Transcript Quality Assurance (QA)

Quality
Control
QUALITY ASSURANCE (QA)
• 1. The operational techniques and
activities that sustain the product or
service quality to specified
requirements.
• 2. The use of such techniques and
activities.
•.
QUALITY ASSURANCE (QA)
• 3. Operations intended for the
assessment of the quality of products at
any stage of processing or distribution
.
• 4. Part of quality assurance intended to
verify that components and systems
correspond to predetermined
requirements.
QUALITY CONTROL (QC)
• Quality control, focuses on the end result,
such as testing a sample of items from a
batch after production.
• Inspection takes place at all stages of the
process from design to dispatch
•
QUALITY CONTROL (QC)
• Basically quality control tests that
the standards laid out by the
quality assurance standards have
been met
QUALITY INSPECTION
• Inspection takes place at stages
• Goods inward
• During production
• Final inspection
QUALITY ASSURANCE VS. QUALITY
CONTROL
Quality Assurance
Quality Control
A series of
An overall
analytical
management plan to measurements used
guarantee the
to assess the
integrity of data
quality of the
(The “system”)
analytical data
(The “tools”)
TRUE VALUE VS.
MEASURED VALUE
True Value
Measured Value
The known,
accepted value
of a quantifiable
property
The result of an
individual’s
measurement of
a quantifiable
property
REPRODUCABILITY
The ability of a system
to achieve the same
results when using
different operators and
different measuring
equipment
ACCURACY VS.
PRECISION
Accuracy
Precision
How well a measurement
agrees with an accepted value
How well a series of
measurements agree with
each other
ACCURACY VS.
PRECISION
ISO 9000
• Is an international standard that many
companies use to ensure that their
quality assurance system is in place
and effective. Conformance to ISO
9000 is said to guarantee that a
company delivers quality products and
services.
ISO 9001
• ISO 9001 is for all organisations
large or small and covers all
sectors, including charities and the
voluntary sector. It will help you to
be more structured and
organised. it is a process
standard, not a service or product
standard.
ISO 9001
• ISO 9001 gives the requirements for
what the organisation must do to
manage processes affecting quality of
its products and services. It does this
through the creation of a Quality
Management System.
ISO 9001
• The standard requires you to have
certain documented procedures. They
must meet the requirements as
described in the following 6 clauses
as mentioned in the standard:
ISO 9001
• (clause
4.2.3) Control of documents
• (clause 4.2.4) Control of records
• (clause 8.2.2) Internal audit
• (clause 8.3) Control of nonconforming product
• (clause 8.5.2) Corrective action
• (clause 8.5.3) Preventative action
BENEFITS OF ISO
9001
BENEFITS OF ISO 9001
• Improved consistency of service and
product performance
• Higher customer satisfaction levels.
• Improved customer perception
• Improved productivity and efficiency
BENEFITS of ISO 9001
• Cost reductions
• Improved communications, morale
and job satisfaction
• Competitive advantage and
increased marketing and sales
• opportunities.
STANDARD FOR QUALITY
MANAGEMENT SYSTEMS
• Products should conform to standards of
quality assurance and demonstrate conformity
to product requirements. Action should be
taken to eliminate non conformity. Action
should be taken prevent the use of non
conforming products. (without waiting for
the customer to complain)
MEASURING INSTRUMENTS
• Micrometers
• Vernier Calipers
• Dial Indicators
• Telescopic Gauges
• Small Hole Gauges
• Thickness Gauges
• Straight Edge
MICROMETERS
OUTSIDE MICROMETER
Instrument for making precise linear measurements
of dimensions such as diameters, thicknesses, and
lengths of solid bodies.
It consists of a C-shaped frame with a movable jaw
operated by a screw. The accuracy of the
measurements depends on the accuracy of the
screw-nut combination.
IMPERIAL AND METRIC
INSIDE MICROMETER
DEPTH MICROMETER
DIGITAL MICROMETERS
COMBINATION DIGITAL
Metric or Imperial
at the push of a
button
PARTS OF A MICROMETER
READING THE SLEEVE AND
THIMBLE
Number on Sleeve
1
3
Number on
Thimble
Imperial Micrometer
2
Graduation on Sleeve
Thimble numbers go from 0 to 20
SAMPLE READING
Example using a 0-1” Outside Micrometer
First number
is the size of
the Mic
0.000
Second number
is the first
number
on Sleeve
.000
Third number
is .025 graduations
you see on Sleeve
.025 x 2 = .050
Fourth number
is read on the
Thimble
.016
RECORDING MEASUREMENT FROM SAMPLE
READING
 First reading – Range of Mic.
0 – 1” so the first number would be 0.000
 Second reading – number on Sleeve
Number you see is Zero so it would be .000
 Third reading – graduation on Sleeve
Two graduations exposed so number is .050
 Final number is number on the Thimble
Final number is .016
TOTAL READINGS
First reading – Range of Mic.
0.000
 Second reading – number on Sleeve
0.000
 Third reading – graduation on Sleeve
0.050
 Final number is number on the Thimble 0.016
______
Total is ?
0.066
Reading an Imperial Micrometer
READING AN IMPERIAL
MICROMETER
EXERCISE 1
(2-3”
MIC)
Answer : 2.550
READING AN IMPERIAL
MICROMETER
EXERCISE 2
(0-1”
MIC)
Answer:
0.802
READING AN IMPERIAL
MICROMETER
EXERCISE 3
(1-2”
MIC)
Answer:
1.645
CALIPERS
INTRODUCTION
• Calipers can be direct reading or
measuring transferring tools.
• Direct reading calipers are capable of a
wider measurement range than
micrometer calipers.
• Six (6), eighteen (18) and twenty four
(24) inch are popular.
INTRODUCTION
• Three common designs of direct
reading calipers;
• Vernier
• Dial
• Digital
VERNIER
CALIPER
• Vernier calipers are an old tool that has been mostly replaced by
dial and digital calipers.
• They are manufactured with decimal scales, metric scales and
fractional scales.
• The Vernier scale is still used on many mechanical measuring
tools.
•
A Vernier is a
mechanical means of
magnifying the last
segment on the main
scale so addition
subdivisions can be
made.
VERNIER
SCALE
• The reference point is the 0 on the vernier scale.
• To read a Vernier, the line of coincidence must be located.
• The line of coincidence (LOC) is the line on the Vernier that coincides with
a line on the main scale.
• Illustration LOC = 19
• In theory only one LOC is possible, but usually when reading the vernier it
appears several exist. When this occurs pick the middle line.
VERNIER CALIPERPRACTICE
Read the Vernier caliper in the illustration.
LOC
•
•
•
•
Smallest whole unit
Tenths of an inch
Twenty five thousands
Vernier scale
Sum (measurement)
1.000
0.200
0.000
0.011
1.211
DIAL
CALIPER
A dial replaces the Vernier.
This makes the caliper easier to read.
The reader must still determine the units and graduations.
READING A VERNIER CALIPER #
1
2.641
READING A VERNIER CALIPER #
2
1.581
READING A VERNIER CALIPER #
2
0.508
MEASUREMENT
TRANSFERRING
TOOLS
INTRODUCTION
• Measurement transferring tools
are tools that collect a
measurement, but do not have
a scale to read the
measurement.
INTRODUCTION
• .
• Common tools are:
• Spring calipers
• Dividers
• Telescoping gauges
• Ball gauges
SPRING
CALIPERS
• Spring calipers are used to
transfer measurements.
• Three types of spring calipers
• Outside
• Inside
• Hermaphrodite
DIVIDERS
• Dividers are very useful for
laying out several equal
distances or transferring a
distance measurement when
other measuring devices
cannot be used.
TELESCOPING
GAGES
• Telescoping gages are
used to measure inside
diameters.
• One or both ends are
spring loaded so they
can be retracted and
inserted into the hole
being measured.
• The measurement is
made with a caliper or
micrometer.
BALL GAUGES
• Ball gauges are use to
transfer measurements
that are too small for
telescoping gauges.
• The ball is split and a
tapered wedge is used to
increase and decrease the
diameter of the ball
halves.
MEASURING STRAIGHTNESS
Measuring straightness manually
with (a) a knife-edge rule and (b) a
dial indicator.
MEASURING FLATNESS
(a)Interferometry method for measuring flatness using an
optical flat.
(b) Fringes on a flat, inclined surface. An optical flat
resting on a perfectly flat workpiece surface will not split
the light beam, and no fringes will be present.
(c) Fringes on a surface with two inclinations. Note: the
greater the incline, the closer together are the fringes.
(d) Curved fringe patterns indicate curvatures on the
workpiece surface.
MEASURING ROUNDNESS
(a) Schematic illustration of out-of-roundess
(exaggerated). Measuring roundess using (b) a
V-block and dial indicator, (c) a round part
supported on centers and rotated, and (d)
circular tracing.
MEASURING GEAR-TOOTH
THICKNESS AND PROFILE
Figure 35.8 Measuring gear-tooth thickness
and profile with (a) a gear-tooth caliper and
(b) pins or balls and a micrometer.
OPTICAL CONTOUR PROJECTOR
A bench-model horizontal-beam contour projector with a 16-in.
diameter screen with 150-W tungsten halogen illumination.
FIXED GAUGES
Figure 35.10 (a) Plug gage for holes with GO
and NOT GO on opposite ends. (b) Plug gage
with GO and NOT GO on one end. (c) Plain
ring gages for gaging round rods. Note the
difference in knurled surfaces to identify the two
gages. (d) Snap gage with adjustable anvils.
ELECTRONIC GAGE
Figure 35.12 An electronic gage for measuring bore diameter. The measuring
head is equipped with three carbide-tipped steel pins for wear resistance. The
LED display reads 29.158 mm. Source: Courtesy of TESA SA.
Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.
ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
ELECTRONIC GAGE MEASURING
VERTICAL LENGTH
Figure 35.13 An electronic
vertical-length measuring
instrument with a resolution
of 1 μm
LASER MICROMETERS
Figure 35.14 (a) and (b) Two types of measurements made with a
laser scan micrometer. (c) Two types of laser micrometers. Note
that the instrument in the front scans the part (placed in the opening)
in one dimension; the larger instrument scans the part in two
dimensions.
COORDINATEMEASURING MACHINE
(b)
(c)
(d)
(a) Schematic illustration of a coordinate-measuring
machine. (b) A touch signal probe. (c) Examples of laser
probes. (d) A coordinate-measuring machine with a
complex part being measured.
COORDINATE-MEASURING
MACHINE FOR CAR BODIES
Figure 35.16 A large coordinatemeasuring machine with two heads
measuring various dimensions on a car
body.
Tolerance is the range
of sizes in within which
a component is
acceptable
TOLERANCE CONTROL
METHODS OF ASSIGNING
TOLERANCES
Various methods of assigning dimensions and
tolerances on a shaft:
(a) bilateral tolerance, (b) unilateral
tolerance, and (c) limit
GO AND NO GO GAUGES
GAUGES
SIMPLE PLATE GAUGE
Flatness Gauge
FEELER GAUGES
SNAP GAUGE
EXTERNAL THREAD GAUGE
RING THREAD GAUGE
PLUG GAUGES
THREAD PLUG GAUGE
THREAD PROFILE GAUGE
'GO' LIMIT
• 'go' limit is the one between the two size limits which corresponds to
the maximum material limit
• the upper limit of a shaft and the lower limit of a hole
• 'GO' gauge can check one feature of the component in one pass
'NO GO' LIMIT
• 'no go' limit is the one between the two size limits which
corresponds to the minimum material condition
• the lower limit of a shaft and the upper limit of a hole.
5.2.1 LIMIT PLUG GAUGE
• Limit plug gauges are fixed gauges usually made to
check the accuracy of a hole with the highly finished
ends of different diameters
• If the hole size is correct within the tolerable limits,
the small end (marked “go”) will enter the hole,
while the large end (“not go”) will not.
PLUG GAUGE EXAMPLE
• Dimension on part to gauge
• The nominal hole size on part to gauge is
1.0000”;
• Tolerance of the hole is +0.002”/-0.000” ;
• This means the hole must be
manufactured somewhere between
1.0000” and 1.0020” in size;
5.2.2 LIMIT RING GAUGE
• Limit plug gauges are fixed gauges usually made to check the
accuracy of a shaft with highly finished ends of different
diameters is used
• If the shaft size is correct within the tolerable limits, the large
end (marked “go”) will go through the shaft, while the small
end (“not go”) will not.
RING GAUGE EXAMPLE
• Dimension on part to gauge:
• Post on part to gauge is 1.0000”;
• Tolerance of post on part is +0.002”/-0.000”;
• This means the post will be somewhere between 1.0000”
and 1.0020” in size;
STANDARD
DEVIATION
Find the mean and the standard deviation for the values 78.2, 90.5,
98.1, 93.7, 94.5.
x = (78.2 + 90.5 + 98.1 +93.7 +94.5) = 91
Find the mean.
5
x
78.2
90.5
98.1
93.7
94.5
x
91
91
91
91
91
x–x
–12.8
–0.5
7.1
2.7
3.5
(x – x)2
163.84
.25
50.41
7.29
12.25
Organize the next
steps in a table.
=
=
(x – x)2
Find the standard
n
deviation.
234.04
5
The mean is 91, and the standard deviation is about 6.8.
6.8
 in either
One standard deviation away from the mean (μ)
direction on the horizontal axis accounts for around 68 percent
of the data. Two standard deviations away from the mean
accounts for roughly 95 percent of the data with three standard
deviations representing about 99.7 percent of the data.
SIX SIGMA
one to six sigma conversion table
'Long Term Yield'
(basically the
percentage of
successful outputs or
operations)
%
99.99966
99.98
99.4
93.3
69.1
30.9
Defects Per
Million
'Processs
Opportunitie Sigma'
s (DPMO)
3.4
233
6,210
66,807
308,538
691,462
6
5
4
3
2
1
• A six sigma process is one in which 99.9999966% of the
products manufactured are statistically expected to be free of
defects (3.4 defects per million),
SIX SIGMA
• Six Sigma team leaders (Black Belts) work
with their teams (team members will
normally be people trained up to 'Green Belt'
accreditation) to analyse and measure the
performance of the identified critical
processes. Measurement is typically focused
on highly technical interpretations of
percentage
DOCUMENT CONTROL
• There must be evidence of the existence of a
system
• A record of the correct operation must be
kept
• This is important to trace evidence of
inspection in case of future complaints or
problems
MTBF
• Mean time between failures (MTBF) is the
predicted elapsed time between inherent
failures of a system during operation
• MTBF can be calculated as the (average)
time between failures of a system