Process Layout. Process Layout. Chapter 7. Chapter 7

D D D D M M M M M M L L L L L L L L Process Layout Process Layout Chapter 7 Chapter 7

Process Layout Planning Def n Planning that involves decisions about physical arrangement of economic activity centers needed by a facility s s various processes. n economic activity center can be anything that consumes space.

Process Layout Planning Choices What centers should we include? Reflect process decisions Maximize productivity How much space and capacity for each center? Inadequate space can reduce productivity and privacy and create hazards. Excess space is costly and can isolate employees. Often use space standards to guide designers. How to configure the space? The amount of space, its shape, and elements in it tmosphere Where should each be located? Two aspects of location: relative and absolute. Relative location can affect travel time, material handling cost,, and communication. bsolute location can affect cost to change layout and customer reactions.

Relative Locations Frozen foods Bread Dry groceries Meats Vegetables (a) Original layout (note relative locations) Figure 7.2

bsolute Locations Meats Vegetables Dry groceries Frozen foods Bread Figure 7.2 (b) Revised layout same relative, different absolute

Layout Types Flexible-flow layout Organizes resources around the process and groups work stations or departments according to function Intermittent, low volume, high-variety Flow strategy of King Soopers cake line dvantages eneral purpose, flexible resources are less capital intensive Less vulnerable to changes in product mix or new market strategies Equipment utilization can be higher, because not dedicated to one product line Employee supervision can be more specialized Major challenge: locate centers so that they bring some order to the apparent chaos of divergent processes with jumbled work flows

Layout Types Line-flow layout layout in which workstations or departments are arranged in a linear path Dedicates resources to a product or closely related product family Repetitive, high-volume, continuous production Less need to decouple one operation from the next Workstations or departments are arranged in a linear path, which is consistent with the routing sequence of the product, although a straight line is not always best, layouts may take an L, O, S, or U shape Challenge in designing product layouts Minimize resources used to achieve desired output rate Balance tasks, equalize the workload assigned to resources

Layout Types rinding Forging Lathes Painting Welding Drills Office Milling machines Foundry Figure 7.3 (a) Layout of a job shop

Layout Types Station 1 Station 2 Station 3 Station 4 (b) Layout of a production line Figure 7.3

Layout Types Hybrid layout Combines elements of both divergent and line-flow processes Facility with both fabrication and assembly operations Cells and flexible automation roup technology (T) One worker-multiple machine (OWMM) stations Flexible manufacturing systems (FMS) Retail

roup Technology Lathing Milling Drilling L L M M D D L L M M D D rinding L L M M L L ssembly Receiving and shipping (a) Jumbled flows in a job shop without T cells Figure 7.5

roup Technology L L M D Cell 1 Cell 2 ssembly area Receiving L M Cell 3 L M D Shipping (b) Line flows in a job shop with three T cells Figure 7.5

Layout Types Fixed-position layout Service or manufacturing site is fixed in place. Resources come to the product, minimizing number of times product must be moved. Used for: Very large products as in building a new office complex, ships, roads, power plants, airplanes Service of fragile or bulky item

Layout Performance Customer satisfaction Using spatial language to show the competitive priorities Layout can influence Customer loyalty Emotional connect Customer convenience Level of sales Capital investment Materials handling Large flows should go short distances Includes stockpicking in warehouse, customer convenience in store, and communication in office Flexibility Facility remains desirable after significant changes Can be easily and inexpensively adapted in response to them Other criteria Labor productivity Equipment maintenance Work environment Organizational structure

Creating Hybrid Layouts One worker, multiple machines (OWMM) cell Is there enough volume to have a one-person line? One worker operates several different machines simultaneously to achieve line flow. The machines operate on their own for much of the cycle. The worker interacts with the machines as required, performing loading, unloading, or other operations that have not been automated. Benefits are similar to those of flow lines: lower WIP inventory, reduced frequency of setup, labor savings through low cost automation, simplified materials handling, reduced cycle time through overlapped operations.

One Worker, Multiple Machines Machine 2 Machine 3 Machine 1 Materials in Finished goods out Figure 7.4 Machine 5 Machine 4

Designing Flexible Flow Layouts ather Information Space requirements by center and available space and closeness factors. Tie space requirements to capacity and staffing plans. Calculate specific equipment and space needs for each center dd circulation space such as aisles. Consult with the managers and employees involved Closeness factors Which items need to be close to each other, and which should not be close to each other? Closeness Matrix table that gives the relative importance of each pair of centers being located close together. Closeness factors are indicators of the need for proximity based on an analysis of information flows and the need for face-to to-face meetings. For the general case of n centers in a layout, there are n-1 n closeness factors found either in the row or column assigned to the center. t a manufacturing plant, the closeness factor could be the number of trips between each pair of centers per day.

Office of Budget Management Department rea Needed (ft 2 ) 1. dministration 3,500 2. Social services 2,600 3. Institutions 2,0 4. ccounting 1,600 5. Education 1,500 6. Internal audit 3,0 Total 15,000 3 6 4 100' 1 2 5 Figure 7.6 150'

OBM Closeness Matrix 3 6 4 1 2 5 150' 100' Trips between Departments Department 1 2 3 4 5 6 1. dministration 3 6 5 6 10 2. Social services 8 1 1 3. Institutions 3 9 4. ccounting 2 5. Education 1 6. Internal audit Education needs to stay by library. dministration shouldn t t move because of boardroom.

Designing Flexible Flow Layouts ather Information (Continued) Other considerations bsolute location criteria departments fixed in place: relocation costs, foundations, noise levels, and so forth. Develop a block plan Most elementary way is trial and error, looking for patterns. Can supplement effort with computer help, such as the Process Layout Solver from the OM5 software. Use a closeness matrix when evaluating a block plan and spotting possible improvements in it.

Office of Budget Management Departments 1 and 6 close together 3 6 4 1 2 5 150' 100' 6 100' 1 5 Figure 7.7 150'

Office of Budget Management Departments 1 and 6 close together Departments 3 and 5 close together 3 6 4 1 2 5 150' 100' 6 3 100' 1 5 Figure 7.7 150'

Office of Budget Management Departments 1 and 6 close together Departments 3 and 5 close together Departments 2 and 3 close together 3 6 4 1 2 5 150' 100' 6 2 3 100' 1 4 5 Figure 7.7 150'

Designing Flexible Flow Layouts Consider Distance & Other Measures Euclidean distance is the straight-line, shortest distance between two points... as the crow flies, so to speak. Rectilinear distance assumes that the trip between two points is made with a series of 90 turns. Calculating a weighted-distance distance score Multiply each load (weight or trips per time period) between facilities times the distance (Euclidean or rectilinear) the load travels. The load- distance score is the sum of the products. Compare weighted-distance distance scores for alternative locations. Locations that generate big loads going short distances reduce ld. Of the points investigated, the location minimizing ld is the tentative best location. l Other factors, price of land, zoning, suitability of land for building, etc. may require consideration of other sites.

Distance Measures Euclidian Distance d B = (x( x B ) 2 + (y( y B ) 2 Rectilinear Distance d B = x x B + y y B

Office of Budget Management Load Distance nalysis Current Plan Proposed Plan 3 6 4 1 2 5 Dept Closeness Distance Distance Pair Factor, w d wd Score d wd Score 1,2 3 1 3 2 6 1,3 6 1 6 3 18 1,4 5 3 15 1 5 1,5 6 2 12 2 12 1,6 10 2 20 1 10 2,3 8 2 16 1 8 2,4 1 2 2 1 1 2,5 1 1 1 2 2 3,4 3 2 6 2 6 3,5 9 3 27 1 9 4,5 2 1 2 1 2 5,6 1 2 2 3 3 Example 7.2 ld = 112 ld = 82 150' 100'

Designing Flexible Flow Layouts Design a detailed layout More exact sizes, shapes, and detail; show aisles, stairs, machines, desks, and the like Other Decision Support Tools Spreadsheet approach of OM Explorer utomated Layout DEsign Program (LDEP): sequence of entering departments First, randomly choose one. Each successive department should have a strong closeness factor with one just entered. If no such relationship, choose randomly. Computerized Relative llocation of Facilities Technique (CRFT) Origins in space program and backboard wiring problem Successive pair exchanges Improvement heuristics, some of most effective to this day

Office of Budget Management 3 6 4 1 2 5 150' 100' Figure 7.8

Office of Budget Management 3 6 4 1 2 5 150' 100' Figure 7.9

Designing Flexible Flow Layouts Warehouse Layouts Out-and and-back selection pattern Simplest situation One item picked at a time; go from dock to storage area and back Decision rule to minimize score Equal areas: Place departments with most trips closest to the dock. Unequal areas: Place departments with highest trip-to to-area ratio closest to the dock. Various Options Shifting demand High density designs Different layout patterns Out-and and-back pattern Route collection system Batch picking system Zone system

Out-and and-back Warehouse Storage area 3 5 5 6 4 2 7 Dock isle 1 5 5 4 4 2 7 Storage area Figure 7.10

Zone Systems Zones Zones Control station Click to add title Shipping doors Tractor trailer Feeder lines Feeder lines Overflow Tractor trailer Figure 7.11

Designing Line Flow Layouts Common characteristics rranges work stations in sequence Line flow from station to station, with each performing a set of work elements Small or nonexistent inventory buffers Production line or assembly line Line Balancing Two basic questions How many stations are needed? What work elements are assigned to each? Immediate predecessors Precedence diagram ON network Cannot add a work element until all of its immediate predecessors s are shown. Desired output rate Matching demand to the production plan. Job specialization and number of shifts worked: typical automobile assembly plant is 60 cars per hour.

Designing Line Flow Layouts Cycle time / Takt Time Inverse of desired output rate; convert to same time units as given for work elements In general, c = 1 / r (r is desired production rate) Theoretical minimum number of stations Productivity is maximized by minimizing the number of stations. The ultimate in balance is when the sum of work-element times at each station equals c. The theoretical minimum assumes perfect balance, which may not be possible. In general, TM = (sum of work element times) / c (always rounded up to nearest integer)

Line Balancing reen rass, Inc. Big Broadcaster

Line Balancing Big Broadcaster Example 7.3 Work Element B C D E F H I Description Time (sec) Bolt leg frame to hopper None Insert impeller shaft 30 ttach axle 50 ttach agitator B ttach drive wheel 6 B ttach free wheel 25 C Mount lower post 15 C ttach controls 20 D, E Mount nameplate 18 F, Total 244 Immediate Predecessor(s)

Line Balancing Big Broadcaster Work Element Description Time (sec) Immediate Predecessor(s) Bolt leg frame to hopper None B Insert impeller shaft 30 C ttach axle 50 D ttach agitator B E ttach drive wheel 6 B F ttach free wheel 25 C Mount lower post 15 C H ttach controls 20 D, E I Mount nameplate 18 F, Total 244 Example 7.3

Line Balancing Big Broadcaster Work Element Description Time (sec) Immediate Predecessor(s) Bolt leg frame to hopper None B Insert impeller shaft 30 C ttach axle 50 D ttach agitator E ttach drive wheel 6 B F ttach free wheel 25 C Mount lower post 15 C H ttach controls 20 30 D, E I Mount nameplate 18 F, Total 244 Example 7.3

Line Balancing Big Broadcaster Work Element Description Time (sec) Immediate Predecessor(s) Bolt leg frame to hopper None B Insert impeller shaft 30 C ttach axle 50 D ttach agitator E ttach drive wheel 6 B F ttach free wheel 25 C Mount lower post 15 C H ttach controls 20 30 D, E I Mount nameplate 18 F, Total 244 C 50 Example 7.3

Line Balancing Big Broadcaster Work Element Description Time (sec) Immediate Predecessor(s) Bolt leg frame to hopper None B Insert impeller shaft 30 C ttach axle 50 D ttach agitator E ttach drive wheel 6 B F ttach free wheel 25 C Mount lower post 15 C H ttach controls 20 30 D, E I Mount nameplate 18 F, Total 244 C 50 D E 6 Example 7.3

Line Balancing Big Broadcaster Work Element Description Time (sec) Immediate Predecessor(s) Bolt leg frame to hopper None B Insert impeller shaft 30 C ttach axle 50 D ttach agitator E ttach drive wheel 6 B F ttach free wheel 25 C Mount lower post 15 C H ttach controls 20 30 D, E I Mount nameplate 18 F, Total 244 Example 7.3 C 50 F 25 D 15 E 6 H 20 I 18

Line Balancing Big Broadcaster B 30 D E H 20 C F 25 6 Desired output rate = 20/week Plant operates hours/week 50 I 18 Example 7.4 15

Line Balancing Big Broadcaster B 30 D E H 20 C F 25 6 Desired output rate = 20/week Plant operates hours/week 50 r = 20/ = 60 units/hour I 18 Example 7.4 15

Line Balancing Big Broadcaster B 30 D E H 20 C 50 F 25 6 Desired output rate = 20/week Plant operates hours/week I r = 20/ = 60 units/hour Example 7.4 15 18 c = 1/60 = 1 minute/unit = 60 seconds/unit

Line Balancing Big Broadcaster c = 60 seconds/unit Example 7.4 C 50 B 30 F 25 D 15 E 6 H 20 Desired output rate = 20/week Plant operates hours/week TM = 244 seconds/60 seconds = 4.067 or 5 stations I 18

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.4 C 50 B 30 F 25 D 15 E 6 H 20 Desired output rate = 20/week Plant operates hours/week TM = 244 seconds/60 seconds = 4.067 or 5 stations I 18 Efficiency = [244\5(60)]100 = 81.3%

Designing Line Flow Layouts Finding a solution Step 1. Begin with station k = 1. Make a list of candidate work elements to assign to station k. Each candidate must satisfy three conditions: It has not yet been assigned to this or any previous station. ll its predecessors have been assigned to this or a previous station. Its time cannot exceed the station s s idle time, which accounts for all work elements already assigned. If none has been assigned, the station s s idle time equals the cycle time. If no such candidates can be found, go to step 4. Step 2. Pick a candidate. Two decision rules are commonly used for selecting from the candidate list. Pick the candidate with the longest work-element time. Works in the most difficult ones first, saving the smaller ones for rounding out each station. Pick the candidate having the largest number of followers. Keeps options open for rest of solution. ssign the candidate chosen to station k. If there are ties, break them randomly.

Designing Line Flow Layouts Finding a solution (Continued) Step 3. Calculate the cumulative time of all tasks assigned so far to station k. Subtract this total from the cycle time to find d the station's idle time. o to step 1, and generate a new list of candidates. Step 4. If some work elements are unassigned, but none are candidates for station k, start a new station k + 1 and go to step 1. Otherwise, you have a complete solution.

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.5 C 50 B 30 F 25 D 15 E 6 H 20 Cumm Idle Station Candidate Choice Time Time I 18

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.5 C 50 B 30 F 25 D 15 E 6 H 20 Cumm Idle Station Candidate Choice Time Time S1 20 I 18

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.5 S1 C 50 B 30 F 25 D 15 E 6 H 20 Cumm Idle Station Candidate Choice Time Time S1 20 I 18

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.5 S1 C 50 B 30 F 25 D 15 E 6 H 20 Cumm Idle Station Candidate Choice Time Time S1 20 S2 B,C C 50 10 I 18

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.5 S1 S2 C 50 B 30 F 25 D 15 E 6 H 20 Cumm Idle Station Candidate Choice Time Time S1 20 S2 B,C C 50 10 I 18

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% Example 7.5 S1 S2 C 50 B 30 S3 F 25 D 15 E 6 H 20 Cumm Idle Station Candidate Choice Time Time S1 20 S2 B,C C 50 10 S3 B,F, B 30 30 E,F, 18 F 55 5 I

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% S1 S2 C 50 B 30 S3 F 25 D E 6 H 20 I 18 Example 7.5 15

Line Balancing Big Broadcaster c = 60 seconds/unit TM = 5 stations Efficiency = 81.3% S1 S2 C 50 B 30 S3 F 25 D S4 E 6 H 20 S5 I 18 Figure 7.13 15

Designing Line Flow Layouts Other Considerations Pacing llows material handling to be automated Requires less storage area Is less flexible in handling unexpected delays Behavioral factors Controversial aspect of line-flow layouts Employees generally favor inventory buffers as a means of avoiding mechanical pacing Number of models produced Mixed-model line Modify cycle times May increase efficiency Rebalancing frequency