This experiment utilized Plaster of Paris in making the mold and polymer resin in casting through thermosetting. The quality of the mold and casted product were observed after and from observations it was determined that the quality of cast product not on

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SIGNIFICANCE OF THE QUALITY OF MOLD TO THE CAST PRODUCT

Abstract

Gravity casting is a process wherein the liquid metal is poured into molds without application of any external pressure. The liquid metal enters the cavity by gravity. This experiment utilized Plaster of Paris in making the mold and polymer resin in casting through thermosetting. The quality of the mold and casted product were observed after and from observations it was determined that the quality of cast product not only depends on the raw material to be used but also on the quality of the mold. Obtained porosity volume of the mold contributed to gas defects as seen in the micrographs.

Introduction

Gravity casting or permanent mold casting as the name suggests is a process wherein the liquid metal is poured into metallic molds without application of any external pressure. The liquid metal enters the cavity by gravity.

The start of casting technology, which forms casting by pouring melted metal into a mold and solidifying it, origins back to around 3,600 B.C. at Mesopotamia. Back then, bronze was melted and poured into a mold. On a papyrus from about 1500 B.C. of Egypt, it can be seen that a drawing of people using their legs on bellows to send air. By inventing “bellows”, human being has achieved to obtain higher heating technology. This was how the Bronze Age arrived. By the way, the melting point of bronze is approximately 800 with Cu-25%Sn. Considering casting, it could be assumed that the melting temperature could have been exceeded 1000°C.Since iron is oxidized on earth, it would not function as iron if not been deoxidized. It is believed that in 1700 B.C., the Hittite empire has first obtained iron by deoxidizing iron ore. The casting technology, which produces product by pouring melted metal into a mold, was first developed in China, approximately 7th century B.C. It is generally thought that the Chinese bronze ware technology achieved an extremely high temperature by utilizing bellows and from this line of technology, it is assumed that pig iron was developed by melting iron with high carbon content. The brittle characteristic probably led to a factor for iron casting technology not being introduced to Europe until 14th century. It was not until 1779, when the Iron Bridge was constructed in England, that cast iron with non-chill structure and high Si content was found. From 7th century B.C. to 18th century at the time of Industrial Revolution, cast iron was made hard and brittle. Thus, no wonder iron with stickiness which could be hardened by hardening used for forging products was more valued. However, by increasing Si content, the property of cast iron has shifted largely. This non-chill cast iron came to become an important material to support the industry. All sorts of casting products as bridge and cannon begun to appear on manufacturing line. [7]

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The Gravity casting process has several advantages. The process is suitable for mass production with better reproduction; dimensional accuracy and surface finish than conventional sand castings. The GDC process is capable of achieving 20% higher mechanical properties than that of a sand casting because of faster rate of solidification imparting better grain size. The process can be automated and can produce semi-gravity die-castings employing sand or plaster of Paris cores for production of interior details.

The process has certain disadvantages. Limitation of geometry/size is a main disadvantage, as it is difficult to cast large size highly complex shapes. Beyond a ...

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