IE272 Manufacturing Processes and Operations Analysis - Lecture Notes

Plant Layout (Process Layout)

Facility Layout

• Definition: Refers to the size and shape of a facility as well as the relative locations and shapes of functional areas (e.g., departments), equipment, workstations, storage spaces, aisles, and common areas (e.g., restrooms).

• Main Concerns:

  • Laying out a new facility.

  • Making changes in an existing facility.

• Alternate Name: Often called plant layout.

• Association: Usually associated with production plants.

Objectives in Layout Planning

• Efficient Movement: Ensure efficient movement of materials and people.

• Logical Workflow: Create a logical workflow with minimum travel distances.

• Utilization of Space: Efficient utilization of space is essential.

• Safety & Satisfaction: Safety and satisfaction of those who use the facility are prioritized.

• Flexibility: Design must provide flexibility to meet changing future requirements.

• Operational Mission: Layouts should advance the operational mission of the facility.

Systematic Layout Planning

• Developer: Developed by Richard Muther.

• Popularity: It is the most widely used layout planning approach.

• Applicability: Most applicable to process layout design and appropriate for designing a new plant.

Step 1: Requirements and Data

• Starting Specifications:

  • Specific product or set of products to produce.

  • Specific manufacturing and/or assembly processes to be performed.

  • Specified quantities of parts and products to be produced.

• Variability: Specifications can vary significantly between different plants.

Step 2: Analyze Material Flows

• Charting Techniques for Material Flows:

  • Operation Chart: Displays the sequence of processing, assembly, and inspection operations.

  • Flow Process Chart: Illustrates processing steps for parts production with details.

  • From-To Chart: Shows quantities and directions of material flows between departments.

  • Part Routing Matrix: Shows which operations each part is routed through during production.

Example of From-To Charts

• Item A Flow: R.M. → Saw → Drill → Mill → F.G. (8 pallets/day).

• Item B Flow: R.M. → Drill → Saw → Mill → F.G. (2 pallets/day).

• Item C Flow: R.M. → Saw → Mill → Saw → F.G. (7 pallets/day).

• Quantities:

  • From-To Chart displays relationships as numbers indicating the daily flow of pallets.

Step 3: Activity Relationships

• Purpose: Indicate relative need to place activities or departments in close proximity based on closeness ratings:

  • A: Absolutely necessary to be next to each other.

  • E: Especially important.

  • I: Important.

  • O: Ordinary.

  • U: Unimportant.

  • X: Undesirable to locate nearby.

Activity Relation Chart

Closeness Rating Factors

• Material Flow: Most important, sometimes the only factor.

• Contact Needs: Need for contact between personnel.

• Equipment Sharing: Use of the same equipment.

• Records Sharing: Sharing of common records.

• Supervision Sharing: Sharing of supervision or technical staff.

• Utilities Sharing: Use of same utilities.

• Environment Factors: High noise levels, emission of fumes or odors.

Step 4: Activity Relationship Diagram

• Description: Graphical depiction of closeness ratings among activities (departments) using nodes to represent activities.

• Connections: Nodes are connected by lines with closeness ratings identified by different colors and line types.

• Objective: Arrange nodes so those with high closeness ratings are nearby.

Step 5: Space Requirements

• Objective: Determine area requirements for each activity (department).

• Procedure:

  • List all workstation types identifying by subscript i.

  • Identify floor space requirement for each station type as $A_i$ = area for station type i.

  • Determine the number of stations of each type: n_i = ext{Min Int} egin{pmatrix} rac{WLi}{ATi} \ ext{where: } WLi = ext{Total workload} ext{, } ATi = ext{Area per Station} ext{.} \ ext{If workload consists of multiple parts/products, } WLi = rac{ ext{Total produced parts}}{ ext{Cycle time}}.

Step 6: Space Relationship Diagram

• Extension of Activity Relationship Diagram: Nodes now assigned areas proportional to the areas calculated in the previous step.

• Node Shapes: Shapes of nodes may be changed to fit, while maintaining relative positioning as in the last iteration.

Step 7: Adjustments and Allowances

• Considerations:

  • Personnel requirements (e.g., restrooms, locker rooms).

  • Material handling methods affecting floor space and building height.

  • Storage facilities treated as separate departments or allowances added.

  • Aisle space needing additional percentage allowances.

  • Offices specific to individual departments.

  • Building features like walls and columns.

  • Site conditions (e.g., parking, landscaping).

Step 8: Develop Block Layout

• Description: Develop alternative layout plans based on space relationship diagram.

• Evaluation: Evaluate different shapes and aspect ratios, select the best option taking into account competing objectives, modifying considerations, and practical limitations.

Constructing the Layout

• Procedure:

  • Iteration: For $i = 1 ext{ to } n$

  • Selection: Select an activity not placed yet, then place the selected activity.

  • Diversity: Select and place procedure may differ among algorithms.

Planet Method A

• Selection Process: Select two departments with the strongest relationship and place one next to the previously selected department.

• Tie-Breaking: Ties are broken arbitrarily.

Planet Method A Placement Order

• Sequence: A-C-D-B-E with noted relationship strengths.

Planet Method B

• Selection Process: Similar to Method A but considers the total strength of relationships with all already selected departments for placement.

Evaluating the Layouts

• Scoring Methods: Numerical scoring methods to assess block layout:

  • Adjacency Score

  • Layout Efficiency Rating

Adjacency Score

• Calculation: Computed by summing numerical closeness rating values for all contacting pairs of departments using:

  • $x_{ij} = ext{adjacency variable (1 if common border, 0 if none)}$

  • $CR_{ij} = ext{numerical value of closeness ratings (A=4, E=3, I=2, O=1, U=0, X=-5)}$

• Formula: AS = egin{pmatrix} ext{sum } (x_{ij}CR_{ij}) ext{ for all departments} \ ext{with } i, j = 1 ext{ to } n ext{ where } n ext{ is the number of departments} \ ext{.} \ ext{For } i, j: AS = ext{Adjacency Score}

Layout Efficiency Rating (LER)

• Formula: $LER = rac{AS}{AS_{max}}$ where:

  • $AS = ext{Adjacency Score}$

  • $AS_{max} = ext{Maximum possible adjacency score relevant to closeness ratings}$

Distance-based Scoring

• Parameters: $c_{ij}$ = total cost per unit distance of flow between activities i and j, and $D_{ij}$ = distance between activities i and j.

• Calculation: $ext{Total Distance Cost} = ext{Sum of total costs across all activity pairs}.$

Example: Placement of Department D

• Sample Data: Cost of flow between departments A and C: 1x36=36.

  • Distances from A: (2, 1, 1, 1, 2, 2)

  • Distances from C: (1, 2, 2, 2, 1, 1)

  • Cost of flow when D is placed: (48, 42, 42, 42, 48, 48).

  • Selection: Arbitrarily choose location 4.

PLANET Example: Placement of Department B

• Sample Data: Flow between A, B, C, D with associated distances.

• Calculation of Costs: Costs for various placements calculated similarly as before,

• Selection: Selected location 6.

PLANET Example: Final Layout

• Configuration of Layout: Displays following design placement for departments A, C, D, B, and E.

Step 9: Develop Detailed Layout

• Objective: Fill in the block layout with specifics of arrangement for each department.

• Considerations: Locations and areas for workstations, equipment, aisles, office spaces, storage areas, etc.

• Layout Design Check: Ensures original calculations are valid and details fit within the assigned spaces; discrepancies may indicate errors in previous calculations.