## 1 Introduction  
Industrial 3D printing technology has become more and more important due to its fast manufacturing time, low cost, and the un-moldable printing [1]. According to the report proposed by Wohlers Associates [2], industrial applications in 3D printing technology approached around 12.5 billion US dollars in the year of 2018 and it will attain around 21.2 billion US dollars in the year of 2020. Major applications in 3D printing technology include mechanical manufacturing, aerospace industry, food, and biology-related technologies. In the applications of biology-related technology,such as bone and tissue engineering, 3D printing technology has been employed because of the clinical requirements of orthopedic suffers [3; 4; 5]. In the clinical requirements of bone and tissue engineering, 3D and porous bone or tissue supports with suitable surface areas for attachments and growths of cells are often used in the treatments of complex musculoskeletal wounds [3; 4; 5]. Several possible manufacturing methods such as electrospinning, solvent casting/particulate leaching, freeze drying, and gas forming have been reported for the production of these 3D supports [6; 7]. However, it is difficult for these methods to obtain 3D supports with uniform pore size distribution and suitable shapes that meet the clinical requirements. In contrast, complex 3D supports with uniform pore size distribution can be easily manufactured using 3D printing technology. Three-dimensional printing technology based on the selective laser sintering was employed to prepare porous Ti\({}_{6}\)-Al\({}_{4}\)-V supports with mechanical property similar to the bone tissue [6]. Three-dimensional printing technology based on the fused deposition modeling for the preparation of supports (e.g., low-crystalline polymers such as poly lactic acid (PLA)) in the application of bone-tissue engineering was also reported in the literatures [4; 5; 7]. Traditional Ti-based supports (e.g., Ti\({}_{6}\)-Al\({}_{4}\)-V) have been employed for the treatments of musculoskeletal wounds [8]. Even the metal-based supports have been applied in orthopedic suffers; major problems for the treatments of musculoskeletal wounds using Ti-based supports are the metal ions released from these metal supports caused by corrosion in the human body and the mismatch elastic moduli between the human bone (7-30 GPa) and the metal supports (\(\sim\)110 GPa for the Ti-based metal supports) [5; 9]. Low-crystalline polymer supports applied in the bone-tissue engineering cannot maintain long-term stability in the human body if these supports are used in the treatments of orthopedic suffers. Recently, an interesting polymer called polyetheretherketone (PEEK) has been proposed in the applications of bone and tissue engineering [5; 9]. PEEK is a semi-crystalline polymer with good elastic modulus (3-4 GPa), which is similar to that for human bone (7-30 GPa) [5; 9]. Similar elastic moduli for the PEEK material and the human bone can minimize the effect of stress shielding, which can result in prolonging implant lifespan and in better mechanical compatibility than the Ti-based metal supports [10]. Good thermal and chemical properties for PEEK are also reported in the literatures [9; 10; 11; 12; 13] and make it a good candidate for orthopedic applications. Although the PEEK is a good candidate that can be applied in the orthopedic implant, relative high melting (\(\sim\)340 \({}^{\circ}\)C) and glass-transition (\(\sim\)190 \({}^{\circ}\)C) temperatures for PEEK compared with traditional low-crystalline polymers used in commerical 3D printers based on fused modeling result in difficulty in their fast manufacture [5]. Major 3D printing technologies used for the printing of these PEEK supports are the powder bed, inkjet head 3D printing (3 DP) [12], or the selective laser sintering (SLS) [13]. Generally, the sintering (surface sintering) or binding of high-melting powder materials (e.g., PEEK) with low melting binders was employed to prepare the complex 3D supports by using the 3 DP technology [12].