FOUNDRY AND PATTERN MAKING

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• Q1: Define Molding.
  Ans: Molding is the process of preparing a hollow cavity (mould) in sand or other materials into which molten metal is poured to produce a casting of desired shape.
• Q2: What is a Cavity?
  Ans: A cavity is the hollow space inside the mould which is formed by the pattern and into which molten metal is poured to obtain the casting.
• Q3: State some Molding Techniques.
  Ans: Some of the molding techniques are as follows:

  • ➔ Bedding
  • ➔ Molding of loose piece pattern
  • ➔ Use of draw back
  • ➔ Use of two parting surfaces
  • ➔ Molding of three piece pattern
• Q4: Briefly explain Bedding in Molding.
  Ans: Bedding is a molding technique in which a part of the pattern is embedded in the molding sand to obtain proper alignment and support during mould preparation.
• Q5: Briefly explain Molding of Three Piece Pattern.
  Ans: In molding of a three piece pattern, the pattern is divided into three sections to make complex shapes easier to mold.
  Each part is removed separately to avoid damage to the mould cavity.
• Q6: Briefly explain Molding by the Use of Draw Backs.
  Ans: Draw back molding is a technique in which a portion of the mould is moved or withdrawn to allow easy removal of the pattern without damaging the mould cavity.
• Q7: Briefly explain Molding by the Use of Two Parting Surfaces.
  Ans: In this method, the mould is divided into two parting surfaces so that complex patterns can be easily removed in separate directions without breaking the mould.
• Q8: Briefly explain Molding of Loose Piece Pattern.
  Ans: In loose piece pattern molding, additional detachable pieces are attached to the main pattern.
  These pieces are removed separately before withdrawing the main pattern from the mould.
• Q9: Define Core.
  Ans: A core is a sand object placed inside a mould cavity to create hollow sections or internal holes in a casting.
• Q10: What is Core Making?
  Ans: Core making is the process of preparing cores using sand and binders to produce internal cavities in castings.
• Q11: What is a Self Core Pattern?
  Ans: A self core pattern is a pattern that automatically forms its own core during molding without using a separate core box.
• Q12: State the types of Cores.
  Ans: Types of cores:

  • ➔ Green sand core
  • ➔ Dry sand core
  • ➔ Balanced core
  • ➔ Hollow core
  • ➔ Solid core
  • ➔ Hanging core
  • ➔ Vertical core
  • ➔ Horizontal core
  • ➔ Cover core
  • ➔ Ram up core
  • ➔ Wing or chair core
  • ➔ Kiss core
• Q13: Briefly explain Green Sand Core.
  Ans: A green sand core is made from the same sand used in moulding and is used in a moist condition without baking.
• Q14: Briefly explain Dry Sand Core.
  Ans: A dry sand core is made from sand mixed with binders and then baked to increase strength and hardness before use.
• Q15: Briefly explain Balanced Core.
  Ans: A balanced core is supported at both ends inside the mould so that it remains stable during pouring of molten metal.
• Q16: Briefly explain Hollow Core.
  Ans: A hollow core is a core that is made hollow inside to reduce weight and improve gas ventilation during casting.
• Q17: Briefly explain Solid Core.
  Ans: A solid core is a completely filled sand core used to form internal cavities in castings.
• Q18: Briefly explain Hanging Core.
  Ans: A hanging core is supported from the top of the mould and remains suspended inside the cavity during casting.
• Q19: Briefly explain Vertical Core.
  Ans: A vertical core is placed in a vertical position inside the mould to form vertical holes or passages in the casting.
• Q20: Briefly explain Horizontal Core.
  Ans: A horizontal core is placed horizontally inside the mould to form horizontal cavities in the casting.
• Q21: Briefly explain Cover Core.
  Ans: A cover core is used to close or cover openings in the mould cavity during casting.
• Q22: Briefly explain Ram up Core.
  Ans: A ram up core is formed directly inside the mould cavity by ramming sand instead of preparing it separately.
• Q23: Briefly explain Wing or Chair Core.
  Ans: A wing or chair core is supported on special projections called chairs to maintain its position inside the mould.
• Q24: Briefly explain Kiss Core.
  Ans: A kiss core is a small core that just touches or “kisses” the mould surface to create minor internal features in casting.
• Q25: What are Core Boxes?
  Ans: Core boxes are wooden, metal, or plastic boxes used to prepare sand cores in the desired shape and size.
• Q26: State the types of Core Boxes.
  Ans: Types of core boxes:

  • ➔ Half core boxes
  • ➔ Split core boxes
  • ➔ Gang core boxes
  • ➔ Dump core boxes
  • ➔ Strickle core boxes
  • ➔ Loose piece core boxes
  • ➔ Right and left hand core boxes
• Q27: Briefly explain Half Core Boxes.
  Ans: Half core boxes are used to make one half of the core at a time, which is then joined with the other half.
• Q28: Briefly explain Split Core Boxes.
  Ans: Split core boxes are divided into two equal halves that can be opened and closed for easy removal of the core.
• Q29: Briefly explain Gang Core Boxes.
  Ans: Gang core boxes are used to produce multiple identical cores at the same time in a single operation.
• Q30: Briefly explain Dump Core Boxes.
  Ans: Dump core boxes are designed so that the prepared core can be easily removed by turning or dumping the box upside down.
• Q31: Briefly explain Strickle Core Boxes.
  Ans: Strickle core boxes use a template (strickle) to remove excess sand and form the correct shape of the core.
• Q32: Briefly explain Loose Piece Core Boxes.
  Ans: Loose piece core boxes contain removable parts that help in easy removal of complex shaped cores without damage.
• Q33: Briefly explain Right and Left Hand Core Boxes.
  Ans: Right and left hand core boxes are used to make symmetrical cores in two separate halves for accurate assembly.
• Q34: What is Core Sand and Binder?
  Ans: Core sand is a special type of sand used for making cores in casting, which helps to form internal cavities in the casting.
  Binder is a material added to core sand to give strength and bonding so that the core keeps its shape during handling and pouring of molten metal.
• Q35: State the properties of Core Sand.
  Ans: Properties of core sand:

  • ➔ High strength
  • ➔ Good permeability
  • ➔ High refractoriness
  • ➔ Good collapsibility
  • ➔ Smooth surface finish
• Q36: State the composition of Core Sand.
  Ans: Composition of core sand:

  • ➔ Silica sand
  • ➔ Binder (such as clay, oil, or resin)
  • ➔ Moisture (small amount)
  • ➔ Additives (for improving strength and finish)
• Q37: State the Characteristics of Core Sand.
  Ans: Characteristics of core sand:

  • ➔ It should maintain shape under heat and pressure
  • ➔ It should allow gases to pass easily
  • ➔ It should not break during handling
  • ➔ It should be easy to remove after casting
• Q38: What is Green Strength of Core Sand?
  Ans: Green strength is the ability of core sand to retain its shape and strength when it is in a moist (green) condition before drying or baking.
• Q39: What is Dry Strength of Core Sand?
  Ans: Dry strength is the ability of core sand to maintain its strength after it has been dried or baked and becomes hard.
• Q40: What is Refractoriness?
  Ans: Refractoriness is the ability of core sand to withstand very high temperatures without melting, deforming, or breaking down during pouring of molten metal.
• Q41: What is Core Baking?
  Ans: Core baking is the process of heating the prepared core in an oven to remove moisture and improve its strength and hardness before use in casting.
• Q42: What is Core Baking?
  Ans: Core baking is the process of heating a prepared sand core in an oven to remove moisture and to increase its strength, hardness, and durability before it is used in casting.
• Q43: Name the ovens used for Core Baking.
  Ans: The ovens used for core baking are:

  • ➔ Batch type oven
  • ➔ Continuous type oven
  • ➔ Dielectric oven
• Q44: State the stages of Core Baking.
  Ans: The stages of core baking are:

  • ➔ Preheating stage (removal of moisture slowly)
  • ➔ Heating stage (increase temperature gradually)
  • ➔ Soaking stage (maintain uniform temperature for proper hardening)
  • ➔ Cooling stage (core is cooled before removal from oven)
• Q45: Briefly explain Batch Type Oven.
  Ans: A batch type oven is a core baking oven in which a fixed number of cores are placed inside the oven at a time and baked together in a single batch.
  After baking is completed, the oven is unloaded and a new batch is loaded.
• Q46: Briefly explain Continuous Type Oven.
  Ans: A continuous type oven is a core baking oven in which cores are continuously moved through the oven on a conveyor system.
  The cores are baked while moving through different temperature zones.
• Q47: Briefly explain Dielectric Oven.
  Ans: A dielectric oven uses high-frequency electrical energy to heat and bake the core from inside.
  It provides fast and uniform heating, making it suitable for mass production of cores.