Where is foundry slide master

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Related Products. Surface to finished are painted by red colour. Seats for loose pieces are marked by red strips on yellow background 4. Core prints are painted by yellow colour. Stop-offs is marked by diagonal black strips on yellow background. What is moulding? Moulding is a process in which a cavity of a desired casting is formed in a mould material like sand, gelatin and metal. Thus, the empty space formed after withdrawing the pattern from the sand compaction forms a mould.

Write short note on foundry tools. Hand Tools: The hand tools a moulder uses are fairly numerous. A brief description of the most important tools is given here. Shovel: A shovel Fig. Page 13 Riddle: A riddle, sometimes called a screen, consists of a circular or square wooden frame fitted with a standard wire mesh at the bottom as shown in Fig.

It is used for removing foreign materials such as nails, shot metal, splinters of wood, etc. Rammer: A hand rammer Fig. One end, called the peen, is wedge shaped, and the opposite end, called the butt, has a flat surface. Trowels are employed in order to smooth or sleek over the surfaces of moulds. A moulder also uses them in repairing the damaged portions of a mould.

As the peg is withdrawn it removes the sand, leaving an opening for the metal. This opening is called the sprue through which the metal is poured. The sprue pin forms the riser pin. Page 14 Fig. A hand blower is shown in Fig. Moulding machines are also provided with a compressed air jet to perform this operation. Moulding boxes: Sand moulds are prepared in specially constructed boxes called flasks.

The purpose of the flask is to impart the necessary rigidity and strength to the sand in moulding. They are usually made in two parts, held in alignment by dowel pins. The top part is called the cope and the lower part the drag. If the flask is made in three sections, the centre is called the cheek. These flasks can be made of either wood or metals depending upon the size required.

Two types of flasks are used in a foundry: 1 the snap flask, and 2 the tight or box flask. A snap flask Fig. The snap flask is of advantage in that many moulds can be made for the same pouring from a single flask. Page 15 A box flask shown in Fig. These boxes are usually made of metal and are very suitable for small and medium sized moulding.

Mechanical tools: The mechanical tools in the foundry include the many types of moulding machines that will ram the mould, roll it over, and draw the pattern. Besides, there are power operated riddles, sand mixers, sand conveyors, etc. The mould is even poured and shaken out mechanically, and the casting is taken by machine to the cleaning department.

The amount of mechanization, however, varies considerably from one foundry to the other. Mass-production foundries making large quantities of relatively few types of castings are in a position to mechanize more completely than the job-shop foundries.

What are the constituents of the moulding sand? Moulding sand contains silica sand grains, clay, moisture and miscellaneous material as ingredients. It is a product of the breaking of quartz rock or decomposition of graphite. Clay: They are particles of sand having diameter less than 20 microns. Moisture: When it is present in required quantity, it improves bonding strength of clay. Miscellaneous material: Iron oxide, lime stone, magnesia, soda and potash are miscellaneous materials.

Give classification of moulding sand on the basis of composition and use. The requirements of these sands are satisfied by IS: , which has classified them Page 16 into three grades A, B and C according to their clay content and sintering temperature.

It is also obtained from sedimentary origin. Bentonite and water can be added to get desired strength and bonding properties. Special sand: Zircon, Olivine, Chromite and Chrome-magnesite are often used as special sands. Zircon sands are suitable for cores of brass and bronze casting. Olivine sands are suitable for non- ferrous castings of an intricate shape. Chamotte is suitable for heavy steel casting. According to use Green sand: It is a mixture of silica sand with 18 to 30 per cent clay, having a total water of from 6 to 8 per cent.

The clay and water furnish the bond for green sand. Moulds prepared in this sand are known as green sand moulds. Dry sand: Green sand that has been dried or baked after the mould is made is called dry sand.

They are suitable for larger castings. Moulds prepared in this sand are known as dry sand moulds. Loam sand: Loam sand is high in clay, as much as 50 per cent or so, and dries hard. This is particularly employed for loam moulding usually for large castings. Facing sand: Facing sand forms the face of the mould.

It is used directly next to the surface of the pattern and it comes into contact with the molten metal when the mould is poured. It is made of silica sand and clay, without the addition of used sand. Page 17 Backing sand: Backing sand or floor sand is used to back up the facing sand and to fill the whole volume of the flask.

Old, repeatedly used moulding sand is mainly employed for this purpose. The backing sand is sometimes called black sand because of the fact that old, repeatedly used moulding sand is black in colour due to the addition of coal dust and burning on coming m contact with molten metal. System sand: The used-sand is cleaned and reactivated by the addition of water, binders and special additives.

This is known as system sand. Since the whole mould is made of this system sand the strength, permeability and refractoriness of the sand must be higher than those of backing sand.

Parting sand: Parting sand is used to keep the green sand from sticking to the pattern and also to allow the sand on the parting surface of the cope and drag to separate without clinging. This is clean clay-free silica sand which serves the same purpose as parting dust. Core sand: Sand used for making cores is called core sand, sometimes called, oil sand.

This is silica sand mixed with core oil which is composed of linseed oil, resin, light mineral oil and other binding materials. Pitch or flours and water may be used in large cores for the sake of economy. Also, the molten metal, coming in contact with the moist sand, generates steam or water vapor.

If these gases and water vapor evolved by the moulding sand do not find opportunity to escape completely through the mould they will form gas holes and pores in the casting. Flow ability: Flow ability of moulding sand refers to its ability to behave like a fluid, so that, when rammed, it will flow to all portions of a mould and pack all-around the pattern and take up the required shape. The sand should respond to different moulding processes.

High flow Page 18 ability is required of a moulding sand to get compacted to a uniform density and to obtain good impression of the pattern in the mould. Collapsibility: After the molten metal in the mould gets solidified, the sand mould must be collapsible so that free contraction of the metal occurs, and this would naturally avoid the tearing or cracking of the contracting metal. Adhesiveness: The sand particles must be capable of adhering to another body, i. It is due to this property that the sand mass can be successfully held in a moulding box and it does not fall out of the box when it is removed.

Cohesiveness or strength: This is the ability of sand particles to stick together. Insufficient strength may lead to a collapse in the mould or its partial destruction during conveying, turning over or closing. The mould may also be damaged during pouring by washing of the walls and core by the molten metal. The strength of moulding sand must, therefore, be sufficient to permit the mould to be formed to the desired shape and to retain this shape even after the hot metal is poured in the mould.

Refractoriness: The sand must be capable of withstanding the high temperature of the molten metal without fusing. Moulding sands with a poor refractoriness may bum on to the casting.

Refractoriness is measured by the sinter point of the sand rather than its melting point. Classify the moulding processes. What is Core?

Why it is used? Cores are separate shapes of sand that are generally required to from the hollow interior of the casting or a hole through the casting. Sometimes cores are also used to shape those parts of the casting that are not otherwise practical or physically obtainable by the mould produced directly from the pattern.

The core is left in the mould in casting and is removed after the casting. Which are the requirements for the core? Or Which characteristics are needed for the core? Cores must be strong enough to retain its shape without deforming, to withstand handling and to resist erosion and deformation by metal during filling of the mould. Cores must be permeable to allow the core gases to escape easily.

Cores should be highly refractory in nature to withstand high temperature of the molten metal. Cores must be sufficiently low in residual gas-forming materials to prevent excess gas from entering the metal. Write short note on core sand and binders. Core sands: The ingredients of core sands are sand and binder. Core sands are usually silica, but zircon, olivine, carbon and chamotte sands are used. Sand that contains more than 5 per cent clay cannot be used for cores.

Excessive clay reduces not only permeability but also collapsibility. Core binders: Core sand has no natural bond, as almost pure sand is used for preparing cores. Hence some other materials are added to the sand to act as binders which cement the sand particles together before and after the cores are baked. Various commercial binders are available in the market which consists mainly of oils, cereals, dextrine, resins, sulphite-liquor, molasses and protein.

Page 20 Core oils, as mentioned earlier, are more popular as they are very economical and produce better cores. The chief ingredients of these core oils are vegetable oil, for instance, linseed oil and corn oil. Oil sands are very popular because: 1. They are easy to use for core making. An oil-sand core is more collapsible than clay bonded core known as loam core. The green and dry strengths of the oil sand mixture can be, controlled by quite simple variations in the proportions of dextrine and oil respectively.

The baked cores are very hard and not easily damaged in handling or during closing of the moulds. Write the procedure for Core making. Core making consists of the following operation: 1 core sand preparation, 2 core moulding, 3 baking, and 4 core finishing.

Core sand preparation: The first consideration in making a core is to mix and prepare the sand properly. The mixture must be homogeneous so that the core will be of uniform strength throughout. The core sands are generally mixed in 1 roller mills and 2 core mixers. Core moulding: Cores are then made manually or with machines. Normally a core box is required for the preparation of cores. Green sand cores are made by ramming the sand mixtures into boxes, the interiors of which have desired shapes and dimensions.

The methods used to ram core are usually done by machines. Core-making machines can be broadly classified as 1 core blowing machines, 2 core ramming machines, e. Page 21 Core baking: After the cores are prepared and placed on metal plate or core carriers, they are baked to remove the moisture and to develop the strength of the binder in core ovens at temperature from 0 C to 0 C, depending on the type of the binder used, the size of the cores, and the length of baking time.

Core finishing: After the baking operation, cores are smoothed. All rough places and unwanted fins are removed by filing some cores are made in two or more pieces which must be assembled usually by pasting together with dextrin or other water-soluble binders. The last operation in the making of a core is to apply a fine refractory coating or core wash to the surface. This coating prevents the metal from penetrating into the core and provides a smoother surface to the casting.

Some materials used for core washes include finely ground graphite, silica, mica, zircon, flour, and a rubber-base chemical spray. Coatings may be applied to the core surfaces by brushing, dipping, or spraying. Explain the types of cores. The cores used in foundries are typed according to their shape and their position in the mould. The common types of cores, illustrated in Fig. Horizontal cores: The most common type is the horizontal core. The core is usually cylindrical in form and is laid horizontally at the parting line of the mould.

The ends of the core rest in the seats provided by the core prints on the pattern. Vertical core: This is placed in a vertical position both in cope and drag halves of the mould.

Usually top and bottom of the core are provided with a taper, but the amount of taper on the top is greater than that at the bottom. Page 22 Balanced core: When the casting is to have an opening only one side and only one core print is available on the pattern a balanced core is suitable.

The core print in such cases should be large enough to give proper bearing to the core. In case the core is sufficiently long, it may be supported at the free end by means of a chaplet Hanging and cover core: If the core hangs from the cope and does not have any support at the bottom of the drag, it is referred to as a hanging core. In this case, it may be necessary to fasten the core with a wire or rod that may extend through the cope.

On the other hand, if it has its support on the drag it is called cover core. In this case, the core serves as a cover for the mould, and also as a support for hanging the main body of the core. What is Core shifting and how it is avoided? A core must be securely fixed to withstand the upward thrust of the molten metal. If a core does not stay in just the right place in its mould, the walls 01 the cavity it produces will not be of proper thickness. To keep the cores in place during casting some form of chaplets are required.

Chaplets are the supporters of cores. These are rods with flat or curved plates riveted to them. Various types of chaplets are used in supporting Page 23 different types of cores. Some of the more generally used forms are shown in Fig. What are Core prints? Explain their types.

Castings are often required to have holes, recesses, etc. These print impressions are obtained by using sand cores which are separately made in boxes known as core boxes. For supporting the cores in the mould cavity, an impression in the form of a recess is made in the mould with the help of a projection suitably placed on the pattern.

This projection on the pattern is known as the core print. A core print is, therefore, an added projection on a pattern, and it forms a seat which is used to support and locate the core in the mould. There are several types of core prints, viz. The core print is often found on the split or two-piece pattern. Vertical core print: This stands vertically in the mould. This is why this type of core is referred to as a vertical core print. The taper on drag print is only 1.

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