report selective

8/2/2019 Report Selective

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Introduction

Quality is one of the important things for any product in this competitiveworld. Customer wants the product with high precision at a reasonable price. Any

product has more number of parts to be assembled. The parts which are in contactwith each other are called mating parts. The clearance between the mating parts hasmore impact in deciding the quality of the product. Variability is unavoidable in allthe manufacturing processes. When the parts are manufactured in differentmachines the parts have more variability in dimensions. Certainly the clearance

between the mating parts decides the quality of the product.

When the components are assembled, the resulting variation will be the sumof the component tolerances. To achieve high precision assembly, the parts have to

be manufactured with closer tolerances which will lead to higher cost. When theacceptable variation is less than the sum of the available component tolerances, theinterchangeable assembly system can not be followed. The only solution isselective assembly system.

Selective Assembly

Selective assembly is the process of selecting the mating parts to achieve a certainclearance or interference during assembly. Selective assembly in hi-techmanufacturing area is to assemble parts with known values to obtain desired

performance characteristics. The mating parts with hole are called as female partsand parts that makes with the hole are called as male parts. In other way they arecalled as hole and shaft. In selective assembly, high precision assemblies areobtained from relatively low precision components. The mating parts populationsare partitioned with respect to the dimensional distributions to form groups. Thecorresponding groups of the mating parts are assembled interchangeably.

The dimensional variation is considered to follow normal distribution. The

dimensional distribution of shaft population is called as 6s and that of hole iscalled as 6h. By following this method there are no surplus parts. But there will be more clearance in between the assembled parts. The clearance variation is dueto the difference in its standard deviation of the mating parts.

Linear assemblies are the assemblies in which the components areassembled linearly. The example for linear assembly is arranging gear wheels in a


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shaft of an automobile gear box. Here the clearances of individual gears are addedto get the total clearance of the given assembly. Radial assemblies are theassemblies in which the components are assembled radialy. The example for radialassembly is a hole and shaft assembly. If the radius of the shaft is 1mm smaller than the hole radius, the assembly clearance will be 2mm. Here the clearance of individual components will have a doubled effect in the assembly clearance. Pugh(1986) developed a computer program to generate group partitions for the givencomponent distribution and to decide the number of classes for selective assembly.

Fugino (1987) proposed a new method, the batch oriented system, whichreduces the computing time where lot sizes are large. Berzak (1992) discussedabout the robotic techniques in selective assembly to improve product quality andreduce the cost. Yamada (1994) proposed a new method for optimizing theselective assembly process in an automated continuous production system. Iyamaet al used a Markov model to analyze a three part ball bearing assembly. Kannan

and Jayabalan (2001a) proposed a new method of grouping for grouping a complexassembly with three parts. In their work they minimized the surplus parts. Kannanand Jayabalan(2001b) got lesser assembly variation in linear assembly withminimum surplus parts by following selective assembly. Kannan and Jayabalan(2001c) proposed to manufacture the mating parts with a design in its mean to haveminimum surplus parts in selective assembly.

Fang and Zhang (1995) proposed a method of making groups with equal probabilities. In that the parts are manufactured within tolerance specification andgrouping is done after manufacturing. But this method is having a condition tohave clearance specifications greater than difference in standard deviations of themating parts. Allen Pugh truncated the component distribution with larger variances. The resulting component variances are equal. The parts manufactured atthe extremes of the distribution are described during the assembly process. AllenPugh (1986) suggested a method of partitioning the mating parts population for selective assembly. But it is having a limitation of number of groups. Chan andLinn (1998,1999) proposed to have a selective assembly method for matingcomponents with dissimilar distribution. Based on the cumulative probability of the mating parts, the grouping is made. This method adopts the principle of equal

probabilities to minimize surplus parts. Mansoor (1961) classified the selective

assembly problem based on the natural tolerance on the fit. Shan and Shatyawadi(1989) described for a procedure for one to one pairing of component parts to beassembled.

Kannan and Jayabalan (2003) proposed to find a better selective groupcombination to minimize the assembly variation and surplus parts when the partsare assembled linearly using genetic algorithm (GA).Asha etal (2007) proposed tominimize the clearance variation and surplus parts in an assembly using Non-


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dominated sorting genetic algorithm (NSGA). Kannanetal (2008) proposed toobtain minimum assembly clearance in an assembly based on the effect of meanshift in the manufacturing of mating components and the selection of number of groups for the selective assembly.

The concept of Taguchis loss function is also applied into the selectiveassembly method to evaluate the loss due to deviation from the mean. Kannan etal(2009) proposed that selective assembly can be effectively used to meet thespecification requirements without any surplus parts with componentscharacteristics with skewness also. David Mease defined selective assembly as acost effective approach for reducing overall variation and thus improving thequality of an assembled product.

David E Goldberg gave an introduction about genetic algorithm. Geneticalgorithm works by generating a population of individuals over a number of generations. A fitness value is assigned to each individual in the population where

fitness computation depends on application. For each generation, the individualsare selected from the population for reproduction. Then they underwent crossover and mutation process to generate new individuals. Genetic algorithm performs amultidirectional search by maintaining a population of potential solutions. The

population undergoes a simulated evolution at each generation; the relatively goodsolutions reproduce, while the relatively bad solutions die.


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Problem Background

Selective assembly has been applied to cases when only linear or radialvariation exists. However there are cases where both exist. The rotor and stator assembly in a turbine shown in figure -1 is one of such cases. Here the clearance

between rotor and stator is so critical. The effect of angular variation with respectto the axis of rotation of rotor and stator plays an important role. The clearance

between the rotor and stator should be made minimum. Very smaller and negligibleangular variation of the rotor and stator affects the clearance largely. Though high

precision manufacturing methods are followed, it may not be possible to achievethe assembly requirements by interchangeable assembly. Hence in this paper, asimple method is proposed to achieve the assembly requirements using selectiveassembly.

Figure 1 Rotor and stator assembly of a turbine

Referring to figure.1, the stator and rotor assembly of a turbocharger workseffectively when the clearance variation between the stator and rotor is minimum.If the groove width of the stator is more, the clearance between the stator and rotor will be more, so that effective functioning of the assembly will be reduced. If thegroove width is less compared to the rotor thickness, the clearance between therotor and the stator may become interference between them which will lead to the


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faulty functioning of turbocharger assembly. If the rotor thickness is more than thegroove width of the stator, there are possibilities of interference of stator and rotor which will lead to the faulty functioning of turbocharger assebly. If the rotor thickness is less, the clearance will be more in between the stator and rotor of theassembly, which will lead to ineffective functioning of the turbocharger assembly.

The angle between the axis of rotation of rotor and the plane of the rotor should be 90. If the angular variation is more, the rotor may touch the stator onone side and the clearance will be more on other side which will lead to the faultyfunctioning of turbocharger assembly. Refering to fig. no.1 the clearancespecification between stator and rotor is 36 microns. It can be taken as 18 micronson each side of the rotor. The radius of the rotor is considered as 60 mm. Theangular variation of the rotor is calculated as follows.

The significant criterion of the assembly is that the rotor should not have directcontact with the stator when the former rotates over later. When one side of rotor contacts with the stator, its other side will have clearance, which has to be either minimized or nullified. When the thickness of the rotor is minimum and the groovewidth of the stator is maximum, the clearance is maximum, ie., 80m.

The selective assembly is planned such that the clearance variation isminimum when they are assembled. The tolerance given is the natural tolerance of the manufacturing process. The problem is to minimize the clearance between thestator and rotor. The components are manufactured in the same production centre


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and the standard deviation of the manufacturing process is following normaldistribution as shown in figure 2.

The dimensional distribution of the components is equivalent to the processcapability 6 ( 3 ) of the process. Therefore, the process capability 6 of the

process is considered for the analysis. When the components are assembledinterchangeably, the tolerance range of the population is more. Here the variationoccurs with respect to the thickness of the rotor and the groove width of the stator and angular variation of the rotor. The dimensions of groove width of stator (GW),rotor thickness (RT) and angular variation clearance of rotor with respect to rotor shaft are considered as follows:

This selective assembly has two parts i.e., one group for the rotor thicknessand in another group for angular variation. Referring figure 2 the stator is

partitioned in to six groups based on the groove width. The rotor is also partitionedinto six groups based on the thickness and angular variation = 0 degree 2 minutes3.761 seconds. The components are partitioned using digital micrometer speciallymade for this purpose. Hence the selective assembly grouping is done based onthree following design factors such as:(i) Groove width(ii) Root thickness and(iii) Angular variation.Here the purpose of analyzing clearance, the angular variation is converted intolinear variation at the tip of the rotor. Then the rotor is grouped based on thisvariation. The calculation for converting angular variation to linear variation isgiven below. For the maximum angular variation of 0 degree 1 minute 1.88seconds the linear variation is 18 microns. Those 18 microns are divided into six

equal groups that are 3 microns each.


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CONVEYOR BELT

A conveyor belt (or belt conveyor ) consists of two ormore pulleys, with a continuous loop of material - the conveyorbelt - that rotates about them. One or both of the pulleys arepowered, moving the belt and the material on the belt forward.

The powered pulley is called the drive pulley while the unpoweredpulley is called the idler. There are two main industrial classes of belt conveyors; those in general material handling such as those

moving boxes along inside a factory and bulk materialhandling such as those used to transport industrial andagricultural materials, such as grain, coal, ores, etc. generally inoutdoor locations. Generally companies providing generalmaterial handling type belt conveyors do not provide theconveyors for bulk material handling. In addition there are anumber of commercial applications of belt conveyors such asthose in grocery stores.

The belt consists of one or more layers of material. They canbe made out of rubber. Many belts in general material handlinghave two layers. An under layer of material to provide linear


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strength and shape called a carcass and an over layer called thecover. The carcass is often a cotton or plastic web or mesh. Thecover is often various rubber or plastic compounds specified byuse of the belt. Covers can be made from more exotic materials

for unusual applications such as silicone for heat or gum rubberwhen traction is essential.

Material flowing over the belt may be weighed in transitusing a beltweigher. Belts with regularly spaced partitions, knownas elevator belts , are used for transporting loose materials upsteep inclines. Belt Conveyors are used in self-unloading bulkfreighters and in live bottom trucks. Conveyor technology is also

used in conveyor transport such as movingsidewalks or escalators, as well as on manymanufacturing assembly lines. Stores often have conveyor beltsat the check-out counter to move shopping items. Ski areas alsouse conveyor belts to transport skiers up the hill.

A wide variety of related conveying machines are available,different as regards principle of operation, means and direction of

conveyance, including screw conveyors, vibrating conveyors,pneumatic conveyors, the moving floor system, which usesreciprocating slats to move cargo, and roller conveyor system,which uses a series of powered rollers to convey boxes or pallets.

Types of belt conveyors

I. Channel Stringer Belt ConveyorsII. Truss Frame Conveyors

III. Slider Bed Belt ConveyorsIV. U-Trough Belt ConveyorsV. Flat Slide Belt ConveyorsVI. Totally Enclosed Belt ConveyorsVII. Custom engineering conveyors

Advantages of belt conveyor over other system


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1. Can be operated over long distances over any kind of terrain.2. Having high load carrying capacity and carry all kinds of loads.3. Noiseless as compared to chain conveyors.4. Much simpler to maintain and dont require any major lubrication system likechain conveyors.5. Their reliability has been proved over a long period by its use in the industry.6. Environmentally more acceptable.7. Low labor and low energy requirements.8. Unlike screw conveyors, belt conveyors can be easily used for performing

processes functions in a production line.

Linear Variable Differential Transformer

The Linear Variable Differential Transformer (LVDT) is a type

of electrical transformer used for measuring linear (i.e.translational) displacement. A counterpart to this device that isused for measuring rotary displacement is called a Rotary VariableDifferential Transformer (RVDT). The linear variable differentialtransformer has three solenoidal coils placed end-to-end around atube. The center coil is the primary, and the two outer coils arethe secondaries. A cylindrical ferromagnetic core, attached to theobject whose position is to be measured, slides along the axis of the tube.

An alternating current is driven through the primary, causinga voltage to be induced in each secondary proportional to itsmutual inductance with the primary. The frequency is usually inthe range 1 to 10 kHz. As the core moves, these mutual


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inductances change, causing the voltages induced in thesecondaries to change. The coils are connected in reverse series,so that the output voltage is the difference (hence "differential")between the two secondary voltages. When the core is in its

central position, equidistant between the two secondaries, equalbut opposite voltages are induced in these two coils, so theoutput voltage is theoretically zero. In practice minor variations inthe way in which the primary is coupled to each secondary meansthat a small voltage is output when the core is central.

When the core is displaced in one direction, the voltage inone coil increases as the other decreases, causing the outputvoltage to increase from zero to a maximum. This voltage isin phase with the primary voltage. When the core moves in theother direction, the output voltage also increases from zero to a

maximum,but its phase is opposite to that of the primary. Themagnitude of the output voltage is proportional to the distancemoved by the core (up to its limit of travel), which is why thedevice is described as having a "linear" response to displacement.

The phase of the voltage indicates the direction of thedisplacement. Because the sliding core does not touch the inside


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of the tube, it can move without friction, making the LVDT a highlyreliable device. The absence of any sliding or rotating contactsallows the LVDT to be completely sealed against the environment.LVDTs are commonly used for position feedback

in servomechanisms, and for automated measurement inmachine tools and many other industrial and scientificapplications

USES Automation Machinery Civil/Structural Engineering Power Generation Manufacturing Metal Stamping/Forming OEM Pulp and Paper Industrial Valves R & D and Tests Automotive Racing

DC Operated

Ease of installation Simpler data conditioning Operate from dry cell batteries (remote locations) Lower System CostAC Operated Smaller than DC More accurate than DC Operate well at high temperaturesArmature Types

o Unguided Armature


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Fits loosely in bore holeLVDT body and armature are separately mounted must ensure

alignmentFrictionless movementSuitability

Short-range high speed applications High number of cycles

o Captive (Guided) Armature

Restrained and guided by a low-friction bearing assemblySuitability

Longer working range Alignment is a potential problemo 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 measuredSuitability

Static slow moving application (joint-opening in pavement slabs)

Drive unit for belt conveyor

A) Direct gear motor drive


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B) Drive through parallel shaft gear boxC) Drive through primary reduction by v belt and secondary by gear boxD) Drive through spiral bevel or worm gear box

Motor

Motor is a prime source of the energy to run the whole belt conveyor system.By taking current, it produces the mechanical work and this mechanical work isgiven to head pulley or tail pulley of the conveyor by means of gear box drive asdiscussed above. We can also use an induction motor with variable speed drive bychanging its frequency.

CIRCUIT DIAGRAMSMAIN CIRCUIT DIAGRAM


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POWER SUPPLY

WORKING OF POWER SUPPLYThe Power supply unit consists of a battery of 12volt DC. It is fed to avoltage regulator that is LM7805 regulate 5v which is fed to micro controller

board. Microcontroller board controls all working of the system and 5v is also fedto the LCD display. The power supply unit also has two capacitors used for filtering and the smoothening the DC supply.

COMPONENTS DESCRIPTION

RECTIFIER

MICW10MFeatures Low cost This series is UL recognized under component index ,file number E127707 High forward surge current capability Ideal for printed circuit board High temperature soldering guaranteed:260 oC/10 second, 0.375(9.5mm)lead length at 5 lbs. (2.3kg) tension.

Mechanical data Case: Molded plastic body Terminal: Lead solderable per MIL-STD-202E method 208C. Polarity: Polarity symbols molded on case Mounting position: Any Weight:0.042ounce,1.2grams


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WorkingFull Wave Bridge Rectifier Another type of circuit that produces the same output waveform asthe full wave rectifier circuit above is that of the Full Wave Bridge Rectifier. Thistype of single phase rectifier uses four individual rectifying diodes connected in aclosed loop "bridge" configuration to produce the desired output. The mainadvantage of this bridge circuit is that it does not require a special center tappedtransformer, thereby reducing its size and cost. The single secondary winding isconnected to one side of the diode bridge network and the load to the other side asshown below.

FIG. The Diode Bridge Rectifier

The four diodes labeled D 1 to D 4 are arranged in "series pairs" with only twodiodes conducting current during each half cycle. During the positive half cycle of the supply, diodes D1 and D2 conduct in series while diodes D3 and D4 are reverse

biased and the current flows through the load as shown below.The Positive Half-cycle


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FIG positive half cycleDuring the negative half cycle of the supply, diodes D3 and D4 conduct in series,

but diodes D1 and D2 switch "OFF" as they are now reverse biased. The currentflowing through the load is the same direction as before.

The Negative Half-cycle

FIG. negative half cycleAs the current flowing through the load is unidirectional, so the voltage developedacross the load is also unidirectional the same as for the previous two diode full-wave rectifier, therefore the average DC voltage across the load is 0.637V max .However in reality, during each half cycle the current flows through two diodesinstead of just one so the amplitude of the output voltage is two voltage drops ( 2 x0.7 = 1.4V ) less than the input V MAX amplitude. The ripple frequency is now twicethe supply frequency (e.g. 100Hz for a 50Hz supply)


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FIG. Typical Bridge Rectifier Although we can use four individual power diodes to make a full wave bridgerectifier, pre-made bridge rectifier components are available "off-the-shelf" in arange of different voltage and current sizes that can be soldered directly into a PCBcircuit board or be connected by spade connectors. The image to the right shows a

typical single phase bridge rectifier with one corner cut off. This cut-off corner indicates that the terminal nearest to the corner is the positive or +ve outputterminal or lead with the opposite (diagonal) lead being the negative or -ve outputlead. The other two connecting leads are for the input alternating voltage from atransformer secondary winding.

VOLTAGE REGULATOR LM 7805

Description

The KA78XX/KA78XXA series of three-terminal positive regulator areavailable in the TO-220/D-PAK package and with several fixed output voltages,making them useful in a wide range of applications. Each type employs internalcurrent limiting, thermal shut down and safe operating area protection, making it

essentially indestructible. If adequate heat sinking is provided, they can deliver over 1A output current. Although designed primarily as fixed voltage regulators,these devices can be used with external components to obtain adjustable voltagesand currents.

Features Output Current up to 1A


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Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V Thermal Overload Protection Short Circuit Protection Output Transistor Safe Operating Area Protection

PIC16F73

High Performance RISC CPU: High performance RISC CPU Only 35 single word instructions to learn All single cycle instructions except for program branches which are two-cycle Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes of DataMemory (RAM) Interrupt capability (up to 12 sources) Eight level deep hardware stack Direct, Indirect and Relative Addressing modes Processor read access to program memory Special Microcontroller Features: Power-on Reset (POR)


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Power-up Timer (PWRT) and Oscillator Start-up Timer (OST) Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation Programmable code protection Power saving SLEEP mode Selectable oscillator options In-Circuit Serial Programming (ICSP) via two pins

Peripheral Features: Timer0: 8-bit timer/counter with 8-bit prescaler Timer1: 16-bit timer/counter with prescaler, can be incremented during SLEEPvia external crystal/clock Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler Two Capture, Compare, PWM modules- Capture is 16-bit, max. resolution is 12.5 ns- Compare is 16-bit, max. resolution is 200 ns- PWM max. resolution is 10-bit 8-bit, up to 8-channel Analog-to-Digital converter Synchronous Serial Port (SSP) with SPI (Master mode) and I2C (Slave) Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI) Brown-out detection circuitry for Brown-out Reset (BOR) CMOS Technology: Low power, high speed CMOS FLASH technology

Fully static design Wide operating voltage range: 2.0V to 5.5V High Sink/Source Current: 25 mA Industrial temperature range Low power consumption:- < 2 mA typical @ 5V, 4 MHz- 20 A typical @ 3V, 32 kHz


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- < 1 A typical standby currentKey features

COMMON BOARD FABRICATIONSOLDERING OF COMPONENTS

Soldering is the process of joining metals by using lower malting point metal to weld or alloy with their joining surfaces.SOLDER

It is the lining material that melts below 427 degree Celsius. Soldered jointsin electronic circuits will establish strong electrical connections betweencomponent leads. The popularly used solders are alloys of tin lead that melt belowthe melting point of tin.FLUXIn order to make the surface accept the solder readily, the component terminalsshould be free from oxides and other obstructing films. The leads should becleaned chemically or by abrasion using blades or knives.


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A small amount of lead coating can be done on the cleaned portion of the leadsusing soldering iron. This process is called tinning. Zinc chloride or ammoniumchloride separately or in combination is mostly used as fluxes. These are availablein petroleum jelly as paste flux. The residues which remain after soldering may bewashed out with more water accomplished by brushingSOLDERING IRON

It is a tool used to melt and supply at the joints in the ckt.Itoperates on 230V supply. The iron bit at the tip of it gets heated within fewminutes. Soldering irons are completely used for soldering purposes.SOLDERING STEPS1. Make the layout of the components in the circuit. Plug in the code of solderingiron in the mains to get heated.2. Straighten and clean the components using a blade or knife. Apply a little fluxon the leads. Care must be taken to avoid the component get heated up.

3. Mount the components on the common board by bending the leads of thecomponents using nose-pliers.4. Apply the flux on the joints and solder the joints. Soldering must be done inminimum time to avoid dry soldering and heating up of components. Wash theresidue using alcohol and brush.

MICROCONTROLLER PROGRAMMING

PIC Programming

By using a programming kit and development kit.

MPLAB ICD2 is used as the programming kit.RS232 is the port that connects programming kit to the PC.C language is used for programming the 40 pin IC 16F877A.

The program is code in HEX assembler.The development kit is used for testing purpose


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