Total Quality Manufacturing

1
Chapter 12

• Total Quality Manufacturing

2
Attributes of Quality

• Quality Definitions
• Transcendent innate excellence or I know it
  when I see it view.
• Product-based function of product attributes or
  more is better view.
• User-based customer satisfaction or beauty is
  in the eye of the beholder view.
• Manufacturing-based conformance to
  specifications, related to do it right the
  first time view.
• Value-based price/performance or affordable
  excellence or getting your moneys worth view.

3
Attributes of Quality (cont.)

• Customer Orientation
• Customer satisfaction depends on external quality
• External quality depends on internal quality
• Quality must address product, process, system

4
Attributes of Quality (cont.)

• Internal Quality conformance with quality
  specifications inside the production operations
• Error prevention
• Inspection improvement
• Environment enhancement
• Measured through scrap, rework, etc
• External Quality how the customer views the
  product
• Measured through customer satisfaction
• Return rate
• Customer surveys
• Field sales data

5
Statistical Process Control

• Starts with a measurable quality attribute ie
  plate thickness, dimensions etc
• Variability will always exist
• Natural variability small and caused by
  uncontrollable sources
• Assignable cause variation larger and can be
  traced to their causes
• A process that is operating stably within its
  natural variation is in statistical control
• Caveat adjusting process to reduce natural
  variation will likely deteriorate the performance
  to specification
• See example on Page 386

6
Quality and Operations

• Quality and Cost
• Traditional IE view - Cost increases with
  quality? (e.g., better materials)
• TQM view - Cost decreases with quality? (e.g.,
  less correction cost)
• Reality is a balance
• Quality Supports Operations
• Law Variability causes congestion.
• Law Congestion increases nonlinearly with
  utilization.
• Yield loss and rework are major sources of
  variability and lost capacity.
• Operations Supports Quality
• Excess WIP obscures problems and delays/prevents
  diagnosis
• Excess cycle time degrades quality of service

7
Rework on a Single Station
t 1
1- p
r 1/3
p
8
Rework in a Line
2/3
1
2/3
2/3
1- p
p
9
Rework

• Law ( Rework) For a given throughput level,
  rework increases both the mean and standard
  deviation of the cycle time of a process
• Throughput Effects if the rework is high enough
  to cause a bottleneck or is on the bottleneck, it
  can substantially alter the capacity of the line
• WIP Effects Rework on a non-bottleneck increases
  variability in the line thereby requiring higher
  WIP and Cycle Time for a given level of
  throughput
• Lead Time Effects Rework decreases capacity,
  increases variability, increases WIP and
  therefore increases lead times
• Possible Cures
• Eliminate rework.
• Use non-bottleneck for reworking.
• Shorten rework loop.

10
Quality and the Supply Chain

• Importance
• All manufacturing systems involve purchased parts
• Trend toward outsourcing and virtual
  manufacturing
• A chain is only as good as its weakest link
• Vendor Quality
• Product quality
• Service quality
• Assembly Systems
• Magnify impacts of vendor quality problems
• Require effective vendor selection/management

11
Safety Lead Times in Assembly Systems

• Required Service
• Single Component 95 service level
• 10 Component Assembly If each has 95 service
  then
• ProbAll components arrive on time (0.95)10
  0.5987
• so to get 95 service on the assembly we need
  each component to have p service, where
• p10 0.95
• p 0.951/10 0.9949

12
Conclusions

• Good quality supports good operations
• Quality production
• Increases Capacity
• Increases throughput
• Reduces WIP, cycle time and lead times
• Good operations supports quality improvement
• Reducing WIP reduces the amount of product
  generated between the cause of a defect and its
  detection
• Good quality at the supplier level promotes good
  operations and quality at the plant level
• Promotes reliability