History of SPC

• World War 2 and aftermath

• 1980’s

• Taguchi, Design of Experiments

Cost of Manufacturing

Cost

$

LSL USL

Rework

Good

Scrap

Traditional View

Taguchi Loss Function

LSL USL

Target

Lossin $

Loss = k (x-target)2

Accounting for:

Defects

Inspection

Customer Dissatisfaction

Rework

Engineering Attention

Modern Day Quality

• Deming Award, Baldrige Award, ISO9000

• Legacy of Deming and Juran

• Motorola, IBM, GE >>>> 6 Sigma

Motorola’s Process Improvement Flowchart

3 Map the process flow / critical processes3 Map the process flow / critical processes

1 Prioritize opportunities for improvement1 Prioritize opportunities for improvement

2 Select a viable team2 Select a viable team

4 Perform measurement system analysis4 Perform measurement system analysis

5 Verify critical processes5 Verify critical processes

• 8 Monitor processes - keep them stable -

do not over-correct

8 Monitor processes - keep them stable -do not over-correct

9 Experiment for reduction of common variation for continuous improvement.

9 Experiment for reduction of common variation for continuous improvement.

7 Implement optimal operating conditions,preventive and corrective action plans.

7 Implement optimal operating conditions,preventive and corrective action plans.

6 Apply SPC, remove special causes of variation, perform process capability

6 Apply SPC, remove special causes of variation, perform process capability

10 Implement engineering changes fromexperiment results and re-check capabilities

10 Implement engineering changes fromexperiment results and re-check capabilities

Quality Costs

• Prevention - pay now to improve later

• Appraisal • Failure

Advantages of Histograms

Pictures are easily understood

Measure the effect of corrective actions (histograms before and after)

Compare parallel processing equipment

Compare sample data to specifications

Some disadvantages of histograms:

Large sample sizes are needed

Time effects are not visible

• Special cause variability is not easily separated

Homework for Sept 9 from Text Problems on p.77-81, 2-2, 2-6, 2-35, 2-38.Also: #1A - Referring to prevention, appraisal, and failure costs, what is the preferred method for a company to manage its total quality cost ? Write a paragraph.