PATTERN MAKING

                       PATTERN MAKING 

The Pattern is the principle tool during the casting process, it may be define as modle of anything, so constructed then it may be used for forming and the impression called mould in the dome shape. When this mould is filled with the molten metal and the metal is allow to solidify , it form a reproduction of pattern is known as casting . The process of making the pattern is known as pattern making.

Foundary engineering deals with the process of making casting in mould prepared by the metal to mould process of producing casting may be classified into five stages -: 

1. Pattern making                                                  2. Moulding                                                            3. Casting and melting                                          4. Fettling                                                                5. Testing and inspection.                   

Pattern material 

1. Wood -: Wood is the most commonly used material for pattern. it is easy to work and is rapidly available , wood can be cut and also fabricated into the numerous form by bend-ing and curling. It may be preserved with the shell.

2. Metal -: Metal is used when large number of casting are desired for a pattern or when conditions are to serves for wooden pattern.

(a) Cast iron  -: Cast iron is used for some of the highly specialised type of the pattern. It is strong give a smooth surface with  Sharp edges and is resistance to the abrasive action of the sand.

(b) White metal -: It is not generally used for the patterns but it is the best material for the making of five shape.

3. Non-Metal -: 

(a) Brass -: The Brass is normally used in the pattern making perticularly when the metal pattern are small.

(b) Aluminium -: It is the best metal because it melts at a relatively low temperature. It is soft and easy to work.

(c) plastic -: Plastic is not finding their place as a the pattern material because, they don't absorb moisture . They are strong resistance to wear have a very smooth surface. 

(d) Rubber -: Originally it is in liquid form and mould over master pattern or into a die and forming a solid shape.

(e) Wax -: Wax pattern are excellent for the investment casting process, the normal prac-tice of forming wax pattern this to inject the liquid or semi-liquid wax into a straight die.

VERNIER CALIPER

                       Vernier caliper

This is a linear measuring instrument and it is used to measure the dimension to second decimal. The vernier caliper is shown in fig. 

 

Main parts of vernier caliper -: 

1. Main scale A  -: It is the fixed beam scale having a fixed jaw at left end and is graduat-ed in millimetre. This is called a metric scale .

2. Vernier scale B -: It consist of sliding jaw and this scale slides over the main scale A . These scale is also graduated in 10 , 20 and 25 divisions. 

3. Jaw C-:These jaw are used to measure the dimensions such as inner radius of inside of the hollow cylinders. 

4. Jaw D  -: These jaw are used to measure the outside diameter of the object like width, thickness etc.

5. Thumb screw E -: It is provided with the vernier scale and used to lock the position of the vernier scale. 

6. Blade F -: The blade is used for measuring depth of the slots.

Least count -:

( 1 ). If there are 10 divisions on the vernier scale, and the smallest division on the main scale is of 1.0 mm.                                          

Then, Least count                                                  =    Smallest division on main scale                         no. of division on vernier scale                    =      1.0            =  0.1 mm.                                              10 

(2). If there are 25 divisions on vernier scale and the smallest division on the main scale is 0.5 mm. Then ,                     

 Least count =   0.5                =  0.02 mm.                                         25

Procedure -: Fix the jaw on the workpiece and then lock the jaw with the help of thumb screw. Then note the reading on main scale angaist zero on vernier scale.  Count the no. of division on vernier scale which co-insides with a division on main scale. Multiply this number by least count and add to the main scale reading. 

Hence ,                                                                    Total reading   = Reading on the main scale   + ( Least count  × no. of division on vernier scale which co-inside with division on main scale ).

DIAL GAUGE

                          DIAL GAUGE 

The dial gauge is graduated in the small units such as 0.01 mm. The gauge carry zero reading at the center with positive and negative readings on either side. It is used to check the size and truness of a finished work to an accuracy of 0.01 mm.TheDial gauge can be used with the various attachments such as inside cali-per and depth gauge, V- block etc which make it situable to check the roundness , flatness, parallelism, ovality, taper and squarness etc. 

         

 

               It is also used to compare to heights           or distances between narrow limits. It             is mostly used for checking diamension           for this purpose the dial gauge is fixed             at a standard dimensions, the needle is           showing showing zero reading.                             Then the parts to be checked are kept           below the pointer.The needle show the           deviation form and the standard size .            The Dial gauge is a sensitive instrument           and it should be handled carefully.

MICROMETER

                        Micrometer

The micrometer is a measuring instrument a which is  used to measure the external  and internal dimensions as well as the depth and heights. It has five main parts frame, anvil, sleeve thimble and spindle . The frame is ' U ' shaped and made of steel. In this the gap of the frame permits the maximum dimension that can be measure on the left end of the frame, the anvil is fixed at a right end, there is a screwed spindle. 

 

The diameter of the anvil and spindle should be equal . A lock nut is provided to lock the spindle to retain the reading. The sleeve has reference line and main scale on it. A tubler cover  fixed with spindle is called thimble . Thimble moves with spindle on main scale . Thimble has 50 equal parts on it's bevelled edges. This is called as circular or vernier scale. Reatchet  screw is provided to tighten the thimble. When correct reading  achieved ratchet slips automatically. 

Least count-: The least distance which can be measured accurately with micrometer is called least count.

Least count = pitch of the spindle screw 

                         No. Of division on thimble 

                     = 0.5 / 50    = 0.01 mm

Reading of micrometer -:  

Reading uncovered on sleeve + ( least count × no of division on thimble with R.F. line )

Reading = 10.5 + ( 0.01 × 15 ) = 10.65 mm

Types of micrometer -: 

1. Outside micrometer 

2. Inside micrometer 

3. Screw thread micrometer 

4. Depth gauge micrometer 

Mechanical MCQ

 Q.1 Which refrigerant is used in central air conditioning?

A. Ammonia

B. R-11

C. R-12

D. Freon 

Ans-: B

Q.2 The radius for which the heat transfer rate is maximum known as ___.

A. Mean radius

B. Radius of heat transfer 

C. Critical radius 

D. None of these 

Ans -: C

Q.3 The rate at which radiation leaves a surface called ?

A. Viscosity 

B. Capacity ratio

C. Reflectivity 

D. Radiosity

Ans-: D

Q.4 Which surface has zero reflectivity?

A. Black body

B. White body

C. Rough surface

D. Finished surface

Ans-: A

Q.5 Cork is a good insulator because it has _______.

A. Black body

B. Porous body

C. Rough body

D. None of these 

Ans-: B

Q.6 Which type of calorific value is measured by bomb calorimeter?

A. Higher calorific value 

B. Lower calorific value 

C. All calorific value 

D. None of the above 

Ans-: A

Q.7 In-viscous fluid is ______.

A. Frictionless fluid

B. Real fluid

C. A+B

D. None of these

Ans-: A

Q.8  The cable attached to the supports and carries its own weight is called?

A. Supporting cable

B. Joining cable

C. Catenary cable

D. Balancing cable

Ans-: C

Q.9 What is the bending moment at hinge of beam? 

A. One

B. Zero

C. Maximum 

D. Minimum 

Ans-: B

Q.10 The beam has more than 2 support below the beam is known as ___?

A. Continuous beam

B. Cantilever beam

C. Simple beam

D. None of the above 

Ans-: A

Q.11 The radius of Mohr circle represents the value of maximum ______.

A. Stress

B. Strain

C. Shear stress 

D. Shear strain

Ans -: C

Q.12 How much is shear stress on the principal planes?

A. Zero

B. One

C. Two

D. 1 / 2

And -: A

Q.13 How many time second pendulum have?

A. 5 seconds 

B. 10 seconds 

C. 2 seconds 

D. 1 second

Ans -: C

Q.14 What is the value of shear force ,where bending moment is maximum?

A. 1.5 

B. 2.5

C. Zero

D. 1.15

Ans -: C

Q.15 The rate of change of bending moment along the length of the beam is known as ___.

A. Shear force 

B. Shear stress

C. Bending force

D. Inertia force 

Ans -: A

SOLAR PHOTOVOLTAIC SYSTEM

                 Solar photovoltaic system                

A photovoltaic power generation is a device which convert the electromagnetic energy directly into electrically. The basic compon-ent in the photovoltaic power generation is the photovoltaic cell. 

The photo-voltaic effect can be described easily for a p-n junction in a semi-conductor material. In a piece of a pure intrinsic semi-conductor such as silicon there are no free electron at absolute zero,since each valance electron of material atom is tied in chemical bond.If this piece of the silicon is doped with phosphorus or arsenic, there will be the ex-cess of electrons leading to a n-type semicon-ductor. Similarly if another piece of the sili-con is doped with boron , there will be a deficiency of electrons leading to a p- type semiconductor. If these two pieces of silicon are connected , a p-n junction is obtained . In tendency will be for the free electron of n-side to flow to the p-side, and the holes of the p-side will tends to flow to the n-region to compensate for their respective deficiencies. Thus a built-in potential barrier is formed.

When light strike on the p-n junction photo-ns with energy above that required to break the covalent bonds will create an electron hole pair. The hole is formed in the valance band,or an electron is added to the conduct-ion band. For a photon in a visible range the diffusion length i.e. average distance which the carrier diffuse before they recombine, has the magnitude of a micron. Those charge carriers that are within a diffusion length of the potential barrier will be trapp-ed by the barriers and caused to flow across it in an attempt to reduce their energy. Therefore a potential energy between the layer is formed and it is used to force the electrons through an external circuit. 

The solar photo-voltaic cells convert incident solar light energy directly to direct current electrical energy. Power delivered depends on intensity of sun light and the load resista-nce. several solar cells can be connected in series on parallel to get desired the voltage, current and power. Solar cells connected in parallel form a module, and the modules are connected in series,parallel ,series-parallel configuration to form a solar PV panel. Solar PV panels are installed outdoors so as to the receive maximum sun light during tha day and thoughtout the year. Solar PV panels are usually fixed type as they à simple ,cheap and maintenance free.

Since solar PV panels deliver DC electrical power only during favourable conditions of  sun light, energy storage batteries as used to supply power during nights and the cloudy weather. For feeding loads t 50 Hz AC supply , DC power supplied by the solar PV panel is converted by means of static inverters to the single phase or three phase. Power conditio-ning unit provided for improving AC wave-form, regulating the voltage, inverting DC to AC and protective control, and monitoring functions. 

Solar energy MCQ-: 01

 Q.1 The diameter of the sun is about ____.

A. 1.2 × 10^4 KM

B. 1.5 × 10^4 KM

C. 2.5 × 10^6 KM

D. 1.39 × 10^6 KM

Ans-: D

Q.2 The mean distance between the sun and the earth is _______.

A. 1.49 × 10 ^8 KM

B. 2.49 × 10 ^6 KM

C. 1.52 × 10 ^5 KM

D. 2.05 × 10 ^4 KM

Ans -: A

Q.3 In the form of electromagnetic radiation from sun, earth receives ______ energy / day.

A. 2.9 × 10 ^13

B. 2.9 × 10 ^11

C. 2.9 × 10 ^15

D. 2.9 × 10^17

Ans-: C

Q.4 A single solar cell has an open circuit voltage of ______.

A. 2.5 to 7.0 V

B. 7.0 to 10.0 V

C. 1.0 to 2.5 V

D. 0.6 to 1.0 V

Ans-: D

Q.5  The solar radiation received per unit area normal to sun rays, in a space outside the earth's atmosphere at earth is called __________.

A. Solar energy 

B. Solar constant

C. Heat energy 

D. Solar collector

Ans-: B

Q.6 Flat-plate collectors are used for _____ temperature applications. 

A. High

B. Constant

C. Low

D. Variable 

Ans-: C

Q.7 Solar power has _____ density.

A. High

B. Low

C. Variable 

D. None of the above 

Ans-: B

Q.8 The solar radiation on a particular location on the earth is affected by _____.

A. Seasonal variation

B. Atmospheric clarity 

C. Daily

D. All of the above 

Ans-: D

Q.9 The solar radiation received outside the earth's atmosphere is called _____.

A. Terrestrial solar radiation 

B. Extra-Terrestrial solar radiation 

C. Outer solar radiation 

D. Non- terrestrial solar radiation 

And-: B

Q.10 The radiation received by the earth is with parallel rays is called ?

A. Beam radiation 

B. Diffuse radiation 

C. Thermal radiation 

D. None of the above 

Ans-: A