Casting process viva questions and answers

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Casting process viva questions and answers

Q: What is casting?

A: Casting is a manufacturing process in which a liquid material is poured into a mold cavity and allowed to solidify, taking the shape of the cavity. This process is commonly used to create complex parts with a high level of accuracy and repeatability.

Q: What are the types of casting processes?

A: There are many types of casting processes, including sand casting, investment casting, die casting, centrifugal casting, and continuous casting.

Q: What is sand casting?

A: Sand casting is a process in which a mold is made from a mixture of sand and a binder, and then molten metal is poured into the mold. After the metal has solidified, the sand is removed from the casting.

Q: What is investment casting?

A: Investment casting, also known as lost-wax casting, is a process in which a wax pattern is coated with a ceramic material and then the wax is melted out, leaving a cavity that is filled with molten metal. After the metal has solidified, the ceramic material is removed from the casting.

Q: What is die casting?

A: Die casting is a process in which molten metal is forced into a mold cavity under high pressure. The mold is typically made of two halves, and the metal is injected into the cavity through a gate. After the metal has solidified, the two halves of the mold are separated and the casting is removed.

Q: What is centrifugal casting?

A: Centrifugal casting is a process in which molten metal is poured into a spinning mold. The centrifugal force generated by the spinning mold distributes the metal evenly, creating a casting with a fine grain structure.

Q: What is continuous casting?

A: Continuous casting is a process in which molten metal is poured into a water-cooled mold, which solidifies the metal into a continuous strand. The strand is then cut into the desired lengths.

Q: What are the advantages of casting?

A: Casting offers several advantages, including the ability to create complex parts with a high level of accuracy and repeatability, the ability to use a wide range of materials, and the ability to produce large quantities of parts quickly and cost-effectively.

Q: What are the disadvantages of casting?

A: The disadvantages of casting include the need for a mold, which can be expensive and time-consuming to make, the potential for defects in the casting, and the need for post-casting processing such as machining and finishing.

Q: What are some of the factors that affect casting quality?

A: Factors that affect casting quality include the design of the mold, the properties of the material being cast, the temperature and pressure of the casting process, and the skill and experience of the casting operator.

Q: What are some of the common materials used in casting?

A: Common materials used in casting include iron, steel, aluminum, copper, brass, and various alloys.

Q: What is the purpose of a mold release agent?

A: A mold release agent is used to prevent the casting from sticking to the mold. It also helps to improve the surface finish of the casting.

Q: What is the difference between a permanent mold and a disposable mold?

A: A permanent mold is made of metal and is designed to be used multiple times, while a disposable mold is made of a material such as sand or plaster and is used only once.

Q: What is the difference between an open mold and a closed mold?

A: An open mold has a single cavity that is open to the atmosphere, while a closed mold has multiple cavities that are enclosed within the mold.

Q: What is the purpose of gating and risering in casting?

A: Gating and risering are used to control the flow of molten metal into the mold and to help prevent defects such as shrinkage and porosity in the casting.

Q: What is the difference between gravity casting and pressure casting?

A: Gravity casting relies on gravity to fill the mold with molten metal, while pressure casting uses a pressure difference to force the metal into the mold.

Q: What is the difference between hot-chamber and cold-chamber die casting?

A: Hot-chamber die casting is used for metals with low melting points, such as zinc and magnesium, while cold-chamber die casting is used for metals with higher melting points, such as aluminum and copper.

Q: What is the difference between investment casting and sand casting?

A: Investment casting is a more precise process than sand casting and is typically used for smaller, more complex parts. Sand casting is used for larger, less complex parts.

Q: What is the difference between green sand and dry sand casting?

A: Green sand casting uses a wet sand mixture that is compacted around the pattern, while dry sand casting uses a dry sand mixture that is compacted around the pattern.

Q: What is the difference between single-use and multiple-use molds?

A: Single-use molds are used once and then discarded, while multiple-use molds can be used multiple times. Multiple-use molds are typically made of metal and are more expensive than single-use molds.

Q: What are some of the safety precautions that should be taken during casting?

A: Safety precautions during casting include wearing protective clothing and equipment, using proper ventilation, and following proper procedures for handling and disposing of materials.

Q: What is porosity in casting?

A: Porosity is a defect in casting where small voids or bubbles are present in the casting, which can weaken the structure of the part.

Q: What is the purpose of heat treatment in casting?

A: Heat treatment is used to modify the properties of the casting by altering its microstructure, such as increasing its hardness, strength, or toughness.

Q: What is a gating system in casting?

A: A gating system is a network of channels, gates, and risers that control the flow of molten metal into the mold during casting.

Q: What is sand conditioning in casting?

A: Sand conditioning is the process of adding additives to the sand mixture used in sand casting to improve its properties, such as its strength, permeability, and collapsibility.

Q: What is a core in casting?

A: A core is a separate mold component that is used to create internal cavities or features in a casting, such as holes or passages.

Q: What is a pattern in casting?

A: A pattern is a replica of the part being cast, which is used to create the mold. It is typically made of wood, metal, or plastic.

Q: What is a parting line in casting?

A: A parting line is the line where the two halves of the mold meet, which separates the mold into two parts.

Q: What is a gating system in casting?

A: A gating system is a network of channels, gates, and risers that control the flow of molten metal into the mold during casting.

Q: What is fettling in casting?

A: Fettling is the process of removing excess material or imperfections from a casting using grinding, cutting, or other methods.

Q: What is the difference between a mold and a pattern?

A: A pattern is a replica of the part being cast, which is used to create the mold. The mold is the cavity created by the pattern and is used to cast the part.

Q: What is the difference between investment casting and lost foam casting?

A: Investment casting involves creating a mold from a wax pattern that is coated in a ceramic shell, while lost foam casting involves creating a mold from a foam pattern that is vaporized during the casting process.

Q: What is the difference between sand casting and die casting?

A: Sand casting uses a mold made of sand and a pattern, while die casting uses a mold made of metal and is typically used for higher production volumes and more complex parts.

Q: What is the difference between centrifugal casting and static casting?

A: Centrifugal casting involves rotating the mold during casting to distribute the molten metal evenly, while static casting involves pouring the molten metal into the mold without any rotation.

Q: What is the purpose of a parting compound in casting?

A: A parting compound is used to prevent the mold from sticking to the pattern, allowing for easier removal of the pattern and reducing the risk of damage to the mold.

Q: What is draft in casting?

A: Draft is the taper or angle applied to the walls of the mold to allow for easier removal of the casting from the mold.

Q: What is flashing in casting?

A: Flashing is excess material that forms at the parting line of the mold due to misalignment or excess pressure during casting.

Q: What is a sprue in casting?

A: A sprue is the channel that allows molten metal to flow from the gating system into the mold cavity.

Q: What is a runner in casting?

A: A runner is a channel that connects the sprue to the individual cavities in the mold, allowing for proper distribution of molten metal.

Q: What is a riser in casting?

A: A riser is a reservoir of molten metal that feeds the casting as it cools and solidifies, compensating for any shrinkage or porosity in the part.

Q: What is the difference between green sand casting and dry sand casting?

A: Green sand casting uses a sand mold that is moistened with water and bentonite clay, while dry sand casting uses a sand mold that is dried and hardened using a chemical binder.

Q: What is the purpose of a chaplet in casting?

A: A chaplet is a metal support that is used to hold a core in place within the mold during casting.

Q: What is the difference between single-use molds and reusable molds?

A: Single-use molds are used for one casting only and are typically made of materials like sand or plaster, while reusable molds are made of materials like metal or ceramic and can be used for multiple castings.

Q: What is a parting surface in casting?

A: A parting surface is the surface where the two halves of the mold meet, which separates the mold into two parts.

Q: What is the difference between investment casting and sand casting?

A: Investment casting uses a wax pattern and a ceramic shell mold, while sand casting uses a pattern made of wood, metal, or plastic and a sand mold.

Q: What is a draft angle in casting?

A: A draft angle is the angle applied to the walls of the mold to allow for easier removal of the casting from the mold.

Q: What is a filter in casting?

A: A filter is a device used to remove impurities and contaminants from the molten metal as it is poured into the mold.

Q: What is a pattern allowance in casting?

A: Pattern allowance is the amount of additional material added to the pattern to compensate for shrinkage during solidification and machining of the final part.

Q: What is a mold release agent in casting?

A: A mold release agent is a material applied to the pattern or mold to prevent the mold from sticking to the pattern and to facilitate the release of the casting from the mold.

Q: What is a core in casting?

A: A core is a pre-formed sand or metal shape that is placed within the mold to create hollow or internal features in the casting.

Q: What is the difference between pressure die casting and gravity die casting?

A: Pressure die casting uses a high-pressure injection of molten metal into a die, while gravity die casting relies on gravity to fill the die with molten metal.

Q: What is a pattern in casting?

A: A pattern is a replica of the final part that is used to create the mold.

Q: What is a gating system in casting?

A: A gating system is the network of channels and cavities that are used to deliver molten metal from the sprue to the mold cavity.

Q: What is a pattern plate in casting?

A: A pattern plate is a flat plate used to support and secure the pattern during molding.

Q: What is a sand mold in casting?

A: A sand mold is a mold made of sand and a pattern, which is used to cast metal parts.

Q: What is a sprue cutter in casting?

A: A sprue cutter is a tool used to remove the sprue from the casting after it has solidified.

Q: What is the difference between hot chamber and cold chamber die casting?

A: Hot chamber die casting uses a molten metal injection system that is contained within the die, while cold chamber die casting uses an external molten metal injection system.

Q: What is a mold in casting?

A: A mold is a container used to shape molten metal into a desired form during the casting process.

Q: What is a gating and risering system in casting?

A: A gating and risering system refers to the network of channels and cavities that are used to deliver molten metal to the mold cavity and to compensate for any shrinkage or porosity in the part.

Q: What is shrinkage in casting?

A: Shrinkage in casting refers to the reduction in size of the casting as it cools and solidifies.

Q: What is the difference between sand casting and investment casting?

A: Sand casting uses a sand mold and a pattern made of wood, metal, or plastic, while investment casting uses a wax pattern and a ceramic shell mold.

Q: What is gating efficiency in casting?

A: Gating efficiency in casting refers to the ability of the gating system to deliver molten metal to the mold cavity with minimal turbulence and entrainment of air or other contaminants.

Q: What is a parting line in casting?

A: A parting line is the visible line on the surface of the casting where the two halves of the mold meet.

Q: What is a mold cavity in casting?

A: A mold cavity is the space within the mold where the molten metal is poured to create the casting.

Q: What is sand core in casting?

A: Sand core is a pre-formed sand shape used to create internal features in the casting, such as holes or hollow sections.

Q: What is an ingate in casting?

A: An ingate is a channel in the mold that delivers molten metal from the runner to the mold cavity.

Q: What is gating balance in casting?

A: Gating balance in casting refers to the even distribution of molten metal throughout the mold cavity to ensure uniformity in the final casting.

Q: What is an ejector pin in casting?

A: An ejector pin is a mechanical device used to push the casting out of the mold cavity after it has solidified.

Q: What is a mold box in casting?

A: A mold box is a container used to hold the molding material and pattern during the molding process.

Q: What is a core print in casting?

A: A core print is a projection on the pattern that creates a space in the sand mold for the core to fit.

Q: What is a draft angle in casting?

A: A draft angle is the angle between the vertical axis of the casting and the surface of the mold, which allows for easier removal of the casting from the mold.

Q: What is a match plate in casting?

A: A match plate is a two-sided pattern plate used to create two halves of a mold simultaneously.

Q: What is backdraft in casting?

A: Backdraft is a type of undercut in the casting that causes difficulty in removing it from the mold.

Q: What is a gating system design in casting?

A: Gating system design in casting is the process of designing the optimal layout and dimensions of the gating system to ensure uniform filling of the mold cavity and minimize defects in the final casting.

Q: What is a chiller in casting?

A: A chiller is a device used to cool the molten metal and reduce the temperature in the mold during the casting process.

Q: What is a parting powder in casting?

A: A parting powder is a substance, such as graphite or talc, applied to the pattern to prevent it from sticking to the mold material.

Q: What is shell molding in casting?

A: Shell molding is a casting process in which a thin shell of sand and thermosetting resin is used to create a mold cavity.

Q: What is a gating ratio in casting?

A: A gating ratio is the relationship between the cross-sectional area of the ingate and the total cross-sectional area of the runner system, which affects the filling rate and quality of the casting.

Q: What is a vacuum casting process?

A: Vacuum casting is a process in which molten metal is poured into a mold under vacuum, which reduces porosity and improves the quality of the casting.

Q: What is a lost foam casting process?

A: Lost foam casting is a process in which a pattern made of expanded polystyrene foam is coated with a refractory material, and then the foam is vaporized during pouring of the molten metal, creating the mold cavity.

Q: What is a green sand casting process?

A: Green sand casting is a process in which a mixture of sand, clay, and water is used to create a mold that is reusable and allows for easy removal of the casting.

Q: What is a permanent mold casting process?

A: Permanent mold casting is a process in which a metal mold is used to create multiple castings, which allows for higher production rates and improved consistency.

 

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