Module 5

Quality refers to the ability of a product or service to consistently

meet or exceed customer requirements or expectations.

Quality

2
  Product quality is often judged on eight dimensions of quality:
1. Performance —main characteristics of the product.
2. Aesthetics —appearance, feel, smell, taste.
3. Special features —extra characteristics.
4. Conformance —how well a product corresponds to design
specifications.
Product Quality 5. Reliability —dependable performance.
6. Durability —ability to perform over time.
7. Perceived quality —indirect evaluation of quality (e.g.,
reputation).
8. Serviceability —handling of complaints or repairs.

3
  Some of the major areas affected by quality are:
 Loss of business.
 Liability.
 Productivity.
 Costs.
Consequences of
Poor Quality  Cost of Quality:
 Prevention costs
 Appraisal and control costs
 Internal failure costs
 External failure costs

4
 1. Prevention costs include costs of quality training, design reviews,
and other activities aimed at preventing errors. The cost of quality
planning is a prevention cost.

2. Appraisal and control costs relate to the evaluation of products

and processes, including product reviews, audits, tests, and
inspections.
Cost of Quality 3. Internal failure costs are costs associated with nonconformities
identified by the producer, such as the cost of scrap, rework, and
retest.

4. External failure costs are costs incurred after delivery to a client

and include cost for replacements, warranty repairs, liability, and
lost sales as a result of a damaged reputation. All of these costs
are associated with failures identified by the customers.

5
 In the absence of quality, the following will result:

 Dissatisfied customers due to increased maintenance and operating

costs of products/ services
Need for
 Increased rework cost while manufacturing products/providing
Controlling services
Quality
 Difficulty in maintaining consistency in quality

 Reduced life time of the products/services

 Reduced flexibility with respect to usage of standard spare parts.

6
  Eliminates waste through continuous improvement and focus on
exactly what the customer wants
 Lean operations are driven by workflow initiated by the “pull” of
the customer’s order.
Lean
 Just-in-time (JIT) is an approach of continuous and forced problem
Operations solving via a focus on throughput and reduced inventory.
 The Toyota Production System (TPS), with its emphasis on
continuous improvement, respect for people, and standard work
practices, is particularly suited for assembly lines
  Overproduction: Producing more than the customer orders or
producing early (before it is demanded) is waste.
 Queues: Idle time, storage, and waiting are wastes (they add no
value).
 Transportation: Moving material between plants or between work
centers and handling it more than once is waste.
 Inventory: Unnecessary raw material, work-in-process (WIP),
Seven Waste finished goods, and excess operating supplies add no value and are
wastes.
 Motion: Movement of equipment or people that adds no value is
waste.
 Overprocessing: Work performed on the product that adds no value
is waste.
 Defective product: Returns, warranty claims, rework, and scrap are
wastes.
  Sort/segregate: Keep what is needed and remove everything else
from the work area; when in doubt, throw it out. Identify nonvalue
items and remove them. Getting rid of these items makes space
available and usually improves workflow.
 Simplify/straighten: Arrange and use methods analysis tools to
improve workflow and reduce wasted motion. Consider long-run
and short-run ergonomic issues. Label and display for easy use only
what is needed in the immediate work area.
5S  Shine/sweep: Clean daily; eliminate all
contamination, and clutter from the work area.
forms of dirt,

 Standardize: Remove variations from the process by developing

standard operating procedures and checklists; good standards make
the abnormal obvious. Standardize equipment and tooling so that
cross-training time and cost are reduced. Train and retrain the work
team so that when deviations occur, they are readily apparent to all.
 Sustain/self-discipline: Review periodically to recognize efforts
and to motivate to sustain progress. Use visuals wherever possible
to communicate and sustain progress.
  Variability is any deviation from the optimum process that delivers
a perfect product on time, every time.
 Variability is a polite word for problems.
Sources of variability are:
Remove  Poor processes that allow employees and suppliers to produce
Variability improper quantities or nonconforming units
 Inadequate maintenance of facilities and processes
 Unknown and changing customer demands
 Incomplete or inaccurate drawings, specifications, and bills of
material
Reduce
Inventory and
Variability

High levels of inventory hide problems (a), but as we reduce inventory, problems are
exposed (b), and finally after reducing inventory and removing problems, we have
lower inventory, lower costs, and smooth sailing (c).
Reduce Lot
Sizes
  The rate at which units move through a process is called as
throughput.
Improve  Manufacturing cycle time: The time between the arrival of raw
Throughput materials and the shipping of finished products.
 Pull system: A concept that results in material being produced only
when requested and moved to where it is needed just as it is needed
Lean and JIT
  One way to achieve small lot sizes is to move inventory through the
shop only as needed rather than pushing it on to the next
workstation whether or not the personnel there are ready for it.
Kanban  Kanban is the Japanese word for card, which has come to mean
“signal”; a kanban system moves parts through production via a
“pull” from a signal.
Diagram of
Storage Area
with Warning-
Signal Marker
  Hobbs Bakery produces short runs of cakes that are shipped to
grocery stores. The owner, Ken Hobbs, wants to try to reduce
inventory by changing to a Kanban system. He has developed the
following data and asked you to finish the project.

Kanban  Production lead time = Wait time + Material handling time +

Processing time = 2 days
Problem  Daily demand = 500 cakes
 Safety stock = 1/2 day
 Container size (determined on a production order size EOQ basis) =
250 cakes
  Demand during lead time
= Lead time * Daily demand = 2 days * 500 cakes = 1,000
 Safety stock = 1/2 * Daily demand = 250
Solution  Number of kanbans (containers) needed
= (Demand during lead time + Safety stock)/Container size
= (1,000 + 250) / 250 = 5
 Once the reorder point is hit, five containers should be released.
  Toyota Motor’s Eiji Toyoda and Taiichi Ohno are given credit for
the Toyota Production System (TPS; see the Global Company
Lean and the Profile that opens this chapter).
Toyota  Three components of TPS are
 continuous improvement
Production  respect for people
System  standard work practice
which are now considered an integral part of Lean.
  Respect and develop employees by improving job design,
providing constant training, instilling commitment, and building
teamwork.
 Empower employees with jobs that are made challenging by
pushing responsibility to the lowest level possible.
 Develop worker flexibility through cross-training and reducing job
Building a classifications.
Lean  Build processes that destroy variability by helping employees
produce a perfect product every time.
Organization
 Develop collaborative partnerships with suppliers, helping them
not only to understand the needs of the ultimate customer, but also
to accept responsibility for satisfying those needs.
 Eliminate waste by performing only value-added activities. Material
handling, inspection, inventory, travel time, wasted space, and
rework are targets, as they do not add value.
 Quality management consists of quality planning, quality assurance
and quality control.
 Quality planning is a process to guide future quality activities; it
sets the requirements and standards to be met, as well as the actions
necessary to meet those requirements and standards.
Processes of  Quality assurance is the process to perform the planned quality
Quality activities and to ensure that the processes necessary to meet the
quality standards and products requirement.
Management  Quality control is the process to ensure that quality assurance
activities are being performed (or have been performed) according
to approved quality plans, and that product/service requirements
and standards are being met. In the event that unsatisfactory
performance or nonconformities (defects) are identified, the causes
must be determined and eliminated.

21
  Quality planning should provide confidence that everything
necessary to ensure quality has been thought through.

It has two aspects:

Quality Planning
1. Establishing quality management procedures and policies for the
entire organization

2. Establishing a quality plan as part of the master plan (Master

schedule material planning) in manufacturing process.

22
 Quality assurance relates to the execution of the quality management plan.
It reduces the risks related to not meeting desired features or performance
requirements of deliverables.

1. Activities performed in a specific product/service to ensure that

Quality requirements are being met and that the product/ service is being
produced/ provided according to the quality plan.
Assurance
2. Activities that contribute to the continuous improvement of current
and future products/services, and to the quality management maturity
of the organization.

23
  Quality control is the on-going process of monitoring and
appraising work, and taking corrective action so as to achieve the
planned quality outcomes.
 The process also verifies that quality assurance activities are
being performed according to the quality plan, and that product
Quality Control requirements and specifications are being met.
 Whenever nonconformities are uncovered, the causes are
determined and eliminated.
 It must be integrated with production planning, cost control,
inventory control, and risk control. It is a responsibility of the
production manager.

24
  Management of an entire organization so that it excels in all aspects
of products and services that are important to the customer.
 Seven concepts for an effective TQM program:
(1) continuous improvement

Total Quality (2) Six Sigma

Management (3) Employee empowerment

(4) Benchmarking,
(5) Just-in-Time (JIT)
(6) Taguchi concepts
(7) Knowledge of TQM tools.
 1. Create consistency of purpose.
2. Lead to promote change.
3. Build quality into the product; stop depending on inspections to catch problems.
4. Build long-term relationships based on performance instead of awarding business on the
Deming’s 14 basis of price.

Points for 5. Continuously improve product, quality, and service.

6. Start training.
Implementing 7. Emphasize leadership.
Quality 8. Drive out fear.
Improvement 9. Break down barriers between departments.
10. Stop haranguing workers.
11. Support, help, and improve.
12. Remove barriers to pride in work.
13. Institute a vigorous program of education and self-improvement.
14. Put everybody in the company to work on the transformation.
Continuous
Improvement
 Check Sheets

TQM Tools
Scatter Diagrams
Cause-and-
Effect
Diagrams
  Pareto charts are a method of organizing errors, problems, or
defects to help focus on problem solving efforts. They are based on
Pareto Charts the work of Vilfredo Pareto, a 19th-century economist.
 Joseph M. Juran popularized Pareto’s work when he suggested that
80% of a firm’s problems are a result of only 20% of the causes.
  Flowcharts graphically present a process or system using annotated
boxes and interconnected lines.
 They are a simple but great tool for trying to make sense of a
process or explain a process.

Flowcharts
Histograms
  Statistical process control (SPC): A process used to monitor
standards, make measurements, and take corrective action as a
product or service is being produced.

Statistical
Process
Control (SPC)
  The term Six Sigma, popularized by Motorola, Honeywell, and
General Electric, has two meanings in TQM.
 In a statistical sense, it describes a process, product, or service with
an extremely high capability (99.9997% accuracy).
 It is a strategy because it focuses on total customer satisfaction.
 It is a discipline because it follows the formal Six Sigma
Six Sigma Improvement Model known as DMAIC.
  Selecting a demonstrated standard of performance that represents
the very best performance for a process or an activity.
 The steps for developing benchmarks are:
1. Determine what to benchmark.
Benchmarking 2. Form a benchmark team.
3. Identify benchmarking partners.
4. Collect and analyze benchmarking information.
5. Take action to match or exceed the benchmark
  The philosophy behind just-in-time (JIT) is one of continuing
improvement and enforced problem solving. JIT systems are designed
to produce or deliver goods just as they are needed.
JIT is related to quality in three ways:
 JIT cuts the cost of quality: This occurs because scrap, rework,
inventory investment, and damage costs are directly related to
inventory on hand. Because there is less inventory on hand with JIT,
Just-in-Time costs are lower. In addition, inventory hides bad quality, whereas JIT
immediately exposes bad quality.
(JIT)  JIT improves quality: As JIT shrinks lead time, it keeps evidence of
errors fresh and limits the number of potential sources of error. JIT
creates, in effect, an early warning system for quality problems, both
within the firm and with vendors.
 Better quality means less inventory and a better, easier-to-employ JIT
system: Often the purpose of keeping inventory is to protect against
poor production performance resulting from unreliable quality. If
consistent quality exists, JIT allows firms to reduce all the costs
associated with inventory.
  The output of every process has a unique pattern that can be
described by its shape, center, and spread.
Patterns of  To determine the distribution or pattern of variability, a statistical
Variability process known as sampling is used to distribute values of a large
amount of data using a relatively small number of observations, or
samples of a given size.
Patterns of
Variability
process
capabIlIty
  The process capability index (Cp) combines the process spread and
the tolerance into one index making it easier for operators and
managers to quickly determine the capability of a process.

Process
Capability
Index, Cp
The tolerance is 1.000 inch  0.005 inch, and the standard deviation of the
process (σ) was 0.0016 inch
 The tolerance is 1.000 inch  0.005 inch, and the standard deviation of the
process (σ) was 0.0016 inch

Patterns of
Variability
  The specification for the weight of a chemical in a compound is 10±0.05
grams. If the standard deviation of the weighing scales is 0.02, is the
process considered capable?

Problem
  This index measures the effect of both center and variation at the
same time.

𝐶𝑝𝑘 Index  The philosophy of the 𝐶𝑝𝑘 index is that if the process distribution is
well within specification on the worst-case side, and is capable
according to the 𝐶𝑝 , then it is sure to be acceptable for the other
specification limit.
Interpretation of the Cpk index is as follows.
  A company produces shafts on a lathe with a nominal diameter of 1
inch and a tolerance of ±0.005 inch. The process has a standard
deviation of 0.001 inch. For each of the following cases, calculate
the 𝐶𝑝𝑘 and evaluate the process capability.
Problem a. A sample has an average diameter of 0.997 inch.
b. A sample has an average diameter of 0.998 inch.
c. A sample has an average diameter of 1.001 inches.
  The specification for the diameter of a hole is 0.80 inch ±0.020
inch. The standard deviation of the drill press is 0.007 inch. Using
Cp, calculate whether the process is capable or not.
 If the process is improved so the standard deviation is 0.0035, is the
process capable now?

Problem
  A company fills plastic bottles with 10 ounces of shampoo. The
tolerance is ±0.1 ounce. The process has a standard deviation of
0.02 ounce. For the following situations, calculate the Cpk and
evaluate the process capability.
Problem a. A sample has an average of quantity of 9.95 ounces.
b. A sample has an average of quantity of 9.98 ounces.
c. A sample has an average of quantity of 10.04 ounces.
Control Charts
for 𝑥ҧ and R
Control Limits
for the 𝑥Chart
ҧ
The constant A2 is tabulated for various sample sizes
Control Limits
for the R Chart
The constants D3 and D4 are tabulated for various values of n
  Statistical Software, Inc., offers a toll-free number where customers
can call from 7 A.M. until 11 P.M. daily with problems involving
the use of their products. It is impossible to have every call
answered immediately by a technical representative, but it is
important customers do not wait too long for a person to come on
the line. Customers become upset when they hear the message
Problem “Your call is important to us. The next available representative will
be with you shortly” too many times. To understand their process,
Statistical Software decides to develop a control chart describing the
total time from when a call is received until the representative
answers the caller’s question. Yesterday, for the 16 hours of
operation, five calls were sampled each hour. This information is
reported on the next page, in minutes until a call was answered.
Problem
𝑥Chart
ҧ
R Chart
 A hard-bake process is used in conjunction with photolithography in
semiconductor manufacturing. We wish to establish statistical control
of the flow width of the resist in this process using 𝑥ҧ and R charts.
Problem 2 Twenty-five samples, each of size five wafers, have been taken when
we think the process is in control. The interval of time between
samples or subgroups is one hour. The flow width measurement data
(in microns) from these samples
Problem 2
PERCENT
DEFECTIVE
CHART
Problem 3
The publisher of the Oak Harbour Daily Telegraph is concerned about the number of misspelled words in
the daily newspaper. They do not print a paper on Saturday or Sunday. In an effort to control the problem
and promote the need for correct spelling, a control chart is to be instituted. The number of misspelled words
found in the final edition of the paper for the last 10 days is: 5, 6, 3, 0, 4, 5, 1, 2, 7, and 4. Determine the
appropriate control limits and interpret the chart. Were there any days during the period that the number of
misspelled words was out of control?

c-BAR CHART
  Acceptance sampling consists of taking a sample of a batch of
product and using it to estimate the overall quality of the batch. Based
on the results of the inspection, a decision is made to reject or accept
the entire batch. There is a chance that a good batch will be rejected
or a bad batch will be accepted. Sampling inspection is necessary
under some conditions.
 The usual procedure is to screen the quality of incoming parts by
Acceptance using a statistical sampling plan. According to this plan, a sample of n
Sampling units is randomly selected from the lots of N units (the population).
This is called acceptance sampling.
 The inspection will determine the number of defects in the sample.
This number is compared with a predetermined number called the
critical number or the acceptance number. The acceptance number is
usually designated c. If the number of defects in the sample of size n
is less than or equal to c, the lot is accepted. If the number of defects
exceeds c, the lot is rejected and returned to the supplier, or perhaps
submitted to 100 percent inspection.
 PROCESS CAPABILITY AND PROCESS CONTROL – HOW ARE THEY DIFFERENT?

https://keyperformance.com/2014/04/process-capability-and-process-control-how-are-they-different/