Process Selection and Facility Layout

Learning Objectives Explain the strategic importance of process selection. Explain the influence that process selection has on an organization. Describe the basic processing types. Discuss automated approaches to processing.

Learning Objectives List some reasons for redesign of layouts. Describe the basic layout types. List the main advantages and disadvantages of product layouts and process layouts. Solve simple line-balancing problems.

Introduction Process selection Deciding on the way production of goods or services will be organized Major implications Capacity planning Layout of facilities Equipment Design of work systems

Process Selection and System Design Forecasting Product and Service Design Technological Change Capacity Planning Process Selection Facilities and Equipment Layout Work Design

Process Strategy Key aspects of process strategy Capital intensive (mix of equipment/labor) Process flexibility Design Volume Technology

Kinds of Technology Operations management is primarily concerned with three kinds of technology: Product and service technology Process technology Information technology All three have a major impact on: Costs Productivity Competitiveness

Technology Competitive Advantage Innovations in Products and services Cell phones PDAs Wireless computing Processing technology Increasing productivity Increasing quality Lowering costs

Process Selection Variety How much Flexibility What degree Volume Expected output Batch Job Shop Repetitive Continuous

Process Types Job shop Batch Repetitive/assembly line Continuous Small scale Batch Moderate volume Repetitive/assembly line High volumes of standardized goods or services Continuous Very high volumes of non-discrete goods

Product and Service Processes Process Type Job Shop Appliance repair Emergency room Ineffective Batch Commercial baking Classroom Lecture Repetitive Automotive assembly Automatic carwash Continuous (flow) Steel Production Water purification Low Volume High Volume

Product – Process Matrix Dimension Job shop Batch Repetitive Continuous Job variety Very High Moderate Low Very low Process flexibility Unit cost Volume of output High Other issues; scheduling work-in-process inventory labor skill

Process and Product Profiling Process selection can involve substantial investment in Equipment Layout of facilities Product profiling: Linking key product or service requirements to process capabilities Key dimensions Range of products or services Expected order sizes Pricing strategies Expected schedule changes Order winning requirements

Automation Automation: Machinery that has sensing and control devices that enables it to operate Fixed automation Programmable automation

Automation Computer-aided design and manufacturing systems (CAD/CAM) Numerically controlled (NC) machines Robot Manufacturing cell Flexible manufacturing systems(FMS) Computer-integrated manufacturing (CIM)

Facilities Layout Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system Product layouts Process layouts Fixed-Position layout Combination layouts

Objective of Layout Design Facilitate attainment of product quality Use workers and space efficiently Avoid bottlenecks Minimize unnecessary material handling costs Eliminate unnecessary movement of workers or materials Minimize production time or customer service time Design for safety

Importance of Layout Decisions Requires substantial investments of money and effort Involves long-term commitments Has significant impact on cost and efficiency of short-term operations

The Need for Layout Design Inefficient operations For Example: High Cost Bottlenecks Changes in the design of products or services The introduction of new products or services Accidents Safety hazards

The Need for Layout Design (Cont’d) Changes in environmental or other legal requirements Changes in volume of output or mix of products Changes in methods and equipment Morale problems

Basic Layout Types Product layouts Process layouts Fixed-Position layout Combination layouts

Basic Layout Types Product layout Process layout Fixed Position layout Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow Process layout Layout that can handle varied processing requirements Fixed Position layout Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

Product Layout Used for Repetitive or Continuous Processing Raw materials or customer Station 1 Station 2 Station 3 Station 4 Finished item Material and/or labor Material and/or labor Material and/or labor Material and/or labor

Advantages of Product Layout High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and equipment Established routing and scheduling Routine accounting, purchasing and inventory control

Disadvantages of Product Layout Creates dull, repetitive jobs Poorly skilled workers may not maintain equipment or quality of output Fairly inflexible to changes in volume Highly susceptible to shutdowns Needs preventive maintenance Individual incentive plans are impractical

A U-Shaped Production Line 1 2 3 4 5 6 7 8 9 10 In Out Workers Ease to cross-travel of workers and vehicles More compact More communication between workers

Used for Repetitive Processing or Continuous Processes Product Layout Product Layout (sequential) Work Station 1 Station 2 Station 3 Used for Repetitive Processing or Continuous Processes

Used for Intermittent processing Job Shop or Batch Processes Process Layout Process Layout (functional) Dept. A Dept. B Dept. D Dept. C Dept. F Dept. E Used for Intermittent processing Job Shop or Batch Processes

Advantages of Process Layouts Can handle a variety of processing requirements Not particularly vulnerable to equipment failures Equipment used is less costly Possible to use individual incentive plans

Disadvantages of Process Layouts In-process inventory costs can be high Challenging routing and scheduling Equipment utilization rates are low Material handling slow and inefficient Complexities often reduce span of supervision Special attention for each product or customer Accounting and purchasing are more involved

Fixed Position Layouts Fixed Position Layout: Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed. Nature of the product dictates this type of layout Weight Size Bulk Large construction projects

Cellular Layouts Cellular Production Group Technology Layout in which machines are grouped into a cell that can process items that have similar processing requirements Group Technology The grouping into part families of items with similar design or manufacturing characteristics

Functional vs. Cellular Layouts Dimension Functional Cellular Number of moves between departments many few Travel distances longer shorter Travel paths variable fixed Job waiting times greater Throughput time higher lower Amount of work in process Supervision difficulty Scheduling complexity Equipment utilization

Service Layouts Warehouse and storage layouts Retail layouts Office layouts

Design Product Layouts: Line Balancing Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.

Cycle Time Cycle time is the maximum time allowed at each workstation to complete its set of tasks on a unit.

Determine Maximum Output

Determine the Minimum Number of Workstations Required

Precedence Diagram a b c d e Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements A Simple Precedence Diagram a b c d e 0.1 min. 0.7 min. 1.0 min. 0.5 min. 0.2 min.

Example 1: Assembly Line Balancing Arrange tasks shown in Figure 6.10 into three workstations. Use a cycle time of 1.0 minute Assign tasks in order of the most number of followers

Example 1 Solution Workstation Time Remaining Eligible Assign Task Revised Time Remaining Station Idle Time 1 1.0 0.9 0.2 a, c c none a - 2 b 0.0 3 0.5 0.3 d e

Calculate Percent Idle Time Efficiency = 100 – Percent idle time

Line Balancing Rules Some Heuristic (intuitive) Rules: Assign tasks in order of most following tasks. Count the number of tasks that follow Assign tasks in order of greatest positional weight. Positional weight is the sum of each task’s time and the times of all following tasks.

Example 2 Plan to produce 400 units in 1 day (8 hours) c d a b e f g h 0.2 0.3 0.8 0.6 1.0 0.4 Immediate Task time Task follower (min) a b 0.2 b e 0.2 c d 0.8 d f 0.6 e f 0.3 f g 1.0 g h 0.4 h end 0.3

Solution to Example 2 a b e f d g h c Station 1 Station 2 Station 3

Bottleneck Workstation 1 min. 2 min. 30/hr. Bottleneck

Parallel Workstations 1 min. 2 min. 60/hr. 30/hr. Parallel Workstations

Copier Example Performance Task Must Follow Time Task Listed Task (minutes) Below A 10 — B 11 A C 5 B D 4 B E 12 A F 3 C, D G 7 F H 11 E I 3 G, H Total time 66 This means that tasks B and E cannot be done until task A has been completed

Copier Example Performance Task Must Follow Time Task Listed Task (minutes) Below A 10 — B 11 A C 5 B D 4 B E 12 A F 3 C, D G 7 F H 11 E I 3 G, H Total time 66 10 11 12 5 4 3 7 C D F A B E G I H Figure 9.13

Production time available per day Minimum number of workstations Copier Example 480 available mins per day 40 units required Performance Task Must Follow Time Task Listed Task (minutes) Below A 10 — B 11 A C 5 B D 4 B E 12 A F 3 C, D G 7 F H 11 E I 3 G, H Total time 66 Cycle time = Production time available per day Units required per day = 480 / 40 = 12 minutes per unit I G F C D H B E A 10 11 12 5 4 3 7 Figure 9.13 Minimum number of workstations = ∑ Time for task i Cycle time n i = 1 = 66 / 12 = 5.5 or 6 stations

Copier Example Line-Balancing Heuristics 1. Longest task time Choose the available task with the longest task time 2. Most following tasks Choose the available task with the largest number of following tasks 3. Ranked positional weight Choose the available task for which the sum of following task times is the longest 4. Shortest task time Choose the available task with the shortest task time 5. Least number of following tasks Choose the available task with the least number of following tasks 480 available mins per day 40 units required Cycle time = 12 mins Minimum workstations = 5.5 or 6 Performance Task Must Follow Time Task Listed Task (minutes) Below A 10 — B 11 A C 5 B D 4 B E 12 A F 3 C, D G 7 F H 11 E I 3 G, H Total time 66 I G F C D H B E A 10 11 12 5 4 3 7 Figure 9.13 Table 9.4

Copier Example 480 available mins per day 40 units required Cycle time = 12 mins Minimum workstations = 5.5 or 6 Performance Task Must Follow Time Task Listed Task (minutes) Below A 10 — B 11 A C 5 B D 4 B E 12 A F 3 C, D G 7 F H 11 E I 3 G, H Total time 66 I G F H C D 10 11 12 5 4 3 7 B E A Station 1 Station 2 Station 3 Station 5 Station 4 Station 6 Figure 9.14

(actual number of workstations) x (largest cycle time) Copier Example 480 available mins per day 40 units required Cycle time = 12 mins Minimum workstations = 5.5 or 6 Performance Task Must Follow Time Task Listed Task (minutes) Below A 10 — B 11 A C 5 B D 4 B E 12 A F 3 C, D G 7 F H 11 E I 3 G, H Total time 66 Efficiency = ∑ Task times (actual number of workstations) x (largest cycle time) = 66 minutes / (6 stations) x (12 minutes) = 91.7%

Example 1 Balance by 1 Longest task time method 2 RPW method Performance Task Must Follow Time Task Listed Task (minutes) Below Balance by 1 Longest task time method 2 RPW method 1 0.20 - 2 0.40 - 3 0.70 1 4 0.10 1,2 5 0.30 2 6 0.11 3 7 0.32 3 8 0.60 3,4 9 0.27 6,7,8 10 0.38 5,8 11 0.50 9,10 12 0.12 11 Total time 4 min.

Example 2 Balance by 1 Longest task time method 2 RPW method Performance Task Must Follow Time Task Listed Task (minutes) Below Balance by 1 Longest task time method 2 RPW method 1 0.5 - 2 0.3 1 3 0.8 1 4 0.2 2 5 0.1 2 6 0.6 3 7 0.4 4,5 8 0.5 3,5 9 0.3 7,8 10 0.6 6,9 Total time 4.3 min.

Designing Process Layouts Information Requirements: List of departments Projection of work flows Distance between locations Amount of money to be invested List of special considerations Location of key utilities

Example 3: Interdepartmental Work Flows for Assigned Departments 1 3 2 30 170 100 A B C

Functional Layout Gear cutting Mill Drill Lathes Grind Heat treat Assembly 111 333 222 444 1111 2222 3333 333333333 44444 333333 22222

Cellular Manufacturing Layout 1111 -1111 2222 - 2222 Assembly 3333 - 3333 4444 - 4444 Lathe Mill Drill Heat treat Gear cut Grind

Linear Programming Used to obtain optimal solutions to problems that involve restrictions or limitations, such as: Materials Budgets Labor Machine time

Linear Programming Model Objective Function: mathematical statement of profit or cost for a given solution Decision variables: amounts of either inputs or outputs Feasible solution space: the set of all feasible combinations of decision variables as defined by the constraints Constraints: limitations that restrict the available alternatives Parameters: numerical values

Graphical Linear Programming Graphical method for finding optimal solutions to two-variable problems Set up objective function and constraints in mathematical format Plot the constraints Identify the feasible solution space Plot the objective function Determine the optimum solution

Linear Programming Example Objective - profit Maximize Z=60X1 + 50X2 Subject to Assembly 4X1 + 10X2 <= 100 hours Inspection 2X1 + 1X2 <= 22 hours Storage 3X1 + 3X2 <= 39 cubic feet X1, X2 >= 0

Linear Programming Example

Linear Programming Example

Linear Programming Example Inspection Storage Assembly Feasible solution space

Linear Programming Example Z=900 Z=300 Z=600

Solution The intersection of inspection and storage Solve two equations in two unknowns 2X1 + 1X2 = 22 3X1 + 3X2 = 39 X1 = 9 X2 = 4 Z = $740

Solutions and Corner Points Feasible solution space is usually a polygon Solution will be at one of the corner points Enumeration approach: Substituting the coordinates of each corner point into the objective function to determine which corner point is optimal.

Simplex Method Simplex: a linear-programming algorithm that can solve problems having more than two decision variables

MS Excel Worksheet for Microcomputer Problem

MS Excel Worksheet Solution