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M.I.E.T. ENGINEERING COLLEGE
TIRUCHIRAPALLI - 620 007
DEPARTMENT OF MECHANICAL ENGINEERING
LABORATORY MANUAL
MF9214 – CIM LAB
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SYLLABUS
MF9214 CIM LAB L T P C
0 0 3 2 AIM: To impart the knowledge on training the students in the area of CAD/CAM.
OBJECTIVE:
To teach the students about the drafting of 3D components and analyzing the sameusing various CAD/CAM software
CAM LABORATORY1. Exercise on CNC Lathe: Plain Turning, Step turning, Taper turning, Threading,
Grooving & canned cycle
2. Exercise on CNC Milling Machine: Profile Milling, Mirroring, Scaling & cannedcycle
3. Study of Sensors, Transducers & PLC: Hall-effect sensor, Pressure sensors,Strain gauge, PLC, LVDT, Load cell, Angular potentiometer, Torque, Temperature& Optical Transducers.
4. Mini project on any one of the CIM elements is to be done. This can be either a
software or hardware simulating a CIM element. At the end of the semester, the
students has to submit a mini report and present his work before a Committee.
CAD LABORATORY
2D modeling and 3D modeling of components such as
1. Bearing2. Couplings3. Gears4. Sheet metal components5. Jigs, Fixtures and Die assemblies.
TOTAL : 45 PERIODS
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LIST OF EXPERIMENTS
Ex no Name of exercise Page no
Study of CNC 1
CNC turning
1 Plain turning 6
2 Step turning 7
3 Taper turning 8
4 Thread cutting and grooving 9
5 Canned cycle 10
CNC milling
6 Profile milling 11
7 Mirroring 12
Study of sensors
Programmable logic controllers 13
Strain gage 16
Torque sensor 20
Linear Variable Differential Transformer
(LVDT)
22
Hall effect sensors 25
Pressure sensor theory 27
Temperature sensor 28
Digital transducer 28
Load cell 31
Introduction of cad 33
8 FOOT STEP BEARING 37
9 FLANGE COUPLING – PROTECTED TYPE 3810 UNIVERSAL COUPLING 39
11 SPUR GEAR 40
12 PROGRESSIVE DIE 41
13 DRILLING JIG AND FIXTURE 42
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Computer numerical control (CNC)
Computer numerical control is defined as NC systems that utilize a dedicated micro computer
to perform some or all of the basic numerical control functions.
Zero points and reference points
Zero point
In CNC machines, tool movements are controlled by coordinate system. The origin of the
coordinate system is considered as zero point. in some of the CNC machines, the zero point
may be located at a fixed place. And cannot be changed. This is known as fixed zero point.
Some other machines, a zero point may be established by moving the slides so that the
cutting tool is placed in the desired position in relation to the work pieces. This known asfloating zero point.
Machine zero point or machine datum (M)
It is a fixed point on a machine specified by the manufacturer. This point is the zero point for
the coordinate system of the machine controller. In turning center, a machine zero point is
generally at the center of the spindle nose face. In machining center, it is either fixed at center
of the table or a point along the edge of the traverse range.
Work piece zero point (W)
In this point determines the work piece coordinate system in a relation to the machine zero
point. In this point is chosen by the part programmer and input to the machine controller.
Position of this point may chosen in such a way that the dimension of work piece drawing
can be easily converted into coordinate values. For turned components, it is placed along the
spindle axis, in line with the right or left end face of the work piece. It is known as program
zero point.
Tool zero point (T)
When machining a work piece, the tool must be controlled in precise relationship with thework piece along the machining path. This requires a point in the tool turret be taken as
reference point, which is known as tool zero point.
As the tools in the tool turret have different shapes and sizes, in the offset distance between
the tool zero point and work piece zero point is measured and entered into the computer.
This is known as tool offset setting.
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The structure of part program used in FANUC controller, is given below
%; (program start)
O3642 (program number)
N010 ………………….
…… ………………….
…………………..
N100 M02; (program end)
Common word address used in word address format
Address Function
N Sequence number to identify a block
G Preparatory word that prepares the controller for instruction given in the block
X,Y,Z Coordinate data for three linear axes
U,V,W Coordinate data for incremental moves in turning in the X, Y and Z
directions respectively.
A,B,C Coordinate data for 3 rotational axes X, Y and Z directions respectively.
R Radius of arc, used in circular interpolation
I,J,K Coordinate values for arc center, corresponding to X, Y and Z axes
respectively.
F Feed rate per minute or revolution in either inches or millimeters
S Spindle rotation speedT Tool selection, used for machine tools with automatic tool changer or turrets.
D Tool diameter word used for offsetting the tool.
P It is used to store cutter radius data in offset register.
It defines first contour block number in canned cycle.
Q It defines last contour block number in canned cycle.
M Miscellaneous function
Block
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G-codeFunction
Turning center Machining centerG00 Rapid positioning
G01 Linear interpolation
G02 Circular interpolation(clock wise)
G03 Circular interpolation(anti clock wise)
G04 Dwell
G10 Setting offset amount
G17 Selection of XY plane
G18 Selection of ZX plane
G19 Selection of YZ plane
G20 Inch input system
G21 Metric input system
G27 Zero return check
G28 Return to zero
G33 Thread cutting ,block by block
G40 Tool nose radius compensation cancel Cutter radius compensation cancel
G41 Tool nose radius compensation left Cutter radius compensation left
G42 Tool nose radius compensation right Cutter radius compensation right
G50 Maximum spindle speed setting
G65 Call of user macro
G70 Finishing turning cycle
G71 Multiple turning cycleG72 Multiple facing cycle
G73 Pattern repeating cycle Peck drilling cycle
G74 Peck drilling cycle
G75 Grooving cycle
G76 Multiple thread cutting cycle Rectangular pocket clearance cycle
G77 Circular pocket clearance cycle
G80 Canned cycle cancel
G81 Drilling cycle, spot boring
G82 Drilling cycle, counter boring
G84 Tapping cycleG85 Boring cycle
G86 Boring cycle
G87 Back boring cycle
G90 Box turning cycle(A) Absolute mode of positioning
G91 Incremental mode of positioning
G92 Thread cutting cycle Preset program zero point
G94 Box turning cycle(B) Feed per minute
G95 Feed per revolution
G96 Constant surface speed (m/min)
G97 Constant RPM
G98 Feed per minuteG99 Feed per revolution
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M-code Function
M00 Program stop
M01 Optional stop
M04 Spindle on counter clock wiseM05 Spindle stop
M06 Tool change
M07 Coolant supply No.1 ON
M08 Coolant supply No.2 ON
M09 Coolant off
M10 Automatic clamping
M11 Automatic unclamping
M13 Spindle ON, clock wise + coolant ON
M14 Spindle ON, counter clock wise + coolant ON
M30 Program end rewindM70 X axis mirror ON
M71 Y axis mirror ON
M80 X axis mirror OFF
M81 Y axis MIRROR OFF
M98 Sub program call
M99 Subprogram end
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EX NO: 01 PLAIN TURNING
Aim:
To produce a plain turning for the given dimension as shown in figure
Tools required:1. Chuck key 2.Turning tool holder 3.Vernier caliper 4.Tool bit
Part program:
[BILLET X32 Z80;
N001 G21 G98;
N002 G28 U0 W0;
N003 M03 S1500;
N004 M06 T0102;
N005 G00 X33 Z1;
N006 G01 X32 Z1 F50;
N007 G01 Z-60;
N008 G01 X33;
N009 G00 Z1;
N010 G01 X31;
N011 G01 Z-60 F50;
N012 G01 X33; N013 G00 Z1;
N014 G01 X30;
N015 G01 Z-60 F50;
N016 G01 X33;
N017 G00 Z1;
N018 G01 X29 F50;
N019 G01 Z-60;
N020 G01 X33;
N021 G01 Z1;
N022 G01 X28;
N023 G01 Z-60 F50; N024 G01 X33;
N025 G28 U0 W0;
N026 M05;
N027 M30;
RESULT:
Thus the plain turning operation was done on the given component by using
CNC lathe.
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EX NO: 03 TAPER TURNING
Aim:
To produce a taper turning for the given dimension as shown in figure
Tools required:1. Chuck key 2.Turning tool holder 3.Vernier caliper 4.Tool bit
Part program:
[BILLET X32 Z80;
N001 G21 G98;
N002 G28 U0 W0;
N003 M03 S1500;
N004 M06 T0102; N005 G00 X33 Z1;
N006 G90 X32 Z1 F50;
N007 X31;
N008 X30;
N009 X29;
N010 X28;
N011 X27;
N012 X26;
N013 G00 X33 Z-20;
N014 G90 X32 Z1 F50;
N015 X32 R-0.5;
N016 X32 R-1.0;
N017 X32 R-1.5;
N018 X32 R-2.0;
N019 X32 R-2.5;
N020 X32 R-3.0;
N021 G28 U0 W0;
N022 M05;
N023 M30;
RESULT:
Thus the taper turning operation was done on the given component by using
CNC lathe.
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EX NO: 04 THREAD CUTTING
Aim:
To produce a manual part programming (canned cycle) for the given component forthe given dimension as shown in figure
Tools required:
1. Chuck key 2.Turning tool holder 3.Vernier caliper 4.Tool bit
Part program:
[BILLET X30 Z76
N020 G50 S4000
N030 G98 N040 G96 S300 M03
N050 M06 T0101
N060 G00 X30 Z0
N070 G71 U1 R1
N080 G71 P090 Q130 U0.5 W0.5 F100
N090 G01 X20 Z0
N100 G01 X24 Z-2
N110 G01 X24 Z-56
N120 G01 X30 Z-56
N130 G01 X30 Z-76
N140 G70 P090 Q130 F0.1
N150 G28 U0 W0
N155 M05
N160 M06 T0606
N170 G00 X24 Z-52
N175 G75 X20 Z-56 I1 K2 F0.2
N178 M05
N180 M06 T0303
N185 G00 X24 Z2
N188 G76 X23 .232 Z-50 A60 I0 K678 D500 F2
N190 G28 U0 W0 N195 M05
N200 M30
RESULT:
Thus the thread cutting operation was done on the given component by using
CNC lathe.
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EX NO: 05 CANNED CYCLE
Aim :
To produce a manual part programming (canned cycle) for the given component for
the given dimension as shown in figure
Tools required:1. Chuck key 2.Turning tool holder 3.Vernier caliper 4.Tool bit
Part program:
[BILLET X32 Z80;
N001 G21 G98; N002 G28 U0 W0;
N003 M03 S1500;
N004 M06 T0101;
N005 G00 X32 Z1;
N006 G71 U0.5 R0.5;
N007 G71 p8 q14 U0.2 W0.1 F50;
N008 G01 X20;
N009 G01 X20 Z-10;
N010 G01 X20 Z-10;
N011 G02 X24 Z-15 R5;
N012 G02 X28 Z-20 R5; N013 G01 X28 Z-28;
N014 G01 X32 Z-36;
N015 G70 p8 q14 S2000 F30;
N016 G28 U0 W0;
N017 M05;
N018 M30;
RESULT:
Thus the counter taper turning operation was done on the given component by
using CNC lathe.
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EX NO: 06 PROFILE MILLING
Aim:
To produce a profile milling for the given dimension as shown in figure
Tools required:
1. Chuck key 2.Turning tool holder 3.Vernier caliper 4.Tool bit
Part program:G21 G94
G91 X0 Y0 Z0
M06 T01M03 S2000
G90
G00 X-15 Y-25 Z10
G01 X-15 Y-25 Z-2 F30
G01 X15 Y-25 Z-2
G03 X25 Y-15 R10
G01 X25 Y15
G02 X15 Y25 R10
G01 X-15 Y25
G03 X-25 Y15 R10
G01 X-25 Y-15G01 X-15 Y-25
G01 X-15 Y-25 Z10
G91
G28 Z0
G28 X0 Y0
M05
M30
RESULT:
Thus the PROFILE MILLING operation was done on the given component by
using XLMILL.
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EX NO: 07 MIRRORING
Aim:
To produce a mirroring for the given dimension as shown in figure
Tools required:
1. Chuck key 2.Turning tool holder 3.Vernier caliper 4.Tool bit
Part program:G21 G94
G28 Z0
G28 X0 Y0
M06 T0101M03 S1200
G90
G00 X0 Y0 Z10
M98 P01 4545
M70
M98 P01 4545
M71
M98 P01 4545
M80
M98 P01 4545
M81G91
G28 Z0
G28 X0 Y0
M05
M30
04545
G90
G00 X10 Y10 Z10
G01 X10 Y10 Z-2 F30
G01 X10 Y10 Z-2G01 X10 Y30 Z-2
G01 X30 Y10 Z-2
G01 X10 Y10 Z-2
G00 X0 Y0 Z10
M99
RESULT:Thus the MIRRORING operation was done on the given component by using
XLMILL.
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STUDY OF SENSORS
Programmable Logic Controllers
(Definition according to NEMA standard ICS3-1978)
A digitally operating electronic apparatus which uses a programming memory for the internal storage
of instructions for implementing specific functions such as logic, sequencing, timing, counting and
arithmetic to control through digital or analog modules, various types of machines or process.
POWER SUPPLY
Provides the voltage needed to run the primary PLC components
I/O MODULES
Provides signal conversion and isolation between the internal logic-level signals inside the
PLC and the field’s high level signal.
PROCESSOR
Provides intelligence to command and govern the activities of the entire PLC systems.
PROGRAMMING DEVICE
It is used to enter the desired program that will determine the sequence of operation and
control of process equipment or driven machine.
I/O Module
The I/O interface section of a PLC connects it to external field devices.
The main purpose of the I/O interface is to condition the various signals received from or sent
to the external input and output devices.
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Input modules converts signals from discrete or analog input devices to logic levels
acceptable to PLC’s processor.
Output modules
Output modules converts signal from the processor to levels capable of driving the connected
discrete or analog output devices
Processor
The processor module contains the PLC’s microprocessor, its supporting circuitry, and its
memory system.
The main function of the microprocessor is to analyze data coming from field sensors through
input modules, make decisions based on the user’s defined control program and return signal
back through output modules to the field devices. Field sensors: switches, flow, level, pressure, temp. transmitters, etc. Field output devices: motors, valves, solenoids, lamps, or
audible devices.
The memory system in the processor module has two parts: a system memory and an
application memory.
Basic Function of a Typical PLC
Read all field input devices via the input interfaces, execute the user program stored in
application memory, then, based on whatever control scheme has been programmed by the
user, turn the field output devices on or off, or perform whatever control is necessary for the
process application.
This process of sequentially reading the inputs, executing the program in memory, and
updating the outputs is known as scanning.
While the PLC is running, the scanning process includes the following four phases, which are
repeated continuously as individual cycles of operation:
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PHASE 1 – Input Status scan
A PLC scan cycle begins with the CPU reading the status of its inputs.
PHASE 2 – Logic Solve/Program Execution
The application program is executed using the status of the inputs
PHASE 3 – Logic Solve/Program Execution
Once the program is executed, the CPU performs diagnostics and communication
tasks
PHASE 4 - Output Status Scan
An output status scan is then performed, whereby the stored output values are sent to
actuators and other field output devices. The cycle ends by updating the outputs.
As soon as Phase 4 are completed, the entire cycle begins again with Phase 1 input
scan.
The time it takes to implement a scan cycle is called SCAN TIME. The scan time
composed of the program scan time, which is the time required for solving the
control program, and the I/O update time, or time required to read inputs and update
outputs. The program scan time generally depends on the amount of memory taken
by the control program and type of instructions used in the program. The time to
make a single scan can vary from 1 ms to 100 ms.
Advantages of PLCs
Less wiring.
Wiring between devices and relay contacts are done in the PLC program.
Easier and faster to make changes.
Trouble shooting aids make programming easier and reduce downtime.
Reliable components make these likely to operate for years before failure.
Areas of Application
Manufacturing / Machining
Food / Beverage
Metals
Power
Mining
Petrochemical / Chemical
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Unbounded strain
The unbounded strain gage consists of a wire stretched between two points in an insulating medium
such as air. Four gauges are normally connected in a Wheatstone bridge circuit and arranged so that
two gauges are lengthened and two shortened by the displacement
Bonded strain
A bonded strain-gage element, consisting of a metallic wire, etched foil, vacuum-deposited film, or
semiconductor bar, is cemented to the strained surface
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Semiconductor Strain Gages
Strain-gage technology advanced in the 1960s with the introduction of the semiconductor
strain-gage elements
Silicon gages are formed from single-crystal silicon whose orientation and doping are the
most important design parameters. The gage factor depends on the resistivity (determined by
the doping) and the crystal orientation.
Bonded semiconductor gages are made by slicing sections from specially processed silicon
crystals and are available in both n and p types. The high gage factor is accompanied by high-
temperature sensitivity, nonlinearity, and mounting difficulties.
Diffused semiconductor gages utilize the diffusion process employed in integrated-circuit
manufacture. This type of construction may allow lower manufacturing costs in some designs,
since a large number of devices can be made on a single silicon wafer. The deviation from
linearity is approximately 1%
Principle of Measurement
Mechanical loading produces a change of length in the measurement object, which is
conveyed to the strain gauge. Because there is a change in length, the electrical resistance of
the applied strain gauge also changes in proportion to the strain. If there is excitation voltage,
the circuit supplies an output signal proportional to the change in resistance and therefore also
proportional to the change in length. A carrier frequency or DC amplifier suitable for strain
gauges enables measurement signal evaluation to continue.
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Torque sensor
Torque is measured by either sensing the actual shaft deflection caused by a twisting force, or
by detecting the effects of this deflection.
The surface of a shaft under torque will experience compression and tension, as shown in
Figure.
To measure torque, strain gage elements usually are mounted in pairs on the shaft, one gauge
measuring the increase in length (in the direction in which the surface is under tension), the
other measuring the decrease in length in the other direction.
Torque is a measure of the forces that causes an object to rotate.
Reaction torque sensors measure static and dynamic torque with a stationary or non-rotating
transducer.
Rotary torque sensors use rotary transducers to measure torque
Torque Measurement
The need for torque measurements has led to several methods of acquiring reliable data from
objects moving. A torque sensor, or transducer, converts torque into an electrical signal.
The most common transducer is a strain guage that converts torque into a change in electrical
resistance.
The strain guage is bonded to a beam or structural member that deforms when a torque or
force is applied.
Deflection induces a stress that changes its resistance. A Wheatstone bridge converts the
resistance change into a calibrated output signal.
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The design of a reaction torque cell seeks to eliminate side loading (bending) and axial
loading, and is sensitive only to torque loading. The sensor’s output is a function of force and
distance, and is usually expressed in inch-pounds, foot-pounds or Newton-meters
Classification of torque sensors
Torques can be divided into two major categories, either static or dynamic.
The methods used to measure torque can be further divided into two more categories, either
reaction or in-line.
A dynamic force involves acceleration, were a static force does not.
In reaction method the dynamic torque produced by an engine would be measured by placing
an inline torque sensor between the crankshaft and the flywheel, avoiding the rotational
inertia of the flywheel and any losses from the transmission.
In-line torque measurements are made by inserting a torque sensor between torque carrying
components, much like inserting an excitation between a socket and a socket wrench.
Applications of force/torque sensors
In robotic tactile and manufacturing applications
In control systems when motion feedback is employed.
In process testing, monitoring and diagnostics applications. In measurement of power transmitted through a rotating device.
In controlling complex non-linear mechanical systems
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Linear Variable differential Transformer (LVDT)
Coupled to any type of object/structure
Converts the rectilinear motion of an object into a corresponding electrical signal
Measures Displacement
Precision of LVDT
Movements as small as a few millionths of an inch
Usually measurements are taken on the order of ±12 inches
Some LVDT’s have capabilities to measure up to ±20 inches
Type of LVDT’s
DC Operated
AC Operated
Types of LVDT’s armatures
Unguided Armature
Captive Armature
Spring-extended Armature
Unguided Armature
Fits loosely in bore hole
LVDT body and armature are separately mounted – must ensure alignment
Frictionless movement
Suitability
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Short-range high speed applications
High number of cycles
Captive (Guided) Armature
Restrained and guided by a low-friction bearing assembly
Suitability
Longer working range
Alignment is a potential problem
Spring Extended Armature
Restrained and guided by a low-friction bearing assembly (again!)
Internal spring pushes armature to max. extension
Maintains reliable contact with body to be measured
Suitability
Static – slow moving application (joint-opening in pavement slabs)
LVDT components
Underlying Principle
Electromagnetic Induction:
Primary Coil (RED) is connected to power source
Secondary Coils (BLUE) are connected in parallel but with opposing polarity
Primary coil’s magnetic field (BLACK ) induces a current in the secondary coils
Ferro-Metallic core (BROWN) manipulates primary’s magnetic field
In the null position, the magnetic field generates currents of equal magnitude in both
secondary coils.
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Hall Effect sensors
The change in magnetic field induces a current, the change in intensity and direction of the current
can measure the velocity and direction object producing the magnetic field.
“The basic physical principle underlying the Hall effect is the Lorentz force. When an electron moves
along a direction p The change in magnetic field induces a current, the change in intensity and
direction of the current can measure the velocity and direction object producing the magnetic field.
Perpendicular to an applied magnetic field, it experiences a force acting normal to both directions and
moves in response to this force and the force effected by the internal electric field. For an n-type, bar-
shaped semiconductor shown in Fig.1, the carriers are predominately electrons of bulk density n. We
assume that a constant current I flows along the x-axis from left to right in the presence of a z-directed
magnetic field. Electrons subject to the Lorentz force initially drift away from the current line toward
the negative y-axis, resulting in an excess surface electrical charge on the side of the sample. This
charge results in the Hall voltage, a potential drop across the two sides of the sample. “ (figure one to
the left)
This transverse voltage is the Hall voltage V H and its magnitude is equal to IB/qnd , where I is the
current, B is the magnetic field, d is the sample thickness, and q (1.602 x 10-19 C) is the elementary
charge. In some cases, it is convenient to use layer or sheet density (ns = nd ) instead of bulk density.
One then obtains the equation
ns = IB/q|V H|.(1)
Thus, by measuring the Hall voltage V H and from the known values of I , B, and q, one can
determine the sheet density ns of charge carriers in semiconductors. If the measurement apparatus is
set up as described later in Section III, the Hall voltage is negative for n-type semiconductors and
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positive for p-type semiconductors. The sheet resistance RS of the semiconductor can be conveniently
determined by use of the van der Pauw resistivity measurement technique. Since sheet resistance
involves both sheet density and mobility, one can determine the Hall mobility from the equation
µ = |V H|/ RS IB = 1/(qnS RS).(2)
If the conducting layer thickness d is known, one can determine the bulk resistivity
(r = RSd ) and the bulk density
(n = nS/d ). “
Working
This sensor measures the thickness of nonferrous materials with 1% accuracy by sandwiching
the material being measured between a magnetic probe on one side and a small target steel
ball on the other side.
It measures up to 10 mm. The Hall effect sensor is used to measure the magnetic field, as a dc
measurement; ac Hall effect measurements can be made more precisely because they
eliminate bias and are done with less noise”
As the magnetic field between the sensor and a metal ball changes the sensor can measure it’s
proximity and direction by measuring the direction and intensity of the current induced.
Hall Effect sensors are classified as
Switches
Sensors
Absolute field
Differential field
Special-Purpose
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Limitations
Sensor only devise
Good only in close proximity
Must have a reference point
Magnetic field must be present
Must be calibrated
Pressure Sensor Theory
Two Main Types of Pressure Sensors
Capacitive Sensors
Piezoresistive Sensors
Capacitive Sensors
• Work based on measurement of capacitance from two parallel plates.
• C = εA/d , A = area of plates d = distance between.
• This implies that the response of a capacitive sensor is inherently non-linear.
Worsened by diaphragm deflection.
• Must use external processor to compensate for non-linearity
Piezoresistive Sensors
Work based on the Piezoresistive properties of silicon and other materials.
Piezoresistivity is a response to stress.
Some Piezoresistive materials are Si, Ge, metals.
In semiconductors, Piezoresistivity is caused by 2 factors: geometry deformation and
resistivity changes.
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Temperature sensor
Resistive thermometers
Thermistors
pn junctions
pn junctions
a semiconductor device with the properties of a diode (we will consider
semiconductors and diodes later)
inexpensive, linear and easy to use
limited temperature range (perhaps -50 C to 150 C) due to nature of semiconductor
material
Resistive thermometers
typical devices use platinum wire (such a device is called a platinum resistance
thermometers or PRT)
linear but has poor sensitivity
Thermistors
use materials with a high thermal coefficient of resistance
sensitive but highly non-linear
Digital Transducer
Any transducer that presents information as discrete samples and that does not introduce a
quantization error when the reading is represented in the digital form may be classified as a
digital transducer
Encoder
Any transducer that generates a coded of a measurement can be termed an encoder
SHAFT ENCODERS
They are Digital Transducers that are used for measuring ANGULAR DISPLACEMENTS
and ANGULAR VELOCITIES.
Shaft encoders can be classified into three categories
1. Incremental Encoders
2. Incremental Optical Encoders
3. Absolute Optical Encoders
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Incremental Encoders
1.Optical (photosensor) method
2.Sliding contact (Electrical conducting) method
3.Magnetic saturation (Reluctance) method
Optical Encoder
The optical encoder uses an opaque disk that has one or more circular tracks, with some
arrangement of identical transparent windows.
A parallel beam of light is projected to all tracks from one side of the disk
The light sensor could be a silicon photodiode, a phototransistor, or a photovoltaic cell.
The light from the source is interrupted by the opaque areas of the track, the output signal
from the probe is a series of voltage pulses
Sliding Contact
The transducer disk is made of an electrically insulating material
The conducting regions correspond to the transparent windows on an optical encoder disk
All conducting areas are connected to a common slip ring on a encoder shaft
A constant voltage Vref is applied to the slip ring using a brush mechanism
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Incremental Optical Encoder
The disk has a single circular track with identical and equally spaced transparent
windows.
The area of the opaque region between adjacent windows is equal to the window area.
Two photodiode sensors (pick offs 1 and 2) are positioned facing the track a quarter-pitch
Absolute Optical Encoders
The disk has a circular track with identical and equally spaced transparent windows.
In absolute optical encoders photo sensors are not used.
The output can be binary, gray code, natural binary code.
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LOAD CELL
A load cell is that is used to convert a force into electrical signal.
This conversion is indirect and happens in two stages. Through a mechanical arrangement,
the force being sensed deforms a strain gauge. The strain gauge measures the deformation
(strain) as an electrical signal, because the strain changes the effective electrical resistance of
the wire. A load cell usually consists of four strain gauges in a Wheatstone bridge
configuration. Load cells of one strain gauge (Quarter Bridge) or two strain gauges (half
bridge) are also available.[1] The electrical signal output is typically in the order of a few mill
volts and requires amplification by an instrumentation amplifier before it can be used. Theoutput of the transducer can be scaled to calculate the force applied to the transducer.
The various types of load cells that are present are:
Hydraulic Load cell
Pneumatic Load cell
Strain Gauge Load cell
Hydraulic Load Cell: the piston is placed in a thin elastic diaphragm. The piston doesn’t
actually come in contact with the load cell. Mechanical stops are placed to prevent over strain
of the diaphragm when the loads exceed certain limit. The load cell is completely filled with
oil. When the load is applied on the piston, the movement of the piston and the diaphragm
arrangement result in an increase of oil pressure which in turn produces a change in the
pressure on a bourdon tube connected with the load cells
Pneumatic load cells: the load cell is designed to automatically regulate the balancing
pressure. Air pressure is applied to one end of the diaphragm and it escapes through the
nozzle placed at the bottom of the load cell. A pressure gauge is attached with the load cell to
measure the pressure inside the cell. The deflection of the diaphragm affects the airflow
through the nozzle as well as the pressure inside the chamber.
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Strain gauge load cells are the most common, there are other types of load cells as well. In
industrial applications, hydraulic (or hydrostatic) is probably the second most common, and
these are utilized to eliminate some problems with strain gauge load cell devices. As an
example, a hydraulic load cell is immune to transient voltages (lightning) so might be a more
effective device in outdoor environments.
Other types include piezoelectric load cells (useful for dynamic measurements of force), and
vibrating wire load cells, which are useful in geotechnical applications due to low amounts of
drift, and capacitive load cells where the capacitance of a capacitor changes as the load preses
the two plates of a capacitor closer together.
Every load cell is subject to "ringing" when subjected to abrupt load changes. This stems
from the spring-like behavior of load cells. In order to measure the loads, they have to
deform. As such, a load cell of finite stiffness must have spring-like behavior, exhibiting
vibrations at its natural frequency. An oscillating data pattern can be the result of ringing.
Ringing can be suppressed in a limited fashion by passive means. Alternatively, a control
system can use an actuator to actively damp out the ringing of a load cell. This method offers better performance at a cost of significant increase in complexity.
Load cells are used in several types of measuring instruments such as universal testing
machines.
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INTRODUCTION OF CAD
INTRODUCTION
AUTOCAD was developed by AUTODESK Inc., USA. It is the most
popular PC CAD based system available in the market. In the term auto refers the
Company AUTODESK Inc., and the term cad is the acronym of computer aided design or
drafting. it is one of the worldwide standard for generating various kings of drawing. Auto
cad open architecture has allowed thirty parties develops to write application software by
using programming language like auto lisp etc.., and that has significantly added to its
popularity. Auto cad provides the productivity.
Application of auto cad
It is used by civil engineers in the design of buildings, dams, arches, etc..,
It is used by mechanical engineers in the design of mechanical parts, assembly, automobile
components, consumer products etc.
It is used by electronic engineers in the design of PCBS
It is used by art directors in the film industry for generating 3Dmodels etc..,
Advantages of auto cad
Drawing can be created very easily and quickly
Accurate and high precise drawing can be created
Existing drawing can be edited and modified easily
Dimension of drawing can be done easily
Storage and retrieval of drawing are very easy
Visualization of drawing very easy
Three dimensional modeling
They are geometrical model created with 3Dimension of an object. A 3D model of a part
convey meanings more rapidly than its corresponding ortho. The 3D geometric modeling has
the ability provide all the information required for manufacturing application. There are three
numbers of geometric modeling, they are.
Wire frame model or line model
Surface model
Solid model or volume model
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Wire frame model
It is the simplest geometric model that can be represent an object mathematical in the
computer .it is also called as line model or edge object wire frame model consists of points,
line, arc, circle, conics and curves. The wire frame is related to the fact that one may imaging
a wire that is tent to follow the object edge generate the model. An edge may be straight line,
arc or any other circle defined curves.
Surface model
A surface model of an object is more complete and less confusing representation then its wire
frame model. The procedure for constructing a surface model is selecting a thin piece of
material over a frame work.
Solid modeling
The best for the 3D model construction is solid modeling technique. It provides the user with
complete information about the model. In this approach the model are displayed as solid
model. In this approach the viewer with very little risk of misunderstanding when color is
very realistic. All solid model system for creating, modifying and inspection model of 3D
solid objects.
Construction of solid model solid primitive is called building block approaching or
constructive solid geometry. In the constructive solid geometry approach a solid object
typical primitives utilizes in the model are block, sphere, semi sphere, cylinder, cone, tour
and wedges.
CSG using Boolean operators.
Boolean operators are used for combining the primitives performs the complete solid object.
The available Boolean operators are union (u), intersection (n) and the difference (-).
Union (u)
When two or more solid are combined with the Boolean operators union, the result is solid
shapes incorporation space occupied by any of the individual components. Simply this islike adding components together.
Difference (-)
When two or more solid are combined with the Boolean operators difference, the result is the
single solid shapes incorporation space, which is occupied by first component, but is outside
the entire component. This is like subtraction the first component.
Intersection (n)
When two or more solid are combined with intersection, the result is the single solid shapes
incorporation space, which is occupied in common by each of the components.
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Converting 2D model into 3D model.
There are two techniques which are generally used to convert 2D model into 3D model.
Extrusion
Revolve
General procedure
Create the 2D profile using standard 2D drawing Commands
Create region using region command
Subtract the unwanted region
Extrude or revolve the resulting region.
Example 1(extrusion)
Draw the 2D profile using 2D drawing command
Create region
Command: Region
Select object: specify opposite corner: 2 found
Select object: 2 loops extracted
Subtract the circle from the square
Command: Subtract
Select solid and region to subtract from….
Select object: select the square
Select object:
Select solid and region to subtract……
Select object: select the circle
Select object:
Extrude the resultant region
Command: extrude
Current wire frame density: isolines = 4
Select object: select the resultant region
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Select object:
Select height or extrusion [path]: specify suitable height
Specify angle (or) extrusion of taper<0>:0
Example 2:
Creating region
Command: region
Tool bar: draw >
Menu: draw >region
This command is used to convert an object. That encloses an area into the region object.
Regions are two dimensional that enclosed area are creating from objects that are fro closed
loops. Loops can be combined of lines or combination of lines. Poly lines, circle, arc, ellipse,
elliptical arcs and spines. The object that make up the other object.
Procedure:
Select object to create a region. This object should from an enclosed area such as a circle or a
enclosed poly line.
Press enter. A message command line indicates many loops curve detected and hoe many
region curve created.
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FOOT STEP BEARING
Ex No: 8
Aim:
To create the solid model Foot step bearing shown in figure using Auto CAD
Procedure:
Set the LIMITS 300,300
Draw the casting as per diagram
Using draw commends complete draw the casting part.
Using REGION commend to closed casting part
EXTRUDE the resultant region to a width of 115mm
To complete pad Draw circle ø 45 and EXTRUDE the resultant region to a height of
13mm
Draw shaft as per diagram
Using REGION commend to closed shaft
REVOLVE the resultant region to 360˚
Draw BUSH as per diagram
Using REGION commend to closed bush
REVOLVE the resultant region to 360˚
Assemble all parts using ALIGN commend
Result:
The solid model of Foot step bearing shown in figure using Auto CAD
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FOOT STEP BEARING
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FLANGE COUPLING – PROTECTED TYPE
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UNIVERSAL COUPLING
Ex No: 10
Aim:
To create the solid model universal coupling shown in figure using Auto CAD
Procedure:
Set the LIMITS 400,400
Draw the FORK as per diagram
Using draw commends complete draw the fork part.
Using REGION commend to closed fork part
EXTRUDE the resultant region to a width of 162 mm
Draw center block as per diagram
Using REGION commend to closed shaft
REVOLVE the resultant region to a 360˚
Draw the collar as per diagram
Using draw commends complete draw the collar part.
Using REGION commend to closed collar part
EXTRUDE the resultant region to a width of 13 mm
Draw pin & tapper as per diagram
Using REGION commend to closed bush
REVOLVE the resultant region to 360˚
Assemble all parts using ALIGN commend
Result:
The solid model universal coupling shown in figure using Auto CAD
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UNIVERSAL COUPLING
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SPUR GEAR
Ex No: 11
Aim:
To create the solid model spurs gear shown in figure using Auto CAD
Procedure:
Set the LIMITS 400,400
Draw the CIRCLE of radius 90mm
Create the teeth using draw commend
Create 42 teeth using POLAR ARRAY
Create CIRCLE of radius 25mm
Create slot for key of length 5mm, width 3mm
Create REGIONS
EXTRUDE the resultant region to a width of 30mm
Result:
The solid model spurs shown in figure using Auto CAD
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PROGRESSIVE DIE
Ex No: 12
Aim:
To create the solid model progressive die shown in figure using Auto CAD
Procedure:
Set the LIMITS 500,500
Draw the DIE as per diagram
Using draw commends complete draw the DIE part.
Using REGION commend to closed DIE part
EXTRUDE the resultant region to a height of 26 mm
Draw the PUNCH HODER as per diagram
Using draw commends complete draw the PUNCH HODER part.
Using REGION commend to closed PUNCH HODER part
EXTRUDE the resultant region to a height of 20 mm
Draw blanking and pearsing punch as per diagram
Using REGION commend to closed bush
REVOLVE the resultant region to 360˚
Assemble all parts using ALIGN commend
Result:
The solid model progressive die shown in figure using Auto CAD
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PROGRESSIVE DIE
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DRILLING JIG AND FIXTURE
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