Front Cover: When using material extrusion (MEX) method to print parts made of Polyether‐ether‐ketone (PEEK), due to the uneven distribution of temperature field and stress field, the parts prone to warping deformation. Reveals the influence rules of each printing parameter and the coupling effect between them on the warpage deformation. This lays a foundation for the realization of PEEK denture forming by MEX. This is reported by Jiang Han, Ju Tong, Xiaoqing Tian, Lian Xia, Dingyifei Ma in article 2000055.

Ceramic materials, including alumina and zirconium oxide are mainly formed by 3D printing (3DP) and sintering. [8,9] However, this technique results in up to 40% volume shrinkage in the model and finding an appropriate binder is an enormous challenge. [10] Recently, polyether-ether-ketone (PEEK) has been proposed as a dental implant material. Studies have shown that PEEK is a semicrystalline thermoplastic with a melting point of 343 °C and a glass transition temperature of 143 °C. It has beige appearance, reasonable dimensional stability, outstanding biocompatibility, and excellent mechanical properties. [11] Moreover, it transmits X-rays. [12] Its elastic modulus is close to that of the cortical bone, which can reduce the stress shielding after implantation. [12,13] Therefore, it is an effective material to replace conventional implant materials. It is worth noting that complex parts can be quickly manufactured through the material extrusion (MEX) method. However, it is difficult to produce ideal PEEK parts using MEX. Literature review has indicated that many scholars have studied the warping deformation of parts printed by the MEX technology. Zhang et al. [14] established a mathematical model for calculating the amount of warping deformation of parts. They observed that increasing the printing speed and reducing the layer thickness can reduce the warping deformation of the printed parts. Wu et al. [15] explored the effect of the molding chamber temperature and nozzle temperature on the warping deformation of printed PEEK samples using the single factor method. Their results showed that the warping deformation is minimal when the temperatures of the chamber and nozzle are set to 130 and 350 °C, respectively. Lv et al. [16] designed a heating baseplate that can achieve temperature compensation, thereby increasing the heat at the boundary of the baseplate. Therefore, the warping deformation of parts can be effectively reduced. Liu et al. conducted experiments and studied effects of the printing speed and nozzle temperature on the warping deformation of polylactic acid specimens printed by the MEX method. [17] Furthermore, studies have shown that, compared to the experimental method, the finite element method is more economical and effective in the optimization of the process parameters. [18] Ni and Song studied the temperature and stress fields of acrylonitrile butadiene styrene specimens produced by MEX. They pointed out that the warpage deformation could be Polyether-ether-ketone (PEEK) is a high-performance biomaterial, which can be used to fabricate dentures, mandible, and other human implants. However, when the material extrusion (MEX) method is employed to print parts using PEEK material, the parts are prone to warpage deformation, which affects the fabrication quality of PEEK parts. Moreover, the uneven temperature field adversely affects the crystallization of PEEK, causing the printed objects with hazel appearance which affects the beauty of the denture. In this paper, finite element analysis is initially...

In the silicone material extrusion (MEX) process, product profile error and performance defects are common problems due to changes in strand shape. A process optimization method considering strand morphology, denoted as SMO, which allows adjustment of the strand shape by adjusting process parameters during the printing process is presented. The relation between process parameters (extrusion speed, moving speed, nozzle height, and nozzle radius) and the geometric parameters (strand width and strand height) of the cross-section, as well as the relationship between strand spacing, layer height, and process parameters in no void constraint is discussed and verified. SMO was utilized to produce specimens with tunable strand width and strand height. Tensile tests and profile scans were performed to compare SMO with other methods to verify its feasibility. Specimens fabricated using the SMO method have up to a 7% increase in tensile strength, up to a 10% reduction in processing time, and about a 60% reduction in strand height error over unused ones. The results show that the SMO method with adjustable strand width can effectively balance efficiency and mechanical properties compared to uniform infill, and the SMO method with adjustable strand height can provide higher accuracy compared to uniform strand height. The proposed method is validated and improves the efficiency and accuracy of silicone MEX.

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