cim lab manual

8/9/2019 CIM LAB Manual

http://slidepdf.com/reader/full/cim-lab-manual 1/58

M.I.E.T. ENGINEERING COLLEGE

TIRUCHIRAPALLI - 620 007

DEPARTMENT OF MECHANICAL ENGINEERING

LABORATORY MANUAL

MF9214 – CIM LAB



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



1

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



2

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.



4

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



5

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



6

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



7



8

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.



9



11



12

EX NO: 03 TAPER TURNING

Aim:

To produce a taper turning for the given dimension as shown in figure


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.



13



14

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.



15



16

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


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.



18

EX NO: 06 PROFILE MILLING

Aim:

To produce a profile milling for the given dimension as shown in figure

Tools required:


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.



19



20

EX NO: 07 MIRRORING

Aim:

To produce a mirroring for the given dimension as shown in figure

Tools required:


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.



21

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.



22

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:



23

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



25

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



26

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.



28

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.



29

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



30

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



31

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.



33

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

http://www.eeel.nist.gov/812/fig1.htm






34

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



35

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.



36

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



37

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



38

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.



39

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.

http://en.wikipedia.org/wiki/Force

http://en.wikipedia.org/wiki/Electrical_signal

http://en.wikipedia.org/wiki/Strain_gauge

http://en.wikipedia.org/wiki/Strain_%28materials_science%29

http://en.wikipedia.org/wiki/Wheatstone_bridge

http://en.wikipedia.org/wiki/Load_cell#cite_note-1



http://en.wikipedia.org/wiki/Instrumentation_amplifier

http://en.wikipedia.org/wiki/Instrumentation_amplifier


http://en.wikipedia.org/wiki/Wheatstone_bridge

http://en.wikipedia.org/wiki/Strain_%28materials_science%29

http://en.wikipedia.org/wiki/Strain_gauge

http://en.wikipedia.org/wiki/Electrical_signal

http://en.wikipedia.org/wiki/Force



40

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.

http://en.wikipedia.org/wiki/Piezoelectric

http://en.wikipedia.org/w/index.php?title=Vibrating_wire&action=edit&redlink=1

http://en.wikipedia.org/w/index.php?title=Geomechanical&action=edit&redlink=1

http://en.wikipedia.org/wiki/Drift_%28telecommunication%29

http://en.wikipedia.org/wiki/Capacitor

http://en.wikipedia.org/wiki/Normal_mode

http://en.wikipedia.org/wiki/Control_system


http://en.wikipedia.org/wiki/Actuator

http://en.wikipedia.org/wiki/Universal_testing_machine





http://en.wikipedia.org/wiki/Actuator




http://en.wikipedia.org/wiki/Normal_mode

http://en.wikipedia.org/wiki/Capacitor

http://en.wikipedia.org/wiki/Drift_%28telecommunication%29

http://en.wikipedia.org/w/index.php?title=Geomechanical&action=edit&redlink=1

http://en.wikipedia.org/w/index.php?title=Vibrating_wire&action=edit&redlink=1

http://en.wikipedia.org/wiki/Piezoelectric



41

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



42

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.



43

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



44

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.



45

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


Assemble all parts using ALIGN commend

Result:

The solid model of Foot step bearing shown in figure using Auto CAD



46

FOOT STEP BEARING



48

FLANGE COUPLING – PROTECTED TYPE



49

UNIVERSAL COUPLING

Ex No: 10

Aim:

To create the solid model universal coupling shown in figure using Auto CAD

Procedure:


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




Result:

The solid model universal coupling shown in figure using Auto CAD



50

UNIVERSAL COUPLING



51

SPUR GEAR

Ex No: 11

Aim:

To create the solid model spurs gear shown in figure using Auto CAD

Procedure:


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



53

PROGRESSIVE DIE

Ex No: 12

Aim:

To create the solid model progressive die shown in figure using Auto CAD

Procedure:


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




Result:

The solid model progressive die shown in figure using Auto CAD



54

PROGRESSIVE DIE



DRILLING JIG AND FIXTURE

cim lab manual

Documents