Improving Stable Processes

Improving Stable Processes - Improving Stable Processes...

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Improving Stable Processes Professor Tom Kuczek Purdue University Using process knowledge to identify uncontrolled variables and control variables as inputs for Process Improvement 1
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Process may be off Target or Have Excess Variation X-double bar is the estimate of the process mean which may be off target. Sigma(X) is the estimate of Common Cause Variation. Both of these contribute to the Capability of the process, . pk C 2
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Improving Common Cause Common causes of variation usually cannot be reduced by trying to explain differences between values when the process is stable. Uncontrolled variation and control variables must be understood to partition Common Cause Variation into basic sources. Stable processes will require some degree of change to improve Common Cause. 3
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Partitioning Uncontrolled and Controlled Variables into Sources 4
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Sources of variation Describe where in the preceding flowchart one can find sources of variation: 5
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Analyze Between and Within Supplier Variation Different suppliers are a between source of variation. Raw materials from a single supplier is a within source of variation. Control charts can be used to look for special cause between suppliers to reduce variability between suppliers. 6
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Variables in the Production Process Variables in the production process may be uncontrolled variables or control variables. Uncontrolled variables are variables which may affect the output of the process, but which are not currently controlled. Control variables are variables such as process settings which affect the outcome of the process. 7
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Partitioning Uncontrolled and Controlled Variables into Sources 8
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Controllable and uncontrollable Where in the flowchart are variables controllable and/or uncontrollable and to what extent? 9
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Output Variables Output Variables are measurements of the resulting product. The chosen measures for the product are measures of the product characteristics important to the customer. Customers may be internal or external to the organization. 10
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Part I: Reducing Output Variation Around the Target Output variation of the product may be broken down into two sources: 1. Actual variation of the “true” product characteristic, often around a target value, usually designated by the symbol tau τ “. 2. Variability in the measurement process, which may introduce bias or added variation to the measurement of the characteristic, which occurs in the measurement process itself. 11
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Measuring things Give examples of products/services that we measure for quality characteristics and how: 12
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Product Characteristic Variation: Parameter Design Let us first concentrate on the product characteristic value of interest to our customer. There are two main issues here: 1. To center our product as close to the target value , τ , as possible.
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This note was uploaded on 02/20/2012 for the course STAT 513 taught by Professor Na during the Spring '11 term at Purdue University-West Lafayette.

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Improving Stable Processes - Improving Stable Processes...

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