The tensile test samples samples Unit 1.pptx

The tensile test samples were machined to dimensions based

1. TEXT BOOKS Manufacturing Processes for Engineering Materials - Kalpakjian S and Steven R Schmid - Pearson publications. Manufacturing Techonlogy Vol I-P . N.Rao . Fundamentals of Modern Manufacturing - Mikell P Groover -Wiley Publ. REFERENCE BOOKS Manufacturing science -A Ghosh&A.K.Malik-East West press Pvt ltd Process and materials of manufacture – Lindberg-PHI. Production Technology – R.K.Jain - khanna . Production Technology – P C Sharma – S. Chand. Manufacturing Processes – H.S. Shaun – Pearson. Manufacturing Processes – J.P. Kaushish – PHI.

2. What is manufacturing ? Representation of ‘manufacturing’ in a technological way manufacturing is the application of physical and chemical processes to alter the geometry, properties, and appearance of a given starting material to make parts or products Introduction

3. Representation of ‘manufacturing’ in a economical way manufacturing is the transformation of materials into items of greater value by means of one or more processing and assembly operations What is manufacturing ?

4. Products go through a series of processes before they are produced Design Material selection Process selection Manufacture Inspection and evaluation Feedback

5. Manufacturing Processes Four basic categories Casting processes Material removal processes Deformation processes or Metal Forming processes Consolidation processes or Joining processes Decisions should be made after all alternatives and limitations are investigated

6. Manufacturing Processes The four manufacturing processing families with subgroups and typical processes.

7. - Metal casting processes Casting is one of the oldest manufacturing process. It is the first step in making most of the products. Casting is the process of producing metal parts by pouring molten metal into the mould cavity of the required shape and allowing the metal to solidify. The solidified metal piece is called as "casting". OR Casting is the process in which molten metal flows by gravity or other force into a mould where it solidifies in the shape of the mould cavity

8. Casting Terms Flask A metal or wood frame, without fixed top or bottom, in which the mould is formed Cope Upper moulding flask Drag Lower moulding flask Parting Line Interface that separates the cope and drag mould Cavity The hollow mould area in which metal solidifies into the part moulding sand Sand, which binds strongly without losing its permeability. It is a mixture of silica sand, clay, and moisture in appropriate proportions. Facing sand The small amount of carbonaceous material sprinkled on the inner surface of the mould cavity to give a better surface finish to the castings.

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10. - Pattern It is the replica of the final object to be made. The mould cavity is made with the help of pattern. Core A separate part of the mould , which is used to create openings and various shaped cavities in the castings. Generally, made of sand. Chaplets Chaplets are used to support the cores inside the mould cavity to take care of its own weight.

11. Pouring basin A small funnel shaped cavity at the top of the mould into which the molten metal is poured. Sprue The passage through which the molten metal, from the pouring basin, reaches the mould cavity. In many cases it controls the flow of metal into the mould . Runner The channel through which the molten metal is carried from the sprue to the gate. Gate A channel through which the molten metal enters the mould cavity. Riser An extra cavity to store additional metal to prevent shrinkage

12. Typical sand mould Mould Section and casting nomenclature pattern attached with gating and risering system

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14. - Applications Big parts Engine blocks and heads for automotive vehicles, Machine tool structure, motor casing, impellers, turbine blades, nozzles, pistons, piston rings, wood burning stoves, door handles, machine frames, railway wheels, water supply pipes, bells, big statues, and machine parts, Turbine vanes and aircraft jet engine blades. Small parts Dental crowns, jewelry, small statues, frying pans

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16. Ice cutter used in an industrial ice machine Heat exchanger used for a steam-generation application

17. - Advantages of Casting Molten material can flow into very small sections so that intricate shapes can be made by this process . As a result, many other operations, such as machining, forging, and welding, can be minimized. It is possible to cast practically any material that is ferrous or non-ferrous.. The necessary tools required for casting moulds are very simple and inexpensive . There are certain parts (like turbine blades) made from metals and alloys that can only be processed this way. Turbine blades: Fully casting + last machining .

18. - Size and weight of the product is not a limitation for the casting process. Wastage of raw material is less

19. Disadvantages of Casting Different disadvantages for different casting processes: Poor dimensional accuracy and surface finish for some processes; e.g., sand casting Safety hazards to workers due to hot molten metals Metal casting is a labour intensive process Limitations on mechanical properties

20. Steps in Making Sand Casting Pattern making Core making moulding Melting and Pouring Cleaning Inspection The six basic steps in making sand castings are

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22. 1. Pattern making The pattern is a physical body of the casting used to make moulds . The mould is made by packing moulding sand around the pattern. The mould is usually made in two parts so that the pattern can be withdrawn. When the patterns withdrawn from the molding material (sand or other), the imprint of the pattern provides the cavity. 2. Core making Cores are forms, usually made of sand, which are placed into a mold cavity to form the interior surfaces of castings. All sides of core are surrounded by the molten metal and are therefore subjected to much more severe thermal and mechanical conditions and as a result the core sand should be of higher strength than the moulding sand.

23. 3. Moulding Moulding is nothing but the mould preparation activities for receiving molten metal. Moulding usually involves : ramming sand around the pattern placed in flask, removing the pattern, setting cores in place, and creating the gating/feeding system to direct the metal into the mould cavity Finishing and closing the mould 4. Melting and Pouring The preparation of molten metal for casting is referred to simply as melting. The molten metal is transferred to the pouring area where the moulds are filled.

24. 5. Cleaning Cleaning involves removal of adhering sand, scale, and excess metal from the casting. Excess metal, in the form of wires, parting line fins, risers gates and other foreign material is removed. 6. Inspection Inspection follows, to check for defects in the casting as well as tonsure that the casting has the dimensions specified on the drawing and/or specifications.

25. Functions of Patterns: A Pattern prepares a mould cavity for the purpose of making a casting. Pattern establishes the parting line and parting surfaces in the mould A Pattern may contain projections known as core prints if the casting requires a core and need to be made hollow. A pattern makes a provision for runner, gates and riser Patterns properly made and having finished and smooth surfaces reduce casting defects. Properly constructed patterns minimize overall cost of the casting.

26. Characteristics of pattern material Easily worked, shaped and joined. Light in weight. Strong, hard and durable. Resistant to wear and abrasion . Resistant to corrosion, and to chemical reactions. Dimensionally stable and unaffected by variations in temperature and humidity. Available at low cost. -

27. Pattern Materials Wood Metal Plastic Plaster of Paris Wax -

28. 1. Wood Patterns The most common material used for pattern because it satisfies many of the desired requirements. These are used where the no. of castings to be produced is small and pattern size is large. Advantages: Inexpensive Easily available in large quantities Easy to fabricate Light in weight They can be repaired easily Easy to obtain good surface finish -

29. - Limitations : Susceptible to shrinkage and swelling Possess poor wear resistance Abraded easily by sand action Absorb moisture, consequently get warped Cannot withstand rough handling Life is very short Commonly used woods for making patterns: Teak Pine Mahogony etc..

30. 2. Metal Patterns Metallic patterns are used where repetitive production of casting is required in large quantities. Different metals like cast iron, brass and aluminum alloys etc. Advantages: Do not absorb moisture More stronger Possess much longer life Do not warp, retain their shape Greater resistance to abrasion Accurate and smooth surface finish Good machinability

31. - Limitations : Expensive Require a lot of machining for accuracy Not easily repaired Ferrous patterns get rusted Heavy weight , thus difficult to handle Commonly used metals for making patterns: Cast iron Aluminium and its alloys Steel White metal Brass etc..

32. 3. Plastic Patterns Advantages : Durable Provides a smooth surface Moisture resistant Does not involve any appreciable change in size or shape Light weight Good strength Wear and corrosion resistance Easy to make Abrasion resistance Good resistance to chemical attack Limitations : Plastic patterns are Fragile These are may not work well when subject to conditions of severe shock as in machine molding (jolting).

33. 4. Plaster of Paris Advantages : It can be easily worked. Intricate shapes can be cast without any difficulty. It has high compressive strength. Cheap and easily available Light in weight. Limitations : Expands on solidification Strength is not so much as that of metals

34. 5. Wax Wax patterns find applications in Investment casting process. Advantages: Provide very good surface finish. Impart high accuracy to castings. After being molded, the wax pattern is not taken out of the mould like other patterns; rather the mould is inverted and heated; the molten wax comes out and/or is evaporated. Thus there is no chance of the mould cavity getting damaged while removing the pattern.

35. Pattern A pattern is a replica of the object to be made by the casting process, with some modifications The main modifications are The addition of pattern allowances, The provision of core prints, and Elimination of fine details, which cannot be obtained by casting and hence are to be obtained by further processing -

36. Pattern Allowances Shrinkage or contraction allowance Machining or finish allowance Draft or taper allowance Distortion or camber allowance Shake or Rapping allowance -

37. 1. Shrinkage or contraction allowance - All most all cast metals shrink or contract volumetrically on cooling. The metal shrinkage is of two types : Liquid Shrinkage :- reduction in volume when the metal changes from liquid state to solid state at the solidus temperature. Compensated by riser in the mould Solid Shrinkage :- Reduction in volume caused when metal loses temperature in solid state. Compensated by providing shrinkage allowance on the Pattern.

38. The metal shrinkage depends upon: The cast metal or alloy. Pouring temp. of the metal/alloy. Casted dimensions(size). Casting design aspects. Molding conditions(i.e., mould materials and molding methods employed)

39. Shrinkage Allowance for different metals

40. 2. Machining or finish allowance Machining Allowance is provided for It is the intended to remove surface roughness and other imperfections from the castings. It is required to achieve exact casting dimensions. Surface finish is required on the casting. - For machining, extra metal is needed to be provided on casting, this extra metal is called machining or finish allowance

41. The machining allowance depends upon: Nature of metals. Size and shape of casting. The type of machining operations to be employed for cleaning the casting. Casting conditions.

42. Machining allowance for various metals -

43. 3. Draft or Taper Allowance - Draft allowance is given to all the vertical surfaces of the pattern. so that the pattern can be easily removed from the molding material with out damaging the mould cavity and without excessive rapping by the molder. The amount of draft depends upon the length of the vertical side of the pattern to be extracted; the intricacy of the pattern; the method of molding; and pattern material

44. Draft values for patterns -

45. 4. Distortion or cambered allowance If the shape of the casting changes that is called distortion of the casting Sometimes casting get distorted, during solidification, due to their typical shape. Reasons for distortion Internal Stresses Non-uniform cooing of casting -

46. Measures to be taken to prevent distortion Providing machining allowance to cover the distortion effect Providing suitable allowance on the pattern, called camber or distortion allowance. That is called inverse reflection -

47. 5. Shake or Rapping allowance A Pattern is shaked or wrapped to take it out of mould . This in turn enlarges the mould cavity. Hence a – ve allowance is given to pattern. If the draft angle is provided, shake allowance reduces. -

48. Types of pattern Solid or single piece pattern Split pattern or two piece pattern Multi piece or three piece pattern Match plate pattern Gated pattern Sweep pattern Lose piece pattern Skeleton pattern Cope and drag pattern Follow board pattern

49. 1. Single piece (solid) pattern Made from one piece and does not contain loose pieces or joints. Inexpensive. Used for large size simple castings. Pattern is accommodated in the drag box. There is no difficulty in withdrawing the pattern from the mould as the broadest portion of the pattern is at the top Examples : Bodies of regular shapes. stuffing box of steam engine.

50. Fig: Single piece pattern

51. Examples Single-piece pattern for a pinion gear. Single-piece pattern for stufing box.

52. 2. Split or Two piece pattern The upper and the lower parts of the split piece patterns are accommodated in the cope and drag portions of the mold respectively. Parting line of the pattern forms the parting line of the mould. Dowel pins are used for keeping the alignment between the two parts of the pattern. Examples: Spindles Hollow cylinder steam valve bodies water stop cocks and taps etc.,

53. Fig: Split or Two piece pattern

54. 3.Three-piece or multi-piece pattern Some patterns are of complicated kind in shape and hence can not be made in one or two pieces because of difficulty in withdrawing the pattern. Therefore these patterns are made in either three pieces or in multi-pieces. Multi molding flasks are needed to make mold from these patterns. -

55. 4. Match plate pattern This pattern is made in two halves and is on mounted on the opposite sides of a metallic plate, known as match plate. Plate may carry one or group of patterns mounted on match plate. Along with pattern gates and runners are also attached. After the cope and drag have been rammed with the molding sand, the match plate pattern is removed from in between the cope and drag. Produces accurate castings at faster rates.

56. Fig: Match plate pattern

57. Fig: Match plate pattern

58. 5. Gated pattern In this the pattern are usually made of metals. In this multi-cavity moulds are produced by joining a number of patterns and gates and providing a common runner for the molten metal. Can produce many castings at one time and hence saves time as well as cost. APPLICATIONS: Used for small castings such as corner bracket.

59. Fig: Gated pattern

60. 6. Sweep pattern It is used for generating large shapes which are symmetrical. It is made on wooden board and its sweeps the sand in casting shape all around the circumference. Making a sweep pattern saves a lot of time, money and labour as compared to making a full pattern A sweep pattern is preferred for producing large casting of circular sections and symmetrical shapes. -

61. Fig: Sweep pattern APPLICATIONS: Symmetrical shapes such as wheels, rims, large kettles of cast irons & bell shapes

62. 7. Loose piece pattern In some cases, the casting may have small projections or overhanging portions. Loose parts or pieces remain attached with the main body of the pattern, with the help of dowel pins. The main body of the pattern is drawn first from the molding box and thereafter as soon as the loose parts are removed, the result is the mold cavity. -

63. Fig: Loose piece pattern

64. 8. Skeleton pattern Pattern is the Skeleton of desired shape, generally mounted on the metal base. Skeleton is made from wooden strips and is filled with loam sand and rammed. Extra sand is removed by stickle. Cores are required if necessary. Applicable for large castings and is very economical as less material costs. APPLICATION: Large castings such as turbines, water pipes, L-bends etc. -

65. Fig: Skeleton pattern

66. 9.Cope and drag pattern A cope and drag pattern is another form of split pattern. Each half of the pattern is fixed to a separate metal/wood plate. Each half of the pattern(along the plate) is molded separately in a separate molding box by an independent molder or moulders . The two moulds of each half of the pattern are finally assembled and the mould is ready for pouring. Cope and drag patterns are used for producing big castings which as a whole cannot be conveniently handled by one moulder alone. -

67. Fig: Cope and drag pattern

68. Fig: Cope and drag pattern

69. 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 Acts like a base seat for pattern. With the follow board support under the weak pattern, the drag is rammed, and then the follow board is with drawn, The rammed drag is inverted, cope is mounted on it and rammed. -

70. Fig: Follow Board Pattern

71. GATING SYSTEM The term gating system refers to all those elements connected with the flow of molten metal from ladle to mould cavity . The gating system is composed of Pouring basin Sprue Sprue well Runner Gates Risers

72. Functions of gating system A gating system should fill the mould cavity before freezing. The metal should flow smoothly into the mould without any turbulence. Unwanted materials such as slag, dross and other mould materials should not be allowed to enter the mould cavity. Metal flow should be maintained in such a way that no gating or mould erosion takes place.  The gating system should ensure that enough molten metal reaches the mould cavity.  It should be economical and easy to implement and remove after casting solidification.

73. Pouring Basin Design Molten metal is poured into a pouring basin which acts as a reservoir from which it moves smoothly into the sprue. The pouring basin stops the slag from entering into the mould cavity by the help of skimmer or skim core. One of the walls of the pouring basin is made inclined at about 45° to the horizontal. -

74. To avoid vortex forming, it is necessary that the pouring basin be kept full and constant conditions of flow are established. A stainer core restricts the flow of metal into the sprue and thus helps in quick filling of the pouring basin.

75. Pouring basin should be deep enough. Entrance into sprue be a smooth radius of 25mm. pouring basin depth should be 2.5 times the sprue entrance diameter.

76. Sprue Design Sprue is a vertical channel through which the molten metal flows downward in the mould . The sprues should be tapered down to take into account the gain in velocity of the metal as it flows down reducing the air aspiration. The exact tapering can be obtained by equation of continuity. -

77. 1 2 3 h 1 1 = free surface of metal 2 = sp u e top 3 = sprue bottom po u ring bas i n sprue h 2 Assumi n g e n ti r e mou l d is at at mo s p h e r ic p r e s sure (n o po i n t b e l ow at mo s p h e r ic) met a l in the p our i ng ba s in is at zero ve l oc i ty ( r e s e r vo ir a s su mp t i on)

78. Mass flow rate =  A V = constant Applying continuity equation between point 2 and 3 we get- That is why the sprue is generally made tapered to gradually reduce the cross-section

79. Sprue Base Design As the molten metal leaves the sprue, it travels at its highest velocity and develops its maximum energy. At the sprue base, the direction of flow is abruptly changed, which causes severe turbulence. By increasing the area of sprue base, both the velocity and the turbulence of metal is reduced. For the sprue base to function properly, its bottom surface must be flat. Sprue base well area should be 5 times the sprue choke area and well depth should be approximately equal to that of the runner. -

80. Runner Design The runner takes the molten metal from sprue to the Ingates of casting. This is the final stage where the molten metal moves from the runner to the mold cavity. -

81. Gate Design These are the opening through which molten metal enters into the mould cavity. Depending on the application, the various types of gates are 1.Top Gating System 2.Bottom Gating System 3.Parting Gating System 4. Step Gating System

82. Top Gating System - The molten metal enters into the mould cavity from the top. These are only used for ferrous alloys. Suitable for simple casting shape. There may be chance of mould erosion.

83. Bottom Gating System - This type of gating system is used for very deep moulds . It takes higher time for filling of the mould cavity

84. Parting Gating System - This is most widely used gate in sand casting. The metal enters into the mould at the parting plane. This is easiest and most economical

85. Step Gating System - These types of gates are used for heavy and large casting. The molten metal enters into the mould cavity through a number of ingates arranged in vertical steps. The size of ingates are increased from top to bottom ensuring a gradual filling of mould cavity.

86. Gating Ratio Refers to the proportion of the cross-sectional area between the sprue, runner and ingates Denoted as sprue area : runner area : ingate area It is selected depending on the characteristics of molten metal being cast Whether the total cross- section decreases towards the mould cavity. It is an pressurized system . Whether the total cross-sectional area increases so that the passages remain incompletely filled. It is an unpressurized system .

87. S.No . Pressurized gating systems Unpressurized gating systems 1. The total cross sectional area decreases towards the mold cavity The total cross sectional area increases towards the mold cavity 2 Gating ratio may be of the order of 3: 2: 1 Gating ratio may be of the order of 1: 3: 2 3. Air aspiration effect is minimum Air aspiration effect is more 4. Volume flow of liquid from every ingate is almost equal. Volume flow of liquid from every ingate is different. 5. They are smaller in volume for a given flow rate of metal. T herefore the casting yield is higher. They are larger in volume because they involve large runners and gates as compared to pressurized system and thus the cast yield is reduced. 6. Because of the restrictions the metal flows at high velocity leading to more turbulence and chances of mold erosion Velocity is low and turbulence is reduced.

88. - Two Categories of Casting Processes Expendable mould processes – uses an expendable mould which must be destroyed to remove casting mould materials: sand, plaster, and similar materials, plus binders Permanent mould processes – uses a permanent mould which can be used over and over to produce many castings Made of metal (or, less commonly, a ceramic refractory material