Progress in domestic polyetheretherketone (PEEK) FDM 3D printing technology
PEEK is an excellent engineering plastic with high temperature resistance, self-lubricity, chemical stability, radiation and electrical properties, and excellent mechanical properties for use in machine building and aerospace manufacturing. In the field of biomedicine, polyetheretherketone has excellent biocompatibility, and its elastic modulus and human bone elastic modulus are closer than those of metal materials, which greatly reduces the elastic modulus of metal materials and human bones. The problem of stress shielding, bone resorption, bone inflammation, secondary surgery caused by excessive gap, the mechanical properties of polyetheretherketone implants can meet the normal physiological needs of the human body, so PEEK is a good orthopedic implant. material.
Regarding PEEK's progress in FDM 3D printing technology, Roboze has introduced FDM 3D printers that can print medical grade PEEK wires. INDMATEC has also introduced a desktop-grade FDM 3D printer for PEEK printing.
Before PEEK's multi-purpose printing method was SLS and 3DP technology, what progress has domestic enterprises made in the field of 3D printing of PEEK through FDM technology? In this issue, we will learn about the development of domestic PEEK 3D printing through two case nets.
Solve the problem of high melting point
PEEK can be used as a 3D printed material to make mechanical parts and orthopedic implants, but due to the higher melting point of PEEK materials, most 3D printer nozzles do not work well to melt PEEK material better. This problem is for PEEK 3D printing, especially FDM. 3D printing brings a certain degree of difficulty.
Shaanxi Hengtong Intelligent Machine Co., Ltd. has developed a 3D printer of PEEK material. PEEK material has higher melting point and glass transition temperature, and the continuous use temperature is 260 °C. For the problem of high melting point of PEEK material, Shaanxi Hengtong has developed PEEK material. High temperature resistant 3D printer nozzle with a nozzle temperature of 400 ° C (error ± 2 ° C).
Image: Shaanxi Hengtong 3D printed PEEK sample
A typical FDM printer is mainly composed of a heat sink block, a throat pipe, a heating block, and a nozzle. The print head uses friction as a power to push the unmelted material behind, thereby extruding the material melted in the front section from the nozzle. Since the inner diameter of the throat is larger than the diameter of the wire, if the heat dissipation of the throat is not timely in printing, the material melted in the front section will not only be extruded from the nozzle, but also backflow in the gap between the throat and the wire, thereby making the wire and the throat The friction between them increases, and even causes the material to overflow from the rear end of the throat, resulting in no wire.
Since the wire is extruded from the nozzle, it relies on the forward thrust of the unmelted material behind. As the printing time increases, if the temperature at the rear end of the throat reaches the glass transition temperature of the material, the wire softens and the forward thrust becomes smaller. , the amount of spinning is reduced, and the extrusion width of the wire is narrowed, so that the precision of the part is lowered. Especially for high performance polymers such as PEEK and polyimide, on the one hand, the viscosity of the material is large, the tolerable backflow distance is shorter than ABS and PLA, and the melting point of the material is high. The nozzle printing temperature is generally above 350 °C. The heat dissipation of the heat sink block makes it difficult to lower the temperature at the rear end of the throat below the glass transition temperature of the material, so that the phenomenon of "plugging" often occurs.
For high melting point and high viscosity materials such as PEEK and polyimide, the existing print head structure cannot meet the heat dissipation requirements of the throat, and can not achieve long-term continuous fine printing of such materials. A fluid circulation temperature-controlled fused deposition forming print head developed by Shaanxi Hengtong can reduce the temperature of the throat in time by adding a fluid circulation temperature control system in the print head, and improve the backflow of the gap during high-temperature printing. Maintain stable print accuracy.
3D printed custom PEEK implants
If PEEK implants are traditionally processed by injection molding or machining, different molds are required for different implants, which increases manufacturing costs, especially for customized PEEK implants, which cannot be reused. This is a waste of resources. At the same time, because it takes a long time to open the mold, it takes too long to wait for patients who need to implant artificial bones. Not only that, but for some complex implants with complex shapes, it is more difficult to manufacture. Jilin University has achieved rapid manufacturing of customized PEEK implants through 3D printers.
The 3D printing manufacturing method of the PEEK implant includes: acquiring medical image data of the patient to be implanted, extracting the required bone tissue data from the acquired medical image data, establishing a three-dimensional digital model of the bionic artificial bone, and three-dimensional digital modeling of the artificial bone. The digital model was formatted, and the artificial bone digital model was imported into the polyetheretherketone 3D printing system made by Jilin University for the three-dimensional physical manufacture of the implant. After the completion of the manufacturing, the cytotoxicity test, animal test and clinical test were carried out.
When printing, the PEEK wire with a diameter of 1.6 mm was first dried in a drying oven for 12 hours, and the 3D printing system nozzle, aluminum alloy, and printing chamber were preheated by a self-made temperature control system. Next, the printing nozzle is adjusted to the printing platform by the control system, and then the double-gear wire feeding mechanism feeds the PEEK wire with a diameter of 1.6 mm into the preheated nozzle at a constant speed, and the 3D printing system nozzle generates the plant according to the layering software. The trajectory of the material is printed layer by layer on the PEEK implant. In order to alleviate the problems of brittle fracture, delamination, warpage caused by internal stress during the forming process of the PEEK implant, the temperature of the printing chamber is gradually cooled to room temperature, and then the PEEK implant is taken out.
Jilin University has realized 3D printing manufacturing of PEEK implants with high melting point, high viscosity, poor fluidity and crystalline polymer biocompatible materials, eliminating the time and cost of manufacturing molds and greatly shortening the manufacturing cycle. The software is set to adjust the shape of the part at any time to meet the patient's individual needs for the implant.
Reference materials:
Patent: fluid circulation temperature control fused deposition forming print head
Patent: 3D printing manufacturing method of polyether ether ketone bionic artificial bone
Patent: HIGH-DENSITY COMPOUNDS FOR 3D PRINTING
(Editor)
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