EIN6227-03Control - Outreach Engineering Management EIN...

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Outreach Engineering Management EIN 6227: Lecture 3 Process Control Joseph C. Hartman Industrial and Systems Engineering University of Florida Gainesville, FL OEM 2009 Orlando, FL, Fall 2008
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Outreach Engineering Management Our process has been designed and verified…. We are now “up and running” Important to monitor the process: Defines a process as being in control (or not) Allows for changes/errors to be detected and corrected (after investigation) Allows for capability to be measured Process Control
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Outreach Engineering Management Variation is a deviation from mean (norm) Cannot be avoided: no process is perfect Common Causes Interactions of machinery, people, materials leads to process variations Should appear random Assignable Causes Changes from normal operations cause “spikes” in output – outside normal variation range Examples: new operator, worn machine, bad materials, etc. Variation Exists
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Outreach Engineering Management Increases unpredictability More variation clouds process outcomes Reduces capacity Must plan for “down” times Increases “bullwhip” effect Leads to increases in inventory Makes it difficult to detect problems Goal: Reduce Variation
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Outreach Engineering Management Statistical Process Control Detect assignable variation Can then fix it Common variation not “treatable” Only way to reduce is through a process re-design (i.e., new machinery, etc.) Goal: Reduce Variation
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Outreach Engineering Management For tracking variables (continuous data) x-bar charts R-charts s-charts x-charts Cusum charts For tracking attributes (binary data) p and np charts c and u charts Process Control Tools
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Outreach Engineering Management Control Chart Selection Quality Characteristic variable attribute n>1? n>=10 or computer? x and MR no yes x and s x and R no yes defective defect constant sample size? p-chart with variable sample size no p or np yes constant sampling unit? c u yes no
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Outreach Engineering Management 1. Prepare Choose measurement (temp, speed, output, etc.) Determine how to collect data, sample size, and frequency of sampling n = 3 to 5 samples every fixed time period Want homogeneous samples (more needed for finer variance detection) 2. Collect Data Record data Calculate appropriate statistics (mean, range) Plot statistics on chart Building a Control Chart
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How Many Samples? Large sample size increases probability of detection, at a cost.
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This note was uploaded on 05/12/2010 for the course EIN 6227 taught by Professor Hartman during the Fall '08 term at University of Florida.

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EIN6227-03Control - Outreach Engineering Management EIN...

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