Question

Matching supply with Demand (3rd Edition) - Question 10.2

(Process with Rework) Consider the following three-stage production process of glass ceramics, which is operated as a worker-paced line. Q10.2 Components 6 min./unit 5 min./unit min. /unit Finished Units Rework The process is experiencing severe quality problems related to insufficiently trained work- ers. Specifically, 20 percent of the parts going through operation 1 are badly processed by the operator. Rather than scrapping the unit, it is moved to a highly skilled rework opera- tor, who can correct the mistake and finish up the unit completely within 15 minutes. Quality Management, Statistical Process Control, and Six-Sigma Capability 221 The same problem occurs at station 2, where 10 percent of the parts are badly processed, requiring 10 minutes of rework. Station 3 also has a 10 percent ratio of badly processed parts, each of them requiring 5 minutes by the rework operator. a. What is the utilization of station 2 if work is released into the process at a rate of 5 units per hour? Where in the process is the bottleneck? Why? (Remember, the bottleneck is the resource with the lowest capacity, independent of demand.) What is the process capacity? b. c.

Answer 1

a)

Work is released in process at 5 units per hour.

It will arrive at station 2 at the rate (5*80%) 4 units per hour

Capacity of Station 2 = 12 units per hour (5 minutes per unit)

Utilization = 4/12 = 0.33

b)

Since the processing time for Station 1 is the highest (capacity is lowest) hence station 1 will be the Bottleneck.

c)

Bottleneck is station 1.

Capacity of station 1 = 60/6 = 10 units per hour.

Since the capacity of bottleneck station is 10 units per hour hence process capacity will be equal to bottleneck capacitty.

Process Capacity = 10 units per hour.