Project 2

Part 2 (group project):

This part of the project is to be completed the same groups as for Part 3 of project #1 (each group will hand in a single report). Your task for Part 2 of project #2 is to find the optimal configuration of a quality control check that is intended to minimize the costs of the disk drive and to write a report about your findings. The report is expected to follow the same formatting, quality and clarity goals as the report you did for Part 3 of project #1.

If the air gap is too small, then there is a certain chance that the slider might accidentally touch the rotating disk during operation. This situation is called a “head crash” and if it happens the disk drive is damaged and must be replaced. If this happens during the warranty period then the manufacturer guarantees its customers a full replacement of the product at no cost. Investigations of the disk drives being returned under this warranty policy have shown that the probability of the product being damaged due a head crash is a function of the air gap in the following form:

P_head_crash = exp(-8.5*E7 * b2)

To handle this problem the manufacturer wants to implement an extra check during the quality control process of the disk drive. During this extra check the air gap b 2of every manufactured disk is measured and if the air gap is smaller than a limit value b 2,limit, then the slider would be replaced by another one. For the limit b 2,limit the following values are discussed:

0.5e-7m 0.6e-7m 0.7e-7m 0.8e-7m 0.9e-7m 1.0e-7m

Assume that the costs (or financial loss) of replacing a slider, because of a too small air gap is US$ 10.- and the cost (or financial loss) of replacing an entire disk drive under warranty policy is US$ 150.-. To answer the questions requested for the report use the expected loss defined as:

Expected Loss = probability of an event * costs if event occurs