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Ans: Draw back molding is a technique in which a portion of the mould is moved or withdrawn to allow easy removal of the pattern without damaging the mould cavity.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.
