Case 1: Quality Management
An operation manager of a food can company wants to know if the company can save regarding raw material (bean, vegetables, …) cost by slightly lowering the content of each can. The standard weight of one of the major products is 80 grams (net weight).
She has randomly taken four boxes from the filling machine and weighed. Each box contains 16 food cans.
Data for approximately 2.5 hours of inspection are shown below.
a) Compute upper and lower limit of control charts.

• Refer to excel
b) Draw appropriate control charts that helps the operation manager to make decision.
• Refer to Excel worksheet
c) Is the process in control?
• The process is in control because the sample is within the UCL and LCL range. Sample
1 2 3 4 5 6 7 8
Box 1 78.53 83.68 82.41 76.3 83.85 81.39 78.96 83.59
Box 2 76.01 82.63 78.46 82.87 76.7 77.84 76.06 78.37
Box 3 84.88 81.78 75.33 78.94 79.68 77.54 84.98 82.41
Box 4 76.3 82.71 81.69 75.66 81.3 79.25 79.47 82.48
Sample
9 10 11 12 13 14 15 16
Box 1 84.05 83.73 75.82 75.69 84.51 79.34 83.4 79.91
Box 2 83.71 83.09 76.63 81.95 81.56 79.08 78.72 83.82
Box 3 75.66 81.51 79.97 77.33 77.59 83.78 78.79 75.32
Box 4 76.55 76.39 82.68 75.07 75.5 75.79 82.91 83.8

Case 2: Layout Strategy
An operation manager of a small furniture workshop wants to assign 12 tasks to workstations in order to achieve better efficiency for its chair production line. The workshop works 10 hours per day and average daily demand is 400 chairs.
Task a b c d e f G h i j k l
Duration (minutes) 0.1 0.2 0.9 0.6 0.1 0.2 0.4 0.1 0.2 0.7 0.3 0.2
Follows Task – a b c – d, e F g h i j k

a) Draw the process network.

• Refer to Excel
b) What is the theoretical minimum number of workstations for this shop?
• Refer to Excel
c) Assign tasks to optimum number of workstations
• Workstation 1 = a, b, c, e
• Workstation 2 = d, f, g, h, i
• Workstation 3 = j, k, l

d) How much total idle time is present each day?

• Refer to excel
e) What is the overall efficiency of assembly line?
• Refer to excel

Case 3: Inventory Management
A manager of a car wash has received a price list from two suppliers of the liquid soap. She knows the annual usage of soap is 4,250 liters. The car wash is open 360 days a year. The ordering cost is \$10 and holding cost rate is 30 percentage of unit cost.

Supplier A Supplier B
Quantity Unit Price Quantity Unit Price
1 – 499 \$6.00 1 – 399 \$6.10
500 – 999 \$5.50 400 – 799 \$5.60
1000 and more 5.00 800 and more \$5.10

a) What is the economic order quantity (EOQ) of each supplier?

• Refer to excel
b) What are ordering cost, holding cost, and total cost of each supplier according to their EOQ in part a?
• Refer to excel
c) Compute the number of orders per year and time between orders for each supplier according to their EOQ in part a.
• Refer to excel
d) Which supplier should be used? Why?
• Supplier A should be used. Because the total cost from supplier A is the least expensive.

Case 4: MRP
A small furniture company has just received an order to deliver 100 tables in eight workdays. Suppose the table is assembled in a work center. The BOM information of the all parts are as follows:
Item Name Top board Leg Leg Extender Metal plate Metal screw
Quantity 1 4 4 4 20
The procurement team needs to plan for the purchase of parts and based on assembly. The purchase lead time for any order is one workday, except metal plates have 2 days lead time. Also, the company has some inventory of parts from previous purchases: 20 top boards, 160 legs, 40 metal plate, and 90 metal screws. The procurement team knows top board, leg, and metal plate are purchased in lot-for-lot, metal screw in a lot size of 200, leg extender in a lot size of 80.
a) Develop the material requirements plan for this order.

• Refer to excel
b) Suppose the table is not assembled in a work center. In one small paragraph, identify the production process strategy for the table. Explain why you would choose this process strategy.
• The production process strategy for the table is Repetitive Focus. They are producing the same assembly parts and there are no new additions to the part. It is consistent and unchanged, Hence the repetitive focus strategy.

Sample Solution