Influence of printing parameters on the transformation efficiency of 3D-printed plaster of paris to hydroxyapatite and its properties

Purpose - The purpose of this paper is to study the influence of changing printing parameters (powder layer thickness and binder saturation) in a three dimensional printing machine (3DP) on the transformation of 3DP printed plaster of paris to hydroxyapatite by low temperature phosphorization. Design/methodology/approach - Plaster of paris-based powder mixture was used to print specimens using different powder layer thickness (0.080, 0.10 and 0.20 mm) and saturation ratio (1 and 2). Subsequently, density, microstructure, mechanical properties, transformation rate and phase composition were analyzed to compare the influence of such printing parameters on properties. Findings - It was found that printing parameters strongly affect the transformation efficiency and properties of the samples. The sample printed at layer thickness of 0.10 mm and saturation ratio of 1 yielded the highest transformation rate, density and greatest flexural modulus and strength after conversion. This was related to the sufficiently low density structure with good mechanical properties of the as-fabricated 3DP sample which was suitable for the low temperature phosphorization process. Hydroxyapatite and monetite were found to be the main phases after conversion and the content of each phase depended on the conversion time and on also the printing parameters. Research limitations/implications - The optimal printing parameters were true for the materials used in this study. In the case of using other materials formulation, the optimal printing parameters might be different from these values. Practical implications - The results presented here can be used as a guideline for selecting printing parameters in 3DP machine for achieving properties as desired for specific applications or post-processing techniques. Originality/value - The paper demonstrates the printing parameters that were needed to be considered for efficient phase transformation and high mechanical properties.