ChIII-ProcessSelection_SingleSlide

ChIII-ProcessSelection_SingleSlide - MGMT MGMT 36100...

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Unformatted text preview: MGMT MGMT 36100 Operations Management (OM) III: Process Selection ProcessSelection 1 Process/ Process/ Production systems types: types: These can be classified in different ways. diff Classifications I Make-toMake-to-order Assemble-toAssemble-to-order Make-to-stock e- o- Classifications II Job Shop Batch Repetitive Continuous ProcessSelection 2 Classifications Classifications I Make-to-order Process e- o- Raw Material Manufacture Assemble Ship Delivery Lead Time Order Received Received Delivery Date Date Characteristics: Customization, Long delivery times, high costs ProcessSelection 3 Classifications Classifications I Assemble-to-order order Process Process Manufacture W.I.P. Assemble Ship Characteristics: Mass Customization medium Customization, medium delivery delivery times, medium costs Delivery Lead Time Order Received Delivery Date ProcessSelection 4 Classifications Classifications I Make-to-stock stock Process Process W.I.P. Manufacture Assemble Ship Characteristics: standardization, Characteristics: short delivery times, low costs Delivery Lead Time Delivery Date Order Received ProcessSelection 5 Production Production Systems Classifications II Job Shop Emergency Room Commercial Bakery Automatic Carwash Petroleum Refinery Repetitive Repetitive Continuous Variety Batch Volume ProcessSelection 6 Classification Classification II: Comparison Job shop shop Batch Repetitive Description Customized SemiSemiStandardized standardized Advantages Wide Variety Flexible Variety Low unit Low unit cost, cost, high volume, efficient efficient Disadvantages Slow, high Moderate Low unit cost, cost/unit , flexibility, complex complex moderate moderate high cost of high cost of planning planning & scheduling downtime scheduling downtime scheduling complexity Continuous Highly standardized Very efficient Very efficient, very high volume Very rigid, lack of variety, costly variety, costly to to change, very high cost of downtime 7 ProcessSelection Process Process Selection: How to organize production of goods or services? How to organize production of goods or services? Major implications • • • • Capacity planning Layout of facilities Equipment Design of work systems ProcessSelection 8 Process Process Design We will consider assembly lines. will consider assembly lines Design Single model: 26” TV sets. I-pods / ovens I(with different colors). Mixed Mixed models: Vans and sedans. Layout: Serial, cell,.. Conveyor, Conveyor, manual. Equipment selection. Line balancing. Line balancing. Management Management New product learning period. Day to day: absenteeism, motivation, quality, equipment failure. Improvements Improvements Better balancing. Better methods. Time reduction. We will discuss only Assembly Line Balancing Balancing for single model. How do assemblies for - airplane, sandwich, automobile, furniture, p.c. p.c. differ? ProcessSelection Unidirectional flo Unidirectional flow 9 Suppose Suppose we want to assemble chairs. Precedence information 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 1 2 Precedence diagram diagram 5 6 3 7 8 4 Join legs & seat 1, 2 50 If we do one task per station, 35 we get min. CT = 90 [sec/unit]. 40 If we do all tasks in 1 station, we we get max. CT = 500 [sec/unit]. 90 Total time (sec.) 500 Suppose the desired rate: 24 chairs / hour Target Cycle Time: = 3600 [sec/hr] / 24 [units / hr] = 150 [sec/unit] ProcessSelection 10 Example Example 1 5 2 Precedence diagram for chair assembly Task Description Time 1 2 3 4 5 6 Set legs Unpack seat Set back-rest backPrepare box Join legs & seat Full assembly assembly 75 90 60 60 50 35 7 6 8 3 4 Desired rate: 24 chairs / hour 7 Inspect 40 Target Cycle Time: 8 Pack 90 3600 [sec/hr] 24 [units hr] = 3600 [sec/hr] / 24 [units / hr] Total time (sec.) 500 = 150 [sec/unit] 150 Minimum number of stations needed (theoretically): Each station will do the work for 150 sec (max). So, 500/150 = 3.33. Each station will do the work for 150 sec (max). So, 500/150 3.33. That That means, we need at least 4 stations. Minimum cycle time = 90 [sec/unit]. Maximum cycle time = 500 [sec/unit]. ProcessSelection One task / station All tasks in 1 station 11 Effective Effective Cycle Time 75 = maximum station time 50 40 1 2 90 5 90 = 150 sec/unit 7 6 35 60 8 Effective CT should not exceed exceed Target CT Efficiency = 100 * (total task time) (total task time) . No. of stations * Effective CT = 100 * (500) = 83.3% 4 * 150 150 St. 4 3 60 4 Target Cycle Time: Time: 150 [sec/unit] St. 1 St. 2 St. 3 2, 3 150 1, 5 125 4, 6, 7 135 8 90 ProcessSelection 12 Here Here are two more designs: Target CT = 150 sec. / unit Target CT 150 sec. unit 75 75 1 50 40 50 1 2 90 40 5 6 35 90 5 2 90 90 7 6 35 60 7 8 8 3 3 2,3 150 60 1,5 125 4 60 6,7 75 4,8 150 60 4 1,3 135 2,5 140 4,6 95 7,8 130 Effective CT = 150 sec. / unit Efficiency = 83.3% ProcessSelection Effective CT = 140 sec. / unit Efficiency = 89.3% 13 Suppose Target CT = 130 [sec/unit] Minimum number of stations 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 Rules: 1: SPT: Smaller the processing time, higher processing time, higher the the priority 75 75 Total Total time = 500 [sec/unit] 1 2 90 50 40 5 90 7 6 35 60 8 3 60 4 SPT order 6753 412 8 For tie-breaking we can use rules such as: select smallest / largest tietask number first largest number of followers etc task number first, largest number of followers, etc. Eligible Eligible task: A task is eligible if all tasks that precede this task have been selected. ProcessSelection 14 Example Example 1 We used this in Ch. 2 Suppose we want 0 to to produce 420 units in 7 hours. 1, 20 3, 10 2, 50 50 4, 40 6, 30 5, 30 30 7, 20 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 ) 4 stations Priority Rules: (use appropriate tie-breaker) 1: SPT: Smaller the processing time, higher the priority SPT order 3 1 7 5 6 4 2 2: LPT: Higher the processing time, higher the priority LPT Hi th ti hi th For tie-breaking we can use rules such as: select smallest / largest tietask number first, largest number of followers, etc. We will now add a “dummy task 0”, to our diagram (shown in green). “d 0” di ProcessSelection 15 Example 1 Part (a): SPT rule A task is eligible task is eligible if if all tasks that 0 precede this task have been task have been selected. selected. 1, 1, 20 3, 3, 10 2, 50 4, 40 Target CT = 60 [sec/unit] 6, 6, 30 7, 20 5, 30 SPT order St I II II III IV 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 Effective cycle time: 60 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 ProcessSelection 16 Example 1 Part (b): LPT rule Target CT = 60 [sec/unit] Total task time = 200 [sec] Lower bound: 4 stations LPT order Station 1, 1, 20 3, 10 2, 50 50 6 1 7 3 4, 40 6, 30 5, 30 30 7, 20 2 4 5 Effective CT: 60 [sec./unit]. 60 Efficiency: (100 * 200) / (4 * 60) = 83.3%. 83.3%. Selected Cum. Time Eligible I II III IV IV V 2 ,3 5 ,1 4 6 ,7 50 , 60 30 , 50 40 30 , 50 2,1 / 5, 1, 3 / 5,1 5,1 / 1 / 4 4 /6 6 /7 ProcessSelection 2, 3 60 5, 1 50 4 40 6, 7 50 17 Assembly Assembly Line Balancing (ALB) Objective: To get a layout with minimum number of minimum stations stations for a specified target cycle time. Procedure: Procedure: Start with the precedence diagram. Determine target CT. Select priority rule (SPT LPT RPW) and tie breaking rule Select a priority rule (SPT, LPT, RPW) and a tie-breaking rule. Start with work station 1. Include as many eligible tasks as possible in each work station without exceeding target cycle time. If a task cannot be selected, ith ti If skip and try the next one. If no eligible task can be selected, create a new station. If all tasks have been included, stop. Eligible task: A task is eligible if all tasks that precede this task have been selected and there are no other restrictions. ProcessSelection 18 Example Example 2 - SPT Need 1800 units in Need 1800 units in 7.5 hours. hours Target CT = 15 [sec. /unit] Total task time = 74 sec. Need at least 5 stations. at least stations St Selected C. Time Eligible I II 2, 6 1, 4 , 5 5 , 10 10 01 6 04 4 5 5 8 09 05 02 5 06 5 10 12 2,1,3 / 6,1,3 /1,3 6, 6 ,10,15 1, 3 / 4,5,3 / 5,9,3 / 10,9,3 5 10, 9, 3 10 03 5 07 9 III 10 08 6 6 11 We will show the remaining solution in one click. SPT order ProcessSelection 4 2 5 6 7 10 1 8 11 9 12 3 19 01 6 04 05 4 5 5 8 09 Example 2 - SPT Target CT = 15 [sec. /unit] /unit] St I II Selected C. Time Eligible 2, 6 1 , 4, 5 5, 10 2,1,3 /6,1,3 /1,3 02 5 06 5 10 12 6,10, 15 1, 3 / 4,5,3 / 5,9,3 5, 13 10, 15 6, 12 9 10, 9, 3 / 9, 3 / 3 9, 3 / 7, 8 / 8 7, 8 / 11 / 12 11 12 9 Efficiency: 100*[ 74/ (6*15)] = 82.2% 3, 7 15 8, 11 11 12 12 9 10 03 08 III 10, 9 IV 3, 7 V 8, 11 VI 12 5 07 6 11 9 6 Effective CT: 15 sec /unit. 2, 6 10 ProcessSelection 1, 4, 5 15 10, 9 13 20 Example Example 2 – SPT, continued Target CT = 15 [sec. /unit] /unit] St Select Cum. T Eligible I 2,6 II 1,4,5 5,10 2,1,3 / 6,1,3 / 1,3 6,1,3 1,3 6,10,15 1, 3 / 4,5,3 /5,9,3 01 6 04 4 5 5 09 8 05 What if tasks 2 & 6 cannot be done in the same station? 02 5 06 5 10 12 9 07 5 10 We make task 6 temporarily ineligible for the current station. 03 08 6 11 6 St Select Cum. T II SPT order ProcessSelection Eligible 5,6,9,3 I 2 1 4 5 11 15 2, 1, 3 / 6,1,3 / 4,5,6,3 / 5, 6, 9, 3 6,1,3 4,5,6 4 2 5 6 7 10 1 8 11 9 12 3 21 Back to Ex. 1 110 Part (c): RPW rule Target CT = 60 [sec/unit] Total task time = 200 [sec] Lower bound: 4 stations 1, 20 4, 40 3, 10 90 50 6, 30 20 7, 20 180 2, 50 100 5, 30 80 4 5 6 7 RPW order Station Selected Cum. Time Eligible 2 1 3 I II III IV 2 ,3 1,4 5 ,6 7 50 , 60 20 , 60 30 , 60 20 2, 1 / 1, 3, 5 / 1, 5 1, 5 / 4, 5 / 5 5 /6 /7 7 2, 3 60 1, 4 60 5, 6 60 After getting RPW order, do not use weights. Use only task times. Effective CT: 60 [sec./unit]. Efficiency: 100 * 200 / (60 * 4) = 83.3%. 7 20 ProcessSelection 22 Ex. 1 Which layout do you prefer? you prefer? 1, 20 3, 10 2, 50 5 30 4 40 40 5, 6 60 3, 4 50 4 40 6, 7 50 50 7 20 6, 7 50 6, 7 50 4, 40 6, 30 5, 30 7, 20 1 20 2, 3 60 60 2, 3 60 2 50 ProcessSelection 2, 3 60 5, 1 50 50 1, 4 60 1, 5 50 How about this one? 23 Example 2 R.P.W. method: method: 01 6 4 04 8 21 5 09 17 37 29 02 19 05 Need 1800 units in 7.5 hours. Target CT = 15 [sec. /unit] Total task time = 74 sec. Need at least 5 stations. stations. 5 19 5 06 14 5 10 9 9 12 14 36 03 10 5 10 6 11 07 5 21 08 9 12 6 15 11 Weight 6 Time Task 6 1 5 2 10 3 4 4 5 5 5 6 5 7 6 8 8 9 1 2 3 37 29 36 24 ProcessSelection Example Example 2 Target C.T.= 15 [sec. /unit ]. Station Selected Cum. Time 37 01 6 21 19 04 4 5 8 09 17 05 29 02 I 1, 2, 4, 6, 11, 15 5 19 5 06 14 10 5 9 12 9 14 36 03 10 07 5 08 6 21 11 6 15 RPW order: 01 03 02 04 08 05 06 09 11 07 10 12 order: 01 03 02 04 08 05 06 09 11 07 10 12 ProcessSelection 25 Example Example 2 Target C.T.= 15 [sec. /unit ]. Station Selected I II III IV V VI 1, 2, 4 3, 5 8, 6 9, 11 7, 10 12 Cum. Time Time 6, 11, 15 10, 15 6, 11 8, 14 5, 10 9 37 01 6 21 19 04 4 5 8 09 17 05 29 02 5 19 5 06 14 10 5 9 12 9 14 36 03 10 07 5 08 6 21 12 9 11 6 15 Effective CT = 15 sec /unit. Efficiency = 100 *74 / (6 * 15) = 82.2% 1, 2, 4 15 ProcessSelection 3, 5 15 8, 6 11 9, 11 14 7, 10 10 26 Ex. 2: Solving by inspection. Target CT = 15 sec/unit inspection. I 1,2,4 II 5,6,10 III 3,7 IV 8,9 V 11,12 01 6 04 4 5 5 8 09 IV I 02 05 5 II 06 5 10 12 9 98.7% III 03 10 07 5 V 6 27 08 6 11 ProcessSelection Various Various layouts Line flow, flow shop / product layout Job shop: shop: • New products. • Shifting bottlenecks. • Capacity? • Need skilled operators. Hybrid A B 1: A - C - D 2: 2: C - B 3: B - D – C - A Job Shop C ProcessSelection D 28 MGMT 460 Layout: Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system. th th 1: Product layout: Layout uses standardized processing operations to achieve smooth, processing operations to achieve smooth, rapid, highrapid, high-volume flow. Advantages: • High rate of output rate of output • Low unit cost • Labor specialization • Low material Low material handling handling cost • High utilization of labor and equipment • Established routing and scheduling • Routing accounting and purchasing ProcessSelection Disadvantages: • Creates dull, repetitive jobs 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 29 2. Process layout: Layout that can 2. Process layout: Layout that can handle handle varied processing requirements. Dept. A Dept. B Dept. C Dept. D Dept. E Dept. F Advantages: • Can handle a variety of processing requirements • Not particularly vulnerable to equipment failures failures • Equipment used is less costly • Possible to use individual incentive plans Disadvantages: • WIP 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 Accounting and purchasing are more more involved 30 ProcessSelection 3. 3. Fixed Position layout: Layout in which the product or project remains stationary and workers materials stationary, and workers, materials, and equipment are moved as needed. Airplanes. Ships, PrePrefabricated homes homes 4. Cellular Production: Layout in which machines are grouped Cellular Production: Layout in which machines are grouped into into a cell that can process items that have similar processing requirements 5. Group Technology: The grouping into part families of items with similar design or manufacturing characteristics Service Layouts Warehouse and storage layouts Retail layouts Office layouts Service layouts must be aesthetically pleasing as well as functional ProcessSelection 31 Producing Producing with different layouts Example 3 13 4 B G 5 3 Suppose we want to H E 5 9 3 make product with the make a product with the A C 12 J M K 8 precedence precedence diagram I 7 10 shown to the right. 5 D F Times are in minutes Times are in minutes. A, B, C, D require machine type X. E, F, I require machine type type Y and G,H,J,K,M require machine type Z. G, type If we plan to make this product in large numbers over many months / years, we should think in terms of either a product layout (line flow) or production cells. (li fl For low to moderate amounts we may want to use batch production in an existing departmental layout process layout. ProcessSelection 32 3A: 3A: Line layout Suppose we use a target CT = 20 min / unit. One possible layout is shown below. A, B 18 C, D 19 F, E, I 20 5 A B 13 E 5 G J I 5 4 H 8 3 9 K 3 M C 12 7 10 D F J, G, H 15 K, M 12 Effective CT 20 min unit. Effective CT = 20 min / unit. We will produce (7 * 60 / 20) = 21 units per day (7 hour working) If If we need to produce 100 units per 100 day, we will need 100 / 5 lines in parallel (with capacity = 21*5 = 105 units per day units per day. ProcessSelection 33 3B: 3B: Cell layout A single worker builds the entire 5 product. We need to provide A 3 machines to each worker. Total time needed = 5 + 13 + .. +9 + 3 = 84 min / unit B 13 E 5 G J I 5 4 H 8 3 9 K 3 M C 12 7 10 D F Worker capacity = 420[min / day] / 84[min/unit] = 5 [units / day] # of worker s = 100 [units/day] / 5 [units/day * worker] = 20 workers. workers. Capacity = 100 units/day Costing for the cell layout - Total workers: 20 Daily salary = 20[workers]*16[$/hr * worker]*8[hrs/day] = 2560 [$ /day ] Overheads = 2560 [$/ day ] * 0.6 = 1536[$/ day ] Production cost = (2560 + 1536) [$/ day ] / 100 [units / day] = $40.96/ unit Unit Product cost = Material cost + Production cost = $125.52 + $40.96= $166.48 $125 $40 $166 ProcessSelection 34 3C: 3C: Batch process We will now calculate ca number of workers needed for each department. All workers work for 7 hours (420 min) and we need to produce 100 units in one day. X Time/unit Time for 100 units Workers needed Dept. capacity 5 A B 13 E 5 G J I 5 4 H 8 3 C 12 7 10 D F 9 K 3 M Y Z 27 min 2700 min 7 108 37 min 5 + 10 + 5 = 20 min 3700 min 100*20 = 2000 min 9 102 2000 / 420 5 5 * 420 / 20 105 420 20 Bottleneck ProcessSelection Total workers = 21. Capacity = 102 102 35 Example 4: We now have the same We now have the same precedence precedence diagram but 6 different machines are needed. 5 A B 13 E 5 G J I 5 4 H 8 3 9 K 3 M C 12 7 10 D F 4A: Line layout We can use the same layout we saw earlier but we can use the same layout we saw earlier but we will will have to move machines to appropriate locations. AB 18 CD 19 FEI 20 J GH 15 KM 12 4B: Cell layout Calculations will not change from the previous example but we will have to provide all 6 machines to each worker. ProcessSelection 36 4C: 4C: Batch process Machines in departments depa X, Y, Z are shown below with other calculations in the table. 5 A B 13 E 5 G J I 5 4 H 8 3 9 K 3 M C 12 7 10 D F X Time/unit Workers Capacity 30 min 8 112 Y 24 min 6 105 Z M 30 min 8 112 H A, C F Routing will be very inefficient in this layout; job travels back and fro between departments due to precedence relationships. ProcessSelection D, E B I, G J, K 37 Right Right to Work Law Alabama Alabama Arizona Arkansas Arkansas Florida Georgia Idaho Iowa Kansas Louisiana Nebraska Nebraska Nevada North Carolina North Dakota Oklahoma South Carolina South Dakota Tennessee Texas Utah Wyoming Mississippi Virginia If you are employed in the states listed, you are probably protected by the state's Right to Work law and cannot be required to join or pay dues or fees to a union. Under federal labor law and the state's Right to Work law, you have the right to resign from membership in a union at any time. If you resign, you cannot be disciplined by the union for any post union for any postresignation conduct. ProcessSelection 38 ...
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