Problem 4.2: Part (a)
Take
wash
order
mix
6/1-2 doz
spoon
load
bake
& set
2
TFT = 6+2+1+9+5+2+1 = 26
1
unlo-
cool
pack
ad
9
get
pay
5
2
1/order
Part (a): Gant Chart and the theoretical flow time for 1 doz orders
Take
wash
order
mix
spoon
load
bake
unlo-
& set
6/1-2 doz
2
wash
cool
pack
get
ad
1
pay
9
5
2
1/order
spoon
mix
l
u
s
l
pack
g
p
bake
cool
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Part (b): general explanations; mix can handle 2 doz, oven 1 doz
Take
wash
order
mix
6/1-2 doz
spoon
load
bake
& set
2
1
unlo-
cool
pack
ad
9
get
pay
5
2
1/order
Flow unit = 1 order of 2 dozen.
Certain activities can be performed in parallel.
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 8th 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 9th minute and completes baking at the 18th minute.
Meanwhile, You spoon the second dozen into another tray.
At the 18th 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 19th 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 28th 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 35th minute.
Finally, payment for the order and delivery to customer takes place in the 36th minute.
The theoretical flow time for an order of 2 dozen cookies is 36 minutes.
Part (b): Gant Chart and the theoretical flow time for 2 doz orders
Take
wash
order
mix
spoon
load
bake
unlo-
& set
6/1-2 doz
2
wash
spoon
cool
pack
get
ad
1
pay
9
5
2
1/order
spoon
mix
l
u l
s
l s
pack
u
l
bake
bake
cool
cool
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Part (b): Gant Chart and the theoretical flow time for 2 doz orders (cont.)
Take
wash
order
mix
spoon
load
& set
6/1-2 doz
2
1
2
pack
g
p
cool
31
32
33
34
35
bake
36
37
38
39
40
unlo-
cool
pack
ad
9
get
pay
5
2
1/order
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
5
2
Part (b): CPM
0
0
Take
order
0
6
wash
6
spoon
8
mix
6/1-2 doz
8
spoon
2
1018load
10
18
2
28 28
19 19
bake
unlo-
& set
28 28
33 33
cool
35
pack
ad
1
9
5
35
2
35
25
36
get
pay
1/order
8
load
9 9
18 18
bake
& set
1
unlo-
18 18
23 23
cool
25
pack
ad
9
5
2
Forward Path
Max = 30
35
10
35
30
20
35
5
Part (b): CPM
0
0
Take
0
6
wash
order
6
spoon
8
mix
0
0
8
0
spoon
6/1-2 doz
6
6
2
18
10 load
10
18
18
16
8
bake
1
28 28
unlo-
& set
18
2
28 28
19
33 33
cool
35
pack
ad
19 19
9
28 28
28 28
5
33 33
2
35
35
25
8
load
9 9
bake
1818
& set
8
1
18 18
23 23
18
unlo-
cool
25
pack
ad
9 9
9
18 18
18 28
5
33 33
2
35
35
36
get
35
pay
1/order
36
Backward Path
30
Min = 35
30
35
30
30
45
5
Part (b1): theoretical flow time when buying a second oven with 1 doz capacity
Take
wash
order
mix
spoon
load
bake
unlo-
& set
6/1-2 doz
2
wash
spoon
cool
pack
get
ad
1
pay
9
5
2
1/order
spoon
mix
l
l
u
u
s
s
l
l
pack
g
p
bake
bake
cool
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
cool
20
21
22
23
24
25
26
27
28
29
Part (b1): 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
unlo-
cool
pack
ad
9
5
2
Part (b2): theoretical flow time when buying a large oven with 2 doz capacity
Take
wash
order
mix
spoon
load
bake
unlo-
& set
6/1-2 doz
2
wash
spoon
cool
pack
get
ad
1
pay
9
5
2
1/order
spoon
mix
l
u
s
l
pack
g
p
bake
cool
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
We do not need CPM since activities are sequential
19
20
21
22
23
24
25
26
27
28
29
30
Part (b3): theoretical flow time when buying a fast oven with 1 doz capacity
Take
wash
order
mix
spoon
load
bake
unlo-
& set
6/1-2 doz
2
wash
spoon
cool
pack
get
ad
1
pay
9
5
2
1/order
spoon
mix
l
u l
s
l s
pack
u
3
4
5
6
7
8
9
10
p
bake
cool
2
g
l
bake
1
pack
11
12
13
14
15
16
cool
17
18
19
20
21
22
23
24
25
26
27
28
29
CPM is the same as the CPM for original case, just bake time is 6 min instead of 9 min.
30
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