Problems and development Suggestions of 3D printing titanium alloy for medical use

With the continuous progress and development of 3D printing technology, 3D printing medical titanium alloy products are gradually recognized and accepted by doctors and patients. Its technological advantage is obvious to the revolutionary innovation in the medical field. However, there are still many problems to be solved in the field of 3D printing of medical titanium alloy.

Powders for 3D printing, for example, are expensive. At present, the production of powder for 3D printing in China is dominated by rotary electrode method and gas atomization method. The fine powder yield of this method is not high, and the powder yield of spherical powder that can be used for 3D printing is basically lower than 30%. Meanwhile, domestic high-end powder making equipment is still mainly imported from abroad, and the batch stability of powder products is poor, leading to high cost of powder making, and the price of powder is more than 10 times of its raw materials.

The range of titanium alloy powders used for 3D printing is very limited. Subject to the limitations of powder production technology and powder production cost, titanium alloy 3D printing powder on the market is still dominated by pure titanium or Ti-6Al-4V powder. Although in the past 20 years, researchers around the world have developed several titanium alloy products with good biocompatibility in response to the demand of medical titanium alloy, the research and application of new titanium alloy in 3D printing is still very limited.

The performance stability of 3D printing products needs to be improved. Due to the limitations of powder batch stability and equipment process, the stability of 3D printing products is also poor. Because the physical and chemical properties of powder produced by different manufacturers are different, it is often necessary to adjust and explore the processing parameters according to the properties of powder before printing. In the printing process, real-time monitoring and evaluation of the processing process cannot be carried out, and it is difficult to find problems in time, which requires high technical level and experience of 3D printing engineers.

Tissue defects of 3D printed parts can hardly be avoided. In the process of 3D printing titanium alloy, the cooling speed of printed parts is fast, so it is difficult to avoid the appearance of martensite tissue. In addition, the residual stress caused by uneven temperature field is difficult to be released in the process of machining, which may cause deformation of parts in severe cases. The processing method results in obvious anisotropy of 3D printing materials. Therefore, the processing control of 3D printed parts and the subsequent processing of the parts are worthy of in-depth study.

There is no perfect evaluation system for 3D printed implant products. Although the FDA has approved hundreds of 3D-printed medical devices since it issued the first license for 3D-printed orthopedic implants in 2010, metal implants and their types are still limited, and most of them are unified designs of vertebral bodies, intervertebral fuses and acetabular cups. As for personalized products customized for patients, since FDA and CFDA do not have a separate evaluation system for 3D printed products, such products are difficult to obtain market access certification and can only stay in the stage of clinical trials, unable to give full play to the biggest advantage of 3D printed medical devices.

To sum up, in order to promote the further development of 3D printing medical titanium alloy in the medical field, the following work needs to be further promoted: 1) Improve the preparation method of metal spherical powder, establish the standard and specification of 3D printing metal powder raw materials, and improve the fine powder collection rate and batch stability of 3D printing powder. 2) Increase the diversification of 3D printing powder and introduce the application and research of new medical titanium alloy in 3D printing as soon as possible. Through the combination with the material genome research project, the existing material bottleneck will be broken and new materials more suitable for the 3D printing process will be developed. 3) Establish the mechanism of equipment-material-process collaborative development, and develop 3D printing processing technology combining materials and equipment, so as to produce 3D printing products with better performance and better batch stability. 4) To strengthen the promotion of 3D printing materials and methods in medical applications, set up relevant national and industrial standards and evaluation systems for 3D printing processing methods, reduce the threshold of 3D printing technology promotion and application, and make the technology benefit the people.