Q1. (20%) As the Cottrell Bicycle Co. of St. Louis completes plans for its new assembly line, it identifies 25 different tasks in the production process. VP of Operations Jonathan Cottrell now faces the job of balancing the line. He lists precedences and provides time estimates for each step based on work-sampling techniques. His goal is to produce 1,000 bicycles per standard 40-hour workweek.

 

TaskTime

(sec)

Immediate PredecessorsTaskTime

(sec)

Immediate Predecessors
K360E3109F3
K424K3D653F4
K927K3D772F9, E2, E3
J166K3D878E3, D6
J222K3D937D6
J33C178F7
G479K4, K9B372D7, D8, D9, C1
G529K9, J1B5108C1
F332J2B718B3
F492J2A152B5
F721J3A272B5
F9126G4A3114B7, A1, A2
E218G5, F3   

 

  1. Balance this operation using shortest operation time rule and compute the ef ficiency of the line. (10%)
  2. Discuss the results obtained in (a) including the maximum efficiency we can a chieve and how this balance could be improved. (10%)

 

 

Q2. (20%) Manager Chris Channing of Fabric Mills, Inc., has developed the forecast shown in the table for bolts of cloth. The department has a normal capacity of 275 bolts per month, except for the seventh month, when capacity will be 250 bolts. Normal output has a cost of £40 per bolt. Workers can be assigned to other jobs if production is less than normal. The beginning inventory is zero bolts.

 

Month1234567Total
Forecast2503002503002802752701,925

 

  1. Develop a chase plan that matches the forecast and compute the total cost of your plan. Over time is £60 per bolt, and backlogs are not allowed. (5%)
  2. Would the total cost be less with regular production with no overtime, but using a subcontractor to handle the excess above normal capacity at a cost of £50 per bolt? Backlogs are not allowed. The inventory carrying cost is £2 per bolt. (5%)
  3. Compare and contrast two simple pure strategies, i.e., chase strategy and level strategy, for capacity planning. (10%)

 

 

Q3. (20%) Emery Pharmaceutical uses an unstable chemical compound that must be kept in an environment where both temperature and humidity can be controlled. Emery uses 200 pounds per month of the chemical, estimates the holding cost to be £3.33 (because of spoilage), and estimates order costs to be £10 per order. The cost schedules of four suppliers are as follows:

 

Vendor 1Vendor 2
QuantityPrice/LB (£)QuantityPrice/LB (£)
1-4935.001-7434.75
50-7434.7575-14934.00
75-14933.55150-29932.80
150-29932.35300-49931.60
300-49931.15500+30.50
500+30.75  
Vendor 3Vendor 4
QuantityPrice/LB (£)QuantityPrice/LB (£)
1-9934.501-19934.25
100-19933.75200-39933.00
200-39932.50400+31.00
400+31.10  

 

  1. What quantity should be ordered, and which supplier should be used? (10%)
  2. Discuss factor(s) should be considered besides total cost. (10%)

 

Q4. (20%) A process considered to be in control measures an ingredient in ounces. A quality inspector took 25 samples, each with 5 observations as follows:

 

SamplesObservations
12345
15150495050
24547704636
35035483947
45570503051
54938643647
65962405464
73633494856
85067534340
94452464744
107045504741
115754624536
125654474262
134070584544
145258405246
155742525859
166249423355
174039495948
186450425750
195853524850
206050414150
215247485840
225540564945
234748505048
245050495151
255150515162

 

  1. Using this information, obtain three-sigma (i.e., z=3) control limits for a mean control chart and control limits for a range chart, respectively. It is known from previous experience that the standard deviation of the process is 8.46. (10%)
  2. Discuss whether the process is in control or not. (10%)

 

Q5. (20%) The Model 5 is a new custom-designed electric car. An analysis of the task of building the Model 5 reveals the following list of relevant activities, their immediate predecessors, and their duration:

 

JobDescriptionImmediate PredecessorsNormal Time (Days)
AStart0
BDesignA8
COrder special accessoriesB0.1
DBuild frameB1
EBuild doorsB1
FAttach axles, wheels, gas tankD1
GBuild body shellB2
HBuild transmission and drivetrainB3
IFit doors to body shellG, E1
JBuild engineB4
KBench-test engineJ2
LAssemble chassisF, H, K1
MRoad-test chassisL0.5
NPaint bodyI2
OInstall wiringN1
PInstall interiorN1.5
QAccept delivery of special accessoriesC5
RMount body and accessories and chassisM, O, P, Q1
SRoad test carR0.5
TAttach exterior trimS1
UFinishT0

 

  1. Identify the project duration stating the critical path. (10%)