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Fig. 7. The mold weighed 124 lbs. as originally designed.


Fig. 6. The mold’s interlocking surface could trap runout in place.


too thick, it produces a stepped contour that reduces the roundness of circular features (Fig. 9). Tis jagged appear- ance cannot be entirely eliminated by decreasing the layer thickness, but can be corrected with proper orientation to the printing head. As the layer thickness decreases,


the roundness of the part will increase.


Fig. 8. Removing non-critical areas reduced the total weight by 10 lbs.


Te resolution along the X, Y and Z axes and the orientation of the part based on the required tolerances are especially critical in smaller parts with tighter tolerances. Model degradation is unavoidable


when printing complex parts in 3-D printers. Figure 10 shows a sample triangle with a Z layer thickness of


0.011 in. (0.28mm) and an angle incident of 15 degrees. Te printed layers are green, light blue and blue. Tese layers are the geometry that remain after printing. Te red sections are not printed and the cause of model degradation.


The amount of model degra- dation is based upon the angle


28 | MODERN CASTING May 2015


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