Flow Time Problems Set 2 This is indeed

Flow Time Problems Set 2 This is indeed Christine Cookies modified in MBPF 2 nd Edition

4. 2 - Kristen and her roommate are in the business of baking custom cookies. As soon as she receives an order by phone, Kristen washes the bowl and mixes dough according to the customer's order - activities that take a total of 6 minutes. She then spoons the dough onto a tray that holds one dozen cookies (2 minutes). Her roommate then takes 1 minute to set the oven and place the tray in it. Cookies are baked in the oven for 9 minutes and allowed to cool outside for 5 minutes. The roommate then boxes the cookies (2 minutes) and collects payment from the customer (1 minute) a. Draw a flowchart for the process described here and determine theoretical flow time from the time of order until the time of payment collection. Assume no waiting over the course of the process b. suppose that each other consists of two dozen cookies. Assume that although the mixing bowl can accommodate dough for two dozen cookies at a time, the oven can accommodate only one tray of one dozen cookies at a time. As before, spooning each tray takes 2 minutes, and both trays must be cooled prior to boxing the cookies for customer pickup. Draw a modified flowchart and determine theoretical flow time. Consider the effect on flow time of the following possible alternatives to the system: 1. Buying a second oven that can bake one tray of one dozen cookies 2. Buying a second oven that can hold two trays of one dozen cookies each 3. Buying a faster convection oven that can bake one dozen cookies in 6 minutes instead of 9 minutes. Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 2

Problem 5. 2: Flow unit = 1 order of 1 dozen. Take wash order mix spoon load bake unload & set cool pack get pay Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 3

Problem 4. 2 a) Take order wash mix 6/1 -2 doz spoon 2 6/1 -2 doz 2 load & set 1 1 bake 9 unload ad cool pack 5 2 9 5 2 get pay 1/order TFT = 6+2+1+9+5+2+1 = 26 Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 4

Part (a): Gant Chart and theoretical flow time for 1 doz orders Take wash order mix spoon load bake & set 6/1 -2 doz 2 wash unlo- cool pack get ad 1 pay 9 5 2 1/order spoon mix l u s l pack g p bake cool 1 25 2 26 3 4 5 6 7 Throughput Problems – Set 2 8 9 10 11 12 13 14 15 16 Ardavan Asef-Vaziri 17 18 19 Nov-2011 20 21 22 23 24 5

Part (b): general explanations; mix can handle 2 doz, oven 1 doz Take wash spoon load bake unlo- cool pack get order ad pay Flow unit =mix 1 order of 2 dozen. & set 6/1 -2 doz 5 2 1/order Certain activities can be 2 performed 1 in parallel. 9 For example, while the oven is baking the first dozen, You can spoon the dough for the second dozen into another tray. Therefore, the flow time of such an order is not simply the sum of the activity times. A useful tool is a Gantt chart that shows the times during which different resources of interest are occupied for various activities. The dough for the 2 dozen cookies is mixed by You in 6 minutes and subsequently you spoon dough for 1 dozen in 2 minutes. Therefore in the 8 th minute, the RM is ready to load the oven and set timer, which takes 1 minute. The oven starts baking the first dozen at the 9 th minute and completes baking at the 18 th minute. Meanwhile, You spoon the second dozen into another tray. At the 18 th minute, the RM unloads the first tray from the oven and loads the second tray into the oven and sets the timer. So the second dozen starts baking at the 19 th minute. While the second dozen bakes, the first dozen cookies cool and RM packs them into a bag, which takes a total of 7 minutes. At the 28 th minute the second dozen finishes baking at which time the RM unloads the tray. After cooling for 5 minutes, the RM packs the second dozen in 2 minutes by the 35 th minute. Finally, payment for the order and delivery to customer takes place in the 36 th minute. The theoretical flow time for an order of 2 dozen cookies is 36 minutes. Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 6

Part (b): Gant Chart and theoretical flow time for 2 doz orders Take wash order mix spoon load bake & set 6/1 -2 doz wash 2 spoon unlo- cool pack get ad 1 pay 9 5 2 1/order spoon mix l ul s ls bake pack u l bake cool 1 26 2 27 3 28 4 29 5 30 6 7 Throughput Problems – Set 2 8 9 10 11 12 13 14 15 16 Ardavan Asef-Vaziri 17 18 19 Nov-2011 20 21 22 23 24 2 7

Part (b): Gant Chart and theoretical flow time for 2 doz orders (cont. ) Take wash order mix spoon load bake & set 6/1 -2 doz 2 1 unlo- cool pack ad 9 get pay 5 2 1/order 2 pack g p cool 31 32 33 34 35 36 37 Throughput Problems – Set 2 38 39 40 Ardavan Asef-Vaziri Nov-2011 8

Part (b): CPM Take wash order mix spoon 6/1 -2 doz 2 spoon load bake & set 2 unlo- cool pack ad 1 9 5 2 get pay 1/order load bake & set 1 unlo- cool pack ad 9 Throughput Problems – Set 2 5 2 Ardavan Asef-Vaziri Nov-2011 9

Part (b): CPM 0 0 0 Take order 6 wash 6 spoon 8 mix 6/1 -2 doz 8 spoon 2 1018 load 10 18 2 1 1 9 9 bake 2 2 8 8 & set unlo- 2 2 8 8 cool 3 3 pack 3 5 ad 1 9 5 2 3 25 5 3 5 get 3 6 pay 1/order 8 load 99 18 18 bake & set 1 unload 9 Throughput Problems – Set 2 18 1 8 cool 5 2323 pack 25 2 Ardavan Asef-Vaziri Nov-2011 10

Forward Path Max = 30 10 35 35 30 20 35 5 Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 11

Part (b): CPM 0 0 Take order 8 8 0 spoon 1 6 6 2 load 6/1 -2 doz 6 6 2 8 8 18 10 load 10 18 1 8 99 bake 181 1 unlo- 8 8 1818 1 9 bake 1 cool 9 1 1 8 8 Throughput Problems – Set 2 1 2 8 8 5 unlo- 2 2 8 8 cool 3 3 pack 3 5 3 3 3 5 3 25 5 ad 1 1 9 9 9 2323 pack ad 9 9 2 2 8 8 & set 1 spoon mix 0 8 6 wash 3 3 2 2 2 8 8 5 2 25 3 5 get pay 1/order 3 6 3 5 Ardavan Asef-Vaziri Nov-2011 12

Backward Path 30 Min = 35 30 30 45 5 Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 13

Part (b 1): theoretical flow time when buying a second oven with 1 doz capacity Take wash order mix spoon load bake & set 6/1 -2 doz 2 wash spoon unlo- cool pack get ad 1 pay 9 5 2 1/order spoon mix l l u u s s l l cool pack g p bake 1 25 2 26 3 27 4 28 5 29 6 7 Throughput Problems – Set 2 8 9 10 11 12 13 14 15 16 Ardavan Asef-Vaziri 17 18 19 Nov-2011 20 21 22 23 24 14

Part (b 1): CPM spoon load bake & set 2 1 unlo- cool pack ad 9 5 2 get Take wash order mix 6/1 -2 doz spoon pay 1/order 2 load bake & set 1 Throughput Problems – Set 2 unlo- cool pack ad 9 Ardavan Asef-Vaziri 5 Nov-2011 2 15

Part (b 2): theoretical flow time when buying a large oven with 2 doz capacity Take wash order mix spoon load bake & set 6/1 -2 doz wash 2 spoon unlo- cool pack get ad 1 pay 9 5 2 1/order spoon mix l u s l pack g p bake cool 1 26 2 27 3 28 4 29 5 30 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 We do not need CPM since activities are sequential Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 16 2

Part (b 3): theoretical flow time when buying a fast oven with 1 doz capacity Take wash order mix spoon load bake & set 6/1 -2 doz wash 2 spoon unlo- cool pack get ad 1 pay 9 5 2 1/order spoon mix l ul s ls bake pack u 2 27 3 28 4 29 5 30 6 7 8 g l p bake cool 1 26 pack 9 10 11 12 13 cool 14 15 16 17 18 19 20 21 22 23 24 2 CPM is the same as the CPM for original case, just bake time is 6 min instead o Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 17

Trade-off Analysis No Investment Second Oven Large Oven Fast Ovens 36 28 30 30 The second oven (a)leads to the shortest flow time (b)Perhaps is cheaper than a large oven or 2 fast ovens Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 18

Problem 4. 2 Version 2 - Both Boxed together: Part (a) Take wash order mix 6/1 -2 doz spoon load bake & set 2 1 unlo- cool box ad 9 get paid 5 2 1/order TFT = 6+2+1+9+5+2+1 = 26 Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 19

Part (a): Gant Chart and theoretical flow time for 1 doz orders Take wash order mix spoon load bake & set 6/1 -2 doz 2 wash unlo- cool box get ad 1 paid 9 5 2 1/order spoon mix l u s l box g p bake cool 1 25 2 26 3 4 5 6 7 Throughput Problems – Set 2 8 9 10 11 12 13 14 15 16 Ardavan Asef-Vaziri 17 18 19 Nov-2011 20 21 22 23 24 20

Part (b): general explanations; mix can handle 2 doz, oven 1 doz Take wash spoon load bake unlo- cool box get order ad paid Flow unit =mix 1 order of 2 dozen. & set 6/1 -2 doz 5 2 1/order Certain activities can be 2 performed 1 in parallel. 9 For example, while the oven is baking the first dozen, You can spoon the dough for the second dozen into another tray. Therefore, the flow time of such an order is not simply the sum of the activity times. A useful tool is a Gantt chart that shows the times during which different resources of interest are occupied for various activities. The dough for the 2 dozen cookies is mixed by You in 6 minutes and subsequently you spoon dough for 1 dozen in 2 minutes. Therefore in the 8 th minute, the RM is ready to load the oven and set timer, which takes 1 minute. The oven starts baking the first dozen at the 9 th minute and completes baking at the 18 th minute. Meanwhile, You spoon the second dozen into another tray. At the 18 th minute, the RM unloads the first tray from the oven and loads the second tray into the oven and sets the timer. So the second dozen starts baking at the 19 th minute. While the second dozen bakes, the first dozen cookies cool and RM packs them into a bag, which takes a total of 7 minutes. At the 28 th minute the second dozen finishes baking at which time the RM unloads the tray. After cooling for 5 minutes, the RM packs the second dozen in 2 minutes by the 35 th minute. Finally, payment for the order and delivery to customer takes place in the 36 th minute. The theoretical flow time for an order of 2 dozen cookies is 36 minutes. Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 21

Part (b): Gant Chart and theoretical flow time for 2 doz orders Take wash order mix spoon load bake & set 6/1 -2 doz wash 2 spoon unlo- cool box get ad 1 paid 9 5 2 1/order spoon mix l ul u s ls l bake cool 1 26 2 27 3 28 4 29 5 30 6 7 Throughput Problems – Set 2 8 9 10 11 12 13 14 15 16 Ardavan Asef-Vaziri 17 18 19 Nov-2011 20 21 22 23 24 22 2

Part (b): Gant Chart and theoretical flow time for 2 doz orders (cont. ) Take wash order mix spoon load bake & set 6/1 -2 doz 2 1 unlo- cool box ad 9 get paid 5 2 1/order 2 box g p cool 31 32 33 34 35 36 37 Throughput Problems – Set 2 38 39 40 Ardavan Asef-Vaziri Nov-2011 23

Part (b): CPM Take wash order mix spoon 6/1 -2 doz 2 spoon load bake & set 2 load 1 bake & set 1 unlo- cool box 5 2 ad 9 get paid 1/order cool ad 9 Throughput Problems – Set 2 5 Ardavan Asef-Vaziri Nov-2011 24

Part (b): CPM 0 0 0 Take order 6 wash 6 spoon 8 mix 6/1 -2 doz 8 spoon 2 1018 load 10 18 2 8 load & set 99 18 18 bake unload 9 Throughput Problems – Set 2 18 1 8 cool 2 2 8 8 unlo- 2 2 8 8 cool ad 1 & set 1 1 1 9 9 bake 9 5 3 3 box 23 3 5 get 3 6 paid 2 1/order 23 5 Ardavan Asef-Vaziri Nov-2011 25

Forward Path Max = 30 10 35 35 30 20 35 5 Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 26

Part (b): CPM 0 0 Take order 8 8 0 spoon 1 6 6 2 load 6/1 -2 doz 6 6 2 8 8 18 10 load 10 18 1 8 99 bake 181 1 unlo- 8 8 1818 1 9 bake 2 2 8 8 & set 1 spoon mix 0 8 6 wash 1 cool unlo- 2 2 8 8 cool 3 3 box ad 1 1 9 9 9 2 2 8 8 5 3 3 2 3 5 3 5 get 3 6 paid 3 5 1/order 3 6 23 ad 9 9 9 1 1 8 8 Throughput Problems – Set 2 1 2 8 8 5 3 3 Ardavan Asef-Vaziri Nov-2011 27

Backward Path 30 Min = 35 30 35 3 0 30 45 5 Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 28

Part (b 1): theoretical flow time when buying a second oven with 1 doz capacity Take wash order mix spoon load bake & set 6/1 -2 doz 2 wash spoon unlo- cool pack get ad 1 pay 9 5 2 1/order spoon mix l l u u s s l l cool box g p bake 1 25 2 26 3 27 4 28 5 29 6 7 Throughput Problems – Set 2 8 9 10 11 12 13 14 15 16 Ardavan Asef-Vaziri 17 18 19 Nov-2011 20 21 22 23 24 29

Part (b 1): CPM spoon load bake & set 2 1 unlo- cool ad 9 5 box Take wash order mix 6/1 -2 doz spoon get paid 2 1/order 2 load bake & set 1 Throughput Problems – Set 2 unlo- cool ad 9 Ardavan Asef-Vaziri 5 Nov-2011 30

Part (b 2): theoretical flow time when buying a large oven with 2 doz capacity Take wash order mix spoon load bake & set 6/1 -2 doz wash 2 spoon unlo- cool box get ad 1 paid 9 5 2 1/order spoon mix l u s l box g p bake cool 1 26 2 27 3 28 4 29 5 30 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 We do not need CPM since activities are sequential Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 31 2

Part (b 3): theoretical flow time when buying a fast oven with 1 doz capacity Take wash order mix spoon load bake & set 6/1 -2 doz wash 2 spoon unlo- cool box get ad 1 paid 9 5 2 1/order spoon mix l ul u s ls l bake 2 27 3 28 4 29 5 30 6 7 8 g p bake cool 1 26 box 9 10 11 12 13 cool 14 15 16 17 18 19 20 21 22 23 24 2 CPM is the same as the CPM for original case, just bake time is 6 min instead o Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 32

Trade-off Analysis No Investment Second Oven Large Oven Fast Ovens 28 30 36 28 The second oven (a)leads to the shortest flow time (b)Perhaps is cheaper than a large oven or 2 fast ovens Throughput Problems – Set 2 Ardavan Asef-Vaziri Nov-2011 33