Introduction of Metrology

INTRODUCTION OF ME TROLOGY

PENGENALAN KEPADA METROLOGI Metrology is of fundamental importance in industry and trade – not only from the point of view of the consumer but also for those involved in manufacturing. Both groups must have confidence in the accuracy and reliability of the measurements upon which they depend. Within the manufacturing process, to ensure the accuracy of measuring instruments, it is essential that they should be periodically calibrated against more accurate standards.

bukan sahaja pada Metrologi adalah asas yang penting dalam perind perindustrian ustrian dan dan perdaganga perdagangan n – bukan pembuatan atan. Kedua-dua golongan ini mesti pandangan pengguna tetapi ia juga melibatkan dalam pembu mempunyai keyakinan terhadap ketepatan dan kesahan pada pengukuran yang mereka bergantung harap kepadanya. Metrology is a very broad field and may be divided into three subfields Metrologi adalah bidang yang sangat penting danterbahagi kepada tiga sub topic (i)

Scientific or fundamental metrology concerns the establishment of measurement units, unit systems, the development of new measurement methods, realization of measurement standards and the transfer of traceability from these standards to users i n society. society .

(i)

perihatin terhadap penubuhan unit pengukuran, unit system, Saintifik atau asas metrology perihatin pembangunan terhadap kaedah pengukuran pengukuran yang baru, merealisasikan standad standad pengukuran dan penghijrahan daripada standard ini kepada pengguna dalan masyarakat.

(ii) Applied or industrial metrology concerns the application of measurement science to manufacturing and other processes and their use in society, ensuring the suitability of measurement instruments, their calibration and quality control o f measurements (ii) Applied atau Metrologi Industri perihatin terhadap terhadap sains pengukuran pada pembuatan dan proses yang lain dan kegunaan dalam masyarakat, masyarakat, memastikan kesesuaian peralatan peralatan pengukuran, penjajaran dan kawalan mutu terhadap pengukuran. (iii) Legal metrology concerns regulatory requirements of measurements and measuring instruments for the protection of health, public safety, the environment, enabling taxation, protection of consumers and fair trade. (iii) Undang-undang metrologi perhatin keperluan keperluan peraturan pengukuran dan alatan mengukur dalam melindungi kesihatan, keselamatan umum, alam sekitar, membolehkan percukaian, perlindungan pengguna dan perniagaan yang adil.

Basic units measurement system Sistem asas unit pengukuran (i) (i)

The English system (inches) Sistem Pengukuran Inggeris (Inci) That system of measurement is based on the inch. When dealing with inches in the machining industry, fractional and decimal measurement and math are both very common Sistem pengukuran ini adalah berasaskan inci. Bila berurusan dengan pengukuran inci dalam industry pemesinan, pengukuran dan pengiraan adalah sangat berkaitan dengan pecahan dan perpuluhan

(ii) The Metric System Or SI (ii) Sistem pengukuran Metrik atau SI The meter is the basic unit used in the metric system of measurement, but the millimeter is most commonly used in the machining industry Unit meter adalah unit yang asas dalam system pengukuran metric, tetapi milimeter (mm) adalah penggunaan yang biasa dalam industry pemesinan.

CHAPTER 2 : SEMI-PRECISION MEASUREMENT BAB 2 : PENGUKURAN SEPARA JITU INTRODUCTION PENGENALAN

Semi-precision measurement usually refer to measurement when results do not need to be more precise than 1/64" or 1/100" ,0.5mm, or 1 degree. this unit will explore several types of semi-precision measuring instruments or tools Biasanya pengukuran spara jitu merujuk kepada pengukuran yang tidak memerlukan ketepatan kepada kejituan daripada 1/64” atau 1/100”, atau 0.5mm, atau 1 darjah sudut. Unit ini akan meneroka beberapa peralatan atau alat mengukur spara jitu. RULES

Reading English Rules Membaca pembaris inggeris.

There are many styles of graduations g raduations for English rules. The most common graduation style divides inches into 1/8 (one-eighth), 1/16 (one-sixteenth), 1/32 (one/thirty-second), 1/64 (one-sixty-four) divisions. When read the rules with the these graduations, measurement should always be reduced to lowest terms Terdapat banyak gaya pembahagian senggatan pada pembaris Inggeris. Senggatan yang biasa adalah gaya senggatan yang dibahadikan kepada 1/8in,(perlapan), 1/16in (per enambelas), 1/32in,(per tigapuluh dua), 1/64in, (per enam puluh empat) senggatan. Bila membaca pembaris dengan senggatan ini, ukuran seharusnya dikurangkan kepada term yang lebih rendah. Reading Metric Rules Membaca Pembaris Metrik

Metric rules are graduated in millimetre and one-haff (0.5)Millimetre divisions. Quick-reading Quick-reading number every 5 or 10 millimeter simplify measurement Pembaris metric dibahagikan kepada senggatan bergraduasi dalam satu milimeter dan setengah milimeter (0.5mm). Membaca denga ringan dan pantas pada pembaris pada setiap nombor 5 atau 10 milimeter. CALIPERS

Out side and inside caliper

CHAPTER 3 : PRECISION MEASURING INSTRUMENT

WHAT IS PRECISION MEASUREMENT

When preforming precision measuring using English measurement (inch-based), expected accuracy is generally between 0.001 and 0.0001 inches.  In SI (metric-based), expected accuracy is generally between 0.01 and 0.002 millimeters.  Expected angular accuracy is generally within 5 minutes (1/12) of degree. 

SURFACE PLATES

A surface plate is a flat that is used as an accurate reference surface with other precision tools to aid with some measurement tasks.  Some older surface plate are cast iron, but today most are made of granite because granite is stable and the surface will not expend or contract with change of temperature. 

VERNIER MEASURING INSTRUMENT

Venier Calipers  A vernier caliper is similar to semi-percision slide caliper, but its vernier scale allow it to be used for measurement as small as 0.001” or 0.02 mm.  Vernier calipers has three different part solid jaw and moveable jaw that for external dimensions. Nibs between two surface can measured the internal dimension Rod for depth measurement. • •

•

Outside micrometer

The outside micrometer is comman type of micrometer  It is used to measure external external dimension and is available in both English English and metric versions 

Inside micrometer

Inside micrometer used to measure internal dimension are available in the three major types.  The tubular or rod style  Bore micrometer  Internal micrometer caliper 

Inside micrometer The Tubular Or Rod Style

Bore Micrometer

Internal Micrometer Caliper

Have micrometer heads with interchangeable end to cover a large range of size

Measuring hole diameter uses three telescoping legs to make contact inside the hole.

Has jaws and is similar to the outside micrometer, except the graduations on the sleeve are numbered and read from right to left and the graduations of the thimble are in reverse order

Adjust the head while pivoting the tool inside a hole or slot to make contact with two surface and approximately 1-1/2”

A ratchet slip when there is proper contact pressure and divided into smaller units of 0.0002” or 0.005mm

Measure down to approximately 0.200” or 5mm

Depth micrometer

The micrometer depth gage, of depth micrometer, features a base and interchangeable rods for different size ranges.  The rods are produced in 1” or 25-mm increments.  The graduations are numbered and read from left to right. 

Dial and digital calipers  Dial and digital calipers are beginning to replace vernier calipers in industry.  Very versatile because they have ability measure external, internal, depth, and step measurement quickly and easily.  Dial calipers usually have 0.001” or 0.02 -mm  Digital caliper usually read to 0.0005” or 0.01mm Surface Roughness measurement

Surface roughness comparator  Ra Surface roughness is normally inspected by one or two different methods.  Comparator gage shows example of different levels of Ra.  Machined surface are visually compared to there sample to determent if they are withi n acceptable limits. Coordinate Measuring Machine (CMM) Overview     

Coordinate measuring machines (CMMs) are extremely powerful metrological instrument It is a device for measuring the physical geometrical characteristics of an object This machine may be manually controlled by an operator or it may be computer controlled. Measurements are defined by a probe attached to the third moving axis of this machine This probe touches the part of interest and allows collecting discrete points on the object's surface.

Measuring using CMM

THE ROLE OF COORDINATE MEASURING MACHINES 

CMMs play an important role in a large number of industries, including;  Aerospace  Automotive  Food processing  Health care  Paper  Pharmaceuticals  Plastics  Research and development  Semiconductor

THE ROLE OF COORDINATE MEASURING MACHINES 

CMMs are particularly suited for the following conditions:  Short runs  Multiple features  Flexibility  High unit cost  Production interruption

Short run 

We may be producing hundreds or even thousands of part, but the production run is not sufficient to justify the cost of production inspection tooling

Multiple features 

When we have a number of features- both dimensional and geometric- to control, CMM is the instrument that makes control easy and economical

Flexibility 

Because we can choose the application of the CMM system, we can also do short runs and measure multiple features

High unit cost 

Because reworking or scrapping is costly, CMM systems significantly increase the production of acceptable parts

Production interruption interruption 

Whenever you have to inspect and pass one part before you can start machining on the next part, a machining center may actually be able to help a manufacturer save more money by reducing downtime than would be save by inspection

Comparison between conventional and coordinate measuring technology CONVENTIONAL METROLOGY

COORDINATE METROLOGY

Manual, time consuming alignment of the test piece

Alignment of the test piece not necessary

Single purpose and multi-point measuring instruments making it hard to adapt to changing measuring task

Simple adaptation to the measuring test by software

Comparison of measurement with material measures, i.e., gauge block

Comparison of measurement with mathematical or numerical value

Separate determination of size, form, location and orientation with different machines

Determination of size, form, location and orientation in one setup using one reference system

TYPES OF CMMs

The basic CMM has three perpendicular axi s; x,y,z  The physical configuration of CMMs vary widely, but they all provide a way to move a probe in three axes with respect to workpiece  Five basic configurations that are used more frequently 1. Cantilever 2. Bridge 3. Column 4. Horizontal arm 5. Gantry 

Cantilever type       

A vertical probe moves in the z-axis Carried by a cantilevered arm that moves in the y-axis This arm also moves laterally through the x-axis Advantage- a fixed table allows good accessibility to the workpiece Disadvantage- the bending caused by the cantilever design The cantilever design offers a long table with relatively small measuring ranges in the other two axis. Suitable for measuring long, thin part

Moving bridge type 

Most widely used  Has stationary table to support workpiece to be measured and a moving bridge  Disadvantage- with this design, the phenomenon of yawing (sometimes called walking) can occur- affect the accuracy  Advantage- reduce bending effect Fixed bridge type

In the fixed bridge configuration, the bridge is rigidly attached to the machine bed  This design eliminates the phenomenon of walking and provides high rigidity 

Column type

Often referred to as universal measuring machine instead of CMM  The column type CMM construction provides exceptional rigidity and accuracy  These machines are usually reserved for gage rooms rather than inspection 

Horizontal arm type

    

Unlike the previous machines, the basic horizontal armtype CMM Also referred to as layout machine Has a moving arm, and the probe is carried along the yaxis Advantage- provides a large area, unobstructed work area Ideal configuration for measurement of automobile parts

Gantry type 

The support of workpiece is independent of the x and y axes, both are overhead, supported by four vertical columns rising from the floor  This setup allows you to walk along the workpiece with the probe, which is helpful for extremely large pieces

Gantry configuration with dual linear motor drives, laser scales an online compensation compensation

Other configuration configuration

MODES OF OPERATION

Manual  Manual computer assisted  Motorized computer assisted  Direct computer controlled 

Manual

CMM has a free floating probe that operator move along the machine’s three axes to establish contact with the part feature that accessing  The differences among the contact positions are the measurements 

Manual computer assisted 

Add electronic digital displays for these machines, making zero setting, changing sign, converting unit, and printing out data easy and practical  Advantage- save time, minimize calculation, reduce error Motorized computer assisted 

Uses a joystick to drive the machine axes  The operator manipulates the joysticks to bring the probe sensor into contact with the workpiece

Direct computer controlled (DCC)     

programmable Use CAD data to determine where the probe sensor contacts the workpiece, collecting measurement data The fully automated CMM allows operator to place the workpiece in a fixture/ worktable, run a stored program, collect the data points and generate the output report Measurement reports can be saved in the computer to compile a historical record for SPC. A program of DCC machine has three components: 1. Movement commands – direct the probe to the data collection points 2. Measurement command – compare the distance traveled with the standard built into the machine for that axis 3. Formatting command- translate the data into a form for display or print out

TYPES OF PROBES 

Two general categories 1. Contact (see figure)  Touch-trigger probe  Analog scanning probe 2. Noncontact For inspection of printed circuit board, measuring a clay of wax model, when the object being measured would be deformed by the for of stylus  laser probes  video probes

Contact probes

1. Touch trigger probe  As the sensor makes contact with the part, the difference in contact resistance indicates that the probe has been deflected  The computer records this contact poi nt coordinate space  An LED light and an audible signal usually indicate contact  Touch probe assemblies consist consist of three components; probe head, probe probe and stylus

2. Analog scanning probe  Use to measure contour surfaces, complex, irregular  Remains in contact with the surface of the part as it moves  Improve the speed and accuracy Non-contact probe

1. Laser scanning probe  Laser probes project a light beam onto the surface of a part  When the light beam is triggered, the position of beam is read by triangulation through a lens in the probe receptor  Laser tool have a high degree of speed and accuracy 2. Video probe  The feature are measured by computer ‘count’ of the pixels of the electronic image  The camera is capable of generating multitude of measurements points within a single video frame

Probe head, probes and stylus

Multiple shapes of sylus

CMM software 

The programming of the machine or the software of the system enables the CMM to reach its full potential for accuracy, precision and speed  Contour programs allow the CMM to quickly define detailed, complex non-geometric shapes such as gear, cams, and injection molds  These programs also can be used to compare the measurement data with a computer assisted drafting (CAD) model CMM software (cont’) 

Generally software packages contains some or all of the following capabilities:  Resolution selection  Conversion between SI and English (mm and inch)  Conversion of rectangular coordinates to polar coordinates  Axis scaling  Datum selection and reset  Circle center and diameter solution  Bolt-circle center and diameter  Save and recall previous datum  Nominal and tolerance entry  Out-of tolerance computation

Coordinate System 

A coordinate allows the CMM to locate features on a workpiece relative to other features  The coordinate system is similar to a three-dimensional map, providing direction and location  Each machine has a ‘home’ position (an origin) and x, y and z axes identify location that represents the machine coordinate system (MCS)  A manufactured past can also have a part coordinate system (PCS) References

Text book  Bosch, J.A., Coordinate Measuring Machines and System 

CHAPTER 5 : LIMITS, FITS AND TOLERANCE SISTEM BATASAN DAN GEGASAN 16.1 PENGENALAN

Sebelum pertengahan abad ke-19, bolt dan nat dibuat sepasang dan mesti disimpan bersama. Bolt dan nat ini tidak boleh ditukar ganti dengan sepasang bolt dan nat yarig lain. Alat-alat ganti tidak disedia-kan ketifca itu. Dengan demikian, banyak masa terbuang dan pe-nyenggaraan alat-alat ini,amatlah sukar. Pada pertengahan abad ke-9, Sir Jos'eph Whitworth telah mem-perkenalkan satu sistem ulir skru atau piawai yang mengambil sem-pena namanya. Sejak itu wujudlah satu sistem kepiawaian yang di-gunakan hingga kini. Di Malaysia, kita mempunyai SIRIM sebagai institusi kepiawaian. Bagaimanapun, untuk.^kerjakerja kejuru-teraan, kita masih menggunakan sistem kepiawaian British. Dalam pengeluaran kerja-kerja kejuruteraan, tidaklah ekonomi dan amat sukar menghasilkan hanya satu saiz komponen sahaja. Dengan menggunakan sistem batasan dan gegasan, saiz satu komponen itu boleh dibuat mengikut lingkungan had terima yang diberi. Rajah 16.1 menunjukkan dengan jelas istilah-istifah yang diguna-kan dalam sistem batasan dan gegasan bagi aci dan lubang. Istilah-istilah tersebut ialah had tinggi, had rendah, basi minimum, basi maksimum dan telusan. Perbezaan antara had tinggi dan had rendah dikenali sebagai telusan.

Rajah 16.1

Sistem batasan dan gegasan.

16.1.1 Had Terima Had terima tinggi dan had terima rendah ialah saiz satu komp* yang boleh diterima atau dikira betul.

Contoh 16.1

Jika satu dimensi diberi,

ini bermakna

(a)

50.00 + 0.02 = 50.02 ialah had tinggi

(b)

50.00 -.0.03 = 49.97 ialah had rendah

(c)

50.02 - 49.97 = 0.05 ialah telusan

16.1.2 Gegas dan Basi Apabila satu lubang dan satu aci dicantumkan, sistem cantuman ini disebut gegas. Telusan yang berlaku antara aci dan lubang apabila percantuman dilakukan dinamakan basi. Terdapat dua jenis basi dalam sistem ini, iaitu basi maksimum dan basi minimum.

Basi Maksimum Basi jenis ini terjadi apabila aci yang dibuat pada had rendah dicantumkan dengan lubang yang dibuat pada had tinggi.

Basi Minimum Basi minimum terjadi apabila aci yang dibuat pada had tinggi di-•cantumkan dengan lubang yang dibuat pada had rendah.

Contoh 16.2

Jika satu aci dan- lubang mempunyai ukuran yang berikut:

Aci

+ 0.06

50

− 0.03

+ .

Lubang 50

+ .

Basi Maksimum

= Had tinggi lubang-Had rendah aci = 50.05 - 49.94 = 0.11

Basi Minimum

= Had rendah lubang-Had tinggi aci = 50.03 - 49.97 = 0.06

16.1.3 Saiz dan Had Saiz Namaan Saiz namaan merupakan saiz yang disebutkan bagi aci dan lubang. Contohnya, jika aci atau lubang bergaris pusat 50.05 mm, maka ia boleh disebutkan bergaris pusat 50 mm sahaja.

Ini bermakna saiz namaannya 50 mm. Saiz Asas

Saiz asas merupakan saiz sebenar aci atau lubang apabila'had terima diberi kepadanya. Contohnya, jika satu gegasan perlu dilakukan antara satu lubang bergaris pusat 50 mm dan satu aci bergaris pusat 49.70 mm, maka saiz namaan namaan bagi kedua-duanya kedua-duanya ialah ialah 50 mm, tetapi tetapi saiz asas bagi aci tersebut ialah ial ah 49.70 49.7 0 mm. Saiz yang Betul

Saiz komponen yang telah dimesin dalam lingkungan had terima yang diberi merupakan saiz betul bagi komponen tersebut. Contohnya, aci bergaris pusat

50

+0.04 −0.02

Setelah Sete lah aci dimesin dim esin,, ukuran komponen komponen tersebut tersebut ialah 50.02 iaitu dalam

lingkungan had terima yang diberi. Oleh sebab sebab itu 50.02 mm adalah saiz yang betul. betul.

Had Sesisi dan Had Dwisisi

Rajah 16.2 menunjukkan had sesisi dan had dwisisi. Had sesisi ter-jadi apabila kedua-dua had terima satu komponen itu berada sama ada di atas saiz asas atau di bawah saiz asas. Oleh sebab itu, lingkungan telusan tidak akan melintasi saiz asas. Manakala had dwisisi terjadi apabila had terima tinggi komponen itu berada di atas saiz asas dan had terima rendah itu di bawah saiz asas, iaitu telus_an akan melintasi saiz asas. 16.2

PENGELASAN GEGAS DAN PEMILIHANNYA

Dalam sistem gegasan, gegas dapat dikelaskan kepada tiga (Rajah 16.3). iaitu:

1. Gegas kelegaan 2. Gegas peralihan 3. Gegas terganggu. Gegas Kelegaan

Gegas itu berlaku apabila saiz aci lebih kecil daripada saiz lubang tidak kira apa juga kombinasi aci dan lubang itu dipililu la diguna-kan apabila bahagian-bahagian yang dicantumkan boleh bergerak dengan bebas dan senang. Berikut ialah tingkat gegas kelegaan:

(a) (a) (b) (b) (c) (d) (d)

Kelegaan longgar Kelegaan sederhana Kelegaan rapat Kelegaan jitu.

Aci lebi h.kecil daripada lubang

(a)

Gegas kelegaan

Had rendah aci akan menghasilkan gegas kelegaan

Had tinggi aci akan menghasilkan tegasan terganggu

(b)

Gegas peralihan

Aci lebih besar daripada lubang

(

(c)

Rajah 16.3

Gegas terganggu

Kelas-kelas gegas.

Gegas Peralihan

Gegas peralihan boleh menghasilkan dua kelas gegas yang berlain-an apabila komponen itu dibuat mengikut had-had terima yang diberi.

(a) (a) Aci yang paling besar apabila dicantumkan dengan lubang yang paling kecil menghasilkan gegas terganggu. / (b) (b) Aci yang paling kecil apabila dicantumkan dengan lubang yang paling besar menghasilkan gegas kelegaan. Gegas ini digunakan apabila bahagian-bahagian perlu dicantum dengan kemas dan tidak longgar tetapi boleh dipisahkan dipisah kan kembali ke mbali dengan mudah. Berikut Berikut ialah tingkat gegas peralihan: peralihan:

(a) (a) (b) (b) (c) (d) (d)

Sorong Mengunci ringan Mengunci sederhana Mengunci berat.

Gegas Terganggu Gegas ini berlaku apabila saiz aci lebih besar daripada -saiz lubang tidak kira apa juga kombinasi lubang dan aci itu dipilih. la digunakan apabila bahagian-bahagian itu hendak dicantumkan dengan kekal. Yang berikut ialah tingkat gegas terganggu:

(a) (a) Gerakan ringan (b) (b) Gerakan berat (c) Gegas paksa.

16.2.1

Sistem Asas Lubang dan Aci

Rajah 16.4 menunjukkan dua sistem untuk memesin dua komponen yang akan dicantumkan mengikut gegas yang diperlukan. Kedua-dua sistem tersebut ialah:

1. Sistem asas lubang 2. Sistem asas aci. Asas aci aci Tergangg Terganggu u Ke|egaan Ke|egaan Peralihan Peralihan

Rajah 16.4 Sistem asas lubang dan aci.

Sistem Asas Aci Sistem ini digunakan apabila saiz aci pula malar. Dengan ini, bahagian-bahagian kelas gegas dapat diperoleh dengan mengubahkan saiz lubang.

Sistem Asas Lubang Sistem ini digunakan apabila saiz lubang adalah tetap. Berbagai-bagai kelas gegas dapat diperoleh dengan mengubahkan saiz aci. Sistem asas lubang lebih popular kerana saiz lubang boleh dimesin dan dikawal dimensinya dengan menggunakan gerudi dan pelulas yang sama saiznya. Aci yang dipasang itu kemudian boleh dilarik dan dicanai mengikut jenis gegas yang dikehendaki.

16.2.2 Penentuan Had Terima

Rajah 16.5 menunjukkan bagaimana gegas kelegaan ditunjukkan dalam kerja-kerja kejuruteraan. Untuk mendapatkan maklumat lebih lanjut berkenaan dimensi gegas tersebut, seorang pengendali mesin perlulah merujuk Jadual 16.1 iaitu jadual kepiawaian BS 4500. Saiz namaan  60 mm

Rajah 16.5 Penentuan had terima dengan menggunakan menggunakan gegas kelegaan. Contoh 16.3

Rajah di atas menunjukkan had terima yang dipetik dari jadual kepiawaian BS 4500 Saiz namaan-60 garis pusat Jenis gegas yang digunakan — kelegaan kelegaan rapat Dimensi untuk aciDimensi untuk

Introduction Introduction of Metrologi

Piawai BS 4500 Piawai Piawai BS 4500 ialah ialah piawai piawai British British dalam dalam unit metrik metrik yang berdasa berdasar-kan r-kan kepia kep iawai waian an antara ant araban bangsa gsa ISO. ISO . Piawai ini boleh digunakan untuk kesemua kesemua jenis kerja, kerja, sama ada ringan ringan atau berat dan juga boleh digunakan berasaskan aci atau lubang. Jadual 16.1 merupakann sebahagian daripada jadual kepiawaian BS 4500. Keseluruhannya, terdapat 28 tingkat had terima. Setiap tingkat had terima aci dan lubang itu mempunyai 18 gred iaitu 01, 0, 1,2,.. ., 16. Huruf kecil a, b, c, d, . . . menentukan saiz aci manakala huruf besar besar A, B, C, C, D, D, menen menentuk tukan an saiz saiz lubang lubang.. Jadual 16.1 Jadual kepiawaian BS 4500

Saiz namaan Lebih Hingga daripada kepada mm mm 3

Kelegaan longgar

Kelegaan sederhana

Kelegaan rapat

Kelegaan jitu jitu

Peralihan

Gangguan

H9

H8

H7

H7

H7

k6

H7

e9

f7

g6

h6

+ 25 -14 + 0 -39

+ 14 - 6 + 0 - 16

+ 10 - 2 +0 -8

+ 10 - 0 +0 -6

+ 10 +0

+6 +0

+ 10 +0

p6 + 12 +6

3

6

+ 30 -20 + 0 -50

+ 18 -10 + 0 - 22

+ 12 - 4 + 0 - 12

+ 12 - 0 +0 -8

+ 12 +0

+9 +1

+ 12 + 20 + 0 + 12

6

10

+ 36 -25 + 0 -61

+ 22 -13 + 0 -2 8

+ 15 - 5 + 15 - 0 + 0 -14 + 0 - 9

+ 15 +0

+10 +1

+ 15 +0

+ 24 + 15

10

18

+ 43 -32 + 0 -75

+ 27 -16 + 0 -34

+ 18 - 6 + 18 - 0 + 0 - 1 7 + 0 – 11 11

+ 18 +0

+12 +1

+ 18 +0

+ 29 + 18

18

30

+ 52 -40 + 0 -92

+ 33 -20 + 0 -4 1

+ 21 - 7 + 0 - 20

+ 21 - 0 + 0 -1 3

+ 21 +0

+15 +2

+ 21 +0

+ 35 + 22

30

50

+ 62 -50 + 0 -112

+ 39 -25 + 0 - 50

+ 25 - 9 + 0 - 25

+ 25 - 0 + 0 - 16

+ 25 +0

+18 +2

+ 25 +0

+42 + 26

50

80

+ 74 -60 + 0 -134

+ 46 -30 + 0' - 60

+ 30 -10 + 0 -2 9

+ 30 - 0 + 0 -1 9

+ 30 +0

+21 +2

+ 30 +0

+ 51 + 32

80

120

+ 87 72 + 0 -159

+ 54 -36 + 0 -7 1

+ 35 -12 + 35 - 0 + 0 - 34 + 0 - 2 2

+ 35 +0

+ 25 + 35 +3 +0

+ 59 + 37

120

180

+ 100 100 - 85 85 + 63 -43 + 0 -185 + 0 -8 3

+ 40 -14 + 40 - 0 + 0 -3 9 + 0 - 25

+ 40 + 28 +0 +3

+ 40 +0

+ 68 +43

180

250

+ 115 -100 + 0 -215

+ 72 -50 + 0 - 96

+ 46 -15 + 46 - 0 + 0 - 4 4 + 0 - 29

+ 46 +0

+ 33 +4

+ 46 +0

+ 79 + 50

250

315 .

+ 130 -110 + 0 -240

+ 81 -56 + 52 -17 + 0 -108 + 0 -4 9

+ 52 +0

+ 36 - 32

+ 52 '+88 + 0 + 56

315

400

+ 140 – 125 125 + 0 -265

+ 89 +0

+ 57 +40 +0 +4

+ 57 + 98 + 0 + 62

400

500

+ 155 -135 + 0 -290

+ 97 -68 + 63 -20 + 0 -131 + 0 - 60

+ 63 +0

+ 63 + 108 + 0 + 68

+ 52 - 0 + 0 -4 9

-62 + 57 -18 + 57 - 0 -119 + 0 - 5 4 + 0 - 36

18

+ 63 - 0 + 0 -4 0

+ 45 +5


Contoh 16.4 *

Nyataican dimensi untuk aci dan lubang dengan saiz namaan kedua-duanya ialah 45 mm. Kelas gegas yang perlu perlu dihasil dihasilkan kan ialah ialah.. kelega-an kelega-an sederhana. Berdasarkan Berdasarka n Jadual Jad ual 16.1 1 6.1 diperoleh Saiz namaan

H8

f7

+39

-25

+0

-50

30 - 50 mm

Unit had terima : 0.001 mm

Garis pusat lubang

45 45

+ 0.039 + 0.000

= 45.039 (Had tinggi) = 45.000 (Had rendah)

Garis pusat aci :

45 45

-

= 44.975 (Had tinggi) = 44.950 (Had rendah)

Telusan untuk lubang

= 45.039 - 45.000 = 0.039

Telusan untuk aci

= 44.975 - 44.950 = 0.025

Basi maksimum

= Had tinggi lubang - Had rendah aci = 45.039 - 44.950 = 0.089 mm

Basi minimum

= Had rendah lubang - Had tinggi aci = 45.000 - 44.975 = 0.025 mm.

0.025 0.050

19


Chapter

GD&T stands for Geometric Dimensioning & Tolerancing

DIMENSION is a geometric characteristic the size of which is specified such as length,angle,location,or center distance  TOLERANCE on a dimension is the total permissible variation in its size, which is equal to the difference between the limits of size. 

GEOMETRIC DIMENSIONING AND TOLERANCING

Dimensions Of A Part

Geometric Tolerance

A geometric tolerance is the maximum permissible variation of form, profile, orientation, location, and runout from that indicated or specified on a drawing.  Feature control frame for an individual feature is divided into compartments containing, at the least, the geometric tolerance symbol and the geometric tolerance value 

20




Sizes Of Mating Parts Deviations

The difference between the basic size and the maximum and minimum sizes are called the UPPER & LOWER deviations.  The BASIC DIMENSION represents the theoretical exact size or location of a feature. 


Deviations

21


Basic (Exact) Dimensions Are shown in a

Examples of deviation of form when perfect form at the maximum material condition is required

rectangle toindicate that the tolerances in the general tolerance notedo not apply

examples of deviation of form when perfect form at the maximum material condition is required

22


GEOMETRIC CHARACTERISTIC SYMBOLS FEATURE

TYPE OF TOLERANCE

CHARACTERISTIC

FORM

STRAIGHTNESS

INDIVIDUAL

SYMBOL

SEE UNIT

16-2

FEATURES

16-5

MAXIMUM MATERIAL CONDITION

PROJECTED TOLERANCE ZONE

SUPPLEMENTARY SYMBOLS

BASIC DIMENSION

DATUM

16-4

16-9

16-9 16-11

16-6

FEATURE

DATUM TARGET

geometric characteristic symbols

FORM TOLERANCES

FORM TOLERANCES control the straightness, flatness, circularity and cylindricity  Form tolerances apply to individual features and as such do not require locating dimensions.  ORIENTATION TOLERANCES control angularity, parallelism, and perpendicularity 

More on FORM TOLERANCES

Straightness-a condition in which the element of a surface or a median line is a straight line  Flatness of a surface is a condition in which all surface elements are in one plane 


feature control frame

23


Application of feature control frame

Attached using a leader lead er

MMC, RFS, LMC applies to features subject to variations in size 

MMC (Maximum Material Condition) is when a feature or part is at the limit of size, which results in its containing the maximum amount of material.  LMC (Least Material Conditon) refers to the size of a feature that results in the part containing the minimum amount of material. Thus it is the minimum limit of size for an external feature.  RFS (Regardless of feature size) indicates that a geometric tolerance applies to any size of a feature that lies within its size tolerance. Orientation tolerance (16-6)

Angularity, parallelism and perpendicularity are ori entation tolerances applicable to related features  Angularity is the condition of a surface or axis at a specified angle (other than 90⁰or 0⁰) from a datum plane or axis surface at 90⁰ to a datum plane or axis. *A  Perpendicularity is the condition of a surface perpendicularity tolerance for a flat surface specifies a tolerance zone defined by two parallel planes perpendicular to a datum plane or axis  Parallelism is the condition of a surface equidistant at all points from a datum plane. Parallelism for a flat surface specifies a tolerance zone defined by two planes or lines parallel to a datum plane or axis. 

Datum

A DATUM is a theoretical exact feature from which dimensions may be taken.  A DATUM is generally chosen as an edge or feature which has the greatest influence in a specific measurement. 

Datums and the 3-plane concept (16-5)

Datum is a theoretical point, line, plane, or other geometric surface fromwhich dimensions are measured when so specified or to which geometric tolerances are referenced  Datum feature is a feature of a part, such as a surface, that forms the basis for a datum or is used to establish its location 

24


3-plane system

The three planes constitue a datum system from which measurements measurements can be taken. They will appear on the drawing.  Datum feature symbol is used on the drawing to identify these surfaces 


the datum planes

Datum Targets (16-11)

Datum target symbols are used to locate specific reference positions to be used on large datum surfaces*  the surface of a feature may be so large that a gage designed to make contact with the full surface may be too expensive or cumbersome to use  Functional requirements of the part may necessitate the use of only a portion of a surface as a datum feature 

CAD APPLICATIONS

Tolerance dialog box

25

Introduction of Metrology

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