8 Metal Molding Processes

1. What is the main factor that differentiates metal casting processes?. A) The color of the metal. B) The material of the mold and the pouring method. C) The weight of the final part. D) The type of machining used afterward.

2. Why do permanent mold processes have limitations in geometric complexity?. A) The molds melt during pouring. B) The molds must be opened to remove the part. C) The metal solidifies too slowly. D) The patterns cannot be reused.

3. Why do expendable mold and permanent pattern processes struggle with complex geometries?. A) The molten metal reacts with the mold. B) The pattern must be removed without damaging the mold. C) The mold cools too quickly. D) The metal expands excessively.

4. Which type of process allows the greatest freedom in part design?. A) Expendable mold and expendable pattern processes. B) Permanent mold processes. C) Die casting. D) Sand mold casting only.

5. Why are large parts typically made using sand mold casting?. A) Sand molds are extremely strong. D) Sand molds are very cheap. C) Sand molds cool metal faster. B) Sand molds produce the best surface finish.

6. Why can’t high melting point metals be cast in sand molds?. A) They cool too quickly. D) They crystallize and damage the sand. C) They cannot be melted efficiently. B) They require vacuum pouring.

7. Permanent molds are usually made of steel. What limitation does this create?. B) They cannot be reused. A) They can only cast metals with lower melting points. C) They produce poor surface finish. D) They cannot withstand pressure pouring.

8. What determines the surface finish of a sand cast part?. A) The pouring temperature. B) The type of furnace used. C) The grain size of the sand. D) The color of the mold.

9. Why do sand molds sometimes require higher machining allowances?. A) They are too expensive. B) They deform under the weight of the metal. C) They cool the metal too slowly. D) They produce extremely fine grain structures.

10. What type of mold cooling produces finer grain sizes?. A) Slow cooling. B) Natural cooling. C) Fast cooling. D) Vacuum cooling.

11. Which factor makes some casting processes suitable only for short production runs?. A) High flexibility. B) Low mold cost. C) High process rigidity. D) High investment cost.

12. Why is die casting economical for mass production?. A) It uses very cheap molds. B) It requires no pouring system. C) The high mold cost is spread across many parts. D) It produces only simple shapes.

13. Which process is more flexible when part geometry must be changed?. C) Permanent mold casting. B) Die casting. A) Sand mold casting. D) Lost wax casting only.

14. Which process uses an expendable mold and a permanent pattern?. A) Die casting. B) Lost foam casting. C) Sand mold casting. D) Centrifugal casting.

15. Which process uses both an expendable mold and an expendable pattern?. A) Sand mold casting. B) Lost wax casting. C) Die casting. D) Permanent mold casting.

16. Which process uses a permanent mold and a virtual pattern?. A) Lost foam casting. B) Sand mold casting. C) Die casting. D) Lost wax casting.

17. What is a key advantage of expendable pattern processes?. A) They require no mold. B) They allow non demoldable geometries. C) They produce the strongest parts. D) They eliminate the need for pouring systems.

18. What restricts the size of parts that can be cast in permanent molds?. A) The melting point of the metal. B) The cost and strength of the mold material. C) The type of pouring method. D) The cooling rate.

19. Why might a designer choose a slow cooling mold?. B) To reduce the cost of the mold. A) To obtain a more uniform grain structure. C) To increase production speed. D) To improve demolding.

20. What is a disadvantage of permanent mold casting regarding design flexibility?. A) It cannot produce smooth surfaces. B) It requires very high pouring temperatures. C) It is difficult to modify the geometry of the part. D) It cannot be automated.

21. Why is sand mold casting widely used?. A) It produces the highest precision. B) It uses simple and inexpensive molds. C) It requires no patterns. D) It only works for small parts.

22. What type of parts are typically produced with sand mold casting?. A) Very small parts only. D) Medium to large parts with medium complexity. C) Only hollow parts. B) Extremely high precision parts.

23. Which metals cannot be cast using sand molds?. A) Aluminum alloys. B) Magnesium alloys. C) Very high melting point alloys. D) Zinc alloys.

24. Why do sand cast parts usually have poor surface quality?. A) Because of the cooling rate. B) Because sand grains create a rough texture. C) Because the mold is too rigid. D) Because the metal reacts with the pattern.

25. What machining allowance is typically required for sand cast parts?. B) 0.1–0.5 mm. A) 1.5–6 mm. C) 10–20 mm. D) No allowance is needed.

26. What is a flask in sand casting?. A) A tool for compacting sand. D) A metal box that contains the mold. C) A container for molten metal. B) A type of sand additive.

27. What are the two halves of a sand mold called?. A) Top and bottom. B) Shell and core. C) Cope and drag. D) Gate and riser.

28. What is the purpose of cores in a sand mold?. A) To strengthen the mold. B) To create internal cavities in the casting. C) To improve surface finish. D) To increase mold permeability.

29. What are auxiliary elements used for?. A) To cool the mold. B) To generate parts of the gating system. C) To increase mold strength. D) To remove moisture from the sand.

30. What is the main difference between green sand and dry sand molds?. A) Green sand contains moisture. B) Dry sand is only used for small parts. C) Green sand cannot be compacted. D) Dry sand produces more gases.

31. What problem can moisture in green sand molds cause?. A) Excessive hardness. D) Gas formation that becomes trapped in the metal. C) Rapid cooling. B) Mold crystallization.

32. What type of sand is used to fill the molding box but not to form the cavity?. A) Contact sand. B) Core sand. C) Filler sand (coarse and rounded). D) Refractory sand.

33. What type of sand is used to form the cavity in contact with molten metal?. A) Coarse rounded sand. D) Fine angular sand. C) Wet sand only. B) Recycled sand.

34. Which sand property allows it to reproduce fine details of the pattern?. A) Permeability. B) Plasticity. C) Inertness. D) Collapsibility.

35. Which sand property prevents mold deformation under the weight of molten metal?. A) Cohesiveness. B) Permeability. C) Refractoriness. D) Inertness.

36. Which property allows gases to escape from the mold?. A) Plasticity. B) Collapsibility. C) Permeability. D) Cohesiveness.

37. Why must sand have collapsibility?. B) To improve surface finish. A) To allow the metal to contract without cracking the casting. C) To increase mold strength. D) To reduce machining time.

38. What is the purpose of match plate patterns?. A) To reduce mold cost. B) To simplify alignment of cope and drag. C) To eliminate the need for cores. D) To improve cooling rate.

39. Why must pattern plates and auxiliary elements have draft angles?. A) To increase mold permeability. D) To prevent erosion of mold walls during removal. C) To improve surface finish. B) To reduce sand consumption.

40. What happens after the metal solidifies in a sand mold?. A) The mold is reused. B) The mold is destroyed to extract the casting. C) The mold becomes a permanent mold. D) The mold is cooled and stored.

41. What type of parts are best suited for expendable mold and expendable pattern casting?. A) Very large parts with low detail. D) Small parts with high geometric detail. C) Only hollow parts. B) Parts requiring no surface finish.

42. What type of metals can be cast using lost wax or lost foam casting?. A) Only low melting point metals. B) Only ferrous metals. C) Medium to high melting point metals. D) Metals that cannot be melted.

43. What is a key advantage of these processes regarding part quality?. A) Very rough surface finish. B) High porosity. C) High dimensional and geometric accuracy. D) No need for patterns.

44. Why can productivity be increased by using a tree shaped assembly?. A) It reduces mold cost. B) It allows casting multiple parts in one run. C) It eliminates the gating system. D) It avoids the need for wax patterns.

45. In lost wax casting, how are wax gating elements attached to the pattern?. A) Using adhesives. B) By mechanical fastening. C) By heating to melt the surface and weld them. D) By cooling the wax.

46. Why might 3D printed polystyrene patterns be used in lost wax casting?. A) They improve cooling. B) They eliminate the need for molds. C) They are ideal for very short production series. D) They produce stronger castings.

47. What is the purpose of repeatedly dipping the wax pattern into refractory slurry?. A) To cool the wax. B) To create a thick, strong ceramic shell. C) To remove impurities. D) To increase wax flexibility.

48. Why are smaller particles used in the first slurry coating?. A) To reduce cost. B) To increase permeability. C) To improve surface finish. D) To speed up drying.

49. Why are cores usually unnecessary in lost wax casting?. B) The wax is too soft. A) The slurry coats internal cavities of the pattern. C) The mold cannot support cores. D) The metal solidifies too quickly.

50. What happens to the wax during the autoclave stage?. A) It crystallizes. B) It evaporates instantly. C) It melts and is recovered. D) It burns completely.

51. Why is the ceramic shell heated before pouring the metal?. A) To remove all moisture. D) To prevent premature solidification in thin areas. C) To increase mold permeability. B) To melt remaining wax.

52. In lost foam casting, what material is typically used for the pattern?. A) Wax. B) Clay. C) Expanded polystyrene (EPS). D) Aluminum.

53. How are EPS patterns joined together?. A) By heating. B) By welding. C) Using adhesives. D) By melting the surface.

54. Why is the coated EPS pattern placed inside a box filled with sand?. A) To improve surface finish. D) To increase the coating’s resistance to metal pressure. C) To reduce gas formation. B) To cool the metal faster.

55. What happens to the EPS pattern when molten metal is poured?. B) It melts and mixes with the metal. A) It vaporizes due to the heat. C) It remains inside the casting. D) It burns and leaves solid residues.

56. Why must the coating in lost foam casting be permeable?. A) To allow sand to enter. B) To let gases escape during pattern vaporization. C) To improve surface roughness. D) To reduce mold strength.

57. What is a major advantage of lost foam casting regarding mold design?. A) No gating system is needed. B) No parting lines or cores are required. C) The mold can be reused indefinitely. D) The metal cools more slowly.

58. What type of production volume can expendable mold and pattern processes handle?. A) Only mass production. B) Only single piece production. C) Any production volume. D) Only medium sized batches.

59. Why are permanent molds used to create patterns in long series production?. B) They reduce the melting temperature. A) They simplify and speed up pattern production. C) They eliminate the need for wax. D) They improve mold permeability.

60. How are wax pieces joined when assembling a tree for mass production?. A) Using screws. B) Using adhesives. C) By heating until the wax surface liquefies. D) By pressing them together mechanically.

61. What type of molds are used in permanent mold casting processes?. A) Sand molds. B) Ceramic molds. C) Molds made of alloys resistant to thermal fatigue. D) Wooden molds.

62. What is a key limitation of permanent mold casting?. B) It cannot produce small parts. A) It is only suitable for low to medium melting point alloys. C) It produces very rough surfaces. D) It requires no initial investment.

63. Why can’t most permanent molds be used for high melting point metals?. A) They react chemically with the metal. D) They soften and wear out at high temperatures. C) They cannot be machined. B) They cool the metal too quickly.

64. Which materials are commonly cast using permanent molds?. A) Tungsten alloys. B) Titanium alloys. C) Aluminum, magnesium, and zinc alloys. D) Stainless steels.

65. What is a typical advantage of permanent mold casting?. A) Very low surface quality. B) High porosity. C) Tight tolerances and good surface finish. D) Unlimited flexibility in geometry.

66. Why is flexibility limited in permanent mold casting?. A) The molds cannot be opened. B) The molds are destroyed after each use. D) A mold designed for one geometry is difficult to adapt to another. C) The metal solidifies too slowly.

67. Why must permanent molds be designed in two or more parts?. A) To reduce manufacturing cost. B) To allow the mold to be opened and the casting removed. C) To improve thermal conductivity. D) To reduce porosity.

68. What material is typically used to manufacture permanent molds?. A) Plastic. B) Sand. C) Special steels with high mechanical properties. D) Copper.

69. In die casting, what is the mold called?. C) Flask. B) Shell. A) Die. D) Pattern.

70. What is the purpose of guide/sliding systems in a die?. A) To cool the molten metal. B) To guide plates during opening/closing and ensure alignment. C) To increase porosity. D) To remove impurities from the metal.

71. What function do sliding pins serve in die casting?. A) They heat the mold. B) They replace the gating system. C) They create movable sections of the cavity. D) They inject the molten metal.

72. What is the purpose of vent systems in a die?. A) To cool the mold. B) To allow air to escape and prevent trapped bubbles. C) To increase mold strength. D) To lubricate the cavity.

73. Why are cooling systems necessary in die casting dies?. B) To melt the metal. A) To maintain a stable temperature and prevent overheating. C) To increase porosity. D) To reduce mold size.

74. What is the function of the ejection system?. A) To inject molten metal. B) To cool the die. C) To remove the solidified part from the die. D) To align the die plates.

75. Why are die casting dies often built from assembled plates?. A) To reduce the number of cavities. B) To simplify machining and reduce cost. C) To increase mold flexibility. D) To improve porosity.

76. What is the first phase of the die casting cycle?. A) Injection of molten metal. B) Application of release agents. C) Closing the die. D) Post pressure and cooling.

77. What is the purpose of release agents?. B) To increase mold temperature. A) To prevent the part from sticking and to lubricate the cavity. C) To accelerate solidification. D) To reduce metal melting point.

78. What happens during the injection phase?. A) The die is opened. B) Molten metal is injected under high pressure into the cavity. C) The part is ejected. D) The mold is cooled with water.

79. Why is post pressure applied after filling the die cavity?. A) To increase porosity. B) To prevent the die from opening. D) To compensate for metal contraction during solidification. C) To heat the metal further.

80. When is the part ejected from the die?. B) Immediately after injection. A) After the metal has solidified and cooled sufficiently. C) Before solidification. D) After the die is reheated.