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What process is defined as a manufacturing method where a liquid material is poured into a mold to solidify into a predetermined shape?

Casting

Casting is limited to the production of small components.

False

What are the two primary classifications of casting processes based on the nature of the mold?

Sand casting and investment casting

Permanent mold casting and expendable mold casting (correct)

Gravity casting and pressure casting

Centrifugal casting and die casting

Which of these processes involves creating a mold that must be destroyed to remove the casting?

Expendable mold casting Signup and view all the answers

Which of the following materials could be used for an expendable mold?

Plaster Signup and view all the answers

What type of mold is typically made from metal and reusable for multiple castings?

Permanent mold Signup and view all the answers

Which of these casting processes is known for its high accuracy and mass production capability?

Die casting Signup and view all the answers

What type of casting involves pouring molten metal into a rotating mold?

Centrifugal casting Signup and view all the answers

What type of casting is traditionally known as sand molded casting?

Sand casting Signup and view all the answers

Which of these casting types is known as 'lost-wax casting'?

Investment casting Signup and view all the answers

The casting process always produces castings with high dimensional accuracy.

False Signup and view all the answers

What is a significant advantage of the casting process?

All of the above Signup and view all the answers

What is a potential disadvantage of the casting process?

High potential for defects Signup and view all the answers

What is typically used in metal casting to compensate for metal shrinkage during the cooling process?

Shrinkage allowance Signup and view all the answers

What is the purpose of draft or taper allowance in casting?

To facilitate the removal of the pattern from the mold without damaging the mold surfaces. Signup and view all the answers

What allowance is needed for castings that require further machining?

Machining or finish allowance. Signup and view all the answers

What is the purpose of a riser in sand casting?

To compensate for metal shrinkage during solidification and prevent defects. Signup and view all the answers

What is a flask in sand casting?

A metal or wooden frame that holds the mold. Signup and view all the answers

What is the upper half of the mold called?

Cope Signup and view all the answers

What is the bottom half of the mold called?

Drag. Signup and view all the answers

What is the hollow mold area where metal solidifies called?

Mold cavity Signup and view all the answers

What is a pattern in sand casting?

A replica of the final object to be made, used to create the mold cavity. Signup and view all the answers

The pouring cup in sand casting is responsible for:

Holding the molten metal before pouring Signup and view all the answers

What are runners in sand casting?

Channels that carry molten metal from the sprue towards the gate, which directs metal into the mold cavity. Signup and view all the answers

What is a common type of sand used in casting?

Quartz sand Signup and view all the answers

Sand used in casting should be highly porous to prevent air bubbles from forming in the casting.

False Signup and view all the answers

Which of these is NOT considered a common type of pattern used in sand casting?

Core pattern Signup and view all the answers

What is a common cause of misrun defects in casting?

High viscosity of the molten metal or absence of a riser. Signup and view all the answers

What kind of defect is caused by gases trapped in the molten metal, leading to a cavity?

Blow holes. Signup and view all the answers

What is a possible cause of a shift defect in a casting?

Misplaced core or misalignment of the mold halves. Signup and view all the answers

What casting defect involves the presence of foreign materials in the casting, such as slag?

Inclusion. Signup and view all the answers

What is a shrinkage cavity in a casting?

A void or depression caused by the contraction of the metal as it cools, indicating insufficient metal to fill the mold completely. Signup and view all the answers

What are hot tears in a casting?

Internal or external cracks often caused by localized stresses during the final stages of solidification. Signup and view all the answers

What is a swell defect in a casting?

An enlargement of the mold cavity caused by excessive metal pressure during pouring. Signup and view all the answers

Signup and view all the answers

Study Notes

Production Technology: Casting Technology

Casting is a manufacturing process where liquid material is poured into a mold with a hollow cavity of the desired shape. The liquid material solidifies, forming a casting that is removed from the mold.
Topics covered in this presentation include: casting process definition, classifications and types of casting processes, casting advantages and disadvantages, sand casting process, and casting defects.

Casting Process Definition

Casting is a manufacturing method involving pouring liquid material into a mold containing a hollow cavity.
The liquid solidifies, creating a casting.
The casting is then removed from the mold.

Casting Products

Examples of casting products shown include various gears, pump components, and engine parts.

Classifications and Types of Casting Processes

Casting processes are categorized based on the mold's nature.
Expendable mold castings use molds that are destroyed after the casting is removed (e.g., sand casting).
Mold materials: sand, wax, plaster
Binders are also included in expandable mold materials.
Permanent mold castings use molds that are reusable (e.g., die casting).
Mold materials: metal or, less commonly, a ceramic refractory material

Types of Casting Processes

Die casting: A metal casting process that forces molten metal under high pressure into a mold cavity. This process uses hardened tool steel dies and is used for mass production of highly accurate, well-finished parts.
Investment casting: An older manufacturing process pouring molten metal into an expendable ceramic mold. A wax pattern forms the mold, and ceramic slurry hardens the mold. This process can also be referred to as "lost-wax" casting.
Centrifugal casting: Molten metal is poured into rotating permanent molds. Centrifugal force throws the metal outward, solidifying against the mold walls.
Sand casting: A metal casting process using sand as the mold material. Molten metal is poured into a pre-formed sand cavity (the mold). The metal solidifies, and the sand mold is broken apart to retrieve the casting.

Sand Casting Terminology

Flask: A metal or wooden frame used to form the mold halves.
Cope: The upper half of the mold flask.
Drag: The bottom half of the mold flask.
Mold: The flask, sand, and gating system together.
Gating system: A set of channels (pouring cup, sprue, runners, gate) delivering molten metal to the mold cavity and channels for air and gas removal.
Riser: A column of molten metal placed in the mold to compensate for shrinkage
Core: A separate component of the mold, typically made of sand, to create specific shapes/cavities within the casting.
Mold cavity: The hollow area in the mold where the metal solidifies.
Pattern: A replica of the final object created to form the mold cavity.

Steps of Sand Casting

Patternmaking: Creating a replica of the desired casting using materials like wood, metal, or wax.
Core making: Creating a separate part of the mold (core) that defines the internal cavities of the casting.
Molding: Preparing the sand mold around the pattern (and core).
Melting and pouring: Melting the metal before pouring it into the mold.
Cleaning and fettling: Removing sand, excess metal, and other unwanted parts from the casting.
Inspection and tests: Inspecting and testing the casting to ensure quality.

Pattern Allowances

Shrinkage allowance: The design increase added to the pattern to compensate for the contraction of the metal during cooling.
Draft (or taper) allowance: The angle added to the pattern's vertical faces to facilitate its removal from the sand mold without tearing the mold surfaces.
Machining Allowance: Extra metal on the casting surface needed for machining the casting to the necessary dimensions.
Distortion (or camber) allowance: A compensatory allowance to the pattern to compensate for warpage/distortion of the casting during cooling.

Casting Defects

Blow holes: Cavities in the casting caused by gases.
Shifts: External casting defects due to core misplacement or mold mismatching.
Inclusion: Contamination of the casting by external materials (e.g., slag).
Misrun: The molten metal not completely filling the mold cavity, potentially due to high viscosity or missing/small risers.
Shrinkage cavity: A void or depression in the casting due to contraction during cooling.
Hot tears: Internal or external cracks caused by contraction stresses when the metal is cooling and relatively weak.
Swell: Enlargement of the mold cavity due to insufficient ramming of the sand or rapid pouring of molten metal.

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