Essay On Closed Molding System

Introduction There are two types of different molding systems: the open mold and the closed mold. A closed molding system is much preferred in production casting operations. The differences between the open and closed molds are the passageways, or lack thereof in terms of the open mold. A passageway is an opening in the mold connecting the pouring cup and downsprue to the pouring cavity. Having this passageway keeps molten metal from splashing when using the pouring cup. Before metal is poured down this passageway, it must be heated past its melting point, as cooling occurs quickly and blockages can occur as metal hardens along the channel. Closed mold casting process use a gating system, defined as “a casting mold is the channel, or network

Aluminum works well in unpressurized systems because it creates less turbulance at the gates, reducing the oxidation factor.
There are many factors that have an impact on the fluidity of a metal being casted. Some of these include: pouring temperature, metal composition, viscosity, heat transfer, and heat of fusion. In this lab aluminum was used as the casting metal, which has a melting point of approximately 660 degrees Celsius. To increase fluidity when pouring molten aluminum, it is important to heat the aluminum just past its melting point to decrease the chances that the metal will solidify before entering the cavity of the mold. The temperature must, however, be closely monitored, “as viscosity and its sensitivity to temperature (viscosity index) increase, fluidity decreases,” (me311_casting1). Fluidity and freezing temperature, or solidification temperature, is inversely proportional to fluidity. Therefore, alloys with longer freezing ranges tend to have less fluidity. It is additionally important to avoid high surface tension from oxide films during this process (aluminum has a tripled surface tension), as it causes fluidity to