Layer position accuracy in powder‐based rapid prototyping

Abstract

Emerging technologies commonly known as "rapid prototyping" fabricate solid objects directly from computer models by building parts in thin layers. Three-dimensional printing is one such process that creates engineering prototypes and tooling by joining powder particles selectively on a layer-by-layer basis. The powder-based approach offers tremendous flexibility in geometry and materials, but it makes layer position accuracy a fundamental concern for dimensional control in the vertical direction. Ideally, each powder layer is generated at a vertical position that remains fixed, at a prescribed distance with respect to a machine reference. However, compressive loads imparted to a stack of layers (by the weight of subsequent layers, for example) may cause the layers to displace downward. Develops a model for layer displacement using experimental data for compressibility and applied load. Compares predictions made from the model to measured displacements, and the predictions successfully captured the relative magnitudes of actual errors at various positions within layered powder beds. Position changes were most severe in the middle regions of the powder beds, with diminishing magnitude towards the top and bottom. Uses aluminium oxide powder in two different sizes (approximately of 10-micron and 30-micron diameter) and two different shapes (platelet and spherical) in the studies. The average measured displacement in a 76.2mm deep bed ranged from 23 microns for a 30-micron platelet-shaped powder to over 260 microns for a 9micron platelet-shaped sample.

Investigation of process parameter effect on anisotropic properties of 3D printed sand molds

“…Printed specimens may sink during compaction due to squashing if unbound sand particles are present underneath the printed specimens [21,22,24]. Therefore, to improve the repeatability by avoiding this issue, the specimens were always printed over the first 1.4 mm thick sand layer deposited in the jobbox bottom, thin enough to neglect compressibility issues and sub-layer displacements [21].…”

“…Therefore, to improve the repeatability by avoiding this issue, the specimens were always printed over the first 1.4 mm thick sand layer deposited in the jobbox bottom, thin enough to neglect compressibility issues and sub-layer displacements [21]. …”

Biocompatibility of ceramic scaffolds for bone replacement made by 3D printing

“…Another direct RP technique for scaffold design is the 3D printing process [12]. To achieve a powder-based manufacturing process, a computer model provides defined layers, which are printed with a suitable binder onto a powder bed.…”

Design, data and process issues for mega-scale rapid manufacturing machines used for construction

“…These are issues are discussed in a number of publications (Chang, Wysk & Wang H-P 2006, Fadel, Kirschman 1996, Jacob, G. G. K., Fai & Mai 1999, Jamieson, Hacker 1995, Shi et al 2004, Tata et al 1998. A number of articles have focussed on issues on the inherent problem that building models in slices has in limiting surface resolution and finish (Koc 2004, Kumar, Choudhury 2005, Lee, Sachs & Cima 1995, Pandey, Reddy & Dhande 2003, Sabourin, Houser & Bohn 1996.…”