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Manufacturing Processes

This document provides an overview of pattern making and molding processes in manufacturing. It begins with an introduction to manufacturing processes and casting. Key points include that casting allows for complicated shapes to be made in a single piece and reduces assembly work. The document then discusses pattern materials like wood, metal, and plastic and different types of patterns like solid, split, and multi-piece patterns. It also covers allowances given to patterns for shrinkage, draft, and machining. The final sections cover gates, runners, risers, and core making including different core types.

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Mr. ANSAR A. MULLA AUTOMOBILE ENGG DEPARTMENT R.I.T. ISLAMPUR - R.I.T. ISLAMPUR 1 AE 2091 – Manufacturing Processes Chapter 01- Pattern Making & Molding Processes
Contents 1. Introduction to Subject 2. Introduction to manufacturing processes and casting 3. casting advantages, limitations, pattern materials 4. types, allowances, pattern color code 5. Gates, runners and risers, types of core and core making 6. Moulding sand, types and properties of moulding sand, types of moulding processes, 7. Investment casting, Gravity and pressure die- casting, 8. Centrifugal casting, Continuous casting. 2
1. Introduction to Subject 3 •Course Details •Pre requisite •Course Outcomes •Intro •Chapter wise discussion
2. Introduction to manufacturing processes and casting 4 What is Manufacturing Process? A sequence of operations, often done on a machine or at a given area. Examples: welding, casting, cutting, assembling, etc. During a manufacturing process, we add, subtract, or form materials in order to give a desired property/shape to the work piece. Therefore, different manufacturing processes, manufacturability of a material, processing tools, environmental aspects etc., have become important issues for manufacturing processes.
5 2. Introduction to manufacturing processes and casting
6 2. Introduction to manufacturing processes and casting
2. Introduction to manufacturing processes and casting 7 manufacturing processes Primary Shaping Processes Metal Forming Processes Joining Processes Secondary or Machining Processes Surface Finishing Processes Processes Effecting Change in Properties
2. Introduction to manufacturing processes and casting 8 General Casting Process Pattern Making Foundry Process Foundry Layout Importance & Advantages Disadvantages
2. Introduction to manufacturing processes and casting 9 General Casting Process Pattern Making Foundry Process
10 Pattern Making
11 FOUNDRY LAYOUT Whole process of producing casting may be classified into five stages: 1. Pattern Making 2. Moulding & Core making 3. Melting and Casting 4. Fettling 5. Testing & Inspection P.T.O for Image
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13 Advantages / Importance Disadvantages Reduce Assembly work Small quantity – un economical Complicated shapes Dimensional Accuracy-sand casting Metallurgical Nature White Grey & malleable CI Susceptible to porosity Reduce M/C time and Save metal Rejection rate Large and heavy metal objects Internal defects are not easily noticed Inherent Properties Limitations of size shape, dimensional accuracy – makes selection of appropriate casting difficult Simplified const- single piece
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 14 PATTERNS •Pattern is a mirror image or replica of the component that has to be manufactured by casting process. •It may be also defined as a model around which sand is packed to give rise to a cavity called mold cavity. •A pattern is required even if one object has to be cast. •The materials generally used for pattern are wood, metal or plastics. USE •To form a cavity of proper shape and size in the moulding material so that required casting is obtained by molten metal. •Providing seating surface for the core that are used for making cavity i.e. core prints. •Indirectly checks the dimensions and measurements of the casting. •Reduces casting defects •Minimizes the cost of casting
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 15 PATTERN MATERIALS Selection of Pattern Material based on following factors. •Service requirements, e.g. quantity, quality, •Min thickness, degree of accuracy and finishing required •No of castings to be produced. •Method of moulding to be adopted •Casting method to be used •Shape & Size, complexity
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 16 PATTERN MATERIALS Required properties of Pattern Material •Mechan…. ? •To be done by students
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 17 PATTERN MATERIALS WOOD •most popular and commonly used •It is cheap, easily available in abundance •it is susceptible to shrinkage and warpage and its life is short •It can not withstand rough handily and is weak in comparison to metal. •preferred only when the numbers of castings to be produced are less. •The main varieties of woods used in pattern-making are shisham, kail, deodar, teak and mahogany. •Ad & Disad METAL •preferred when the number of castings required is large enough to justify their use •wear and tear of this pattern is very less and hence posses longer life. •The metals commonly used for pattern making are cast iron, brass and bronzes and aluminium alloys.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 18 PATTERN MATERIALS PLASTIC •are lighter, stronger, moisture and wear resistant, non sticky to molding sand, durable and they are not affected by the moisture of the molding sand •they impart very smooth surface finish on the pattern surface. •Phenolic resin plastics are commonly used. •thermosetting resins, foam plastic. etc PLASTER •material belongs to gypsum family which can be easily cast and worked with wooden tools and preferable for producing highly intricate casting. •main advantages of plaster are that it has high compressive strength and is of high expansion setting type which compensate for the shrinkage allowance of the casting metal. •preferred for production of small size intricate castings and making core boxes.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 19 PATTERN MATERIALS WAX are excellent for investment casting process.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 20 PATTERNS TYPES 1. Solid or single piece pattern 2. Split pattern or two piece pattern 3. Multi piece pattern 4. Match plate pattern 5. Gated pattern 6. Skeleton pattern 7. Sweep pattern 8. Pattern with lose pieces 9. Cope and drag pattern 10. Follow board pattern 11. Segmental pattern 12. Built up pattern or shell pattern 13. Legged up pattern follow board pattern 14. Loose piece pattern
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 21 PATTERNS TYPES 1. Solid or single piece pattern • Simplest pattern • Made in one piece • Cheapest pattern APPLICATION: • Soil tamper • Stuffing box • Gland of steam engines
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 22 PATTERNS TYPES 2. Split pattern or two piece pattern Pattern is split into two piece One part is in cope and other is in drag Easy withdrawal of pattern APPLICATIONS: • Spindles • Steam valve bodies • AK-47 rifle stock
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 23 PATTERNS TYPES 3. Multi piece pattern • Pattern is split into more than two parts. • Facilitates an easy moulding and withdrawal of pattern. • Pattern may consists 3,4 or more numbers depending on designs APPLICATIONS: • Lap joint • Dowel joint • Miter joint
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 24 PATTERNS TYPES 4. Match plate pattern • This pattern is made in two halves and is on mounted on the opposite sides of a wooden or • metallic plate, known as match plate. • The gates and runners are also attached to the plate. • This pattern is used in machine moulding. APPLICATIONS: Generally used for small castings such as piston rings of I.C. engines and rotor hub.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 25 PATTERNS TYPES 5. Gated pattern • In the mass production of casings, multi cavity moulds are used. • Such moulds are formed by joining a number of patterns and gates and providing a common runner for the molten metal. • These patterns are made of metals, and metallic pieces to form gates and runners are attached to the pattern.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 26 PATTERNS TYPES 6. Skeleton pattern • When only a small number of large and heavy castings are to be made, it is not economical make a solid pattern. • In such cases, however, a skeleton pattern may be used. • This is a ribbed construction of wood which forms an outline of the pattern to be made. • This frame work is filled with loam sand and rammed. The surplus sand is removed by strickle board. • For round shapes, the pattern is made in two halves which are joined with glue or by means of screws etc.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 27 PATTERNS TYPES 7. Sweep pattern • It is generally used for preparing large symmetrical castings. • It is made on wooden board and its sweeps the sand in casting shape all around the circumference. • Hence it saves lot of labor and time. • It is used for production of large circular sections and symmetrical shapes. APPLICATIONS: Symmetrical shapes such as wheels, rims, large kettles of cast irons & bell shapes
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 28 PATTERNS TYPES 8. Pattern with lose pieces 9. Cope and drag pattern • In this case, cope and drag part of the mould are prepared separately. • This is done when the complete mould is too heavy to be handled by one operator. • The pattern is made up of two halves, which are mounted on different plates.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 29 PATTERNS TYPES 10. Follow board pattern When the use of solid or split patterns becomes difficult, a contour corresponding to the exact shape of one half of the pattern is made in a wooden board, which is called a follow board and it acts as a moulding board for the first moulding operation as shown in Fig.
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3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 31 PATTERNS TYPES 11. Segmental pattern • Patterns of this type are generally used for circular castings, • for example wheel rim, gear blank etc. • Such patterns are sections of a pattern so arranged as to form a complete mould by being moved to form each section of the mould. • The movement of segmental pattern is guided by the use of a central pivot. • A segment pattern for a wheel rim
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 32 PATTERNS TYPES 14. Loose piece pattern • Loose piece pattern is used when pattern is difficult for withdrawal from the mould. • Loose pieces are provided on the pattern and they are the part of pattern. • The main pattern is removed first leaving the loose piece portion of the pattern in the mould. • Finally the loose piece is withdrawal separately leaving the intricate mould.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 33 PATTERN ALLOWANCES 1. Shrinkage Allowance 2. Draft Allowance 3. Machining Allowances 4. Distortion Allowances 5. Shake/Rapping Allowances
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 34 PATTERN ALLOWANCES Draft or Taper Allowance A positive allowance and is given on all the vertical surfaces of pattern so that its withdrawal becomes easier. •The normal amount of taper on the external surfaces varies from 10 mm to 20 mm/m. •On interior holes and recesses which are smaller in size, the taper should be around 60 mm/mt. •These values are greatly affected by the size of the pattern and the molding method. •In machine molding its, value varies from •10 mm to 50 mm/mt.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 35 PATTERN ALLOWANCES Shake/Rapping Allowances •Before withdrawing the pattern it is rapped and thereby the size of the mould cavity increases. •by rapping, the external sections move outwards increasing the size and internal sections move inwards decreasing the size. •This allowance is kept negative and hence the pattern is made slightly smaller in dimensions 0.5- 1.0 mm.
3&4.Casting Advantages, Limitations, Pattern Materials, types, allowances, pattern color code 36 PATTERN COLOR CODE E.g. 1. Surface to be left as Un machined. BLACK 2. Surface to be machined. RED Color Code used in Pattern (Casting) Different color is used to paint pattern so that person making mold comes to know how to treat a particular surface. There is no universal standard for color code But there is commonly and widely used color code in pattern as given below: Without Color: indicates the parting face of the split pattern Red : indicates surface of the work-piece should be left as it is. Yellow: indicates surface needs machining Black: indicates surface needs core and also shows position of the sand core. Yellow strip on Red: indicates the seats for loose pieces. Red strips on : indicates for supports/ stop-offs
05 Gates, runners and risers, types of core and core making 37 CORE •Core produces a hollow casting. •Cores are compact mass of core sand (special kind of moulding sand ) prepared separately that when placed in mould cavity at required location with proper alignment does not allow the molten metal to occupy space for solidification in that portion and hence help to produce hollowness in the casting.
05 Gates, runners and risers, types of core and core making 38 CORE Core must meet the following functions or objectives: - 1. Core produces hollowness in castings in form of internal cavities. 2. It must be sufficiently permeable to allow the easy escape of gases during pouring and solidification. 3. It may form a part of green sand mould 4. It may be deployed to improve mould surface. 5. It may provide external under cut features in casting. 6. It may be inserted to achieve deep recesses in the casting. 7. It may be used to strengthen the mould. 8. It may be used to form gating system of large size mould.
05 Gates, runners and risers, types of core and core making 39 CORE Essential Characteristics of Core: - 1. Sufficient strength to support itself and to get handled without breaking. 2. Smooth surface to ensure smooth casting. 3. High refractoriness. 4. ….
05 Gates, runners and risers, types of core and core making 40 CORE Core Making Procedure: - 1. Core Sand Preparation 2. Making the cores 3. Baking the cores 4. Finishing of cores 5. Setting the cores
05 Gates, runners and risers, types of core and core making 41 CORE Types of CORES: - A. State or condition of core 1. Green sand core 2. Dry sand core B. Nature of core materials employed 1. Oil bonded 2. Resin bonded 3. Shell 4. Sodium silicate
05 Gates, runners and risers, types of core and core making 42 CORE Types of CORES: - A. State or condition of core B. Nature of core mtrls employed C. Types of core hardening process employed 1. CO2 process 2. Hot box process 3. Cold set 4. Fluid or castable sand 5. Furan No-Bake system 6. Oil No-Bake system
05 Gates, runners and risers, types of core and core making 43 CORE Types of CORES: - A. State or condition of core B. Nature of core mtrls employed C. Types of core hardening process employed D. Shape and Position of core 1. Hz 2. Vertical 3. Hanging or Cover core 4. Balanced 5. Drop core or Stop off core 6. Ram up core.
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05 Gates, runners and risers, types of core and core making 47 CORE BOX Cores are made by means of core boxes comprising of either single or in two parts. Core boxes are generally made of wood or metal and are of several types The main types of core box are half core box, dump core box, split core box, strickle core box, right and left hand core box and loose piece core box.
05 Gates, runners and risers, types of core and core making 48
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 49 A suitable and workable material possessing high refractoriness in nature can be used for mould making. MOLDING SAND The general sources of receiving molding sands are the beds of sea, rivers, lakes, granular elements of rocks, and deserts. The common sources of molding sands available in India are as follows: 1 Batala sand ( Punjab) 2 Ganges sand (Uttar Pradesh) 3 Oyaria sand (Bihar) 4 Damodar and Barakar sands (Bengal- Bihar Border) 5 Londha sand (Bombay) 6 Gigatamannu sand (Andhra Pradesh) and 7 Avadi and Veeriyambakam sand (Madras)
06 Moulding sand, Types and properties of moulding sand, types of moulding processes, 50 classified according to their use into number of varieties, Green sand • Green sand is also known as tempered or natural sand which is a just prepared mixture of silica sand with 18 to 30 percent clay, having moisture content from 6 to 8%. • The clay and water furnish the bond for green sand. • It is fine, soft, light, and porous. • Molds prepared by this sand are not requiring backing and hence are known as green sand molds. • This sand is easily available and it possesses low cost. • It is commonly employed for production of ferrous and non-ferrous castings.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 51 • classified according to their use into number of varieties, • Dry sand • Green sand that has been dried or baked in suitable oven after the making mold and cores, is called dry sand. • It possesses more strength, rigidity and thermal stability. • It is mainly suitable for larger castings. • Mold prepared in this sand are known as dry sand molds. • Loam sand • Loam is mixture of sand and clay with water to a thin plastic paste. • Loam sand possesses high clay as much as 30-50% and 18% water. • Patterns are not used for loam molding and shape is given to mold by sweeps. This is particularly employed for loam molding used for large grey iron castings.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 52 • classified according to their use into number of varieties, • Facing sand • Facing sand is just prepared and forms the face of the mould. • It is directly next to the surface of the pattern and it comes into contact molten metal when the mould is poured. • Initial coating around the pattern and hence for mold surface is given by this sand. • This sand is subjected severest conditions and must possess, therefore, high strength refractoriness. • It is made of silica sand and clay, without the use of used sand. • Different forms of carbon are used to prevent the metal burning into the sand. • A facing sand mixture for green sand of cast iron may consist of 25% fresh and specially prepared and 5% sea coal. • They are sometimes mixed with 6-15 times as much fine molding sand to make facings. • The layer of facing sand in a mold usually ranges from 22-28 mm. From 10 to 15% of the whole amount of molding sand is the facing sand.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 53 • classified according to their use into number of varieties, • Backing sand • Backing sand or floor sand is used to back up the facing sand and is used to fill the whole volume of the molding flask. • Used molding sand is mainly employed for this purpose. • The backing sand is sometimes called black sand because that old, repeatedly used molding sand is black in color due to addition of coal dust and burning on coming in contact with the molten metal. • System sand • In mechanized foundries where machine molding is employed. • A so-called system sand is used to fill the whole molding flask. • In mechanical sand preparation and handling units, no facing sand is used. • The used sand is cleaned and re-activated by the addition of water and special additives. This is known as system sand.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 54 • classified according to their use into number of varieties, • Parting sand • Parting sand without binder and moisture is used to keep the green sand not to stick to the pattern and also to allow the sand on the parting surface 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 • Core sand is used for making cores and it is sometimes also known as oil sand. • This is highly rich silica sand mixed with oil binders such as core oil which composed of linseed oil, resin, light mineral oil and other bind materials.
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06 Moulding sand, types and properties of moulding sand, types of moulding processes, 56 Refractoriness • Refractoriness is defined as the ability of molding sand to withstand high temperatures without breaking down or fusing thus facilitating to get sound casting. • It is a highly important characteristic of molding sands. • Refractoriness can only be increased to a limited extent. • Molding sand with poor refractoriness may burn on to the casting surface and no smooth casting surface can be obtained. • The degree of refractoriness depends on the SiO2 i.e. quartz content, and the shape and grain size of the particle. • Refractoriness is measured by the sinter point of the sand rather than its melting point.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 57 Permeability • It is also termed as porosity of the molding sand in order to allow the escape of any air, gases or moisture present or generated in the mould when the molten metal is poured into it. • Permeability is a function of grain size, grain shape, and moisture and clay contents in the molding sand. • Permeability of mold can be further increased by venting using vent rods Cohesiveness • It is property of molding sand by virtue which the sand grain particles interact and attract each other within the molding sand. • Thus, the binding capability of the molding sand gets enhanced to increase the green, dry and hot strength property of molding and core sand.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 58 Green strength • The green sand after water has been mixed into it, must have sufficient strength and toughness to permit the making and handling of the mould. • For this, the sand grains must be adhesive, i.e. • The green strength also depends upon the grain shape and size, amount and type of clay and the moisture content. Dry strength • As soon as the molten metal is poured into the mould, the moisture in the sand layer adjacent to the hot metal gets evaporated and this dry sand layer must have sufficient strength to its shape in order to avoid erosion of mould wall during the flow of molten metal. • The dry strength also prevents the enlargement of mould cavity cause by the metallostatic pressure of the liquid metal.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 59 Flowability or plasticity • It is the ability of the sand to get compacted and behave like a fluid. • It will flow uniformly to all portions of pattern when rammed and distribute the ramming pressure evenly all around in all directions. • Flowability increases with decrease in green strength, an, decrease in grain size. • The flowability also varies with moisture and clay content. Adhesiveness • It is property of molding sand to get stick or adhere with foreign material such sticking of molding sand with inner wall of molding box
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 60 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. • In absence of this property the contraction of the metal is hindered by the mold and thus results in tears and cracks in the casting. • This property is highly desired in cores Miscellaneous properties • In addition to above requirements, the molding sand should not stick to the casting and should not chemically react with the metal. • Molding sand should be cheap and easily available. • It should be reusable for economic reasons. • Its coefficients of expansion should be sufficiently low.
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06 Moulding sand, types and properties of moulding sand, types of moulding processes, 62 STEPS INVOLVED IN MAKING A SAND MOLD 1. Initially a suitable size of molding box for creating suitable wall thickness is selected for a two piece pattern. • Sufficient care should also be taken in such sense that the molding box must adjust mold cavity, riser and the gating system (sprue, runner and gates etc.). 2. Next, place the drag portion of the pattern with the parting surface down on the bottom (ram-up) board as shown in Fig. 12.6 (a). 3. The facing sand is then sprinkled carefully all around the pattern so that the pattern does not stick with molding sand during withdrawn of the pattern. 4. The drag is then filled with loose prepared molding sand and ramming of the molding sand is done uniformly in the molding box around the pattern. Fill the molding sand once again and then perform ramming. Repeat the process three four times,
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 63 STEPS INVOLVED IN MAKING A SAND MOLD 5. The excess amount of sand is then removed using strike off bar to bring molding sand at the same level of the molding flask height to completes the drag. 6. The drag is then rolled over and the parting sand is sprinkled over on the top of the drag [Fig. 12.6(b)]. 7. Now the cope pattern is placed on the drag pattern and alignment is done using dowel pins. 8. Then cope (flask) is placed over the rammed drag and the parting sand is sprinkled all around the cope pattern. 9. Sprue and riser pins are placed in vertically position at suitable locations using support of molding sand. It will help to form suitable sized cavities for pouring molten metal etc. [Fig. 12.6 (c)].
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 64 STEPS INVOLVED IN MAKING A SAND MOLD 9. Sprue and riser pins are placed in vertically position at suitable locations using support of molding sand. It will help to form suitable sized cavities for pouring molten metal etc. [Fig. 12.6 (c)]. 10. The gaggers in the cope are set at suitable locations if necessary. They should not be located too close to the pattern or mold cavity otherwise they may chill the casting and fill the cope with molding sand and ram uniformly. 11. Strike off the excess sand from the top of the cope. 12. Remove sprue and riser pins and create vent holes in the cope with a vent wire.
06 Moulding sand, types and properties of moulding sand, types of moulding processes, 65 STEPS INVOLVED IN MAKING A SAND MOLD The basic purpose of vent creating vent holes in cope is to permit the escape of gases generated during pouring and solidification of the casting. 13. Sprinkle parting sand over the top of the cope surface and roll over the cope on the bottom board. 14. Rap and remove both the cope and drag patterns and repair the mold suitably if needed and dressing is applied 15. The gate is then cut connecting the lower base of sprue basin with runner and then the mold cavity. 16. Apply mold coating with a swab and bake the mold in case of a dry sand mold. 17. Set the cores in the mold, if needed and close the mold by inverting cope over drag. 18. The cope is then clamped with drag and the mold is ready for pouring, [Fig. 12.6 (d)].
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07 Investment casting, Gravity and pressure die-casting, 69 PERMANENT MOLD OR GRAVITY DIE CASTING
07 Investment casting, Gravity and pressure die-casting, 70 This process - permanent mold casting - U.S.A gravity die casting - England. • A permanent mold casting makes use of a mold or metallic die which is permanent. • No external pressure is applied to force the liquid metal into the mold cavity. • The metallic mold can be reused many times before it is discarded or rebuilt. • These molds are made of dense, fine grained, heat resistant cast iron, steel, bronze, anodized aluminum, graphite or other suitable refractoriness. • The mold walls of a permanent mold have thickness from 15 mm to 50 mm. • The thicker mold walls can remove greater amount of heat from the casting. PERMANENT MOLD OR GRAVITY DIE CASTING
07 Investment casting, Gravity and pressure die-casting, 71 Advantages (i) Fine and dense grained structure is achieved in the casting. (ii) No blow holes exist in castings produced by this method. (iii) The process is economical for mass production. (iv) Because of rapid rate of cooling, the castings possess fine grain structure. (v) Close dimensional tolerance or job accuracy is possible to achieve on the cast product. (vi) Good surface finish and surface details are obtained. (vii) Casting defects observed in sand castings are eliminated. (viii) Fast rate of production can be attained. (ix) The process requires less labor. Disadvantages (i) The cost of metallic mold is higher than the sand mold. The process is impractical for large castings. (ii) The surface of casting becomes hard due to chilling effect. (iii) Refractoriness of the high melting point alloys. PERMANENT MOLD OR GRAVITY DIE CASTING
07 Investment casting, Gravity and pressure die-casting, 72 Applications (i) This method is suitable for small and medium sized casting such as carburetor bodies, oil pump bodies, connecting rods, pistons etc. (ii) It is widely suitable for non-ferrous casting. PERMANENT MOLD OR GRAVITY DIE CASTING
07 Investment casting, Gravity and pressure die-casting, 73 • Molten metal is forced into metallic mold or die under pressure in pressure die casting. • The pressure is generally created by compressed air or hydraulically means. • The pressure varies from 70 to 5000 kg/cm2 and is maintained while the casting solidifies. • The application of high pressure is associated with the high velocity with which the liquid metal is injected into the die to provide a unique capacity for the production of intricate components at a relatively low cost. • This process is called simply die casting in USA. • The die casting machine should be properly designed to hold and operate a die under pressure smoothly. • There are two general types of molten metal ejection mechanisms adopted in die casting set ups which are: (i) Hot chamber type - (a) Gooseneck or air injection management (b) Submerged plunger management (ii) Cold chamber type PRESSURE DIE-CASTING,
07 Investment casting, Gravity and pressure die-casting, 74 • Die casting is widely used for mass production and is most suitable for non-ferrous metals and al1oys of low fusion temperature. • The casting process is economic and rapid. • The surface achieved in casting is so smooth that it does not require any finishing operation. • The material is dense and homogeneous and has no possibility of sand inclusions or other cast • impurities. • Uniform thickness on castings can also be maintained. • The principal base metals most commonly employed in the casting are zinc, aluminum, and copper, magnesium, lead and tin. • There are four main types of die-casting machine which are given as under. 1. Hot chamber die casting machine 2. Cold chamber die casting machine. 3. Air blown or goose neck type machine 4. Vacuum die-casting machine PRESSURE DIE-CASTING,
07 Investment casting, Gravity and pressure die-casting, 75
08 Centrifugal casting, Continuous casting. 76 • In centrifugal casting process, molten metal is poured into a revolving mold and allowed to solidify molten metal by pressure of centrifugal force. • It is employed for mass production of circular casting as the castings produced by this process are free from impurities. • Due to centrifugal force, the castings produced will be of high density type and of good strength. • The cylindrical parts and pipes for handling gases are most adoptable to this process. • Centrifugal casting processes are mainly of three types which are discussed as under. (1) True centrifugal casting (2) Semi-centrifugal casting and (3) Centrifuged casting
08 Centrifugal casting, Continuous casting. 77 • In centrifugal casting process, molten metal is poured into a revolving mold and allowed to solidify molten metal by pressure of centrifugal force.
08 Centrifugal casting, Continuous casting. 78 CONTINNOUS CASTING • Molten metal is continuously poured in to a mold cavity around which a facility for quick cooling the molten metal to the point of solidification. • The solidified metal is then continuously extracted from the mold at redetermined rate. • This process is classified into two categories namely Asarco and Reciprocating.
08 Centrifugal casting, Continuous casting. 79 Advantages of Continuous Casting (i) The process is cheaper than rolling (ii) 100% casting yield. (iii) The process can be easily mechanized and thus unit labor cost is less. (iv) Casting surfaces are better. (v) Grain size and structure of the casting can be easily controlled. Applications of Continuous Casting (i) It is used for casting materials such as brass, bronzes, zinc, copper, aluminium and its alloys, magnesium, carbon and alloys etc. (ii) Production of blooms, billets, slabs, sheets, copper bar etc. (iii) It can produce any shape of uniform cross-section such as round, rectangular, square, hexagonal, fluted or gear toothed etc.
80 Ansar Allauddin Mulla ansarmulla212@gmail.com

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Manufacturing Processes

  • 1.
    Mr. ANSAR A.MULLA AUTOMOBILE ENGG DEPARTMENT R.I.T. ISLAMPUR - R.I.T. ISLAMPUR 1 AE 2091 – Manufacturing Processes Chapter 01- Pattern Making & Molding Processes
  • 2.
    Contents 1. Introduction toSubject 2. Introduction to manufacturing processes and casting 3. casting advantages, limitations, pattern materials 4. types, allowances, pattern color code 5. Gates, runners and risers, types of core and core making 6. Moulding sand, types and properties of moulding sand, types of moulding processes, 7. Investment casting, Gravity and pressure die- casting, 8. Centrifugal casting, Continuous casting. 2
  • 3.
    1. Introduction toSubject 3 •Course Details •Pre requisite •Course Outcomes •Intro •Chapter wise discussion
  • 4.
    2. Introduction tomanufacturing processes and casting 4 What is Manufacturing Process? A sequence of operations, often done on a machine or at a given area. Examples: welding, casting, cutting, assembling, etc. During a manufacturing process, we add, subtract, or form materials in order to give a desired property/shape to the work piece. Therefore, different manufacturing processes, manufacturability of a material, processing tools, environmental aspects etc., have become important issues for manufacturing processes.
  • 5.
    5 2. Introduction tomanufacturing processes and casting
  • 6.
    6 2. Introduction tomanufacturing processes and casting
  • 7.
    2. Introduction tomanufacturing processes and casting 7 manufacturing processes Primary Shaping Processes Metal Forming Processes Joining Processes Secondary or Machining Processes Surface Finishing Processes Processes Effecting Change in Properties
  • 8.
    2. Introduction tomanufacturing processes and casting 8 General Casting Process Pattern Making Foundry Process Foundry Layout Importance & Advantages Disadvantages
  • 9.
    2. Introduction tomanufacturing processes and casting 9 General Casting Process Pattern Making Foundry Process
  • 10.
  • 11.
    11 FOUNDRY LAYOUT Whole processof producing casting may be classified into five stages: 1. Pattern Making 2. Moulding & Core making 3. Melting and Casting 4. Fettling 5. Testing & Inspection P.T.O for Image
  • 12.
  • 13.
    13 Advantages / ImportanceDisadvantages Reduce Assembly work Small quantity – un economical Complicated shapes Dimensional Accuracy-sand casting Metallurgical Nature White Grey & malleable CI Susceptible to porosity Reduce M/C time and Save metal Rejection rate Large and heavy metal objects Internal defects are not easily noticed Inherent Properties Limitations of size shape, dimensional accuracy – makes selection of appropriate casting difficult Simplified const- single piece
  • 14.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 14 PATTERNS •Pattern is a mirror image or replica of the component that has to be manufactured by casting process. •It may be also defined as a model around which sand is packed to give rise to a cavity called mold cavity. •A pattern is required even if one object has to be cast. •The materials generally used for pattern are wood, metal or plastics. USE •To form a cavity of proper shape and size in the moulding material so that required casting is obtained by molten metal. •Providing seating surface for the core that are used for making cavity i.e. core prints. •Indirectly checks the dimensions and measurements of the casting. •Reduces casting defects •Minimizes the cost of casting
  • 15.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 15 PATTERN MATERIALS Selection of Pattern Material based on following factors. •Service requirements, e.g. quantity, quality, •Min thickness, degree of accuracy and finishing required •No of castings to be produced. •Method of moulding to be adopted •Casting method to be used •Shape & Size, complexity
  • 16.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 16 PATTERN MATERIALS Required properties of Pattern Material •Mechan…. ? •To be done by students
  • 17.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 17 PATTERN MATERIALS WOOD •most popular and commonly used •It is cheap, easily available in abundance •it is susceptible to shrinkage and warpage and its life is short •It can not withstand rough handily and is weak in comparison to metal. •preferred only when the numbers of castings to be produced are less. •The main varieties of woods used in pattern-making are shisham, kail, deodar, teak and mahogany. •Ad & Disad METAL •preferred when the number of castings required is large enough to justify their use •wear and tear of this pattern is very less and hence posses longer life. •The metals commonly used for pattern making are cast iron, brass and bronzes and aluminium alloys.
  • 18.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 18 PATTERN MATERIALS PLASTIC •are lighter, stronger, moisture and wear resistant, non sticky to molding sand, durable and they are not affected by the moisture of the molding sand •they impart very smooth surface finish on the pattern surface. •Phenolic resin plastics are commonly used. •thermosetting resins, foam plastic. etc PLASTER •material belongs to gypsum family which can be easily cast and worked with wooden tools and preferable for producing highly intricate casting. •main advantages of plaster are that it has high compressive strength and is of high expansion setting type which compensate for the shrinkage allowance of the casting metal. •preferred for production of small size intricate castings and making core boxes.
  • 19.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 19 PATTERN MATERIALS WAX are excellent for investment casting process.
  • 20.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 20 PATTERNS TYPES 1. Solid or single piece pattern 2. Split pattern or two piece pattern 3. Multi piece pattern 4. Match plate pattern 5. Gated pattern 6. Skeleton pattern 7. Sweep pattern 8. Pattern with lose pieces 9. Cope and drag pattern 10. Follow board pattern 11. Segmental pattern 12. Built up pattern or shell pattern 13. Legged up pattern follow board pattern 14. Loose piece pattern
  • 21.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 21 PATTERNS TYPES 1. Solid or single piece pattern • Simplest pattern • Made in one piece • Cheapest pattern APPLICATION: • Soil tamper • Stuffing box • Gland of steam engines
  • 22.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 22 PATTERNS TYPES 2. Split pattern or two piece pattern Pattern is split into two piece One part is in cope and other is in drag Easy withdrawal of pattern APPLICATIONS: • Spindles • Steam valve bodies • AK-47 rifle stock
  • 23.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 23 PATTERNS TYPES 3. Multi piece pattern • Pattern is split into more than two parts. • Facilitates an easy moulding and withdrawal of pattern. • Pattern may consists 3,4 or more numbers depending on designs APPLICATIONS: • Lap joint • Dowel joint • Miter joint
  • 24.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 24 PATTERNS TYPES 4. Match plate pattern • This pattern is made in two halves and is on mounted on the opposite sides of a wooden or • metallic plate, known as match plate. • The gates and runners are also attached to the plate. • This pattern is used in machine moulding. APPLICATIONS: Generally used for small castings such as piston rings of I.C. engines and rotor hub.
  • 25.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 25 PATTERNS TYPES 5. Gated pattern • In the mass production of casings, multi cavity moulds are used. • Such moulds are formed by joining a number of patterns and gates and providing a common runner for the molten metal. • These patterns are made of metals, and metallic pieces to form gates and runners are attached to the pattern.
  • 26.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 26 PATTERNS TYPES 6. Skeleton pattern • When only a small number of large and heavy castings are to be made, it is not economical make a solid pattern. • In such cases, however, a skeleton pattern may be used. • This is a ribbed construction of wood which forms an outline of the pattern to be made. • This frame work is filled with loam sand and rammed. The surplus sand is removed by strickle board. • For round shapes, the pattern is made in two halves which are joined with glue or by means of screws etc.
  • 27.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 27 PATTERNS TYPES 7. Sweep pattern • It is generally used for preparing large symmetrical castings. • It is made on wooden board and its sweeps the sand in casting shape all around the circumference. • Hence it saves lot of labor and time. • It is used for production of large circular sections and symmetrical shapes. APPLICATIONS: Symmetrical shapes such as wheels, rims, large kettles of cast irons & bell shapes
  • 28.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 28 PATTERNS TYPES 8. Pattern with lose pieces 9. Cope and drag pattern • In this case, cope and drag part of the mould are prepared separately. • This is done when the complete mould is too heavy to be handled by one operator. • The pattern is made up of two halves, which are mounted on different plates.
  • 29.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 29 PATTERNS TYPES 10. Follow board pattern When the use of solid or split patterns becomes difficult, a contour corresponding to the exact shape of one half of the pattern is made in a wooden board, which is called a follow board and it acts as a moulding board for the first moulding operation as shown in Fig.
  • 30.
  • 31.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 31 PATTERNS TYPES 11. Segmental pattern • Patterns of this type are generally used for circular castings, • for example wheel rim, gear blank etc. • Such patterns are sections of a pattern so arranged as to form a complete mould by being moved to form each section of the mould. • The movement of segmental pattern is guided by the use of a central pivot. • A segment pattern for a wheel rim
  • 32.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 32 PATTERNS TYPES 14. Loose piece pattern • Loose piece pattern is used when pattern is difficult for withdrawal from the mould. • Loose pieces are provided on the pattern and they are the part of pattern. • The main pattern is removed first leaving the loose piece portion of the pattern in the mould. • Finally the loose piece is withdrawal separately leaving the intricate mould.
  • 33.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 33 PATTERN ALLOWANCES 1. Shrinkage Allowance 2. Draft Allowance 3. Machining Allowances 4. Distortion Allowances 5. Shake/Rapping Allowances
  • 34.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 34 PATTERN ALLOWANCES Draft or Taper Allowance A positive allowance and is given on all the vertical surfaces of pattern so that its withdrawal becomes easier. •The normal amount of taper on the external surfaces varies from 10 mm to 20 mm/m. •On interior holes and recesses which are smaller in size, the taper should be around 60 mm/mt. •These values are greatly affected by the size of the pattern and the molding method. •In machine molding its, value varies from •10 mm to 50 mm/mt.
  • 35.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 35 PATTERN ALLOWANCES Shake/Rapping Allowances •Before withdrawing the pattern it is rapped and thereby the size of the mould cavity increases. •by rapping, the external sections move outwards increasing the size and internal sections move inwards decreasing the size. •This allowance is kept negative and hence the pattern is made slightly smaller in dimensions 0.5- 1.0 mm.
  • 36.
    3&4.Casting Advantages, Limitations,Pattern Materials, types, allowances, pattern color code 36 PATTERN COLOR CODE E.g. 1. Surface to be left as Un machined. BLACK 2. Surface to be machined. RED Color Code used in Pattern (Casting) Different color is used to paint pattern so that person making mold comes to know how to treat a particular surface. There is no universal standard for color code But there is commonly and widely used color code in pattern as given below: Without Color: indicates the parting face of the split pattern Red : indicates surface of the work-piece should be left as it is. Yellow: indicates surface needs machining Black: indicates surface needs core and also shows position of the sand core. Yellow strip on Red: indicates the seats for loose pieces. Red strips on : indicates for supports/ stop-offs
  • 37.
    05 Gates, runnersand risers, types of core and core making 37 CORE •Core produces a hollow casting. •Cores are compact mass of core sand (special kind of moulding sand ) prepared separately that when placed in mould cavity at required location with proper alignment does not allow the molten metal to occupy space for solidification in that portion and hence help to produce hollowness in the casting.
  • 38.
    05 Gates, runnersand risers, types of core and core making 38 CORE Core must meet the following functions or objectives: - 1. Core produces hollowness in castings in form of internal cavities. 2. It must be sufficiently permeable to allow the easy escape of gases during pouring and solidification. 3. It may form a part of green sand mould 4. It may be deployed to improve mould surface. 5. It may provide external under cut features in casting. 6. It may be inserted to achieve deep recesses in the casting. 7. It may be used to strengthen the mould. 8. It may be used to form gating system of large size mould.
  • 39.
    05 Gates, runnersand risers, types of core and core making 39 CORE Essential Characteristics of Core: - 1. Sufficient strength to support itself and to get handled without breaking. 2. Smooth surface to ensure smooth casting. 3. High refractoriness. 4. ….
  • 40.
    05 Gates, runnersand risers, types of core and core making 40 CORE Core Making Procedure: - 1. Core Sand Preparation 2. Making the cores 3. Baking the cores 4. Finishing of cores 5. Setting the cores
  • 41.
    05 Gates, runnersand risers, types of core and core making 41 CORE Types of CORES: - A. State or condition of core 1. Green sand core 2. Dry sand core B. Nature of core materials employed 1. Oil bonded 2. Resin bonded 3. Shell 4. Sodium silicate
  • 42.
    05 Gates, runnersand risers, types of core and core making 42 CORE Types of CORES: - A. State or condition of core B. Nature of core mtrls employed C. Types of core hardening process employed 1. CO2 process 2. Hot box process 3. Cold set 4. Fluid or castable sand 5. Furan No-Bake system 6. Oil No-Bake system
  • 43.
    05 Gates, runnersand risers, types of core and core making 43 CORE Types of CORES: - A. State or condition of core B. Nature of core mtrls employed C. Types of core hardening process employed D. Shape and Position of core 1. Hz 2. Vertical 3. Hanging or Cover core 4. Balanced 5. Drop core or Stop off core 6. Ram up core.
  • 44.
  • 45.
  • 46.
  • 47.
    05 Gates, runnersand risers, types of core and core making 47 CORE BOX Cores are made by means of core boxes comprising of either single or in two parts. Core boxes are generally made of wood or metal and are of several types The main types of core box are half core box, dump core box, split core box, strickle core box, right and left hand core box and loose piece core box.
  • 48.
    05 Gates, runnersand risers, types of core and core making 48
  • 49.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 49 A suitable and workable material possessing high refractoriness in nature can be used for mould making. MOLDING SAND The general sources of receiving molding sands are the beds of sea, rivers, lakes, granular elements of rocks, and deserts. The common sources of molding sands available in India are as follows: 1 Batala sand ( Punjab) 2 Ganges sand (Uttar Pradesh) 3 Oyaria sand (Bihar) 4 Damodar and Barakar sands (Bengal- Bihar Border) 5 Londha sand (Bombay) 6 Gigatamannu sand (Andhra Pradesh) and 7 Avadi and Veeriyambakam sand (Madras)
  • 50.
    06 Moulding sand,Types and properties of moulding sand, types of moulding processes, 50 classified according to their use into number of varieties, Green sand • Green sand is also known as tempered or natural sand which is a just prepared mixture of silica sand with 18 to 30 percent clay, having moisture content from 6 to 8%. • The clay and water furnish the bond for green sand. • It is fine, soft, light, and porous. • Molds prepared by this sand are not requiring backing and hence are known as green sand molds. • This sand is easily available and it possesses low cost. • It is commonly employed for production of ferrous and non-ferrous castings.
  • 51.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 51 • classified according to their use into number of varieties, • Dry sand • Green sand that has been dried or baked in suitable oven after the making mold and cores, is called dry sand. • It possesses more strength, rigidity and thermal stability. • It is mainly suitable for larger castings. • Mold prepared in this sand are known as dry sand molds. • Loam sand • Loam is mixture of sand and clay with water to a thin plastic paste. • Loam sand possesses high clay as much as 30-50% and 18% water. • Patterns are not used for loam molding and shape is given to mold by sweeps. This is particularly employed for loam molding used for large grey iron castings.
  • 52.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 52 • classified according to their use into number of varieties, • Facing sand • Facing sand is just prepared and forms the face of the mould. • It is directly next to the surface of the pattern and it comes into contact molten metal when the mould is poured. • Initial coating around the pattern and hence for mold surface is given by this sand. • This sand is subjected severest conditions and must possess, therefore, high strength refractoriness. • It is made of silica sand and clay, without the use of used sand. • Different forms of carbon are used to prevent the metal burning into the sand. • A facing sand mixture for green sand of cast iron may consist of 25% fresh and specially prepared and 5% sea coal. • They are sometimes mixed with 6-15 times as much fine molding sand to make facings. • The layer of facing sand in a mold usually ranges from 22-28 mm. From 10 to 15% of the whole amount of molding sand is the facing sand.
  • 53.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 53 • classified according to their use into number of varieties, • Backing sand • Backing sand or floor sand is used to back up the facing sand and is used to fill the whole volume of the molding flask. • Used molding sand is mainly employed for this purpose. • The backing sand is sometimes called black sand because that old, repeatedly used molding sand is black in color due to addition of coal dust and burning on coming in contact with the molten metal. • System sand • In mechanized foundries where machine molding is employed. • A so-called system sand is used to fill the whole molding flask. • In mechanical sand preparation and handling units, no facing sand is used. • The used sand is cleaned and re-activated by the addition of water and special additives. This is known as system sand.
  • 54.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 54 • classified according to their use into number of varieties, • Parting sand • Parting sand without binder and moisture is used to keep the green sand not to stick to the pattern and also to allow the sand on the parting surface 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 • Core sand is used for making cores and it is sometimes also known as oil sand. • This is highly rich silica sand mixed with oil binders such as core oil which composed of linseed oil, resin, light mineral oil and other bind materials.
  • 55.
  • 56.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 56 Refractoriness • Refractoriness is defined as the ability of molding sand to withstand high temperatures without breaking down or fusing thus facilitating to get sound casting. • It is a highly important characteristic of molding sands. • Refractoriness can only be increased to a limited extent. • Molding sand with poor refractoriness may burn on to the casting surface and no smooth casting surface can be obtained. • The degree of refractoriness depends on the SiO2 i.e. quartz content, and the shape and grain size of the particle. • Refractoriness is measured by the sinter point of the sand rather than its melting point.
  • 57.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 57 Permeability • It is also termed as porosity of the molding sand in order to allow the escape of any air, gases or moisture present or generated in the mould when the molten metal is poured into it. • Permeability is a function of grain size, grain shape, and moisture and clay contents in the molding sand. • Permeability of mold can be further increased by venting using vent rods Cohesiveness • It is property of molding sand by virtue which the sand grain particles interact and attract each other within the molding sand. • Thus, the binding capability of the molding sand gets enhanced to increase the green, dry and hot strength property of molding and core sand.
  • 58.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 58 Green strength • The green sand after water has been mixed into it, must have sufficient strength and toughness to permit the making and handling of the mould. • For this, the sand grains must be adhesive, i.e. • The green strength also depends upon the grain shape and size, amount and type of clay and the moisture content. Dry strength • As soon as the molten metal is poured into the mould, the moisture in the sand layer adjacent to the hot metal gets evaporated and this dry sand layer must have sufficient strength to its shape in order to avoid erosion of mould wall during the flow of molten metal. • The dry strength also prevents the enlargement of mould cavity cause by the metallostatic pressure of the liquid metal.
  • 59.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 59 Flowability or plasticity • It is the ability of the sand to get compacted and behave like a fluid. • It will flow uniformly to all portions of pattern when rammed and distribute the ramming pressure evenly all around in all directions. • Flowability increases with decrease in green strength, an, decrease in grain size. • The flowability also varies with moisture and clay content. Adhesiveness • It is property of molding sand to get stick or adhere with foreign material such sticking of molding sand with inner wall of molding box
  • 60.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 60 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. • In absence of this property the contraction of the metal is hindered by the mold and thus results in tears and cracks in the casting. • This property is highly desired in cores Miscellaneous properties • In addition to above requirements, the molding sand should not stick to the casting and should not chemically react with the metal. • Molding sand should be cheap and easily available. • It should be reusable for economic reasons. • Its coefficients of expansion should be sufficiently low.
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  • 62.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 62 STEPS INVOLVED IN MAKING A SAND MOLD 1. Initially a suitable size of molding box for creating suitable wall thickness is selected for a two piece pattern. • Sufficient care should also be taken in such sense that the molding box must adjust mold cavity, riser and the gating system (sprue, runner and gates etc.). 2. Next, place the drag portion of the pattern with the parting surface down on the bottom (ram-up) board as shown in Fig. 12.6 (a). 3. The facing sand is then sprinkled carefully all around the pattern so that the pattern does not stick with molding sand during withdrawn of the pattern. 4. The drag is then filled with loose prepared molding sand and ramming of the molding sand is done uniformly in the molding box around the pattern. Fill the molding sand once again and then perform ramming. Repeat the process three four times,
  • 63.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 63 STEPS INVOLVED IN MAKING A SAND MOLD 5. The excess amount of sand is then removed using strike off bar to bring molding sand at the same level of the molding flask height to completes the drag. 6. The drag is then rolled over and the parting sand is sprinkled over on the top of the drag [Fig. 12.6(b)]. 7. Now the cope pattern is placed on the drag pattern and alignment is done using dowel pins. 8. Then cope (flask) is placed over the rammed drag and the parting sand is sprinkled all around the cope pattern. 9. Sprue and riser pins are placed in vertically position at suitable locations using support of molding sand. It will help to form suitable sized cavities for pouring molten metal etc. [Fig. 12.6 (c)].
  • 64.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 64 STEPS INVOLVED IN MAKING A SAND MOLD 9. Sprue and riser pins are placed in vertically position at suitable locations using support of molding sand. It will help to form suitable sized cavities for pouring molten metal etc. [Fig. 12.6 (c)]. 10. The gaggers in the cope are set at suitable locations if necessary. They should not be located too close to the pattern or mold cavity otherwise they may chill the casting and fill the cope with molding sand and ram uniformly. 11. Strike off the excess sand from the top of the cope. 12. Remove sprue and riser pins and create vent holes in the cope with a vent wire.
  • 65.
    06 Moulding sand,types and properties of moulding sand, types of moulding processes, 65 STEPS INVOLVED IN MAKING A SAND MOLD The basic purpose of vent creating vent holes in cope is to permit the escape of gases generated during pouring and solidification of the casting. 13. Sprinkle parting sand over the top of the cope surface and roll over the cope on the bottom board. 14. Rap and remove both the cope and drag patterns and repair the mold suitably if needed and dressing is applied 15. The gate is then cut connecting the lower base of sprue basin with runner and then the mold cavity. 16. Apply mold coating with a swab and bake the mold in case of a dry sand mold. 17. Set the cores in the mold, if needed and close the mold by inverting cope over drag. 18. The cope is then clamped with drag and the mold is ready for pouring, [Fig. 12.6 (d)].
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  • 67.
  • 68.
  • 69.
    07 Investment casting,Gravity and pressure die-casting, 69 PERMANENT MOLD OR GRAVITY DIE CASTING
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    07 Investment casting,Gravity and pressure die-casting, 70 This process - permanent mold casting - U.S.A gravity die casting - England. • A permanent mold casting makes use of a mold or metallic die which is permanent. • No external pressure is applied to force the liquid metal into the mold cavity. • The metallic mold can be reused many times before it is discarded or rebuilt. • These molds are made of dense, fine grained, heat resistant cast iron, steel, bronze, anodized aluminum, graphite or other suitable refractoriness. • The mold walls of a permanent mold have thickness from 15 mm to 50 mm. • The thicker mold walls can remove greater amount of heat from the casting. PERMANENT MOLD OR GRAVITY DIE CASTING
  • 71.
    07 Investment casting,Gravity and pressure die-casting, 71 Advantages (i) Fine and dense grained structure is achieved in the casting. (ii) No blow holes exist in castings produced by this method. (iii) The process is economical for mass production. (iv) Because of rapid rate of cooling, the castings possess fine grain structure. (v) Close dimensional tolerance or job accuracy is possible to achieve on the cast product. (vi) Good surface finish and surface details are obtained. (vii) Casting defects observed in sand castings are eliminated. (viii) Fast rate of production can be attained. (ix) The process requires less labor. Disadvantages (i) The cost of metallic mold is higher than the sand mold. The process is impractical for large castings. (ii) The surface of casting becomes hard due to chilling effect. (iii) Refractoriness of the high melting point alloys. PERMANENT MOLD OR GRAVITY DIE CASTING
  • 72.
    07 Investment casting,Gravity and pressure die-casting, 72 Applications (i) This method is suitable for small and medium sized casting such as carburetor bodies, oil pump bodies, connecting rods, pistons etc. (ii) It is widely suitable for non-ferrous casting. PERMANENT MOLD OR GRAVITY DIE CASTING
  • 73.
    07 Investment casting,Gravity and pressure die-casting, 73 • Molten metal is forced into metallic mold or die under pressure in pressure die casting. • The pressure is generally created by compressed air or hydraulically means. • The pressure varies from 70 to 5000 kg/cm2 and is maintained while the casting solidifies. • The application of high pressure is associated with the high velocity with which the liquid metal is injected into the die to provide a unique capacity for the production of intricate components at a relatively low cost. • This process is called simply die casting in USA. • The die casting machine should be properly designed to hold and operate a die under pressure smoothly. • There are two general types of molten metal ejection mechanisms adopted in die casting set ups which are: (i) Hot chamber type - (a) Gooseneck or air injection management (b) Submerged plunger management (ii) Cold chamber type PRESSURE DIE-CASTING,
  • 74.
    07 Investment casting,Gravity and pressure die-casting, 74 • Die casting is widely used for mass production and is most suitable for non-ferrous metals and al1oys of low fusion temperature. • The casting process is economic and rapid. • The surface achieved in casting is so smooth that it does not require any finishing operation. • The material is dense and homogeneous and has no possibility of sand inclusions or other cast • impurities. • Uniform thickness on castings can also be maintained. • The principal base metals most commonly employed in the casting are zinc, aluminum, and copper, magnesium, lead and tin. • There are four main types of die-casting machine which are given as under. 1. Hot chamber die casting machine 2. Cold chamber die casting machine. 3. Air blown or goose neck type machine 4. Vacuum die-casting machine PRESSURE DIE-CASTING,
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    07 Investment casting,Gravity and pressure die-casting, 75
  • 76.
    08 Centrifugal casting,Continuous casting. 76 • In centrifugal casting process, molten metal is poured into a revolving mold and allowed to solidify molten metal by pressure of centrifugal force. • It is employed for mass production of circular casting as the castings produced by this process are free from impurities. • Due to centrifugal force, the castings produced will be of high density type and of good strength. • The cylindrical parts and pipes for handling gases are most adoptable to this process. • Centrifugal casting processes are mainly of three types which are discussed as under. (1) True centrifugal casting (2) Semi-centrifugal casting and (3) Centrifuged casting
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    08 Centrifugal casting,Continuous casting. 77 • In centrifugal casting process, molten metal is poured into a revolving mold and allowed to solidify molten metal by pressure of centrifugal force.
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    08 Centrifugal casting,Continuous casting. 78 CONTINNOUS CASTING • Molten metal is continuously poured in to a mold cavity around which a facility for quick cooling the molten metal to the point of solidification. • The solidified metal is then continuously extracted from the mold at redetermined rate. • This process is classified into two categories namely Asarco and Reciprocating.
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    08 Centrifugal casting,Continuous casting. 79 Advantages of Continuous Casting (i) The process is cheaper than rolling (ii) 100% casting yield. (iii) The process can be easily mechanized and thus unit labor cost is less. (iv) Casting surfaces are better. (v) Grain size and structure of the casting can be easily controlled. Applications of Continuous Casting (i) It is used for casting materials such as brass, bronzes, zinc, copper, aluminium and its alloys, magnesium, carbon and alloys etc. (ii) Production of blooms, billets, slabs, sheets, copper bar etc. (iii) It can produce any shape of uniform cross-section such as round, rectangular, square, hexagonal, fluted or gear toothed etc.
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