Having the correct running system is essential in sand casting to create a high-integrity component.
A conventional running system allows the controlled introduction of molten metal into the mould cavity. Using a well-designed system allows us to filter and regulate the metal flow and ensure directional solidification takes place by supplying molten metal to feed areas which are solidifying.
Good running system design helps to reduce the risk of problems such as turbulence, inclusions, porosity and air entrapment.
In this blog, we will be examining some of the key factors behind an effective running system.
Choosing the right sand casting running system
There are three main types of sand casting running system.
Firstly, there are conventional runner systems, which include a pouring cup, down sprue, filters, runners and gates, and risers.
The second option is Kalpur technology. Using this system, molten metal can be introduced at a single point through an all-in-one pouring cup, filter and sleeve. The thermal insulating sleeve helps to keep the metal ‘live’ and feed the casting. Kalpur technology offers many economic and environmental benefits but it is not suitable for all casting work.
Finally, we have three-part (bottom-fed) systems, which can significantly help in reducing turbulence by introducing metal from below the casting to flow up through the mould.
Our highly experienced foundry team looks at each customer project on a case-by-case basis. They select the most appropriate running system based on casting configuration and integrity requirements.
The number of pouring points
Frequently, the foundry needs to use multiple pouring points to introduce the molten metal into the mould. This is often due to the weight of the casting but also to reduce the risk of premature solidification in thin wall sections.
Our foundry engineers must convey molten metal from the furnace to the pouring cup and this often involves a significant weight/load. With larger castings, using two points of entry divides the load between two ladles – helping to reduce the risk of any manual handling issues.
The speed of pouring
Although this is not a design issue, the speed of pouring and entry into the running system has a critical effect on the quality of the casting.
If poured too slowly, the molten metal may not reach all parts of the mould cavity due to a lack of pressure and premature solidification. However, if the metal is poured too quickly, this can lead to turbulence – which may cause voids and inclusions in the castings.
Our skilled foundry team must carefully judge the speed of pouring to avoid these issues.