ILE_462_Lecture_notes_10 - 28.04.2010 ILE 462 Quality...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
28.04.2010 1 ILE 462 Quality Assurance and Reliability Lecture Notes IE 482 - Quality Engineering Lecture Notes 2 Acceptance Sampling • is an auditing tool • does not control or improve the quality level of the process • used to decide whether or not to accept a lot is a form of inspection applied to lots or batches of items before or after a process, to judge conformance with predetermined standards
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
28.04.2010 2 3 Acceptance Sampling • can be performed – during inspection of incoming raw materials, components, and assemblies – during final product inspection – as a form of product inspection between companies and their vendors, between manufacturers and their customers, between departments within the same company Acceptance Sampling For attributes For variables 4 Results compared with acceptance criteria Accept the lot Send to production or to customer Decide on disposition Sample selected and analyzed Lot received for inspection Reject the lot Acceptance Sampling
Background image of page 2
28.04.2010 3 5 Advantages and Disadvantages of Acceptance Sampling • Arguments for: – More economical and requires less time • If inspection cost is high or if inspection time is long, sampling is preferable – If inspection is destructive, 100% inspection is not feasible – Requires less handling – Reduces inspector fatigue – Provides a strong motivation to improve quality because an entire batch or lot may be rejected • Arguments against: – Risk of rejecting “good” lots (producer’s risk) or accepting “poor” lots (consumer’s risk) – Does not make sense for stable processes – Only detects poor quality; does not help to prevent it – Does not help suppliers improve – Selection and adoption of a sampling plan require more time an effort in planning and documentation 6 Some related definitions Consumer s risk – the risk of accepting a poor lot Producer s risk – the risk associated with rejecting a lot of good quality Acceptance quality level (AQL) – the percentage of defects at which consumers are willing to accept lots as good . In other words, the AQL is the maximum percent defective that is allowed as a process average L ot tolerance percent defective (LTPD)/ Rejectable quality level (RQL) / Limiting quality level (LQL): – the percentage of proportion of nonconforming items or number of nonconformities in a lot for which the consumer wishes the probability of acceptance to be a specified low value
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
28.04.2010 4 7 Operating Characteristic Curve • Operating characteristic (OC) curves are graphs of the probability of acceptance of a lot for all possible lot levels of percent defective – shows the discriminatory power of the sampling plan – constructed from a Poisson probability distribution – can be constructed using Poisson curves • construct the OC curve for a lot of 5000 items and 2% defectives assuming 200 items sample 8 Poisson Probabilities
Background image of page 4
28.04.2010 5 9 OC curve example
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/08/2012 for the course INDUSTRY 462 taught by Professor Nidaikordal during the Spring '12 term at Cyprus International University.

Page1 / 24

ILE_462_Lecture_notes_10 - 28.04.2010 ILE 462 Quality...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online