Abstract
Additive manufacturing machines, based on the multimaterial jetting technology, are widely used for three-dimensional (3D) printing of sophisticated medical models, which are aimed to be used for preoperative planning and surgical training. Gaining knowledge of process-related influences on mechanical and dimensional properties of 3D-printed parts makes up an essential basis for the design and manufacture of medical models. There are few studies on characterization of multimaterial parts, and those are limited to tests that are not based on standardized methods. Within the scope of this work, mechanical and dimensional investigations were performed on multimaterial parts that were printed using an Objet500–Connex3 3D printer (Stratasys Ltd., Minnesota, Eden Prairie, MN, USA). Among test methods listed in DIN EN ISO 17296-3, tensile tests were chosen for mechanical characterization. In the tensile tests, combinations of four different materials (Tango+, VeroClear, VeroPureWhite, MED610) were tested in three build orientations (XY, YX, ZX). To investigate the orientation-dependent printing accuracy, the tensile specimens were further checked for their dimensional accuracy. Statistically significant variations in the mechanical properties were found between different orientation levels. In general, specimens printed in XY orientation show higher tensile strength than YX- and ZX-oriented specimens. The tensile moduli determined are in the range from 0.2 to 2,500 MPa and compare well with the tensile moduli found in soft biological tissues. Dimensional deviations were found highest for the length of ZX-oriented tensile specimens. For this orientation level, it could be observed that multimaterial specimens, which contain higher percentage of the soft material Tango+, are characterized by higher shrinkage. For tensile specimens printed from the pure photopolymer Tango+, a shrinkage of 4.6% in length was determined. In summary, it was found that with multimaterial jetting technology, the increased shrinkage and lower mechanical strength in the ZX direction must be considered in the design process.
Highlights
Applications of additive manufacturing (AM) technologies have quickly expanded from the field of traditional engineering to the field of medicine
The aim of this work was to perform a standardized mechanical and dimensional characterization of multimaterial AM parts, which shall form the basis for manufacturing of medical models with known mechanical and dimensional properties that can be used for surgical training and preoperative planning
For the material mixtures (FLX9950, FLX9970, FLX9995, and RGD8625), it can be seen that the tensile modulus and the tensile strength increase for materials, containing higher percentage of VeroClear, whereas, the strain at break follows an opposite trend
Summary
Applications of additive manufacturing (AM) technologies have quickly expanded from the field of traditional engineering to the field of medicine. The flexibility provided by AM enables surgeons to determine the most appropriate implant for each patient and to adapt and optimize the device design before surgery. This improves the performance of implants, lowers the risk of surgical complications, and reduces the duration of the surgery by eliminating the need for implant adjustments during intervention [1]. Material jetting is one of the most widely applied AM technologies. This technology enables the production of colored and flexible structures. New possibilities for mimicking more complex mechanical structures arise from combining different materials in one build procedure, made possible by, e.g., multimaterial jetting technology
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