Process capability index - asymmetrical positioning, Operation Management

Assignment Help:

Process Capability Index - Asymmetrical Positioning of the Process

As stated earlier, the Cp index assumes that the process mean is centred within the tolerance band, but, in practice, this is often an unreasonable assumption. For this reason, alternative indices have been devised which take account of asymmetrical positioning of the process mean relative to mid-tolerance. Consider the process output represented in this next figure, for which the LSL is 10, the USL is 20, the process mean (µ) is 18 and the standard deviation (σ) is 1.166. For this process the Cp index value is 1.43 [i.e. (20 - 10)/ (6 × 1.166)], which might suggest that the output has a very low level of non-conformance. However, as can be seen from the figure, a significant proportion of the output actually lies beyond the upper specification limit. The Cpk index takes account of the asymmetry by relating the spread of one side of the output distribution (3σ) to the difference between the process mean (µ) and the nearest specification limit. Two calculations are performed, and the lowest value (worst case) is taken as the index value.

1148_Process Capability Index – Asymmetrical Positioning of the Process.png

In the example in the figure above, the Cpk index is 0.57 [ie (20 - 18)/(3 × 1.166)], indicating that the process, as currently set, is not capable of producing to the design specification. The following figure shows the significance of different Cpk values.

1302_Process Capability Index – Asymmetrical Positioning of the Process 1.png


Related Discussions:- Process capability index - asymmetrical positioning

Explain shipment to foreign markets, A U.S. manufacturer that exports goods...

A U.S. manufacturer that exports goods made at its U.S. plants for shipment to foreign markets

Calculate electrical, Test results from an electronic circuit board indicat...

Test results from an electronic circuit board indicate that 50% of board failures are caused by assembly defects, 30% are due to electrical components, and 20% are due to mechanica

Linear trend equation, A cosmetics manufacturers marketing department has d...

A cosmetics manufacturers marketing department has developed a linear trend equation that can be used to predict annual sales of its popular Hand and Foot Cream. We are given F sub

Objectives of production control, Objectives of Production Control An...

Objectives of Production Control An enterprise wishes to obtain the following objectives through production control: 1.Making necessary arrangement for the production of goo

Explain different types of decisions, Explain Different types of Decisions....

Explain Different types of Decisions. Different types of Decisions: Decisions may be of various types. Several of the significant types of managerial decisions are explained

Quality management systems - improving productivity, Quality Management Sys...

Quality Management Systems - Improving Productivity The introduction of approaches such as ISO 9000; Total quality management, business process reengineering, just-in-time ope

Write the facultyids of faculty who are not qualified, Using the following ...

Using the following tables (primary keys are underlined), write the expressions that follow in SQL. STUDENT (StudentID, StudentName) FACULTY(FacultyID, FacultyName) COURSE(CourseID

Explain weeks of supply, The Bawl Corporation supplies alloy ball bearings ...

The Bawl Corporation supplies alloy ball bearings to auto manufacturers in Detroit. Because of its specialized manufacturing process, considerable work-in-process and raw materials

Five focusing steps of theory of constraints, Five Focusing Steps of Theory...

Five Focusing Steps of Theory of Constraints Evaporating clouds  This is a term used to describe a methodology developed by Goldratt to resolve conflicts in a 'win-win' m

Design of goods and services, construct a house of quality matrix for a wri...

construct a house of quality matrix for a wristwatch?

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd