Sand Casting Molds - Overview of Casting Technology

Summary

This tutorial introduces sand casting, the most prevalent casting process in metal casting. It explains the mold structure, consisting of the cope and drag within a flask, and the parting line that separates them. The gating system, including the sprue, runner, and pouring cup, directs molten metal into the cavity. A riser compensates for shrinkage, while the core defines the interior part geometry. The video also touches on the importance of venting to release air and gases, ensuring a complete fill of the mold.

Takeaways

• 📚 Sand casting is the most important casting process, involving the creation of molds and the pouring of molten metal into them.
• 🔨 The mold consists of two main parts: the cope (upper half) and the drag (bottom half), both contained within a box called the flask.
• 📏 The parting line is crucial as it separates the two halves of the mold, allowing them to be opened and closed.
• 🌋 Molten metal is poured into the mold through a gating system, which includes the down sprue, runner, and pouring cup, ultimately reaching the cavity.
• 📈 A riser is incorporated into the mold to act as a reservoir of liquid metal, compensating for shrinkage as the casting solidifies.
• 🛠 The pattern, made from materials like wood, metal, or plastic, determines the shape of the cast part and is packed with sand to form the mold cavity.
• 🔍 The mold cavity provides the external surfaces of the cast part, while the core, usually made from sand, defines the internal geometry.
• 🌐 The gating system is essential for the flow of molten metal into the main cavity and is designed to minimize splash and turbulence.
• 💨 Proper venting is necessary to allow air and gases to escape from the mold, ensuring the metal fills the cavity completely.
• 🔄 The mold is designed to allow for metal shrinkage during solidification, with the cavity being oversized to accommodate this.
• 🔑 The riser is designed to freeze after the main casting, ensuring it provides additional liquid metal as needed during the solidification process.

Q & A

What is the main topic of the video?

The main topic of the video is an overview of casting technology, specifically focusing on sand casting molds.

What are the two halves of a sand casting mold called?

The two halves of a sand casting mold are called the cope and the drag.

What is the purpose of the parting line in a sand casting mold?

The parting line separates the two halves of the mold, the cope and the drag, and is crucial for the mold's assembly and disassembly.

What is the function of the pouring cup in the sand casting process?

The pouring cup is found at the top of the down sprue and is used to minimize splash and turbulence as the molten metal flows into the down sprue.

What is the purpose of the riser in a sand casting mold?

The riser serves as a reservoir of liquid metal in the mold, compensating for shrinkage during solidification and ensuring the main casting is fully filled.

What is the role of the gating system in sand casting?

The gating system is a network of channels that allows molten metal to flow into the main cavity of the mold from outside.

What material is typically used to make the pattern for sand casting?

Patterns for sand casting are typically made of materials such as wood, metal, or plastic.

How is the cavity of a sand casting mold formed?

The cavity in a sand casting mold is formed by packing sand around the pattern, which is usually made oversize to allow for shrinkage as the metal solidifies.

What is the function of a core in sand casting?

A core is used to define the interior geometry of the part in sand casting, and it is generally made from sand and placed inside the mold cavity.

How does the sand casting process handle the evacuation of air and gases from the mold cavity?

The natural porosity of the sand mold allows air and gases to escape through the walls of the cavity, ensuring that the molten metal can completely fill the space.

What additional part may be added in complex sand casting molds besides the cope and drag?

In complex sand casting molds, an additional part called the 'chill' may be added between the drag part and the cope part to enhance cooling and solidification of the metal.