Low pressure sand casting

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The low-pressure sand casting is one of the casting process and is an evolution of sand casting . This opened up new fields of application.

It has proven to be particularly advantageous in vehicle construction , where components that are as light and highly stressable as possible are required, for which aluminum with its alloys has very good requirements. Heavy-duty cast or forged parts made of aluminum are more expensive than corresponding components made of cast iron or steel , but more and more automobile manufacturers are prepared to accept the additional costs. This is because aluminum can often be used to compensate for part of the higher vehicle weight due to safety and comfort equipment and to reduce the unsprung mass.

Low pressure sand casting is a combination of aluminum sand casting and low pressure die casting. Its specialty is the low-turbulence, laminar filling of the mold by the melt rising from below. A very good mold filling and better component properties are associated with it.

Development and scope

The process was developed by various companies. In Germany, for example, from Honsel AG in Meschede and KSM Castings GmbH in Hildesheim. In Switzerland from GF Automotive in Schaffhausen. The company calls its process variant LamiCast and produces it in Garching near Munich in Bavaria.

The casting and molding system there works with a 1320 × 900 × 800 mm molding box and has a variable sprue, which enables it to be quickly adapted to different components. Process analyzes show that LamiCast is also an alternative to pressure and die casting - especially for aluminum components in small and medium-sized series.

GF Automotive has put its process to the test on subframes on the front or rear axles , which accommodate chassis and drive components and which could not previously be produced by sand casting. Common design variants were multi-part welded frames made of steel or hybrid frames made of hydroformed steel tubes and cast connecting elements (cast nodes).

Many individual parts, numerous joints and welds as well as a relatively high weight were the result. In contrast, one-piece subframes with small wall thicknesses and a significantly lower weight can now be produced by low-pressure sand casting.

This opens up new possibilities for the lightweight construction potential of aluminum, because the lower limit for the wall thickness no longer depends on the process, but only on the function of the casting. And while the classic sand casting of large aluminum parts such as oil sumps only allows a wall thickness of five millimeters, with low-pressure sand casting it is three millimeters.

In this way, oil pans that are half as heavy as before can be produced. Since the melt is removed from below the bath surface, the oxide content in the component is reduced , which has a beneficial effect on the material properties.

This can be seen in a chassis part that GF Automotive manufactured using three different casting processes. The tensile strength , yield strength and elongation at break of the wheel carrier produced by low-pressure sand casting achieve the values ​​desired by the automotive industry for safety components made of aluminum. Because these safety-relevant parts should only deform if they are overloaded. You can tear, but not break.

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