2 How to use the seven tools of quality Tools for identifying problems / collecting data Check sheets Scatter diagrams Statistical process control (SPC) chart Tools to organize the data Pareto charts Histogram Tools for generating ideas Cause-and-effect diagrams Flowcharts

DMAIC Process Define Identify customers and their priorities Identify and define a suitable project Identify CTQs (critical-to-quality characteristics) Measure Determine how to measure the process and how it is performing Identify key internal processes that influence CTQs Measure current defects

DMAIC Process Analyze Determine likely causes of defects Understand why defects are generated by identifying key variables that cause process variation Improve Identify means to remove causes of defects Confirm key variables and quantify their effects on CTQs

DMAIC Process Improve Identify the maximum acceptable ranges of the key variables and a system for measuring deviations of the variables Modify the process to stay within the acceptable range Control Determine how to maintain improvements Put tools in place to ensure that key variables remain within acceptable ranges under the modified process

6 Linking the seven tools to the DMAIC quality cycle Define flowcharts (to understand process – baseline knowledge) Measure checksheets (to collect data) scatter diagrams (to collect data / look for patterns) Analyse flowcharts (looking for steps where mistakes occur) cause & effect diagrams (to suggest possible sources of error) histograms (to organise / understand data) pareto charts (ranking errors most important to least important) Improve ????? Control run and control charts (to monitor processes)

Cost of Quality Measurement Cost of quality: Costs associated with avoiding poor quality or those incurred as a result of poor quality Applications Better communication between operations managers and senior-level managers Identify and justify major improvement opportunities Evaluate the importance of quality and improvement in operations

Categories of Quality Costs Prevention costs: Expended to keep nonconforming goods and services from being made and reaching the customer Quality planning costs Process-control costs Information-systems costs Training and general management costs

Categories of Quality Costs Appraisal costs: Expended on ascertaining quality levels through measurement and analysis of data to detect and correct problems Test and inspection costs Instrument maintenance costs Process-measurement and process-control costs

Categories of Quality Costs Internal failure costs: Incurred as a result of unsatisfactory quality that is found before the delivery of a good or service to the customer Scrap and rework costs Costs of corrective action Downgrading costs Process failures

Categories of Quality Costs External failure costs: Incurred after poor-quality goods or services reach the customer Costs due to customer complaints and returns Goods and services recall costs and warranty and service guarantee claims Product-liability costs

All production processes have some variation Time / number of samples Data range UCL LCL mean Resulting normal distribution

Mean and Range Charts (a) These sampling distributions result in the charts below (Sampling mean is shifting upward, but range is consistent) R-chart (R-chart does not detect change in mean) UCL LCL x-chart (x-chart detects shift in central tendency) UCL LCL

Mean and Range Charts R-chart (R-chart detects increase in dispersion) UCL LCL (b) These sampling distributions result in the charts below (Sampling mean is constant, but dispersion is increasing) x-chart (x-chart indicates no change in central tendency) UCL LCL

Patterns in Control Charts Normal behavior. Process is “in control.” Upper control limit Target Lower control limit Figure S6.7

Patterns in Control Charts One plot out above (or below). Investigate for cause. Process is “out of control.” Upper control limit Target Lower control limit Figure S6.7

Patterns in Control Charts Trends in either direction, 5 plots. Investigate for cause of progressive change. Upper control limit Target Lower control limit Figure S6.7

Patterns in Control Charts Two plots very near lower (or upper) control. Investigate for cause. Upper control limit Target Lower control limit Figure S6.7

Patterns in Control Charts Run of 5 above (or below) central line. Investigate for cause. Upper control limit Target Lower control limit Figure S6.7

Patterns in Control Charts Erratic behavior. Investigate. Upper control limit Target Lower control limit Figure S6.7