This study aims to focus on conducting a comprehensive process capability analysis of the selective laser sintering (SLS) process for manufacturing porous bone scaffolds with precise external dimensions, using polyamide-12 (PA2200) powder material.
Sixty porous scaffold specimens were initially fabricated using the EOSINT P395 SLS printer with recycled PA2200 powder. As the printer calibration was overdue, the experiment was subsequently repeated using both recycled and virgin PA2200 powder following proper calibration. Dimensional measurements of specimen length and height were obtained using a coordinate measuring machine. Tolerance grades, dimensional deviations and process capability indices (Cp and Cpk) were analyzed. Furthermore, an in vitro study was performed to evaluate the cytotoxicity of PA2200 using chick embryo fibroblast cells.
Initial specimens fabricated with recycled powder exhibited tolerance grades ranging from IT01 to IT10, with Cp and Cpk values below 1, indicating the process was incapable of meeting the required specifications. Following overdue printer calibration, the process improved, with Cp and Cpk values exceeding 1 and becoming nearly identical, suggesting a centered and more consistent process with tolerance grades ranging from IT0 to IT9. A similar analysis using virgin powder yielded comparable results, showing no notable improvement in process capability. Further analysis with recycled powder revealed that increasing the specification limits from ±0.10 to ±0.13 mm substantially improved Cp and Cpk values, bringing them in line with industry standards. Additionally, in vitro studies confirmed that PA2200 scaffolds support chick embryo fibroblast attachment, indicating good biocompatibility and potential for use in 3D tissue engineering applications.
This study highlights the vital importance of process monitoring and printer calibration in ensuring the dimensional accuracy and part conformity necessary for high-precision applications such as bone tissue engineering.
