Quality Management and Six Sigma

McGraw-Hill/Irwin Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved.

Quality Management and Six Sigma Chapter 10

10-2

Learning Objectives1. Understand total quality management.2. Discuss how quality is measured and the different dimensions of quality.3. Explain the Six Sigma quality philosophy.4. Explain the define, measure, analyze, improve, and control (DMAIC) quality improvement process.5. Show how to calculate the capability of a process.6. Describe how processes are monitored with control charts.7. Understand acceptance sampling concepts.

10-3

Total Quality Management (TQM) Total quality management - managing

the entire organization so that it excels on all dimensions of products and services that are important to the customer

Two fundamental operational goals1. Careful design of the product or service2. Ensuring that the organization’s systems

can consistently produce the design

10-4

The Quality Gurus

10-5

Quality Specifications and Quality Costs Design quality

- inherent value of the product in the marketplace

Conformance quality - degree to which the product or service design specifications are met

10-6

Costs of Quality

10-7

International Organization for Standardization (ISO) Series of standards agreed upon by the

International Organization for Standardization (ISO)

Adopted in 1987 More than 160 countries A prerequisite for global competition? ISO 9000 directs you to "document what you do

and then do as you documented“ ISO 14000 is a family of standards on

environmental management ISO 26000 encourages organizations to discuss

social responsibility issues and possible actions with relevant stakeholders

10-8

Six Sigma A philosophy and set of methods

companies use to eliminate defects in their products and processes

Seeks to reduce variation in the processes that lead to product defects

The name, “six sigma” refers to the goal of no more than four defects per million units

10-9

Six Sigma Methodology

10-10

DMAIC Cycle

10-11

Six Sigma Analytical Tools

10-12

Cause-and-Effect Diagram (Fishbone Diagram)

10-13

Process Control Chart

10-14

Statistical Quality Control (SQC) The

quantitative aspects of quality management

Processes usually exhibit some variation in their output

10-15

Measuring Variation

10-16

Process Capability The ability of a process to consistently

produce a good or deliver a service with a low probability of generating a defect

Specification limits – range of variation that is considered acceptable by the designer or customer

Process limits – range of variation that a process is able to maintain with a high degree of certainty

10-17

Process Capability

Process control limits exceed specification limits – process is not capable of meeting requirements

10-18

Process Capability

Specification control limits exceed process limits (for improved process) – process is capable of meeting requirements

10-19

Ratio of the range of values produced divided by the range of values allowed

Shows how well the parts being produced fit into the range specified by the design specifications

Cpk larger than one indicates process is capable

When the two numbers are not close, indicates mean has shifted Excel: Process

Capability

10-20

Process Control Procedures Concerned with monitoring quality

while the product or service is being produced

Statistical process control - testing a sample of output to determine if the process is producing items within a preselected range

Attributes - quality characteristics that are classified as either conforming or not conforming

Variable - characteristics that are measured using an actual value Excel: Statistic

al Process Control

10-21

Process Control Measurements – p Charts Used when an item (or service) is either

good or bad (a yes-no decision)

10-22

Creating p Charts

10-23

Process Control Measurements – c-Charts Used when an item (or service) may

have multiple defects

10-24

Variable Measurement Process Control Charts – X-bar and R-Charts Size of samples

Preferable to keep small (usually 4 or 5 units) Number of samples

Once chart set up, each sample compared to chart Use about 25 samples to set up chart

Frequency of samples Tradeoff between cost of sampling and benefit of

adjusting the system Control limits

Generally use z=3

10-25

X-bar and R-Charts

10-26

Process Control Charts - Interpretation

10-27

Acceptance Sampling Performed on goods that already exist to

determine what percentage of the products conform to specifications

Executed through a sampling plan Results include accept, reject, or retest

10-28

Acceptance Sampling - Purposes Determine quality level Ensure quality is within

predetermined level

10-29

Acceptance Sampling

Risks of accepting “bad” lots and rejecting “good” lots

Added planning and documentation

Sample provides less information than 100-percent inspection

Economy Less handling damage Fewer inspectors Upgrading of the inspection

job Applicability to destructive

testing Entire lot rejection

(motivation for improvement)

Disadvantages Advantages

10-30

Acceptance Sampling – Designing a Sampling Plan Determine (1) how many units, n, to sample

from a lot, and (2) the maximum number of defective items, c, that can be found in the sample before the lot is rejected

10-31

Operating Characteristic Curve