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Quality Control.

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Presentation on theme: "Quality Control."— Presentation transcript:

1 Quality Control

2 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. .

3 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.

4 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

5 Quality control (QC) Basically quality control tests that the standards laid out by the quality assurance standards have been met

6 Inspection takes place at stages Goods inward During production
Quality inspection Inspection takes place at stages Goods inward During production Final inspection

7 Quality Assurance vs. Quality Control
A series of analytical measurements used to assess the quality of the analytical data (The “tools”) An overall management plan to guarantee the integrity of data (The “system”)

8 True Value vs. Measured Value
The known, accepted value of a quantifiable property Measured Value The result of an individual’s measurement of a quantifiable property

9 reproducability The ability of a system to achieve the same results when using different operators and different measuring equipment

10 Accuracy vs. Precision Precision
Accuracy How well a measurement agrees with an accepted value Precision How well a series of measurements agree with each other

11 Accuracy vs. Precision

12 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 is said to guarantee that a company delivers quality products and services.

13 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.

14 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.

15 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:

16 ISO 9001 (clause 4.2.4) Control of records
(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

17 Benefits of ISO 9001

18 Benefits of ISO 9001 Improved consistency of service and product performance Higher customer satisfaction levels. Improved customer perception Improved productivity and efficiency

19 BENEFITS of ISO 9001 Cost reductions
Improved communications, morale and job satisfaction Competitive advantage and increased marketing and sales opportunities.

20 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)

21 Measuring Instruments
Micrometers Vernier Calipers Dial Indicators Telescopic Gauges Small Hole Gauges Thickness Gauges Straight Edge

22 Micrometers

23 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.

24 Imperial and Metric

25 Inside Micrometer

26 Depth Micrometer

27 Digital Micrometers

28 Combination Digital Metric or Imperial at the push of a button

29 Parts of a Micrometer

30 Reading the Sleeve and Thimble
1 3 Number on Sleeve Number on Thimble Imperial Micrometer 2 Graduation on Sleeve Thimble numbers go from 0 to 20

31 Sample Reading Example using a 0-1” Outside Micrometer Thimble
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

32 Recording Measurement from Sample Reading
First reading – Range of Mic. 0 – 1” so the first number would be 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

33 Total Readings 0.066 First reading – Range of Mic. 0.000
Second reading – number on Sleeve Third reading – graduation on Sleeve Final number is number on the Thimble ______ 0.066 Total is ?

34 Reading an Imperial Micrometer

35 Reading an Imperial Micrometer Exercise 1 (2-3” mic)
Answer :

36 Reading an Imperial Micrometer Exercise 2 (0-1” mic)

37 Reading an Imperial Micrometer Exercise 3 (1-2” mic)

38 Calipers

39 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.

40 Three common designs of direct reading calipers; Vernier Dial Digital
Introduction Three common designs of direct reading calipers; Vernier Dial Digital

41 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.

42 Vernier Scale A Vernier is a mechanical means of magnifying the last segment on the main scale so addition subdivisions can be made. 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.

43 Vernier Caliper-practice
Read the Vernier caliper in the illustration. LOC Smallest whole unit 1.000 Tenths of an inch 0.200 Twenty five thousands Vernier scale 0.011 Sum (measurement) 1.211

44 Dial Caliper A dial replaces the Vernier. This makes the caliper easier to read. The reader must still determine the units and graduations.

45 Reading a Vernier Caliper # 1

46 Reading a Vernier Caliper # 2

47 Reading a Vernier Caliper # 2

48 Measurement Transferring Tools

49 Introduction Measurement transferring tools are tools that collect a measurement, but do not have a scale to read the measurement.

50 Common tools are: Spring calipers Dividers Telescoping gauges
Introduction . Common tools are: Spring calipers Dividers Telescoping gauges Ball gauges

51 Spring Calipers Spring calipers are used to transfer measurements.
Three types of spring calipers Outside Inside Hermaphrodite

52 Dividers Dividers are very useful for laying out several equal distances or transferring a distance measurement when other measuring devices cannot be used.

53 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.

54 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.

55 Measuring Straightness
Measuring straightness manually with (a) a knife-edge rule and (b) a dial indicator.

56 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.

57 (c) Fringes on a surface with two inclinations
(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.

58 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.

59 Measuring Gear-Tooth Thickness and Profile
Figure Measuring gear-tooth thickness and profile with (a) a gear-tooth caliper and (b) pins or balls and a micrometer.

60 Optical Contour Projector
A bench-model horizontal-beam contour projector with a 16-in. diameter screen with 150-W tungsten halogen illumination.

61 Fixed GaUges Figure (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.

62 Electronic Gage Figure 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 mm. Source: Courtesy of TESA SA. Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid. ISBN © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

63 Electronic Gage Measuring Vertical Length
Figure An electronic vertical-length measuring instrument with a resolution of 1 μm

64 Laser Micrometers Figure (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.

65 Coordinate-Measuring 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.

66 Coordinate-Measuring Machine for Car Bodies
Figure A large coordinate- measuring machine with two heads measuring various dimensions on a car body.

67 Tolerance is the range of sizes in within which a component is acceptable
Tolerance Control

68 Methods of Assigning Tolerances
Various methods of assigning dimensions and tolerances on a shaft: (a) bilateral tolerance, (b) unilateral tolerance, and (c) limit

69 Go and No go gauges

70 Gauges

71 Simple plate gauge Flatness Gauge

72 Feeler gauges

73 Snap Gauge

74 External thread gauge

75 Ring thread gauge

76 Plug gauges

77 Thread plug gauge

78 Thread profile gauge

79 '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

80 '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.

81 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.

82 Plug Gauge Example Dimension on part to gauge
The nominal hole size on part to gauge is ”; Tolerance of the hole is ”/-0.000” ; This means the hole must be manufactured somewhere between ” and ” in size;


84 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.


86 Ring Gauge Example Post on part to gauge is 1.0000”;
Dimension on part to gauge: Post on part to gauge is ”; Tolerance of post on part is ”/-0.000”; This means the post will be somewhere between ” and ” in size;

87 Standard Deviation Find the mean and the standard deviation for the values 78.2, 90.5, 98.1, 93.7, 94.5. = = 91   Find the mean. ( ) 5 x Organize the next steps in a table. x x – x (x – x)2  = Find the standard deviation. (x – x)2 n 234.04 5 = The mean is 91, and the standard deviation is about 6.8.

88 One standard deviation away from the mean (μ) in either 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.


90 one to six sigma conversion table
'Long Term Yield' (basically the percentage of successful outputs or operations) Defects Per Million Opportunities (DPMO) 'Processs Sigma' % 3.4 6 99.98 233 5 99.4 6,210 4 93.3 66,807 3 69.1 308,538 2 30.9 691,462 1

91 A six sigma process is one in which 99
A six sigma process is one in which % of the products manufactured are statistically expected to be free of defects (3.4 defects per million),

92 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

93 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

94 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

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