A novel lattice structure for SL investment casting patterns

Abstract

Purpose

The purpose of this paper is to present the study of octagonal lattice structure for investment casting stereolithography (SL) patterns, and compare it with the former hexagonal structure (of the QuickCast 2.0 build style). This research aims to introduce a new internal lattice structure for investment casting SL patterns.

Design/methodology/approach

Applying 3D‐coupled thermal‐mechanical finite element analysis; magnitudes of exerted hoop stresses on ceramic shell (during burnout stage) have been computed. As an experimental observation of stress evaluation for cylindrical hexagonal and octagonal models, magnitudes of hoop and axial strains have been evaluated by installing self‐temperature compensation strain gauges. In addition, practical results have been obtained by the real‐time strain gauging of the cylindrical models during the heating process up to 100°C.

Findings

The performance of SL pattern depends on several factors including the void ratio, drainage ability, dimensional accuracy, and burnout ability (ability of burning out the model without ceramic shell cracking). Numerical results for new octagonal structure indicate that, there is a 62 percent reduction in maximum hoop stresses exerted on the ceramic shell. Moreover, a significant reduction of strain has been observed in both hoop and axial strains applying strain‐gauging analysis (near 50 percent reduction). Besides, the obtained void ratio of the QuickCast 2.0 hexagonal and the new offset octagon structures are 90 and 95 percent, respectively. Deductive investigation has been carried out for explaining the role of the other influencing factors. The 49 percent reduction of internal mass expresses the probability of dimensional accuracy improvement for the octagonal structure.

Research limitations/implications

Several deductive investigations indicate the probability of better performance for the influencing factors including void ratio, dimensional accuracy and drainage ability of the new octagonal structure. However, the main scope of the paper is to compare the performance of models during burnout stage (the magnitudes of exerted stresses and strains on ceramic shell). Therefore, a more analytical and practical approach will be a good future research for other mentioned factors.

Practical implications

This research aims to address the main problem, which is the shell cracking; it is essential to have more practical investigations in other concepts that are not mentioned here though. Despite of that, the new octagonal structure will be a good replacement for former hexagonal structure, ensuring the casting foundries for using the SL patterns.

Originality/value

A new generation of internal structure (or a new build style) for investment casting SL patterns is presented here. The significant reduction of critical loadings on ceramic shell will ensure investment casting foundries for using SL patterns, which are by an octagonal internal structure.

Citation

Norouzi, Y., Rahmati, S. and Hojjat, Y. (2009), "A novel lattice structure for SL investment casting patterns", Rapid Prototyping Journal, Vol. 15 No. 4, pp. 255-263. https://doi.org/10.1108/13552540910979776