ChIII-ProcessSelection_I-Sp10

ChIII-ProcessSelection_I-Sp10 - 1/27/2010 MGMT 36100...

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Unformatted text preview: 1/27/2010 MGMT 36100 Operations Management (OM) III: Process Selection – Part I Process/ Production systems types: types: These can be classified in different ways. Classifications I Make-toMake-to-order Assemble-to-order e-toMake-toMake-to-stock Classifications II Job Shop Batch Repetitive Continuous ProcessSelection-Sp10 1 ProcessSelection-Sp10 2 MGMT 361000 MGMT 361000 Classifications I Make-toMake-to-order Process Classifications I Assemble-toAssemble-to-order Process Raw Material Manufacture Assemble Ship Manufacture W.I.P. Assemble Ship Delivery Lead Time Order Received Delivery Date Characteristics: Mass Customization, medium delivery times, medium costs Delivery Lead Time Characteristics: Customization, Long delivery times, high costs Order Received Delivery Date ProcessSelection-Sp10 3 ProcessSelection-Sp10 4 MGMT 361000 MGMT 361000 Classifications I Make-toMake-to-stock Process Production Systems Classifications II Job Shop Emergency Room Commercial Bakery Automatic Carwash Petroleum Refinery Manufacture Assemble Ship Repetitive Characteristics: standardization, short delivery times, low costs Delivery Lead Time Continuous Delivery Date Order Received Variety W.I.P. Batch Volume 5 ProcessSelection-Sp10 6 ProcessSelection-Sp10 MGMT 361000 MGMT 361000 ProcessSelection‐Sp10 1 1/27/2010 Classification II: Comparison Process Design We will consider assembly lines. Design Management New product learning period. Day to day: absenteeism, motivation, quality, equipment failure equipment failure. Improvements Better balancing. Better methods. Time reduction. Job shop Batch Repetitive Description Customized SemiSemiStandardized standardized Advantages Wide Variety Flexible Low unit cost, high volume, efficient Disadvantages Slow, high Moderate Low unit cost, cost/unit , flexibility, complex moderate high cost of planning & scheduling downtime scheduling complexity Continuous Highly standardized Very efficient, very high volume Very rigid, lack of variety, costly to change, very high cost of downtime 7 Single model: 26” TV sets. I-pods / ovens I(with different colors). Mixed models: Vans and sedans. and sedans. Layout: Serial, cell,.. Conveyor, manual. Equipment selection. Line balancing. We will discuss only Assembly Line Balancing for single model. How do assemblies for - airplane, sandwich, automobile, furniture, p.c. p.c. differ? ProcessSelection-Sp10 Unidirectional flow 8 ProcessSelection-Sp10 MGMT 361000 MGMT 361000 Suppose we want to assemble chairs. Precedence Precedence information Task Description 1 2 3 4 5 6 7 8 Set legs Unpack seat Set back-rest backPrepare box Full assembly Inspect Pack Pred. Time 3, 5 6 4, 7 75 90 60 60 Example Precedence diagram Precedence diagram for chair assembly Task Description Time 1 2 1 5 2 6 3 7 8 1 2 3 4 5 6 Set legs Unpack seat Set back-rest backPrepare box Join legs & seat Full assembly 75 90 60 60 50 5 6 3 7 8 4 Join legs & seat 1, 2 50 If we do one task per station, we min CT 35 we get min. CT = 90 [sec/unit]. 90 40 If we do all tasks in 1 station, we get max. CT = 500 [sec/unit]. Total time (sec.) 500 Suppose the desired rate: 24 chairs / hour 35 Desired rate: 24 chairs / hour 7 Inspect 40 Target Cycle Time: Ti 8 Pack 90 = 3600 [sec/hr] / 24 [units / hr] Total time (sec.) 500 = 150 [sec/unit] Minimum number of stations needed (theoretically): Each station will do the work for 150 sec (max). So, 500/150 = 3.33. That means, we need at least 4 stations. Minimum cycle time = 90 [sec/unit]. Maximum cycle time = 500 [sec/unit]. One One task / station All All tasks in 1 station 10 4 Target Cycle Time: = 3600 [sec/hr] / 24 [units / hr] = 150 [sec/unit] ProcessSelection-Sp10 9 ProcessSelection-Sp10 MGMT 361000 MGMT 361000 Effective Cycle Time 75 = maximum station time 50 40 1 2 90 Here are two more designs: Target CT = 150 sec. / unit 5 90 = 150 sec/unit 7 6 35 60 8 Effective CT should not exceed Target CT Efficiency = 100 * (total task time) . No. of stations * Effective CT = 100 * (500) = 83.3% 4 * 150 150 St. 4 75 75 3 60 4 1 50 40 50 40 1 2 90 5 6 35 90 5 2 90 90 7 6 35 60 7 8 Target Cycle Time: Ti 150 [sec/unit] St. 1 St. 2 8 3 3 St. 3 60 1,5 125 4 60 6,7 75 4,8 150 60 4 2, 3 150 1, 5 125 4, 6, 7 135 8 90 2,3 150 1,3 135 2,5 140 4,6 95 7,8 130 Effective CT = 150 sec. / unit Efficiency = 83.3% ProcessSelection-Sp10 11 ProcessSelection-Sp10 Effective CT = 140 sec. / unit Efficiency = 89.3% 12 MGMT 361000 MGMT 361000 ProcessSelection‐Sp10 2 1/27/2010 Suppose Target CT = 130 [sec/unit] Minimum number of stations needed (theoretically): Each station will do the work for 150 sec (max). So, 500/130 = 3.85. That means, we need at least 4 stations. Priority rule SPT: Smaller the processing time, higher the priority. 75 Total time = 500 [sec/unit] 1 2 90 50 40 5 90 7 6 35 60 8 Example 1 We used this in Ch. 2 Suppose we want 0 to produce 420 units in 7 hours. 1, 20 3, 10 2, 50 4, 40 6, 30 5, 30 7, 20 3 SPT order order 60 4 4 12 8 6 7 53 This means that we need to produce 1 unit every minute, or Target CT = 60 [sec/unit] Total task time = (20 + 50 + 10 + 40 + 30 + 30 + 20) = 200 [sec] We need at least (200 / 60 ) We 200 4 stations stations stations tat SPT: Smaller the processing time, higher the priority SPT order 3 1 7 5 6 4 2 Default rule for tie-breaking: select smallest task number first. tieselect We will now add a “dummy task 0”, to our diagram (shown in green). Eligible task: A task is eligible if all tasks that precede this task have been selected. Which tasks are eligible in the diagram? ProcessSelection-Sp10 13 ProcessSelection-Sp10 14 MGMT 361000 MGMT 361000 Example 1 Part (a): SPT rule 0 Target CT = 60 [sec/unit] 1, 20 3, 10 2, 50 4, 40 6, 30 5, 30 7, 20 SPT order St I II III IV V Selected Cum. Time Eligible 1 2,3 5 4 6, 7 20 50 , 60 30 40 30 , 50 1 20 1, 2 / 2 3 1 7 5 6 4 2 As soon a task is selected, update everything. Effective cycle time: 60 [sec./unit]. Efficiency: Efficiency: (100 * 200) / (5 * 60) = 66.7%. 5 30 4 40 6, 7 50 2 / 3,5 / 5, 4 5, 5, 4 / 4 4 /6 6 /7 2, 3 60 MGMT 361000 ProcessSelection-Sp10 15 ProcessSelection‐Sp10 3 ...
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