## 1 Introduction  
Presently, additive manufacturing technologies are used in various high-tech industries. Additive methods for the production of prostheses and implants from biocompatible polymeric materials are being actively researched and implemented. A large amount of research in this area is devoted to the use of polyetheretherketone (PEEK), polycarbonate (PC), polyamides, and other materials. The additive manufacturing of products from such materials is largely associated with the extrusion type technology of fused deposition modeling (FDM) or fused filament fabrication (FFF) [1, 2, 3]. The additive manufacturing technology of products from thermoplastic material by using melt extrusion (FDM/FFF) is among the most common [4]. The productivity of such (FDM) extruders is usually 10-100 g per hour. One of the most important technological parameters of FDM process is the temperature of the polymer and, hence, the temperature of the heated nozzle. Conventional extruders (CE) do not provide the accuracy and speed required to precisely measure and control the temperature of the nozzle, which leads to significant overheating and underheating of the polymer material during the deposition process, and as a result the fusion quality of the deposited material is not constant, resulting in the loss of geometric shape and thermal deformation of the product, destruction of the product along the boundaries of the layers, and the general deterioration of the mechanical properties of the product [3, 5, 6]. It is known from [5; 7; 8; 9; 10; 11] that the extrusion temperature deviations from the optimum by 10 \({}^{\circ}\)C can lead to a drop in the final physical and mechanical properties of the product by 5-10% and more as the temperature deviation increases. The problem is becoming more serious because such characteristics as the temperature, geometric, and mass characteristics of the previously deposited volume of the product during the additive process are being changed. At the state-of-the-art level, the change in heatsink conditions during the travel along the path is partially compensated by changing the deposition speed (extruder movement speed) of the entire layer or its parts. However, this method does not take into account the relationship between the deposition speed and the polymer extrusion speed and, as a result, the effect of the extrusion speed on the temperature of the extruded polymer. The quality of fusion of the material beads thus depends on the relation between the temperature of the extrudable material and the temperature of the underlying layers, as well as on the heat dissipation conditions on the extruder path. In the hot (heated, hot-end) part of the extruder (E3D V6, E3D Volcano, UK, DyzEnd Pro, Canada), the polymer is melted and subsequent extrusion through the forming nozzle hole. In this case, the heating of the nozzle to a temperature sufficient for melting the polymer is carried out by means of direct heat transfer from a metal heater block, in which the nozzle, the heating element, and the temperature sensor are installed. The problems of FDM/FFF described earlier are caused by a number of disadvantages of CE:  
1. Asymmetric location of the electrical resistance heater at a distance relative to the nozzle leads to inequality of the thermal field of both the nozzle and the extrudable material (up to 20 \({}^{\circ}\)C) [12; 13];
2. Location of the temperature sensor at a distance from the mentioned heater and the nozzle leads to an error in measuring the temperature of the nozzle and polymer in 10-20 \({}^{\circ}\)C [12; 13; 14; 15] (without extrusion). With an increase in the extrusion speed to the level of 30-40 mm/s, the accuracy of measuring the nozzle temperature decreases by another \(\sim\)10 \({}^{\circ}\)C [16], and the accuracy of measuring the polymer temperature decreases to \(\pm\)30 \({}^{\circ}\)C [14; 15; 16; 17; 18] or more with a further increase in the extrusion speed [17];
3.