KKU Engineering Journal (Feb 2016)
Continuous quality inspection in hard disc drive manufacturing: A case study
Abstract
This paper presents the continuous sampling plan CSP-100 that was developed from the continuous sampling plans CSP-1, CSP-4 and CSP-C. The objective of this paper is to apply the continuous sampling plan for the new CSP-100 plan proving a reduction in the delivery inspection time compared to the single lot sampling plan (SSP) while maintaining the same or greater quality conformance. This CSP-100 was studied in Hard Disc Drive manufacturing. The parameters used in the CSP-100 plan are as follows; i (the number of consecutive conforming units), f (the sampling frequency of partial number in 100% inspected units) and c (the acceptance number). CSP-100 computes four performance measures, Average Fraction Inspected (AFI), Average Outgoing Quality (AOQ), Lot Acceptance Rate (LAR) and Defective Parts Per Million (DPPM). The advantage of this CSP-100 plan is not only to reduce the inspection time but also prove higher productivity numbers when compared with SSP. The verified results of using the CSP-100 plan proved a reduced inspection time of 6,722,702 minutes or 15% compared to SSP. CSP-100 also eliminates the work stations and transportation processes due to the inspection area and inspectors are no longer required. The Function Out of Box Audit (FOBA) is introduced to monitor the CSP-100 performance. The FOBA audit results confirm that the CSP-100 maintains the same good quality level as the SSP. The excellent results of implementing the CSP-100 show a reduction in the inspection cost by 3,693,730.04 baht or 60.40% compared to SSP, as well as the additional cost savings by no longer needing to purchase a new tester; a savings of ~44 million baht. The CSP-100 plan also eliminates the issue of delayed delivery that is part of the SSP process. Moreover it is a better choice in inspecting the continuous quality process in Hard Disc Drive manufacturing.
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