Sand Casting - Automotive Components

The classic sand casting process, which aluminium foundries are making use of today, relies on gravity to fill the die in order to manufacture an array of components for the drivetrain and chassis of cars and commercial vehicles. These include gearbox cross members, trapezoidal links, the engine bracket, anti-roll bars, wheel carriers, consoles and the auxiliary frame, as well as intake manifolds and oil sumps.
However, the potential of aluminium for lightweight construction cannot be fully exploited because the process determines the components’ wall thickness, which cannot normally be less than five millimetres.

For components with a large surface area, e.g. oil sumps, three millimetres wall thickness is entirely sufficient, but conventional sand casting cannot be used.


A new process low-pressure sand casting  is now available to give smaller wall thickness.  Sand casting is thus benefitting from new options for the economic manufacture of highly resilient aluminium components.

Low-pressure sand casting combines classic aluminium sand casting with low-pressure chill casting. In Germany it was developed by companies including Honsel AG in Meschede and KSM Castings GmbH in Hildesheim. In Switzerland, GF Automotive in Schaffhausen is a respected supplier with production facilities are located in Garching, close to the Bavarian city of Munich. Using the auxiliary frame and wheel carriers as an example, the company has demonstrated the process’s advantages and that it now offers an alternative to pressure and chill casting.
Because the molten metal rises up from below, there is almost no swirling as the die is filled. This results in better filling of the die and very good mechanical properties, both of which are sought by the car industry for chassis safety components.

http://www.aluminiumindustry.org/en/sand-casting-car-manufacturing.html


Sand Castings vs. Die Castings:  Choice Criteria

Sand castings are used when parts are hollow; there’s no practical
alternative.  An example is automotive (intake exhaust) cylinder heads.  Internal water
passages  preclude the use of die castings for these applications.

Engine blocks  are also traditionally sand cast because they, too, have internal passages, although many modern automotive engines use blocks cast with “hybrid” processes, which may include permanent mold, sand, and multiple injections of metal.

Sand castings are more costly, but can produce shapes that are not possible with die castings.

Lightweight, thin wall castings,  such as those found on simple BBQ enclosures are almost always die castings; a grill lid that costs $10 to die cast costs $100 to produce as a sand casting, even though die castings require more machining. Die castings generally have smoother surfaces, however.

Tooling is less expensive in case of sand casting as the pattern is made with wood or plastic.  One advantage of sand castings over die castings is that, given the short life cycle of many of today’s products, the substantial upfront investment in hard tooling for die castings is avoided.  Sand castings do not commit the customer to costly tooling for a part life with a brief life. Changes are also quite costly for a die casting.


Die casting is economical only for very high-volume production.

http://www.accuformmfg.com/die-castings-vs-sand-castings.htm


http://www.castingquality.com/metal-casting-parts/cast-iron-parts/cast-iron-automobile.html