Te only sample that did not contain the flat defect was the NOR XY.
Results for 90-Layer 0.992-In. Geometry
Te overall X & Y diameters for the
90-layer were noted to be undersized. Additionally, the 34-layer samples were also undersized. Te printed diameters of the 90-layer samples ranged from 0.969-0.982 in. (24.61-24.94 mm). Te observed values for the upper widths and lower widths have a standard deviation of the values ranged from 0.004-0.005 in. (0.10-0.12 mm). Tis was slightly lower than that of the 34-layer samples. As previously observed, there was no
Fig. 7. Shown is a comparison chart of the X values between the horizontal measured points above and below the midpoint of the circle.
were fixed to a predetermined equa- tion throughout all testing. Tis would reduce variability in the data gath- ered, since the measuring points were proportional regardless of the diameter size of the sample being analyzed. Tis would allow comparison of any distor- tion present in the sample geometries. Te measure device for analysis was a Heidenhain Quadra-Chek opti- cal comparator. A gage R&R showed percent equipment variability of 0.13%, percent appraiser variability of 0.18%, percent repeatability and reproduc- ibility of 0.22%, percent part variability of 100%, and a R-dbar of 0.0005 in. (0.0127mm). Tis verified that the calibration, accuracy, and precision of the optical comparator were more than sufficient for the measurement of sand test geometry.
Results for 34-Layer 0.375-In. Diameter Geometry
Te printed diameters ranged from
0.352 in. (8.94 mm) to 0.361 in. (9.16 mm). Te standard deviation of the values ranged from 0.003-0.006 in. (0.07-0.22 mm). No trend was observed when
comparing the upper widths to lower widths lengths. Te X width value for the averaged intervals can be seen in Figure 7. Te standard deviation of the values ranged from 0.003-0.006 in. (0.07-0.22 mm). No egg shape
38 | MODERN CASTING June 2017
distortion was present when compar- ing upper interval X widths to lower internal X widths in any of the printing regardless of printing orientation. If the distortion was present the lower inter- val samples should have been wider than the upper interval samples. Te roundness of the test samples
were compared to the circle radius over- lay and no circular distortion was pres- ent. Te only noted defect was the flat section at the start and stop layers of the circle. Te flat defect was observed in the NOR YZ, Pre YZ, and Pre XY.
apparent trend on the 34-layer sample when comparing upper widths to lower widths. Tis trend was also observed for the 90-layer samples. Te roundness of the normal XY & YZ test samples were compared to the circle radius overlay and no discernible distortion was visually observed. Tis trend matches the observations on the 34-layer samples. Te previously noted flat defect
test geometries were also observed the 90-layer samples. Te flat defect in the 90-layer samples was much larger than that of the 34-layer samples. Tese values ranged from 0.152- 0.185 in. (3.86-4.69 mm). Te only sample in both the 34-layer and 90-layer samples
Fig. 8 The flat defect length increased with larger diameters. The only sample without the flat defect was the Normal XY test geometry.
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