Production
and
Norman Gaither
Operations Management Greg Frazier
Slides Prepared by John Loucks
1999 South-Western College Publishing
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Chapter 8 Facility Layout: Manufacturing and Services
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Overview
Introduction Manufacturing Facility Layouts Analyzing Manufacturing Facility Layouts Service Facility Layouts Wrap-Up: What World-Class Producers Do
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Introduction
Facility layout means planning: for the location of all machines, utilities, employee workstations, customer service areas, material storage areas, aisles, restrooms, lunchrooms, internal walls, offices, and computer rooms for the flow patterns of materials and people around, into, and within buildings
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Locate All Areas In and Around Buildings
Equipment Work stations Material storage Rest/break areas Utilities Eating areas Aisles Offices
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Characteristics of the Facility Layout Decision
Location of these various areas impacts the flow through the system. The layout can affect productivity and costs generated by the system. Layout alternatives are limited by the amount and type of space required for the various areas the amount and type of space available the operations strategy . . . more
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Characteristics of the Facility Layout Decision
Layout decisions tend to be: Infrequent Expensive to implement Studied and evaluated extensively Long-term commitments
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Manufacturing Facility Layouts
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Basic Layout Forms
Process Product Cellular Fixed position Hybrid
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Process (Job Shop) Layouts
Equipment that perform similar processes are grouped together Used when the operations system must handle a wide variety of products in relatively small volumes (i.e., flexibility is necessary)
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Characteristics of Process Layouts
General-purpose equipment is used Changeover is rapid Material flow is intermittent Material handling equipment is flexible Operators are highly skilled . . . more
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Characteristics of Process Layouts
Technical supervision is required Planning, scheduling and controlling functions are challenging Production time is relatively long In-process inventory is relatively high
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Product (Assembly Line) Layouts
Operations are arranged in the sequence required to make the product Used when the operations system must handle a narrow variety of products in relatively high volumes Operations and personnel are dedicated to producing one or a small number of products
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Characteristics of Product Layouts
Special-purpose equipment are used Changeover is expensive and lengthy Material flow approaches continuous Material handling equipment is fixed Operators need not be as skilled . . . more
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Characteristics of Product Layouts
Little direct supervision is required Planning, scheduling and controlling functions are relatively straight-forward Production time for a unit is relatively short In-process inventory is relatively low
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Cellular Manufacturing (CM) Layouts
Operations required to produce a particular family (group) of parts are arranged in the sequence required to make that family Used when the operations system must handle a moderate variety of products in moderate volumes
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Characteristics of CM Relative to Process Layouts
Equipment can be less general-purpose Material handling costs are reduced Training periods for operators are shortened In-process inventory is lower Parts can be made faster and shipped more quickly
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Characteristics of CM Relative to a Product Layout
Equipment can be less special-purpose Changeovers are simplified Production is easier to automate
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Fixed-Position Layouts
Product remains in a fixed position, and the personnel, material and equipment come to it Used when the product is very bulky, large, heavy or fragile
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Hybrid Layouts
Actually, most manufacturing facilities use a combination of layout types. An example of a hybrid layout is where departments are arranged according to the types of processes but the products flow through on a product layout.
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New Trends in Manufacturing Layouts
Designed for quality and flexibility Ability to quickly shift to different product models or to different production rates Cellular layout within larger process layouts Automated material handling U-shaped production lines . . . more
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New Trends in Manufacturing Layouts
More open work areas with fewer walls, partitions, or other obstacles Smaller and more compact factory layouts Less space provided for storage of inventories throughout the layout
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Analyzing Manufacturing Facility Layouts
Process Layouts Product Layouts Cellular Layouts
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Designing and Analyzing a Process Layout
Group like processes together into departments or work centers Determine where in the building these departments will be located relative to one another The objective is to arrange the departments so that some criterion such as material-handling cost is minimized
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Approaches to Process Layout Design
Operations sequence analysis Block diagram analysis Load-distance analysis Computer analysis
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Operations Sequence Analysis
Inputs required an existing or proposed arrangement of departments a projection of the traffic or flow that will take place between one department and each of the other departments during some time period - this is usually displayed as an interdepartmental flow matrix . . . more
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Operations Sequence Analysis
Departments are represented by nodes (circles) Using the interdepartmental flow information, flows between adjacent departments are represented by solid lines. Dashed lines represent traffic between nonadjacent departments. The projected volumes are written above the appropriate lines. . . . more
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Operations Sequence Analysis
Departments (circles) are moved with the objective of reducing the amount of nonadjacent flow. This proceeds until no further improvement can be found
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Block Diagram Analysis
This approach follows the operations sequence analysis and is an effort to make the solution more realistic Each department is represented by a square the relative size of the department Shapes of the squares are altered to fit into the boundaries of the building while retaining the same areas and relative position found in the operations sequence analysis
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Load-Distance Analysis
A way of quantitatively comparing alternative process layouts Inputs Alternative block layouts which will provide the distance between a department and each of the other departments For each product, the path it will follow (routing) and its volume over some time period . . . more
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Load-Distance Analysis
For each alternative process layout, compute the total distance a product must travel using its routing Compute the total distance traveled per time unit for each product by multiplying its total travel distance by its volume per time unit Add the total distance traveled per time unit for each product Select the layout with the smallest sum
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Computer Analysis of Process Layouts
There are several computer programs that perform analyses similar to those outlined above Computerized Relative Allocation of Facilities Technique (CRAFT) uses material handling cost as its criterion . . . more
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Computer Analysis of Process Layouts
Automated Layout Design Program (ALDEP) and Computerized Relative Layout Planning (CORELAP) use closeness ratings, a relative measure of how desirable it is for two departments to be close together, as their criterion
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Designing and Analyzing a Product Layout
Line Balancing
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Designing and Analyzing a Product Layout
Characteristics Inputs Design Procedure How Good Is The Layout?
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Line Balancing Problem
Work stations are arranged so that the output of one is an input to the next, i.e., a series connection
Layout design involves assigning one or more of the tasks required to make a product to work stations . . . more
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Line Balancing Problem
The objective is to assign tasks to minimize the workers’ idle time, therefore idle time costs, and meet the required production rate for the line In a perfectly balanced line, all workers would complete their assigned tasks at the same time (assuming they start their work simultaneously) This would result in no idle time . . . more
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Line Balancing Problem
Unfortunately there are a number of conditions that prevent the achievement of a perfectly balanced line The estimated times for tasks The precedence relationships for the tasks The combinatorial nature of the problem
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Inputs
The production rate required from the product layout or the cycle time. The cycle time is the reciprocal of the production rate and visa versa All of the tasks required to make the product It is assumed that these tasks can not be divided further . . . more
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Inputs
The estimated time to do each task The precedence relationships between the tasks These relationships are determined by the technical constraints imposed by the product These relationships are displayed as a network known as a precedence diagram
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Design Procedure 1. If not provided, find the cycle time for the line. Remember the cycle time is the reciprocal of the production rate. Make sure the cycle time is expressed in the same time units as the estimated task times. 2. Select the line-balancing heuristic that may be used to help with the assignments. (Two heuristics are described at the end of this procedure.) . . . more
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Design Procedure 3. Open a new work station with the full cycle time remaining. 4. Determine which tasks are feasible, i.e., can be assigned to this work station at this time. For a task to be feasible, two conditions must be met: All tasks that precede that task must have already been assigned The estimated task time must be less than or equal to the remaining cycle time for that work station.
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Design Procedure 5. If there are no feasible tasks, assignments to that work station are complete. Go back to step 3 (or stop, if all tasks have been assigned). If there is only one feasible task, assign it to the work station. If there is more than one feasible task, use the heuristic (step 2) to determine which task to assign. Reduce the work station’s remaining cycle time by the selected task’s time and return to step 4.
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Line-Balancing Heuristics
Heuristic methods, based on simple rules, have been used to develop very good, not optimal, solutions to line balancing problems. Incremental Utilization Heuristic - adds tasks to a workstation one at a time in the order of task precedence until utilization is 100% or is observed to fall. Longest-Task-Time Heuristic - adds tasks to a workstation one at a time in the order of task precedence, choosing - when a choice must be made the task with the longest time. 4 3
How Good Is the Design?
Utilization is one way of objectively determining how near perfectly balanced an assignment scheme is. Utilization is the percentage of time that a production line is working. Utilization is calculated as: Minimum number of workstati ons x100 Actual number of workstati ons
or Sum of all task time s x 100 (Cycle Time) x (Actual number of work stations) 4 4
Designing and Analyzing a Cellular Layout
Fundamental questions: Which parts are going to be produced in a cell? Which processes are going to be assigned to a cell?
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Fundamental Requirements for Parts to be Made in Cells
Demand for the parts must be high enough and stable enough that moderate batch sizes of the parts can be produced periodically. Parts must be capable of being grouped into parts families.
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Design Procedure 1. Form the Parts-Machines Matrix. 2. Rearrange the Rows. Place the machines that produce the same parts in adjacent rows. 3. Rearrange the Columns. Place the parts requiring the same machines in adjacent columns. 4. Using the rearranged parts-machines matrix to identify cells, the machines for that cell and the parts that will be produced in that cell.
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Service Facility Layouts
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Characteristics of Services
There may be a diversity of services provided. There are three dimensions to the type of service: Standard or custom design Amount of customer contact Mix of physical goods and intangible services There are three types of service operations: Quasi manufacturing Customer-as-participant Customer-as-product
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Characteristics of Service Facility Layouts
The encounter between the customer and the service must be provided for. The degree to which customer-related features must be provided varies with the amount of involvement and customer contact.
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Analyzing Service Facility Layouts
For quasi manufacturing services, approaches used to design and analyze process and product layouts may be used. Provide for customer waiting lines.
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Wrap-Up: World-Class Practice
Strive for flexibility in layouts Multi-job training of workers Sophisticated preventive-maintenance programs Flexible machines Empowered workers trained in problem solving Layouts small and compact Services follow the above practices plus incorporate customer needs in design
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End of Chapter 8
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