This engine block casting demonstrates how the toolingless 3D precision sand printing additive manufacturing process coupled with the low pressure casting process allows thin-wall, light-weight complex designs to become a reality with feature and part consolidations and tighter dimensional tolerances and accuracy. 

Toolingless precision sand casting offers tremendous design and rigging freedom and allows some complex designs to be manufacturable which would not otherwise be possible with the conventional tooling approach.

This single casting incorporates integrated intake and exhaust ports, as well as cooling and oil passages. The first stage of the project used an iron block; the next evolution of the project was to design the block to be cast in aluminum, which significantly reduces weight over 60% to further improve fuel economy. 3D precision sand printing with low pressure casting enabled a thin-walled, complex structural  lightweight aluminum block with excellent dimensional accuracy, as well as reproducibility and desired soundness and quality validated by CT scan and finished machining.

Complex one-piece casting design through feature and part consolidation.

• Single piece casting configuration comprising of the integrated intake and exhaust ports, cooling and oil passages, consolidating multiple complex features (not manufacturable with the conventional tooling approach) was developed iteratively. The 3D printed sand process allows any complex core shapes to be made irrespective of their location and orientation without any of the drafting constraints typically experienced with conventional sand-casting.

• Such complex cored passages with a thin-wall casting demands a sound gating and risering design. Using a casting process modeling simulation tool allows design and process validations before making the casting!

• Design and development of such a complex casting requires multiple design iterations; the key to succeed is the collaborative engineering between the foundry, OEM, and design/engineering company.

Freedom with feature placements and no drafting constraints with 3DPS.

• It is very important to keep castability and fluidity considerations top of mind, while design engineers have full freedom with the placement of features including ribs, cored holes, draft, thin to thick transition, along with risering and gating design with the 3DPS process. The result is successful manufacturability.

• The absence of drafting achieves uniform wall thickness.

• Complex sand castings require generous fillet, radii for smoother transitions.

• 3DPS is no different than conventional sand-casting process, except the mold making method––melting, pouring, cleaning, and post processing remain identical to the conventional sand-casting process!  Smooth transitions and generous fillet and radii offer better flow of liquid metal. Smoother transitions allow reduced turbulence of liquid metal while filling into the mold cavity.

• Casting orientation with respect to the gravity and gating design determine the location and amount of machining stock. The hole diameter, depth, positional tolerance, and location determine whether to make it as-cast/cored or cast solid and machine or drill afterwards.