Table 1. Selected Test Diameters for Printing Layer Thickness 0.011” (0.28mm)
Inch 0.375 0.5
0.75 1
Diameter Conversion mm
9.525 12.7
19.05 25.4
Layer 34.02 45.36 68.04 90.71
that did not contain the flat defect was normal XY, which supports the slicing method employed by the manufactur- er’s software was indeed method C. Te CLI flat was measured in the associated CLI file for the given diame- ter. Te X distances were graphed (red) with relation to the circle test diameter. Te observed flat (blue) was the average across the YZ normal, YZ precut and XY precut samples. It was determined the actual printed flats were 28% smaller than the value within the CLI outputs for a given test diameter. Te reported analysis was completed
on the all four diameters tested. Results for the 0.375 in. (9.52 mm) and 0.992 in. (25.2 mm) diameter circles were summarized in this report. Te observed trends and defects were similar for the 0.496 in. (12.6 mm) and 0.750 in. (19.04 mm) circles. Tese results were omitted as they did not provide any greater insight than what the 0.375-in. (9.52 mm) and 0.992-in. (25.2mm) diameter circles provided.
Conclusions In additive manufacturing, if the
CLI file contains a defect or distortion, the final printed part would follow a garbage in garbage out principle and would contain the same defect. Tis research confirms the slicing method employed is indeed method C shown in Figure 3. Te measured values of the YZ normal and precut series were comparative to the precut XY series. Additionally, the printed flat defect was still observed in the precut XY samples, even though the greater resolution of the print head removes the flat defect in the normal XY samples. Tis defect remained in the precut XY samples, because the flat was present in the input geometry, whereas the normal XY sample did not have this flat present, as supported by the printed samples. If the egg shape distortion is
present in sand printing, this distor-
Rd 34 45 68 90
Final Test Diameters Inch 0.375 0.496 0.750 0.992
mm 9.52 12.6
19.04 25.2
tion is likely within the variability of printed sand. Tis variability is a combination of the geometry, slice file, and the cleaning of the sand cores themselves. Te overall average grain size was roughly 0.005 in. (0.127 mm). Te variability was comparative to ±2 grains of sand in the X & Y deviations. Te deviation was similar regardless of the diameter of circle examined. If the egg shape distortion was outside the variability of printed sand, this distortion should have become more apparent within the smallest tested geometry. When the roundness of the smallest geometry the 34-layer circle was examined, no egg-shaped distortion was observed. Te larger 90-layer circle also did not exhibit distortion. Te most noted defect in the
printed circles was the flats at the start and finish layers of the through hole.
However, the defect was 28% smaller than the flats contained within the actual sliced geometry file. Te exact reason for this reduction of the flats is still under investigation. While the egg-shaped distortion was not present in the printed samples, all printed samples regardless of tested diameter were undersized. Te scope of this research was limited to distor- tion and the slicing method for 3DSP. Te dimensional accuracy of a specific diameter was not included. Tree-dimensional sand printing
is not exempt from the same limita- tions as other additive manufacturing (AM) methods. Te build orientation, properly exported geometry, and part placement is critical to the success of any AM project. One final consideration is that this
research was conducted on a specific manufacturer’s software. However, the methodology outlined in this paper can be used to determine the slicing method employed by other commercial available CLI generation programs. To read the complete version of this paper, visit
www.moderncasting.com. Tis was originally presented at the 2017 Metalcasting Congress in Milwaukee.
Fig. 9. The comparison printed geometry is compared to the ideal geometry with the observed difference on the secondary axis.
June 2017 MODERN CASTING | 39
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60