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A Design Study in Aluminum Castings - GM Cylinder Block                                          

Green Sand versus Lost Foam

The traditional method of casting cylinder blocks is green sand casting, where the mold cavity is formed  in sand with a wood or metal pattern and multiple sand cores to form the internal passages.  

A comparison of green sand casting to lost foam casting shows a number of distinct advantages for lost foam.

Property

Green Sand Casting

Lost Foam Casting

Complex Internal Features and Part Consolidation.

Complexity determined by sand core limitations -- geometry, strength, and cost. 

Extensive and complex internal features (as small as 0.20") available in lost foam, based on detail duplication and pattern assembly in foam.

Dimensional Tolerances

+/- 0.030" is typical depending on part size, complexity, and geometry

 +/- 0.005"-0.010" is typical depending on part size, complexity, and geometry. 

Surface Finish Capabilities

250-600 microinches typical.  Depends on grain fineness of sand. 

60-250 microinches typical. Depends on bead size and ceramic coating grain fineness.

Feature Accuracy

Core movement and shift between mold halves across the parting line limit feature accuracy. 

No cores or mold halves to shift and degrade feature accuracy.

Parting Line and Draft Angles

Parting lines and draft angles are necessary for molding. 

No parting lines in the mold and minimal draft on tools.

Environmental Costs

Sand recovery requires binder removal and time consuming sand clean-up

Sand is binder free, so it can be easily  and rapidly recovered at low cost. 

Tool Life

Wear on wood and metal tools from sand abrasion 

Low wear and long life with aluminum tool


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Last Modified:August, 2004 by STG

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