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1.0: TITLE : Profile Measurement 2.0: OBJECTIVE : 1. Checking the specimen profile 2. Measure the parameters of the given specimen by using an Optical System 3.0: INTRODUCTION : A screw thread was invented in about 400BC by Archytas of Tarentum (428-350BC). Archimedes developed the screw principle and used it to construct device to raise water. Nowadays the principle of screw thread is been utilizing regarding the engineering scope. A screw thread is a helical structure used to convert between rotational and linear movement and force. A screw thread may be thought of as an inclined plane wrapped around a cylinder or cone. The tightening of a fastener's screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight plastic deformation. In most applications, the pitch of a screw thread is chosen so that friction is sufficient to prevent linear motion being converted to rotary that is so the screw does not slip even when linear force is applied so long as no external rotational force is present. This characteristic is essential to the vast majority of its uses. There are many types of screw thread. The thread types include UNC, UNF, and ISO, whit-worth, buttress and many others. Almost of the thread have triangle shaped threads. On the other hand, square shape and trapezoid shape thread are used moving machinery which needs high accuracy. Figure 2: Screw Terminology 1

Profile Measurement

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Page 1: Profile Measurement

1.0: TITLE: Profile Measurement

2.0: OBJECTIVE :

1. Checking the specimen profile

2. Measure the parameters of the given specimen by using an Optical System

3.0: INTRODUCTION:

A screw thread was invented in about 400BC by Archytas of Tarentum (428-350BC).

Archimedes developed the screw principle and used it to construct device to raise water.

Nowadays the principle of screw thread is been utilizing regarding the engineering scope. A

screw thread is a helical structure used to convert between rotational and linear movement and

force. A screw thread may be thought of as an inclined plane wrapped around a cylinder or

cone. The tightening of a fastener's screw thread is comparable to driving a wedge into a gap

until it sticks fast through friction and slight plastic deformation. In most applications, the pitch of

a screw thread is chosen so that friction is sufficient to prevent linear motion being converted to

rotary that is so the screw does not slip even when linear force is applied so long as no external

rotational force is present. This characteristic is essential to the vast majority of its uses. There

are many types of screw thread. The thread types include UNC, UNF, and ISO, whit-worth,

buttress and many others. Almost of the thread have triangle shaped threads. On the other

hand, square shape and trapezoid shape thread are used moving machinery which needs high

accuracy.

Figure 2: Screw Terminology

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Figure 3: Thread Terminology

Figure 2 and 3 showed a screw and thread terminology. One of the most important

terms used is that of the outer diameter. In the case of a metric thread, a bolt is named in

accordance with its outer diameter; e.g. in this experiment, a specimen (screw) M30-30-ISO 6H

is been used which M30 is referred as metric of 30mm outer diameter. The pitch of thread is

another important feature of thread. The pitch is defined as the interval (distance) between

adjoining thread. Once a bolt is used, the nut must have same pitch as well as diameter if they

need to be used together.

THEORY:

A projector is been selected in this experiment. A PH-3500 Profile projector by Mitutoyo

is used. The projector can produce an enlarge projection shadow of an object. The projection

methods of examination are well adapted to the examination of form tools, profile gauges, press

tools, gear teeth, screw threads, etc. sizes of the object maybe checked by direct measurement

on the enlarge shadow and subsequent division by the multiplication factor. The magnification

factor is accurate and that the design of the apparatus permits maximum latitude in holding and

adjusting the object.

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Major diameter = the distance between the crests of a thread. Major diameter is the widest

diameter on a thread.

Minor diameter = the distance between the roots of a thread. Minor diameter is the smallest

diameter on a thread.

Pitch = the distance from one thread groove to the next measured from crest to crest.

Thread angle = the angle included between the flanks of a thread measured in an axial

plane.

Depth of thread = the amount of material that is removed with one pass of a cutting tool.

4.0: SPECIMEN & EQUIPMENT :

1. Screw thread specimen.

2. Profile projector.

Figure 4: Horizontal Profile Projector Model Mitutoyo PH 3500

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Screen Display Screen Rotor

Angle Reading X,Y Reading

Specimen X Axis Control

Adjustor Table Focusing Knob

Y Axis Control On/Off Button

5.0: EXPERIMENTAL PROCEDURE:

1. A short briefing is conducted by the Assistance Lecturer, Mr Firhan to students.

2. A specimen, a screw M30-3.5-ISO 6H is fixed on projector adjusting table.

3. The projector is turned on and its focusing knob is adjusted for magnification of 10x. A

sharp and clear thread shadow will be displayed on projector’s screen.

4. Using the grid line, which is seemed on screen, the major diameter will be found out by

varying the Y axis control.

5. The initial reading and final reading is been taken in getting the major diameter.

6. Three readings are taken to get average reading.

7. The steps are repeated to find the minor diameter, pitch, thread angle and also the depth

of thread, D.O.P. The X-axis control is used to find the pitch and screen rotator for the

thread angle.

8. The experiment result is written down and followed by experiment discussion and

conclusion.

6.0: RESULT AND DATA ANALYSIS:

(i) Major diameter

Reading R1 (mm) R2 (mm) R = R2 – R1 (mm)

1 3.924 33.944 30.0202 3.957 33.950 29.9933 3.951 33.960 30.009

Average 3.944 33.951 30.007

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Reading 1:

R2 – R1 = 33.944 – 3.924

= 30.020 mm

R average:

= Reading 1 + Reading 2 + Reading 3

3

= 30.020 + 29.993 + 30.009

3

= 30.007 mm

(ii) Minor diameter

Reading R1 (mm) R2 (mm) R = R2 – R1 (mm)

1 6.513 31.367 24.8542 6.486 31.344 24.858

3 6.578 31.384 24.806

Average 6.526 31.365 24.839

Reading 1:

R2 – R1 = 31.367 – 6.513

= 24.854 mm

R average:

= Reading 1 + Reading 2 + Reading 3

3

= 24.854 + 24.858 + 24.806

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= 24.839 mm

(iii) Pitch

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Reading R1 (mm) R2 (mm) R = R2 – R1 (mm)

1 -3.462 0.006 3.468

2 -3.457 0.007 3.464

3 -3.457 0.014 3.471

Average -3.459 0.009 3.468

Reading 1:

R2 – R1 = 0.006 – (-3.462)

= 3.468 mm

R average:

= Reading 1 + Reading 2 + Reading 3

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= 3.468 + 3.464 + 3.471

3

= 3.468 mm

(iv) Thread angle, Φ

Reading Φ1 ( º ) Φ2 ( º ) Φ = Φ2 – Φ1 ( º )

1 -60.83º -120.62º - 59.79º

2 -150.95º -211.45º -60.50º

3 -151.82º -211.10º -59.28º

Average -121.20º -181.06º - 59.86º

Reading 1:

Φ2 – Φ1 = -120.62º – (-60.83º)

= -59.79º

Φ average:

= Reading 1 + Reading 2 + Reading 3

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= (-59.79º) + (-60.50º) + (-59.28º)

3

= -59.86º

(v) Depth of thread

Reading R1 (mm) R2 (mm) R = R2 – R1 (mm)

1 31.384 33.955 2.571

2 31.387 33.931 2.544

3 31.391 33.928 2.537

Average 31.387 33.938 2.551Reading 1:

R2 – R1 = 33.955 – 31.384

= 2.571 mm

R average:

= Reading 1 + Reading 2 + Reading 3

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= 2.571 + 2.544 + 2.537

3

= 2.551 mm

Percentage error for:

a) Major diameter

% error = theoretical reading – experimental reading x 100%

theoretical reading

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= 30.000 – 30.007 x 100%

30.000

= -0.023 %

b) Minor diameter

Minor diameter = major diameter – (1.226869 x pitch)

= 30.000 – (1.226869 X 3.5)

= 25.706 mm

% error = theoretical reading – experimental reading x 100%

theoretical reading

= 25.706– 24.839 x 100%

25.706

= 3.372 %

c) Pitch

% error = theoretical reading – experimental reading x 100%

theoretical reading

= 3.500 - 3.468 x 100%

3.500

= 0.914 %

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d) Thread angle, Φ

% error = theoretical reading – experimental reading x 100%

theoretical reading

= 60.00° - 59.86° x 100%

60.00°

= 0.233 %

e) Depth of thread

Depth = major diameter – minor diameter

2

= 30.000 – 25.706

2

= 2.147 mm

% error = theoretical reading – experimental reading x 100%

theoretical reading

= 2.147 – 2.551 x 100%

2.147

= - 0.188%

7.0: DISCUSSION:

1. Comment on any variations in results for the measured profile.

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From the data obtained in the experiment, there are variations in the readings for each

time the readings are taken from the screw thread. The variations may occur due to

misalignment of the specimen during making the alignment before taking the readings.

Besides, the variations in readings also occur because the specimen not attach or hold

properly by the clamping or holding device. As a result, the specimen can moved from

the right position and exposed to the unnecessary vibrations. The variations also cause

by the insensitivity coordination between eyes and hands when measuring the specimen

at the start and in the end. From the experiment, there are two zone appear around the

shadow which are dark zone and light zone. So, the students are confused whether to

take the reading from the dark or light line. Instead, the measurement was taken by

different person then, result the variation in measurement values during conducting the

experiment. The variations resulting the slightly different for experimental values and

theoretical values.

2. What are possible errors involved?

In the experiment, there are some errors that might be involved or happened when

conducting the experiment. First is parallax error which is occurred because of wrong

eye positioning during taking the values for each parameters. Moreover, different person

was taking the readings during the experiment. This may affect the values of readings

for each parameter. The error also may occur because of the misalignment of the

specimen in the experiment. The environmental error may occur as well as systems

error. The systems errors occur because the apparatus or machine is not well calibrated.

The students may also not familiar with the machine and cannot handle the machine

properly and result the error occurred in readings taken. The error also involved because

of environmental factor such as small vibration or external forces occurred during

conducting the screw thread and the specimen can move freely. This may change the

position of the specimen from the right point and cause slightly different in the values

measured.

3. What are the necessary precautions?

To avoid or minimize the error during the experiment, some precautions can be taken.

Students who handle the machine must properly know how to handle the machine well.

Full attention must be given during conducting the experiment to avoid the errors.

Person that handles the machine must make sure that the alignment of the specimen is

in the correct point. The readings taken should be parallel with eyes level to avoid

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parallax errors. Make sure the specimen is clamped properly so that it will stick to it

position even the external forces will change its position. If the specimen changes

position while the reading is taken, thus the result of the experiment will definitely

become an error and cannot be used. Other than that, the readings should be taken

consistently to minimize or reduce the possible errors.

4. Suggest other methods of checking the profile and dimensions of shapes and objects.

Profile and dimensions shapes and objects also can be checking using coordinate

measuring machine (CMM). A coordinate measuring machine 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.

Figure 5: Coordinate Measuring Machine and Its Controller

Measurements are defined by a probe attached to the third moving axis of this machine.

Probes may be mechanical, optical, laser, or white light, among others. They are often

used for:

• Dimensional measurement

• Profile measurement

• Angularity or orientation measurement

• Depth mapping

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• Digitizing or imaging

• Shaft measurement

The typical CMM is composed of three axes, an X, Y and Z. These axes are orthogonal

to each other in a typical three dimensional coordinate system. Each axis has a scale

system that indicates the location of that axis. The machine will read the input from the

touch probe, as directed by the operator or programmer. The machine then uses the

X,Y,Z coordinates of each of these points to determine size and position. Typical

precision of a coordinate measuring machine is measured in Microns, or Micrometres,

which is 1/1,000,000 of a metre.

The coordinates used are made clear by the picture on the following page:

Figure 6: Coordinate in CMM

Coordinate-measuring machines include three main components:

1) The main structure which include three axes of motion

2) Probing system

3) Data collection and Reduction system - typically includes a machine controller,

desktop computer and application software

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Legend:

Blue arrow: X axis

Purple arrow: Y axis

Green arrow: Z axis

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Figure 7: Main component of CMM

Advantages of CMM

• Best for work piece/sample with considerable amount of depth

Disadvantage of CMM

• Only limited to work piece/sample with considerable amount of depth since the

mechanical probe can only moves down the Z-axis in a very limited distance.

Procedure using CMM

1) The operator required to choose the type or shape of the particular sample for the

computer to set the value of z-axis, example typing PL for “plate” so that the z-axis

will be set to zero.

2) The coordinate points is then been choose. For number of points being more than

four or less than four, NP (“number of points”) is typed down at the computer and the

number of points is typed down. The higher number of points will give effect on

accuracy. A higher number of points will give higher accuracy since the

machine/computer will calculate its average. And the points are also chose best with

considerable distance to each other. This is because sometimes the surface of a big

sample is dissimilar (one point maybe slightly be higher or lower than the others).

3) Next, CS (“coordinate system”) is typed down. From here the operator will choose

the basic shape of the sample to choose the location of (0,0). Several choices are

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given such as typing #1for plate. The operator also need to choose axes used and

this been given 3 choices being XY-axes, XZ-axes or YZ-axes.

4) After that, PA is typed that is “Pattern Alignment”. A few basic type of pattern

alignment is opened to be chosen by the operator.

5) Following this, the operator only need to choose the point of interest as been shown

on the computer screen and direct the probe towards it. The green button on the

controller need to be press in order for the value been transferred to the computer.

The green button also slows down the probe during motion. After that IP is been set

to 0.0 for all axes.

6) Now the (0,0) origin marking is done. The operator only needs to type AP (“actual

position”) and move the probe head via the device the point of origin. After this, the

device can be operated automatically just by selecting Enter.

7) If a new value is required to be taken, the coordinates is been reset via typing RS

after step 6. To shut down the device, the operator only need to type IH that is “In

Home” and the CMM device will automatically being in a storage position.

There are some precaution should be taken when conducting CMM device;

1. Used the green button during the process of marking/touching the work sample with

the probe. This is to avoid hard collision that could damage the probe.

2. Make sure that the surface of working (the granite table) is without any unnecessary

obstacle that could affect the motion of the device especially at the area of the probe and

main structure.

3. The granite table is been carefully cared so that there’s no occurrence of scratches

because this could give deviation on the value obtained.

4. The controller is to be carefully place onto the table to avoid damage.

5. The CMM device is been set to its storage mode after usage to avoid damage.

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8.0: CONCLUSSION

From the experiment we found that the values for major diameter, minor diameter, pitch,

thread angle and depth of thread in experiment are different from theoretical value. The errors

for each parameter except the depth of thread are small. However, the errors are acceptable

since it’s below than 5%. It can be concluded that this experiment have achieved its objective

which are to check the profile and the measure the parameters of the given specimen by using

an optical system.

9.0: RECOMMENDATION

1) The specimen should be clamp perfectly so that there is no movement and the vibration

can be minimize and reduce as low as possible while reading is taken.

2) In order to reduce the percentage error, we have take the reading three times and

calculate its average to obtained accurate reading.

3) The precaution should be taken seriously while conduct this experiment include the

cleanliness because it may affect the reading.

10.0: REFERENCES

i. Serope Kalpakjian, W.R. Schmid, Manufacturing Technology and Fundamental, 5th

edition, Prentice Hall, 2004

ii. Serope Kalpakjian & Steven R. Schmid, Manufacturing Processes for Engineering

Materials, 4th Edition, Illinois Institute Of Technology, Prentice Hall, 2003.

iii. www.wikipedia/coordinate_measuring_machine

iv. www.wikipedia/profile_measurement

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