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Several projects from the Univ. of Northern Iowa illustrate the different design considerations. 3-D printing can print complex


cores in single pieces, rather than a multi-part assembly. Figure 1 shows a core for a train’s airbrake that was produced in eight different sections in a coldbox setting. Previously, this part was produced by gluing eight sand cores together. Now, with the capabilities of the 3-D sand printing technology, this part can be printed as a single core (Fig. 2). Tis process also reduces labor and stacking tolerances, while improv- ing the part’s dimensional accuracy. An important point to remember in the conversion process is to provide or design a method to remove the uncured sand from within the cores themselves, often using compressed air or vacuum.


Critical Surface Finish in the Drag 3-D printing also allows designers


to place the 3-D model in any desired orientation. Tis allows for specific


Figs. 3-4. Initial porosity (left) was reduced with the inclusion of risers and gating system.


placement of critical surface finish sections in the drag. By placing a criti- cal surface face down in the drag, the inclusions and air bubble difects will rise to non-critical finish areas higher in the casting.


Placement of Risers While traditionally produced molds


and cores need draft and do not allow


for undercuts, with 3-D printing, risers can be placed in the ideal location for a sound casting. Figure 3 shows the porosity results from a solidification model of the sculptural table legs with no risers or gating system. In Figure 4, a riser was placed centrally to aid in feeding the legs of the table. Risers also were needed at the top of the legs to remove porosity present in the


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