Proper Gating Design on Sand Casting Mechanical Properties

Advantages of Sand Casting

Sand casting is the most popular and widely used method of creating expendable moulds. With 60% of them being made this way. The following advantages separate it from other manufacturing  processes from a production perspective:

• It can be used to cast materials with very high melting temperature, such as titanium or nickel alloys.
• The process is highly versatile, and can be customized to cast intricate and complex designs.
• It is suitable for smaller as well as bulk production volumes.
• Tooling cost is relatively inexpensive.

These advantages make it a favourable process choice for manufacturers. However, there are several types of defects that are often associated with the problems such as shrinkage, porosity, pinholes, and improper filling.

These defects may lead to poor mechanical properties for the casted parts. What many do not understand is that these defects are not inherent to sand casting, but are the result of poor pattern designs, subpar workmanship or lack of quality control. These defects are typically caused by poor gate design systems which are implemented in patterns.

Importance of Gating System Design

To produce high-quality casted products, the mould should be filled with molten metal as quickly as possible, but without increasing metal temperature, head pressure, or causing turbulence in the metal flow. These conditions can be achieved through proper gating patterns, including the pouring basin, sprue, sprue base well, runner, runner extension, gate, and riser.

Specifically, a gate system allows molten metal to enter the mould cavity (i.e. moulded in the sand by a pattern, a full-size version of the part makes an impression.

In some cases, internal surfaces will be created separately instead of being included in the pattern.),  the metal is poured into a mould via the pouring cup, passes down the sprue (i.e. the vertical part of the system), and then passes through the runners (i.e. horizontal portions of the gate system). Vents allow gases and air displaced by construction to escape. In the mould cavity, the gates are the multiple places where metal is introduced by the runners.

Vents allow gases and air displaced by construction to escape. After cooling, the mould is broken open, and the casted part will be removed. Castings are shaken out to remove sand.

The optimum design may affect both mould filling and head pressure but will have a huge impact on the product quality. Improper gate patterns can lead to turbulence in the molten metal, which causes the formation of oxide films, air entrapment, and sand inclusion defects.

A precise and well-designed system is essential to good quality and outstanding performance of the sand casting process with consistently uncompromised mechanical properties.

Depending on the design, novel gating configurations such as the top  bottom and side gating may also be used. In the right circumstances, these configurations are very effective in preventing defects, but it should be noted that they are highly dependent on the part geometry and size.

Mechanical Properties

Furthermore, scientific research has found that the use of different gating configurations may produce substrates with varying microstructures, which gives slightly different mechanical properties (including tensile strength and hardness) across the final product. So, it is fair to say the choice of choosing a proper configuration and design is absolutely critical to producing consistently high-quality casted products.

Our Services

As a manufacturing and engineering expert, the Omnidex Castings Team can provide best-in-class pattern and tooling outlines with optimized gating systems which produce high-quality and porosity-free products.

Combined with our excellent metal casting craftsmanship, rigorous quality control protocols and professional project management, we have full confidence in delivering top-tier products for any project.

Custom Casting Services

Omnidex works collaboratively with clients to optimise the best-suited pattern and moulding method for each custom casting project. Request a Quote to get more information on how our casting service can match your project requirements.