Special casting process (1.5)

centrifugal casting, investment casting, lost wax process, special casting process, stir casting

1. Special casting process YoucaN 1.5 Carbon Dioxide moulding , Shell moulding , Investment casting, Hot-cold chamber die casting, Centrifugal casting , stir casting

2. Carbon-Dioxide Gas Molding Rapid hardening process Mould material contains pure dry silica sand free from clay , 3-5% sodium silicate as binder and moisture content generally less than 3 %. After packing, carbon dioxide gas at about 1.3-1.5 kg/cm 2 pressure is forced for 20 t0 30 sec. YoucaN

3. Various methods of gassing mould and cores in CO 2 moulding Single probe cover probe Manifold and multiple probe YoucaN

4. Gassing mould after drawing out pattern Gassing previously stripped cores Gassing through hollow pattern YoucaN

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6. Advantages This process has many advantages in comparison to other forms of castings some of them are as follows: Compared to other casting methods cores and molds are strong Reduces fuel cost since gas is used instead of other costly heating generating elements Reduces large requirement for number of mold boxes and core dryers Provides great dimensional tolerance and accuracy in production Moisture is completely eliminated from the molding sand This process can be fully automated. YoucaN

7. YoucaN Quiz How are they manufacturing this componets ?

8. Shell moulding YoucaN

9. Shell mould casting YoucaN

10. Shell mould casting Fine silica sand and (3–6%) thermosetting phenolic resin and liquid catalyst. Cast iron pattern heated to 230 to 315 °C Inverted- few mins - inverted excess sand will drop 10 to 20 mm thickness Combined shells as mould Examples: Gear housings, cylinder heads and connecting rods, crank shaft. It is also used to make high-precision molding cores. YoucaN

11. Shell Molding Casting process in which the mold is a thin shell of sand held together by thermosetting resin binder Figure 11.5 Steps in shell‑molding : (1) a match‑plate or cope‑and‑drag metal pattern is heated and placed over a box containing sand mixed with thermosetting resin. YoucaN

12. Shell Molding Steps in shell‑molding: (2) box is inverted so that sand and resin fall onto the hot pattern, causing a layer of the mixture to partially cure on the surface to form a hard shell; (3) box is repositioned so that loose uncured particles drop away; YoucaN

13. Shell Molding Steps in shell‑molding: (4) sand shell is heated in oven for several minutes to complete curing; (5) shell mold is stripped from the pattern; YoucaN

14. Shell Molding Steps in shell‑molding: (6) two halves of the shell mold are assembled, supported by sand or metal shot in a box, and pouring is accomplished; (7) the finished casting with sprue removed. YoucaN

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19. Crankshaft in engine YoucaN

20. Advantages 1.High suitable for thin sections like petrol engine cylinder. 2)Excellent surface finish. 3)Dimensional accuracy of order of 0.002 to 0.003 mm. 4)Negligible machining and cleaning cost. 5)Occupies less floor space. 6)Skill-ness required is less. 7)Molds formed by this process can be stored until required. 8)Better quality of casting assured. 9)Mass production. Disadvantages The main disadvantages of shell molding are: 1)Higher pattern cost, resin cost. 2) Not economical for small runs. 3) Dust-extraction problem. 4) Complicated jobs and jobs of various sizes cannot be easily shell molded. 5)Specialized equipment is required. 6) Resin binder is an expensive material.7) Limited for small size. YoucaN

21. video 6. Shell Molding YoucaN

22. YoucaN Quiz Identify the componet and its manufacturing process..

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24. INVESTMENT CASTING or LOST WAX PROCESS or CERAMIC SHELL INVESTMENT CASTING Wax is coated with refractory material to make a mould after which the wax is melted away prior to pouring the molten metal. YoucaN

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27. Step 1 Wax patterns are produced; with a help of special steel dies. Wax is injected at 150 F at a pressure range of 7 – 70 kg/cm 2 . YoucaN

28. Step 2 (2) Several patterns are attached to a sprue to form a pattern tree; YoucaN

29. Step 3 The pattern tree is coated with a thin layer of ceramic slurry material . Ceramic slurry Fine grained refractory powders of Zircon (ZrSiO 4 ), Alumina (Al 2 O 3 ), Fused Silica (SiO 2 ) and a liquid chemical binder (Alcohol based Silicon Ester ). YoucaN

30. Step 4 The full mould is formed by covering the coated tree with sufficient thickness. To strengthen it is coated with a fine zircon powder . YoucaN

31. Step 5 The mould is held in an inverted position and heated to melt the wax and permit it to drip out of the cavity; YoucaN

32. Step 6 The mould is preheated to a high temperature, which ensures that all contaminants are eliminated from the mould ; it also permits the liquid metal to flow more easily into the detailed cavity; the molten metal is poured; it solidifies. YoucaN

33. Step 7 YoucaN

34. Step 7 The mold is broken away from the finished casting. Parts are separated from the sprue . YoucaN

35. Applications: Nozzles, vanes,gas turbines Aerospace industry parts Scientific instruments YoucaN

36. Advantages: Complex shape can be made. Good surface finish. Unmachinable alloys can be cast. NO of castings can be made at a time. Can obtain directional solidification components.(high strength) YoucaN

37. Disadvantages: Only small size is possible. More expensive. Location of hole is impossible. YoucaN

38. Video 7. Investment Casting Animation If time permits play this(15.How Its Made - 103 Lost Wax Process Casting) YoucaN

39. Ceramic moulding YoucaN To Remove the binder in the mould it is heated to 980˚C in furnace.

40. Ceramic moulding Ceramic as a mould material. Ceramic slurry prepared by mixing of fine grained refractory powders of Zircon (ZrSiO 4 ), Alumina (Al 2 O 3 ), Fused Silica (SiO 2 ) and a liquid chemical binder (Alcohol based Silicon Ester) for making the mould YoucaN

41. Ceramic moulding A little Vibration helps to fills the cavity. To remove the binder in the mould it is heated to 980˚C in furnace. Applications: used to make tooling, especially drop forging dies , but also injection molding dies, die casting dies, glass molds, stamping dies, and extrusion dies. YoucaN

42. Advantages and disadvantages Highest precision and extremely high finish are obtained. Suitable for all types of cast metals including highly reactive metals such as titanium and uranium. The castings do not require any riser, venting and chilling as the cooling rate is very slow. A ordinary wood metal or epoxy pattern enough. Disadvantages: The process is expensive because the mould material is costly. Impractical to control dimensional tolerances across the parting line. YoucaN

43. YoucaN quiz How can you produce these components?

44. Pressure die casting The molten metal is forced into the die assembly under pressure, with a help of compressed air. The pressure varies from 3 to 5 Mpa . The metal occupies nook and corner of the die cavity. The die is water cooled and the metal become solidifies immediately. Now the die is opened. The casting is removed by ejector pins. This process is suitable for casting lead, magnesium, tin, brass. YoucaN

45. Applications of die casting Used to produce Household equipments such as washing machine parts, vaccum cleaner body, fan case etc Automobile parts such as fuel pump, carburetor body, crank case etc Components for telephones, television sets, speakers, microphones. Toys such as electric trains, model air crafts etc. YoucaN

46. Advantages and disadvantags Advantages: Very accurate castings. Good surface finish. High production rate. Defects is less. Disadvantages: only small parts can be made. Only non-ferrous metals can be cast. Equipment is high cost. YoucaN

47. Hot chamber die casting Tin 230°C, lead 327 °C, zinc 420°C. YoucaN b pressure varies from 3 to 5Mpa permanent mould casting

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50. video 9.hotchamber YoucaN

51. Hot chamber die casting Burner is used to heat the metals like zinc, tin or lead. Gooseneck is submerged. Plunger is moved. Pressure of 3-5Mpa. Water cooled die- solidifications-ejection. YoucaN

52. Advantages & disadvantages It is a simple machine and no moving parts. Disadvantages: Low production rate. Machine life is low due to the attached furnace. YoucaN

53. Cold chamber die casting There is no melting unit in the machine and the molten metal is poured though a ladle. The temperature of the molten metal is lower compared to the hot chamber casting , so that the pressure applied is much higher (70-200Mpa) than the hot chamber casting . Melting temparature Al-660 ° C, Magnesium – 650 °C Brass-940 °C. YoucaN permanent mould casting

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55. YoucaN pressure varies from 70 – 200 Mpa

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57. video 10.coldchamber YoucaN

58. Gravity die casting YoucaN permanent mould casting mould cavity fills with no force other than gravity

59. YoucaN The  die is heated and then sprayed with a refractory coating , and closed. The coating both helps control the temperature of the die during manufacture and it also assists in the removal of the casting. Molten metal is then manually poured into the die , (although in some cases a machine can be used) and allowed to solidify. The  die is then opened and the cast parts either removed  by hand or in some cases ejector pins are used on the mechanised machines. Finally,  the scrap, which includes the gate, runners, sprues and flash, is removed  from the casting(s). The  castings are then processed  to remove sharp edges and excess material, then blast cleaned (if required) prior to despatch to the customer.

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61. YoucaN quiz How can you produce this flywheel?

62. Centrifugal casting Centrifugal casting refers to several casting methods in which the mold is rotated at high speed so that centrifugal force distributes the molten metal to the outer regions of the die cavity. 30 to 300 rpm. The group includes (1) true centrifugal casting, (2) semi-centrifugal casting, and (3) centrifuge casting. YoucaN

63. True centrifugal casting YoucaN

64. True centrifugal casting True centrifugal method of casting is used to produce hollow castings with a round hole. No cores are used. Mould is rotated about the axis of the hole. Axis may be vertical, horizontal or inclined. Speed of rotating should be high enough to hold the metal on to the mould wall till it solidifies. YoucaN

65. True centrifugal casting If low speed means slipiing of metals occurs. Centrifugal force For horizonal moulds 65-75 times of gravity. For vertical moulds 100 times of gravity. Products: Pipes Oil engine cylinders Piston ring stock Bearing bushes YoucaN

66. True Centrifugal Casting OR De lavaud process De lavaud process concept diagram YoucaN

67. De lavaud process De lavaud process YoucaN

68. De lavaud process: Poured in to the rotating mould . Centrifugal force that causes the metal to take the shape of the mould cavity. Without core we can manufacture a hollow section. YoucaN

69. video 8.Centrifugal_Casting_the_Process YoucaN

70. Advantages & disadvantages Advantages: Core is not required. High rate of production. Pattern, runner and riser are not required. Thin casting can be made. Castings have uniform physical properties. Limitations: It is suitable for only cylindrical parts only. Cost of equipment is high. YoucaN

71. Semi centrifugal casting concept diagram for semi centrifugal casting YoucaN

72. concept diagram for semi centrifugal casting YoucaN

73. Semi centrifugal casting Centrifugal force is used to produce solid castings. Outer side parts have high density. Finally the centre part is machined away. Used to produce: Wheels, pulleys, flywheel. YoucaN

74. Semi centrifugal casting Here a core(sand core) is used to form the central cavity(as the hub of the wheel). These are normally vertical type machines. Spinning speed is not to be high as true centrifugal casting. A linear speed of the order of 180-200mpm (meter per minute). YoucaN

75. semi centrifugal casting YoucaN

76. Flywheel production in semi centrifugal process Stack moulding : When castings in multiple layers one above the other are produced in one mould , the method is called stack moulding . YoucaN

77. YoucaN Stack casting is used for small casting. It requires less floor space in the foundary . A common sprue is used to pour all moulds.

78. Flywheel- Energy storage device YoucaN

79. Centrifuged casting Non symmetrical parts can be cast in a group of moulds arranged in a circle to balance each other. The axis of the mould and that of rotation do not coincide with each other. Centrifuging helps in proper feeding of castings resulting in clean, close grained castings. YoucaN

80. Centrifuged casting YoucaN

81. Stir casting process YoucaN

82. Stir casting process Stir casting is a process is used to prepare an adequate homogenous particle distribution throughout the molten material. The stainless steel stirrer blade was coated with zirconia to avoid the reaction between stainless steel and Al alloys at higher temperatures. The Argon gas was supplied into the near the crucible during the stirring to avoid the formation of oxide layer on the surface of matrix melt. The Stirring speed 450 – 1000 rpm was maintained throughout work. The mixture is allowed to solidify in the preheated (300°C) steel die.(RHA- Rice Husk Ash) YoucaN

83. Stir casting process Advantages: High mechanical strength. The cost of preparing composites materials using a casting method is about one third to one half that of a competitive method. So the high volume of production is possible. YoucaN

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85. Slush casting process YoucaN

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87. YoucaN Quiz Identify the casting process shown in fig ?

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