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Manufacturing Process > Week 5 > Flashcards

Week 5 Flashcards

1
Q

What is the function of chaplets in sand casting?

A

Chaplets are used to support the core and hold it in position within the mold cavity during pouring.

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2
Q

Chaplets are used to support the core and hold it in position within the mold cavity during pouring.

A

The buoyancy force is caused by the difference between the weight of the displaced molten metal (Wm) and the weight of the core (Wc).

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3
Q

What is the formula for calculating buoyancy force in casting?

A

Fb = Wm - Wc , where Fb is the buoyancy force, Wm is the weight of the molten metal displaced, and Wc is the weight of the core.

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4
Q

Why is collapsibility an important property of mold materials

A

Collapsibility allows the mold to give way and accommodate the shrinkage of the casting as it solidifies, preventing cracks

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5
Q

What type of metal casting process allows for higher production rates?

A

Permanent mold casting allows for higher production rates because the mold can be reused for multiple castings.

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6
Q

Permanent mold casting allows for higher production rates because the mold can be reused for multiple castings.

A

A closed mold is used when the geometry of the casting is complex and requires a gating system to lead molten metal into the mold cavity.

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7
Q

What is the purpose of a gating system in closed molds?

A

The gating system directs the molten metal into the mold cavity, ensuring it fills the mold properly

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8
Q

The gating system directs the molten metal into the mold cavity, ensuring it fills the mold properly

A

Thermal stability prevents the mold from cracking when it comes into contact with the hot molten metal.

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9
Q

What is the significance of thermal stability in mold materials?

A

Thermal stability prevents the mold from cracking when it comes into contact with the hot molten metal.

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10
Q

Thermal stability prevents the mold from cracking when it comes into contact with the hot molten metal.

A

Most alloys solidify over a range of temperatures, unlike pure metals which solidify at a single, constant temperature.

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11
Q

What is an open mold used for in casting?

A

An open mold is used for simple castings where the mold is just a container in the shape of the desired part.

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12
Q

What are the two main forms of metal casting molds?

A

The two forms are open molds and closed molds.

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13
Q

What is the advantage of using a sand mold in casting?

A

Sand molds are highly versatile and can be used to create complex shapes in expendable mold processes.

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14
Q

What is the main disadvantage of expendable mold processes?

A

The production rates are often limited by the time it takes to create the mold rather than the casting itself.

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15
Q

Why is strength an important property for mold materials?

A

Strength ensures that the mold can maintain its shape and resist erosion during the casting process.

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16
Q

What is the role of the cope and drag in sand casting?

A

The cope is the upper half, and the drag is the lower half of the mold. Together they form the mold cavity where the molten metal is poured

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17
Q

What are the basic steps involved in metal casting?

A

Melt the metal, pour it into a mold, and let it solidify.

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18
Q

What is the main difference between expendable and permanent mold processes?

A

Expendable molds are destroyed after each casting, while permanent molds can be reused multiple times.

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19
Q

What are the advantages of expendable mold processes?

A

They allow for more complex shapes but are limited by the time needed to make the mold.

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20
Q

What are the two halves of a sand casting mold called?

A

The cope (upper half) and the drag (lower half).

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21
Q

What is a core in sand casting?

A

A core is a full-scale model of the internal surfaces of the part, inserted into the mold to form internal cavities.

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22
Q

What are the five desirable properties of molds?

A

Strength, permeability, thermal stability, collapsibility, and reusability.

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23
Q

What is Chvorinov’s Rule used for?

A

It is used to calculate the total solidification time (TST) of a casting.

24
Q

How do pure metals and alloys differ in their solidification process?

A

Pure metals solidify at a constant temperature, while alloys solidify over a range of temperatures.

25
Q

What is the formula for Chvorinov’s Rule?

A

TST = Cm (V/A)^2 , where V is the volume, A is the surface area, and Cm is the mold constant.

26
Q

Why is permeability important in mold design?

A

It allows hot air and gases to pass through the voids in the sand, preventing defects.

27
Q

What is the goal of directional solidification in casting?

A

To ensure freezing occurs in a controlled manner, starting at areas with lower V/A ratios, allowing molten metal to remain available for the rest of the casting.

28
Q

What are some expendable mold casting processes?

A

Shell molding, vacuum molding, expanded polystyrene process, and investment casting.

29
Q

What is shell molding?

A

A casting process where a thin shell of sand is held together by a thermosetting resin binder.

30
Q

How does vacuum molding differ from traditional molding?

A

It uses vacuum pressure to hold the sand mold together instead of a chemical binder.

31
Q

What happens to the polystyrene pattern in the expanded polystyrene process?

A

It vaporizes when molten metal is poured into the mold.

32
Q

It vaporizes when molten metal is poured into the mold.

A

The lost wax process.

33
Q

What is an advantage of permanent mold casting?

A

The mold can be reused multiple times, making it suitable for high-volume production.

34
Q

What are the two main types of die casting machines?

A

Hot-chamber and cold-chamber machines.

35
Q

In centrifugal casting, what is the key factor for feasibility?

A

The G-factor (GF), which must be at least 60 for the operation to be feasible.

36
Q

What are the steps involved after the solidification of a casting?

A

Trimming, core removal, surface cleaning, inspection, repair (if necessary), and heat treatment.

37
Q

Name two common quality issues in casting.

A

Misruns and cold shuts

38
Q

What are important product design considerations in casting?

A

Geometric simplicity, appropriate corner designs, draft angles, and machining allowances.

39
Q

What is the purpose of directional solidification in casting?

A

Directional solidification ensures that the molten metal remains fluid in key areas while other parts freeze, allowing for controlled and defect-free casting.

40
Q

What is a “chill” in casting?

A

A chill is a heat sink, either internal or external, used to cause rapid solidification in specific regions of a casting

41
Q

Name two types of expendable mold casting processes.

A

Shell molding and investment casting (lost wax process).

42
Q

What is shell molding?

A

Shell molding is a casting process where a thin shell of sand, held together by a thermosetting resin, forms the mold.

43
Q

What is vacuum molding?

A

Vacuum molding uses a vacuum to hold the sand mold together rather than a chemical binder.

44
Q

What is the expanded polystyrene process in casting?

A

It is a casting process where a sand mold is packed around a polystyrene foam pattern that vaporizes when molten metal is poured into the mold.

45
Q

What is investment casting also known as?

A

The lost wax process.

46
Q

What materials are commonly cast in permanent mold casting?

A

Aluminum, magnesium, copper-based alloys, and cast iron.

47
Q

What is the main advantage of permanent mold casting?

A

The mold can be reused multiple times, making it ideal for high-volume production.

48
Q

What is the principle behind centrifugal casting?

A

Molten metal is distributed by centrifugal force, creating tubular or cylindrical parts.

49
Q

What is the G-factor in centrifugal casting?

A

The G-factor is a measure of the centrifugal force applied, and it must be at least 60 for the operation to be feasible.

50
Q

What is the G-factor in centrifugal casting?

A

The G-factor is a measure of the centrifugal force applied, and it must be at least 60 for the operation to be feasible.

51
Q

What are the main types of furnaces used in casting processes?

A

Cupolas, direct fuel-fired furnaces, crucible furnaces, electric-arc furnaces, and induction furnaces.

52
Q

What are some additional steps after casting solidification?

A

Trimming, core removal, surface cleaning, inspection, repair (if needed), and heat treatment.

53
Q

Name a common casting defect.

A

Misruns or cold shuts.

54
Q

What is the purpose of draft angles in casting design?

A

Draft angles facilitate the removal of the part from the mold in expendable or permanent mold casting processes.

55
Q

What is the purpose of draft angles in casting design?

A

Draft angles facilitate the removal of the part from the mold in expendable or permanent mold casting processes.

56
Q

What does the term “machining allowance” refer to in casting?

A

It is the extra material left on the casting to be machined off to achieve the final dimensions and surface finish.

57
Q

What is a semi-centrifugal casting used for?

A

It uses centrifugal force to produce solid parts like wheels and pulleys, rather than hollow tubular shapes.

Manufacturing Process (11 decks)

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