Metal casting

Furqan Hameed11013386-031

Bilal Abdul Mateen 11013386-036

Farhan Ghos Butt11013386-014

Ibrar Hussain11013386-040

Muhammad Furqan 11013386-045Group no.7Metal Casting Process3History Definition of castingBasic featuresTypes of mouldsCategories of casting processFurther classification of Expendable and Permanent mould casting

Objective

It is oldest manufacturing process.

Castingis amanufacturingprocess by which a liquid material is usually poured into amold, which contains a hollow cavity of the desired shape, and then allowed to solidify.

The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process.Casting process Casting process Casting materials are usually metals.Almost all metals can be cast.

Casting is most often used for making complex shapes that would be otherwise difficult to make by other methods.

Pattern: A pattern is made of wood or metal, is a replica of the final product and is used for preparing mould cavityRiser: A column of metal placed in the mold to feed the casting as it shrinks and solidifies. Also known as a "feed head." Runner: The channel through which the molten metal is carried from the sprue to the gate.Cores: A separated part of the mold, made of sand and generally baked, which is used to create openings and various shaped cavities in the casting. Gate: A channel through which the molten metal enters the casting cavity.

Basic FeaturesParting Line: Joint where mold separates to permit removal of the pattern and which shows how and where to open the mold.Sand: A sand which binds strongly without losing its permeability to air or gases.Chaplet: A metal support used to hold a core in place in a mold. Not used when a core print will serve.Binders: Materials used to hold molding sand together.Pouring basin: Filling the mold with molten metal. Shrinkage: The decrease in volume when molten metal solidifies.Mould: The mould contains a cavity whose geometry determines the shape of cast part.Mould material should posses refractory characteristics and with stand the pouring temperature

The various casting processes are classified according to these different moulds

open mould closed mouldTypes of moulds Open mould in which the liquid metal is simply poured until it fills the open cavity. (fig. a)

Closed mould the closed mold is provided to permit the molten metal to flow from outside the mold cavity. (fig. b) the closed mold is more important categories in production casting operation.

Types of moulds

Open and Closed MouldCasting process video:Casting process divide onto two broad categories according to types of mold used;

Expandable mould castingPermanent mould castingCategories of casting processExpandable mould means that : the mold in which the molten metal is solidifies must be break or destroyed to remove the casting.OrAfter solidification of molten metal the mold is break to remove the desired casting. (sand casting)

Expandable mould materials: the mold are made out of sand, plaster, and similar materials.

Expandable mould casting

Classification of casting processesExpandable mold casting

SAND CASTING

Expandable mold casting:1.permanent pattern:

Common features

Schematic illustration of sand casting showing various features.AdvantagesDisadvantagesRecommended ApplicationSand CastingLeast Expensive in small quantities (less than 100)

Ferrous and non - ferrous metals may be cast

Possible to cast very large parts.

Least expensive toolingDimensional accuracy inferior to other processes, requires larger tolerances

Castings usually exceed calculated weight

Surface finish of ferrous castings usually exceeds 125 RMSUse when strength/weight ratio permits

Tolerances, surface finish and low machining cost does not warrant a more expensive processSand casting process video:INVESTMENT CASTING:

Use gravity to fill the mold.Mold is destroyed to remove castingMetal flow is slowWalls are much thicker than in die casting.Cycle time is longer than die casting because of inability of mold material to remove heat.The investment casting process uses expendable patterns made of investment casting wax.

Expandable mold casting:Expendable pattern:

Investment CastingAdvantagesDisadvantagesRecommended ApplicationClose dimensional tolerance

Complex shape, fine detail, intricate core sections and thin walls are possible

Ferrous and non-ferrous metals may be cast

As-Cast" finish (64 - 125 RMS)Costs are higher than Sand, Permanent Mold or Plaster process CastingsUse when Complexity precludes use of Sand or Permanent Mold Castings

The process cost is justified through savings in machining or brazing

Weight savings justifies increased costInvestment casting video:Permanent mold casting In permanent mold casting, the mold is reused many times.

The molds are commonly made of steel or cast iron.

The Metals commonly cast in the permanent mold casting include aluminum, magnesium and copper- based alloys( brass , bronze)

Permanent mold casting

Types permanent mold castingTwo basic two types of permanent mold casting as under

Die casting Centrifugal casting

Die casting:Die casting is permanent-mold casting process in which the molten metal is injected into mold cavity under high pressure. The pressure is maintained during solidification, after which the mold is opened and part is removed.Typical pressures are 7 to 350 MPa.The molds used in this casting operation is called dies; hence the name die casting

Die casting:Two types of die casting machines that as under

Hot chamber die casting Cold chamber die casting

Die casting machines:Die casting video:In hot chamber die- casting machines, the molten metal is poured into a heated chamber from an external melting container, and piston is used to inject the molten metal under a high pressure into die cavity.Typically injection pressures are 7 to 35 mpa.This process only used for the low-melting-point metals.(zinc,tin ,lead and, sometimes magnesium)

Hot chamber die casting:In which the molten metal poured into an unheated chamber, and piston is used to inject the liquid metal under a high pressures into the die cavity Injection pressures used in these machine are typically 14 to 140 mpa.

Cold chamber die-casting :In centrifugal casting the mold is rotated at high speed so that the centrifugal force is produced that distributes the molten metal to the outer regions of the cavity.Examples of parts made by this process include pipes, tubes bushing and rings.

Centrifugal casting:

Centifugal casting video:High production rates possible.Close tolerance is possible for small parts.Good surface finish.Thin sections are possible.Rapid solidification.

Advantages of permanent mold casting Only used for low melting point metals.More intricate shapes are not achieved Mold is expensive.

Note:(More intricate shapes are not achieved by the permanent mold casting)

Limitation of permanent mold castingFor any Metal Casting Process, selection of right alloy, size, shape, thickness, tolerance, texture, and weight, is very vital. Views of the Tooling Designer; Foundry / Machine House needs, customer's exact product requirements, and secondary operations like painting, must be taken care of before selecting the appropriate Metal Casting Process. Tool cost. Economics of machining versus process costs. Adequate protection / packaging, shipping constraints, regulations of the final components, weights and shelf life of protective coatings also play their part in the Metal Casting process.

Selecting the Right Metal Casting Processthanks

ANY QUESTION?