrelationships.11. Determine storage requirements.12. Plan service and auxiliary activities.13. Determine space requirements.14. Allocate activities to total space.15. Consider building types.16. Construct master layout.17. Evaluate, adjust, and check the layout with the appropriate persons.18. Obtain approvals.19. Install the layout.20. Follow up on implementation of the layout.Reeds Plant Layout Procedure systematic plan of attack as required steps in planning for and preparing the layout1. Analyze the product or products to be produced.2. Determine the process required to manufacture the product.3. Prepare the layout planning charts.4. Determine workstations.5. Analyze storage area requirements.6. Establish minimum aisle widths.7. Establish office requirements.8. Consider personnel facilities and services.9. Survey plant services.10. Provide for future expansion.

Reed calls the layout planning chart the most important single phase of the entire layout process.1. Flow process, including operations, transportation, storage, and inspections2. Standard times for each operation3. Machine selection and balance4. Manpower selection and balance5. Material handling requirements

Figure 5. Layout Planning Chart

Muthers Systematic Layout Planning (SLP) Procedure developed by Richard Muther, it is a layout procedure he named systematic layout planning, or SLP.

Figure 6. Systematic layout planning (SLP) procedure

The framework is uses activity relationship diagram as a foundation activity.

Figure 7. Activity relationship chart

Based on the input data and an understanding of the roles and relationships between activities, a material flow analysis (from-to-chart) and an activity relationship analysis (activity relationship chart) are performed. From the analysis performed, a relationship diagram is developed.

Figure 8. Relationship chart

The next two steps involve the determination of the amount of space to be assigned to each activity. Departmental service and area requirement sheets would be completed for each department. Once the space assignments have been made, space templates are developed for each planning department and the space is hung on the relationship diagram to obtain the space relationship diagram.

Figure 9. Space relationship diagram

Based on modifying considerations and practical limitations, a number of layout alternatives are developed and evaluated. The preferred alternative is then recommended.

Figure 10. Alternative block layouts

ALGORITHMIC APPROACHES Algorithmic approach is a formal procedure that can help the layout analyst to develop or improve a layout, and it provide objective criteria to facilitate the evaluation of various layout alternatives that emerge in the process.

Algorithmic Classifications Most layout algorithms can be classified according to the type of input data they requires. Qualitative flow data (such as relationship chart) Need input from several individuals Possible inconsistencies should be resolved Not practical for problems with 20 or more departments Quantitative flow data (such as flow matrix expressed as a from-to-chart) Predominantly used in practice Requires more time and effort to practice the from-to chart Some algorithms accepts both relationship chart and from-to-chart Layout algorithms can also be classified according to their objective functions. Minimizing the sum of flows times distances From-to matrix distance based objective Maximizing an adjacency score Relationship chart adjacency based objectiveGraphical representation

Discrete Layout Easy to implement in a computer Selecting appropriate grid size is important Smaller grids computationally burdensomeContinuous Layout Hard to implement in a computer Highly flexible Representing L-shaped, U-shaped departments is not straightforward

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.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

Department cannot be split Any grid assigned to a department must be reachable form any other such grid Enclosed void (atrium)

Layout EvaluationDistance based objective

where: m = the number of departmentsfij = the flow from department i to department j (unit load/unit time)cij = the cost of moving a unit load one distance unit from department i to jdij = the distance from department i to jz = total movement cost per time period (the objective function value) The fij and cij are input data If the cij= 1 for all i and j, z= total travel distance per time period

Adjacency based objective

where: m = the number of departmentsfij = the flow from department i to department j (unit load/unit time)xij = the adjacent of department i and j in the layout Since the numerical scale is arbitrary, another objective function is often used Called an efficiency rating (or normalized adjacency score) It is a relative measure of a layout with respect to the best (sometimes not possible) objective function value

Layout Generation Construction layout methods basically involve developing a new layout from scratch SELECT an activity to be placed PLACE the selected activity in the layout Improvement procedures generate layout alternatives by seeking improvements in an existing layout CHOOSE a pair (or triple) of activities ESTIMATE the effect of exchanging them EXCHANGE them CHECK to be sure the new layout is better REPEAT until no more improvements are possible

Pairwise exchange method For layout improvement Can be used for both adjacency based or distance-based objective The objective is to minimize the total cost of transporting materials among all departments in a facility based on rectilinear distance from centroid to centroid The method does not guarantee the optimality, only local optimum The procedure may cycle back to one alternative Symmetric layout may occur Pairwise exchange can be easily accomplished only if the departments are of the same size

ProcedureStep 1: Calculate total cost for the existing layoutStep 2: For each iteration evaluate all feasible exchanges in the locations of department pairsStep 3: Select the pair that results in the largest reduction in total costStep 4: Recompute the distance matrix each time an exchange is performed.Step 5: If the lowest total cost for your next iteration is worse than the total cost for the previous iteration, the procedure is terminated

Graph- based method The graph-based method is a construction-type layout algorithm Uses the adjacency based objectiveProcedureStep 1: from the relationship chart select a department pair with the largest weight.Step 2: Select the third department to enter, the third department is selected based on the sum of the weights with respect to departments 3 and 4.Step 3: Pick the fourth department to enter by evaluating the value of adding one of the unassigned departments represented by a node on a face of the graph.Step 4: Determine on which face to insert the last department.Step 5: Construct a corresponding block layout.

Relationships are given by weights, rather than the alphabetic closeness ratings The score is very sensitive to the assignment of weights Relationship can have a positive value only when departments are adjacent. Other relationships are ignored The adjacency score does not account for: The distance All he relationships (except those between adjacent departments) Dimensional specifications The length of common boundaries between adjacent departments The arcs do not intersect (planarity)

CRAFT (Computerized Relative Allocation of Facilities Technique) Introduced in 1963 by Armour, Buffa, and Vollman. It is one of the earliest layout algorithms presented in the literature. It uses a from-to-chart as input data for the flow. Is an improvement-type layout algorithm. It begins by determining the centroids of the departments in the initial layout. Is a highly path dependent heuristic.

Example:

BLOCPLAN It was developed by Donaghey and Pire. It is similar to MCRAFT in that departments are arranged in bands. It uses a relationship chart as well as a from-to-chart as input data for the flow. May be used both as a construction algorithm and as an improvement algorithm.

Example:

MIP (Mixed Integer Programming) It is used for continuous population.

LOGIC (Layout Optimization with Guillotine Induced Cuts) It was developed by Tam. It is assume that a from-to chart is given as input data for the flow It also assume that layout cost is measured by the distance-based objective function Used as a layout improvement algorithm. Based on dividing the buildings into smaller and smaller portions by executing successive guillotine cuts- that is, straight lines that run from one end of the building to the other.

Example:

MULTIPLE (Multifloor Plant Layout Evaluation) Developed by Bozer, Meller, and Erlebacher. It was originally developed for multiple-floor facilities. It is similar to CRAFT and uses a from-to chart as input data for the flow The objective function is identical to that of CRAFT and a distanc-based objective with distance measured rectilinearly between departments centroid. It is an improvement type layout algorithm that starts with an initial layout specified by the layout planner.

Example:

DEPARTMENT SHAPES AND MAIN AISLESIn developing alternative block layouts, the main aisles are typically not represented explicitly until the block layout is finalized. As the layout planner messages the final block layout, he or she attempts to correct irregular department shapes and aims for smooth department borders primarily for two reasons: first, a poor department shape may make it virtually impossible to develop an efficient and effective detailed layout for that department; second, since main aisles connect all the the departments by definition, irregular department shapes would lead to irregular main aisles.A third measure, originally appeared in papers concerned with geometric modeling. It is based on the observation that, given an object with a fixed area, the perimeter of the object generally increases as its shape become more irregular.

SIMULATED ANNEALING AND GENETIC ALGORITHMSSimulated annealing (SA) and genetic algorithms (GA) represents relatively new concepts in optimization.

SABLE (Simulated Annealing-Based Layout Evaluation) which was developed by Meller and Bozer. It uses a more general technique for generating candifate layout vectors.

COMMERCIAL FACILITY LAYOUT PACKAGES

Layout Algorithms Intent to familiarize the reader with how different models generate, evaluate, and/or optimize the layout of a facility. Primarily research-based algorithms and most of them are unfortunately not available as commercial layout design packages Do not perform some of the common analyses performed in industry, such as spaghetti charting, which can be helpful visual aid in evaluating alternative layouts

THE IMPACT OF CHANGEThe need for a facility layout study can arise under a variety of circumstances.Common situations that arise in the context of plant layout include the ff:1. Changes in the design of an existing product, the elimination of products from the product line/family, and the introduction of new products.2. Changes in the processing sequences for existing products, replacements of existing processing equipment and changes in the use of general-purpose and special purpose equipment.3. Changes in production quantities and associated production schedule4. Changes in organizational structure5. Incremental changes needed in the layout due to continuous improvement and kaizen events.

Flexibility can be achieved by utilizing modular office equipment, workstations, and material handling equipment: installing general-purpose production equipment: utilizing a grid-based utilities and service system; and using modular construction.

ADAPTING TO CHANGE AND PLANNING FOR FACILITY REORGANIZATION

Manufacturing environment is very dynamic. The facility layout should also be treated as dynamic. In as much as businesses should have long-term business strategies, we must also have a multiyear master plan for facility layout. This master plan should be consistent with the companys business plan and it should attempt to anticipate future requirements and make provisions for adapting to changes in facility requirements.The master layout plan must also provide the means for a facility to react quickly changes, adding capacity in a short period of time, or to be able to operate efficiently at scaled down operating levels. The facility design must be flexible in order to provide this high level of responsiveness.

How to develop such a flexible layout? Harmon and Peterson suggest the use of the following objectives.1. Reorganize factory subplants to achieve superior manufacturing status.2. Provides maximum perimeter access for receiving and shipping materials, components, etc.3. Cluster all subplants dedicated to a product.4. Locate supplier subplants for common component subplants in a central location to minimize component travel distances.5. Minimize the factory size to avoid wasted time and motion of workers.6. Eliminate centralized storage of purchased materials, components and assemblies and move storage to focus subplants.7. Minimize the amount of factory reorganization that will be made necessary by future growth and change.8. Avoid locating offices and support services on factory perimeters.9. Minimize ratio of aisle space to production process space.

DEVELOPING LAYOUT ALTERNATIVESSuggested approaches that have proven beneficial:1. Exert the necessary effort to generate and evaluate the alternatives.2. Set a time limit and use the available time wisely.3. Seek many alternatives.4. Establish goal and layout performance metrics that the stakeholders agree on.5. Make liberal use of the questioning attitude.6. Dont fail to see the forest for the trees.7. Think big, the think little.8. Dont be conservative.9. Refer to analogous problems of others.10. Consult the literature and your peers in other organizations.11. Use the brainstorming technique.12. Divorce your thinking from the existing solution.13. Involve operating people, management, experienced people, and those who promote change.14. Be aware of market trends and what the competition is doing.15. Recognize your own limitations and strengths. 16. Do your homework.17. Dont overlook an improved version of the present method.18. Think long range.

References: Tompkins et al., Facilities Planning. 4th Edition. John Wiley & Sons, Inc. 2010

Alfiler, Ronna C.Introduction, Basic Layout Types, Layout procedures, and Algorithmic approaches (algorithmic classifications, pairwise exchange, graph-based method)

Valencia, Ronald Ron R.Algorithmic approach (CRAFT, BLOCPLAN, MIP, LOGIC, MULTIPLE), Department Shapes and Main Aisles and Simulated Annealing and Genetic Algorithms

Balagon, Bea B.Commercial Facility Layout Packages, The Impact of Change, Adapting To Change and Planning For Facility Reorganization and Developing Layout Alternatives