9 - Quality Control and Improvement

9 - Quality Control and Improvement - Operations Management...

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Unformatted text preview: Operations Management Contemporary Concepts and Cases Chapter Nine Chapter Quality Control and Improvement Outline Outline Design of Quality Control Systems Process Quality Control Attribute Control Variables Control Using Control Charts Process Capability Continuous Improvement Six Sigma Lean and Six Sigma Quality Control and Improvement in Industry 9-2 Design of Quality Control Systems Design Break down production process into Break subprocesses and “internal customers.” subprocesses Identify “Critical points” where inspection or Identify measurement should take place measurement Four steps in designing QC systems. 9-3 Steps in Designing QC Systems Steps Identify critical points • Incoming materials & services • Work in process • Finished product or service Decide on the type of measurement Decide • • variables attribute Decide on the amount of inspection to be used. Decide who should do the inspection 9-4 Types Of Measurement Types Attribute measurement –Product characteristic evaluated with a discrete Product choice: choice: Good/bad, yes/no Variables measurement –Product characteristic that can be measured on a Product continuous scale: continuous Length, size, weight, height, time, velocity 9-5 Process Quality Control Process Basic assumptions (tenets) of Process Quality Basic Control: Control: – Every process has random variation in it. – Production processes are not usually found in a state of Production control. control. “State of Control”; what does it mean? – Unnecessary variation is eliminated. – Remaining variation is because of random causes. 9-6 Process Quality Control Process Assignable (special) causes – Can be identified and corrected Common causes – Occur randomly – Cannot be changed unless process is redesigned 9-7 Attributes & Variables Attributes Attributes are counts, such as the Attributes number (or proportion) of defects in a sample. sample. Variables are measures (mean & Variables range or standard deviation) of critical characteristics in a sample. critical 9-8 LCL = D3R Formulas for SPC (3 Sigma) Formulas p-Chart LCL = D3R x-Bar Chart R-Chart p (1 − p ) p±3 n x ± A2 R LCL = D 3 R UCL = D4 R 9-9 Continuous Improvement Continuous Aim of continuous improvement is to reduce Aim the variability of the product or process the Processes with strategic importance and low Processes process capability should be selected first for improvement improvement Use seven tools of quality control 9-10 Seven Tools of Quality Control Seven (See Figure 9.5) Flow Charts Run (trend) charts Control Charts Cause-Effect (fishbone or Ishikawa) charts Pareto Charts Histogram Scatter (x-y) Diagram 9-11 Six-Sigma Quality Six-Sigma Pioneered by Motorola in 1988 (Juran claims credit for the Pioneered idea). idea). 3.4 defects per million Sample size rules become unusable Most process are 4 sigma, e.g. payroll, prescriptions, baggage Most handling, journal vouchers, restaurant bills. handling, Airline fatalities are 6.4 sigma IRS tax advice is less than 2 sigma Criticism: accepts 3.4 defects/million. Is not zero defects. 9-12 Six Sigma Quality Six Process Improvement steps of Six Sigma Process (DMAIC): (DMAIC): 1. Define 2. Measure 3. Analyze 4. Improve 5. Control 9-13 Six Sigma Quality Six Six Sigma uses a project/team approach. A process is selected for improvement A cross-functional team is formed. A six sigma ‘black belt’ is chosen to head the six team. team. The team uses the DMAIC method for The finding root causes and improving the process. process. 9-14 Lean and Six Sigma Lean Are complementary approaches to Are improvement. improvement. – – Lean seeks to eliminate waste. Six sigma seeks to eliminate defects. Six sigma organization is more formal and Six training intensive. training Six sigma is project focused; lean is more Six broad based. broad 9-15 Quality Control and Improvement in Industry in 75% use process control charts. More use of variable (x-bar and R) charts than More attribute (p) charts because of sample size requirements. requirements. Six Sigma rapidly gaining acceptance Quality control in the service industry Quality (SERVQUAL) (SERVQUAL) 9-16 Summary Summary Design of Quality Control Systems Process Quality Control Attribute Control Variables Control Using Control Charts Process Capability Continuous Improvement Six Sigma Lean and Six Sigma Quality Control and Improvement in Industry 9-17 End of C hapte Nine r 9-18 ...
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This note was uploaded on 06/21/2011 for the course DSCI 304 taught by Professor Gonzalez,m during the Spring '08 term at CofC.

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