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McGraw-Hill/Irwin Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved.
Quality Management and Six Sigma Chapter 10
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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.
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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
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The Quality Gurus
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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
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Costs of Quality
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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
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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
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Six Sigma Methodology
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DMAIC Cycle
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Six Sigma Analytical Tools
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Cause-and-Effect Diagram (Fishbone Diagram)
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Process Control Chart
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Statistical Quality Control (SQC) The
quantitative aspects of quality management
Processes usually exhibit some variation in their output
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Measuring Variation
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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
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Process Capability
Process control limits exceed specification limits – process is not capable of meeting requirements
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Process Capability
Specification control limits exceed process limits (for improved process) – process is capable of meeting requirements
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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
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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
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Process Control Measurements – p Charts Used when an item (or service) is either
good or bad (a yes-no decision)
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Creating p Charts
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Process Control Measurements – c-Charts Used when an item (or service) may
have multiple defects
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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
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X-bar and R-Charts
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Process Control Charts - Interpretation
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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
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Acceptance Sampling - Purposes Determine quality level Ensure quality is within
predetermined level
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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
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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
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Operating Characteristic Curve