Informational Encyclopedia

Molding materials commonly used in the foundry shop are molding sand, sand binders and sand additives.Quartz and other silica rocks are the source of silica sand which are commonly used for molding. The binders added to the sand for holding the sand grains. 

These binders must be clay-type, organic and non organic . The additives such as sea coal, wood flour and silica flour are used to build some extra features.

The molding sand must contain the following properties.

1: Porosity or Permeability

It is very important to permits the steam and other gases to pass through the sand mold. The porosity of sand depends on the grain size, shape , moisture and clay content in the molding sand. If the sand is too fine then its porosity will be low.

2: Plasticity

The quality of sand should be plasticize so the sand flows its all portions to the molding box or flask. The sand must be sufficient plasticizer to produce a good mold.

3: Adhesiveness

It is the property of sand due to which it adhere or cling to the sides of the molding box.

4: Cohesiveness

Property of sand must be cohesiveness by which the sand grains stick together during ramming. It is defined as the strength of the molding sand.

5: Refractoriness

Property of sand by which the sand enables it to resist under high temperature of the molten metal without breaking down or fusing.

For the use of light an power, the system of distribution of electric energy the field of application of A.C. motors are widely used. Due to rapid use of motors the manufacturers have tried over the last few decades, to perfect various types of ac motors suitable for all classes of industrial drives and for both single and three phases a.c. supply.

This has been rise to bewildering multiplicity of types whose proper classification often offers considerable difficulty. Different a.c. motors may, however be classified and divided into various groups and as following as below.

1: Due to their principle of operation

A: Synchronous motors

(i) Plain  (ii) super

B: Asynchronous motors

a: Induction motors

   (i) Squirrel cage ( single / double)   (ii) Slip ring (external resistance) 

b: commutator motors

    (i) series (single phase / universal)        (ii) compensated ( conductively/inductively)        

   (iii) Shunt ( simple / compensated)   (iv) Repulsion (straight / compensated)          (v) repulsion-start induction      (vi) repulsion induction

2: Due to the type of current

(a) single phase        (b) three phase

3: Due to the speed

(a) constant speed     (b) variable speed    (c) adjustable speed

4: Due to Structural features

(a) open        (b) enclosed     (c) semi-enclosed      (d) ventilated     (e) Pipe-ventilated    (f) riveted frame eye 

It is defined as the mass per unit volume of a liquid at the standard temperature and pressure.Its symbols is  ρ  (rho) and its unit is kg/m3.It is also termed as mass density. So we can say

                   density = mass/volume

                      ρ = m/V

Specific Weight

Specific weight or weight density  is the weight per unit volume of liquid at a standard temperature and pressure. It is denoted by w and its unit is KN/ m³  or N/ m³ . So mathematically 

                                   w =  ρ .g

Example : specific weight for water w = 9.81 KN/m³

Specific Volume

It is defined as the volume per unit mass of the liquid. It is denoted by v so mathematically

                               v = V/m

Specific Gravity

Ratio of the specific weight of a liquid to the specific weight of the pure water at the standard temperature( 4 degree Centigrade). It has no unit.

Viscosity

Property of liquid which offers resistance  to the movement of one layer of liquid over anoher adjacent layer of liquid. Viscosity of the liquid is becuase of cohesion and interation between the particles. Viscosity is also known as absolute viscosity or dynamic viscosity.

kinematic viscosity

It can be defined as the ratio of dynamic viscosity to the density of liquid.

Compressibility

Property of a liquid by virtue of which liquids undergo a change in volume with the change in pressure. It is reciprocal of bulk modulus of elasticity.

Surface tension

property of liquid which enables it to resist tensile stress. 

It is denoted by sigma and expressed in N/m.

A phenomenon of rise or fall of a liquid surface in a 

small vertical tube held in a liquid relative to general level of the liquid.  

  

Generator Principle

An electrical generator is a machine which converts mechanical energy or power into electrical energy (or Power). The energy conversion is based on the principle of production of dynamically induced e.m.f.

Whenever a conductor cuts magnetic flux,dynamically induced e.m.f. is produced in it according to Faraday's Laws of Electromagnetic induction. This emf causes a current to flow if the conductor circuit is closed. So there are two basic parts of an electrical generator are

1: a magnetic field            2 : a conductor or conductors which can so move as to cut the flux.

Construction of simple loop generator.

A single turn rectangular copper coil ABCD rotating about its own axis in a magnetic field provided by either permanent magnet or electromagnets. The both ends of the coil is fastened to two slip-rings a and b which are insulated from each other and from the main shaft.

Two collecting bushes of carbon or copper press against the slip-rings. Their function is to receive the current induced from the coil and to pass on it to external load resistance R. The rotating coil can be called "armature" 'and the magnets are as "field magnets".

Working of simple loop generator

Imagine the coil is to be revolving in clock-wise direction.As the coil assumes successive position in the field, the flux connected with the charge. Hence the emf is produced in it which proportional to the rate of change of flux linkage. When the plane of the coil is at the right angles to lines of flux i.e when it is in position,l,then flux connected with the coil is maximum but rate of charge of flux linkage is down. It is due to in position , the coil side AB and CD do not cut the flux, rather they slide along them.(they move in parallel).

 Hence there is no emf produced in the coil. If we consider no emf in the coil at the starting position, the angle of rotation will be calculated from the position. As the coil continues revolving more , the rate of change in the flux linkage increases till the position 3 is reached where angle is 90 degrees. Here the coil plane is horizontal and parallel to the lines of flux. As seen the flux linked with the coil is minimum but rate of change of flux linkage is high. Hence, the maximum emf is induced in the coil when in this position.Next quarter from 90 to 180 degrees the flux linked gradually increases but rate of change of flux decreases. From 180 to 360 degrees revolution  the variation in the magnitude of emf are similar to those in the first half revolution.For making the flow of current unidirectional in the external circuit i, the slip rings are replaced by split-rings.The split rings are conducting cylinder typed material which is used to cut two segments insulated from each other by a thin sheet of mica or other insulated material.

The basic formula for channel capacity is

Q = A x V

Manning's formula for velocity is   

Trapezoidal Watercourse/canal or Channel

Flow measurement or hydraulic formulas are used to measure the discharge/volume of water through canals,irrigation channels,watercourses,drain lines etc. Following is the brief descripion used to calculate the flow measurement or discharge of the trapezoidal sectioned channel.

b = bottom width                                                                              d = flow depth              

B = width at water surface = b + ( 2 x z x d )                                  FB = Free board

D = Total depth of channel = d + FB                                               BW = Bank width

Z = Side slope, ( Such as 1: 1 - 1.5 : 1  & 2 : 1)                              FSL = Full supply level

TW = total width of the ditch = b + ( 2 x Z x D)

So formula for trapezoidal channel flow quantity is

 A = b x d + Z x d²

Rectangular Watercourse/canal or channel

A = b x d

where b is the width of the channel and d is the depth of the channels.

          

Building stone is gotten by taking rock from the earth and decreasing it to the required shapes and sizes for development. It is a characteristic, lavishly various material that can shift incredibly in its science, structure, physical properties, and appearance. Geographically, stone can be classified into three sorts as indicated by how it was formed.

Granite Group: 

The vitality from the sun reaching on  the earth every day ranges from around 600 Btu (British Thermal Unit)/square feet for Northern Europe to around 2000 Btu/square feet for parched locales close to the equator. More vitality from sun strikes the earth in one hour than all vitality expended on the planet in a year! A summer day's sun with full swing provides a  square, meter of area with a power include very nearly a kilowatt. One may ask why sun oriented vitality has not supplanted the customary vitality sources, not even a huge division. So there are unquestionably  more advantages and a few disadvantages of solar power system.

Advantages of Solar Power.

No Pollution and Global warming friendly.

Solar Panels does not create any pollution while producing electricity. Global warming  threatens  the survival of human culture, and in addition the survival of incalculable species. Fortunately, decades (or even hundreds of years) of exploration have prompted effective sun powered board frameworks that make power without creating a worldwide temperature alteration contamination. Sunlight based Solar power is presently plainly a standout among the most critical answer for the global warming.

Cost Comparison

Availability and Reliability 

Most countries of the world have the sun rays and availability of the solar power generation is very easy. All across the world, we know precisely when sun will rise and set each day of the year. While mists might be somewhat less unsurprising, we do likewise have genuinely great regular and day by day projections for the measure of daylight that will be gotten in various areas. All things considered, this makes solar power to a great reliable source of energy.

Energy independence and zero dependence of fuels.

Solar power provides easy energy independence to every one. One time installation and you are free and zero dependent of other sources of energies. The reliance on the fossil energizes can be lessened an awesome arrangement. In one day the sun based vitality falling on India alone is more prominent than the vitality in their present yearly coal utilization.

Creating of new Jobs

Due to new innovation, Solar Power system creates new job opportunities for unemployed skilled workers.In Pakistan there are many several solar power projects creates a lots of jobs. Solar power panel plates companies and other renewable energy firms hires and facilitates the skilled persons.  

No Transportation Charges.

As We said that it has only once time installation charges. When you compare other energy resources it has no transportation charges.

Disadvantages of Solar Power system

Solar power system has very rare disadvantages like covering a lots of space (For large energy production), energy storage is also a disadvantage.

This deformity as a rule appears as round openings like swiss cheese, simply under the adapt surface of the throwing and becomes exposed when light machining. The cause is a wet ladle, where the ladle covering was not appropriately and altogether dried. In compelling cases the metal will kick and bubble in the ladle. The act of pigging the metal in a wet ladle and refilling it with the trusts that the pigged metal wrapped up the ladle is sheer fully.

These happens when the mold pit is not totally filled by the liquid and inadequate material or metal.

It is an extension of the mold depression by liquid metal weight bringing about restricted or general augmentation of the casting.

These are meager projections of the metal not proposed as a piece of casting. These more often than not happens at the separating line of the mold.

It occurs near the gates as a rough spots or lumps on the casting work piece.

It is an inward or outside worn out spasmodically in the metal casting  coming about soon after the metal has cemented.

This defect is also known as honeycombing. These are smooth depression  on the outer surface of the casting.It occurs near the ingrates.

These are patches of sand on the outer surface of the casting work piece.

These grant seepage of the metal from the hole and result in inadequate casting.

This fault is brought about by shaking the casting out too early when a part of it is still fluid. The area runs out leaving an imperfection. In great cases the whole focus segment will run out on the shake out man's feet.

In Autocad 2007 version, exists with the name of Modeling tool bar and In Autocad 2004 version, it exists with the name of Solids. This tool bar has extra features to draw solid geometrical shapes in isometric or 3d. Follow the instructions and step by step procedure are as follows.

1:Click on the box icon from the modeling tool bar.

2: Click first point (starting point) or enter c (for starting your shape from center).

3: Enter your desired rectangular dimension of length and width. You can enter your length and width amount by entering @ 100 , 50 where 100 will be your desired length and 50 will be width. If you enter one dimension it will create square.

4:  Now enter your desired height.

For Wedge draw as same as above mentioned. But you can change your height direction by the help of your mouse.

How to draw  Cone and Cylinder

1: Click any point on the drawing area for center point.

2: Provide Radius of the base circle and provide your desired height.

3: For 3P and 2P options follow the diagram,

4: If you want to draw an elliptical Cylinder or elliptical cone, after click the your desired icon enter e for base ellipse. Provide first axis and second axis dimensions and then enter your third elliptical dimension. After making your base ellipse provide your desired height.

How to Draw Sphere.

1: Click any point for center point of the sphere.

2: Enter your radius or enter d for diameter and twice your dimension.

How to draw Torus.

1: Click the center point to start your torus

2: Enter your desired dimension of radius (Radius of Torus)

3: Then enter your Torus tube's radius dimension.

How to draw Pyramid

1: Click any point to start your pyramid.

2: Enter your desired height of the pyramid.

If you enter e for edge at the start it will create your base from its edges. and if you enter s it asks how many sides are required.

Commonly, the jigs and fixtures devices found in a machine or workshop are for machining operations. Different operations, be that as it may, for example, assembley, layout, testing, and design, are additionally ranges where work holding devices are appropriate. There are numerous  varieties inside every broad arrangement, and numerous work holders are really combination of two or a greater amount of the orders.

Common Applications of Jigs and fixtures are as follows.

1: External Surface Machine Applications

Flat-Surface Machining

   • Milling fixtures

   • Surface-grinding fixtures

   • Planing fixtures

   • Shaping fixtures

Cylindrical-Surface Machining

   • Lathe fixtures

   • Cylindrical-grinding fixtures

Irregular-Surface Machining

   • Band-sawing fixtures

   • External-broaching fixtures

2: Internal Surface Machine Applications

3: Non Machining Application Assembley

   • Welding fixtures

   • Mechanical-assembly fixtures

     (Riveting, stapling, stitching, pinning, etc.)

   • Soldering fixtures

4: Inspection

   • Mechanical-inspection fixtures

   • Optical-inspection fixtures

   • Electronic-inspection fixtures

5: Finishing

   • Painting fixtures

   • Plating fixtures

   • Polishing fixtures

   • Lapping fixtures

   • Honing fixtures

6: Miscellaneous

   • Layout templates

   • Testing fixtures

   • Heat-treating fixtures

7: Modular Fixtures

Modular fixtures accomplish a considerable lot of the benefits of a changeless device utilizing just a temporary setup.Modular work holding join thoughts and components of both lasting and temporary work holding to make reasonable yet-solid work holders.The essential point of interest of modular fixtures is that an apparatus with the advantages of lasting tooling (setup reduction, toughness, profitability upgrades, and precision) can be worked from an arrangement of standard segments.

Multi line 

This line is used to draw parallel two or more offset ed lines in autocad. Highway road center white line and yellow colored outer lines is the example of multi line. 

Formatting of Multi line

1: Click on the Format tab in menu bar

2: Click on the Multi line Style from the drop down list.

3: Click on the modify tab.

4: After clicking the modify tab another menu box will be appear.

There are three portions and there setting are as follows.

(a) Caps

In this portion there are six check buttons, which are used to format multi line start and end round fillets. If you check these buttons round fillets (round circles) will be apply.

Angle can be adjusted by entering the values (Such as 15,30,45,60 degrees etc). First value entry will be appear at the starting point and second value will be appear on the end point.

(b)Fill

This portion is for apply inside color in the multi line. Chose any color and select to apply. Gray color of road is the example.

(c) Elements

In this portion you can format line types, there colors and there offset distance (Parallel line distance). If you want to add more than two lines then click on the add button. 

How To Draw Multi line

Click on the draw tab in menu bar. Scroll down the mouse and pick the multi line and pick the start point and navigate your direction through mouse. Every time your formatting multi line will be set according to your format which was set in the formatting multi line style. To draw different multi line, click on the new tab and save the multi line format style.

  

Line

The basic and most important element of drawing used in auto cad. Short key of line command is "L".

Every time you enter the short key of any command, follow the instructions in the command bar. When you press " L" in the command bar, message appear in the command bar " specify first point".

Click on any point at the drawing area. Navigate your direction through mouse and enter your required length or click any point. As we know basic definition of line is " the distance between two point is called line.In Auto cad 2004 or previous versions supporting lengths and angle does not appear when you navigate the line's direction.(It does not mean that they does not appear, such information if you want to check, appears on the status bar). In Auto cad 2007 and onward versions provide supporting lengths and angles.

Ray

Construction Line

Method to draw construction line is same with ray line, but construction line have both sides extension. These extend lines can be trim after completing the object. These lines are also can be drawn either in vertical or horizontal axis.(or you can draw in diagonal axis.)

Cast Iron

Pig iron alongside scrap iron, coke and limestone is liquefied in a vertical furnace called cupola. Here likewise the carbon and different impurities introduce oxidize in nearness of a little measure of air, to shape slag. The liquid iron got from dome heater can be thrown into forms. It is, thus, known as cast iron. It comprises of 93-94% Ferrous, 2-4% carbon and a small amount of S, P, Si and Mn polluting influences. It is  hard and brittle. It is cast into covers of main holes, channel pipes, casings of machines etc.

Wrought Iron

The most purist form of iron is called wrought iron, which contains up to 99 % of iron and small amount of carbon with impurities such as sulfur , manganese, silicon and phosphorus.wrought iron is malleable, tough, gray and can be welded. It is mold able and has a sinewy structure because of the nearness of thin movies of slag between layers of pure iron. The nearness of slag makes it greatly extreme and safe towards rusting

Manufacturing Process

It is acquired from cast iron by evacuating the significant partition of its impurities influences by the surely understood puddling process.The cast iron alongside some scrap iron is warmed on the hearth of a reverberatory furnace lined with hematite. The hot gasses and flames reflected from the top of the heater falls upon the charge set on the hearth. The cast iron softens down and the liquid mass is blended or puddled at intervals by method for a long pole presented through a channel in the wall of the furnace.  The haematite supplies the oxygen required to oxidize the carbon, sulfur, silicon, manganese and phosphorus show in the cast iron. 

Chemical Reaction

Carbon and sulfur are oxidized to carbon dioxide and sulfur dioxide, individually. Silicon and manganese are oxidized to silica and manganese oxide, which join to frame manga-nous silicate.

3Si + 2Fe₂0₃ —* 3Si0₂ + 4Fe 3Mn + Fe₂0₃ —» 3MnO + 2Fe MnO + Si0₂ —» MnSi0₃

_{Slag Formation}

As the contamination are dispensed with, the liquefying purpose of the metal ascents and iron gets to be pasty. The pasty mass is blended which frames "balls" or "blooms" which are elastic in composition because of a lot of slag. The balls are taken out from the heater and the slag is crushed out by crushing or hammering. At last, iron is moved into sheets or manufactured into bars.

Chemical Reaction

P₂0₅ + Fe₂0₃ —* 2FeP0₄

Fig a :

Given an acute angle, it is required to obtain a circle of any given radius tangential to both its arms.

Method: Suppose the circle is to be drawn on the given dimension. Obtain lines known as loci parallel to diagonal and base lines.(given distance on figure is 3/4"). These lines intersect each other and provide a point where u can draw a circle tangent to both arms.

Fig b:

Given a circle, it is required to obtain circles tangential to its circumference.

Method : Draw three circles at given dimensions. Draw parallel locus (loci drawn in previous method) lines. Draw parallel circles at there tangents points.

Fig c :

Tangency  to  parallel circles tangents.

Method : Draw three parallel lines as drawn on the fig c. (Both horizontal and vertical lines.) Here you will get the circles center points. These circle will intersect each other at there tangency.

Fig d :

Given two circle which are not tangential , it is required to obtain two other of given rad. tangential to them externally.

Method : Draw horizontal and vertical center lines. Draw two circles with given length radius. Draw two circles arc respectively. then you will get small circle center points.

Fig e :

Obtain a circle which shall be tangential to the larger circle internally and to the smaller circle externally.

Fig f: 

Obtain circles tangential to the mid point of the straight vertical line.

Method : Draw a line perpendicular to the horizontal line. This horizontal line consist of the centers of the given radius circles.

Fig g :

Draw an ogee curve between two parallel straight lines.

Fig h-i-j

Draw fillets or rounds when the angles are acute(fig j) , right (fig h) and obtuse (fig i)

Method: The center of any circle tangential to the arms of an angle lies on the bisector of the angle. Therefore we may bisect the angle.

Common tangency practice in engineering drawing/machine parts is shown in fig.

The arc welding is a type of fusion welding process in which the welding warmth is acquired from an electric curve struck between the work(or base metal) and a electrode. The temperature of the warmth created by the electric arc is near to 6000°C to 7000°C. Both the direct current (D.C) and alternate current(A.C) might be utilized for this welding, however the alternate current is favored for generally purposes.At the point when the work is associated with the positive terminal of the D.C welding machine and the negative terminal to a electrode holder, the welding set up is said to have straight polarity.  Then again, when work is associated with negative and the electrode to a positive terminal, then the welding set up is said to have reversed polarity . The straight polarity is ideal for a few welds while for different welds turned around reversed polarity  ought to be utilized.

Following are the two types of arc welding depending upon the type of electrode:

1: Shield Arc Welding

When the electrode rods with covering material of fluxing are used, this type will be called shield arc welding.

2: Non Shield Arc Welding

When a filler rod or electrode is used for welding, this method is called non shield arc welding.

Arc Welding Processes

Various types of arc welding processes are commonly used in the workshop,there are as follows.

(i) Metal Arc Welding

(ii) Carbon Arc Welding.

(iii) Metallic inert gas (MIG) arc welding

(iv) Tungsten inert gas (TIG) arc welding