## 1 Introduction  
In selective laser sintering (SLS), the laser beam energy softens the powder material, resulting in the sintering of particles and the fusion of the newly applied layer with the previously sintered [1; 2; 3]. During this process, the laser beam must simultaneously melt new powder particles in the next layer and sinter this current layer with the already existing one. The possibility of using various materials with different thermal conductivity as well as diverse layer thicknesses requires adequate energy input (energy density (ED)) to sinter the material at all and to unite this material layer with the previous. The laser beam melts a slightly thicker layer of powder every time in every layer, which results in a decrease in powder volume. To avoid excessive sintering, appropriate power must be set according to layer thickness. After the printing process is completed, several protective layers of powder (about 5 mm) are applied. For gradual cooling, the finished product is first left in the working chamber for about 2 h, after which it is removed from the chamber and left in powder outside the machine to cool to room temperature. Such a procedure maintains dimensional accuracy and avoids thermal deformation of the product. The cooling of the product usually takes as long as the production does. After the product has cooled to room temperature, it can be taken out of the unsintered powder and cleaned [3,4]. Energy density depends on the power and speed of the laser and on the hatch distance or on the laser beam diameter [1,4, 5, 6, 7, 8, 9]. The value of laser power during the sintering depends on the material and the thickness of the layer. Laser power and speed can be different for the contour and hatching, and changing these parameters changes energy input and manufacturing time [1,4,7,8]. The accuracy of all additive manufacturing processes depends on how the product is positioned along the \(x\)-\(y\)-\(z\) axis within the chamber. Product resolution, product surface, and manufacturing time depend on product orientation in the working chamber, particularly if the product is manufactured with a large layer thickness (>0.25 mm) and if the material features strong anisotropy. A big drawback of additive manufacturing is the repeatability of accuracy and mechanical properties. The tolerances of dimensions cannot be determined in advance since they depend on material and many processing parameters [10]. Polymerization leads to an increase in the material density and percentage of shrinkage of the product. Therefore, it is necessary to enlarge the product to a different percentage in the \(x\), \(y\), and \(z\) axes to compensate for shrinkage that occurs after hardening and/or cooling. It is extremely difficult to determine the percentage of shrinkage since it requires careful calculation and experience, and for every product, the procedure is different [10]. Final products can be produced in SLS, and therefore the products must have high dimensional accuracy. But they are affected not only by converting the model into STL format and cutting the layers (certain layer thickness), but also by the resolution of the 3D printer, shrinkage of the used material, speed, power, hatch distance, and processing temperature. But one of the biggest causes of the inaccuracy of the product is the shrinkage of the material, which is different in different directions (\(x\), \(y\), and \(z\) directions). Shrinkage is also increased by sintering at higher temperatures, as in the case of thin-walled products. During crystallization, the molecules arrange themselves so that they occupy smaller volumes, which leads to material shrinkage [5,11,12]. In the experiment [10], it was observed that the parameters exhibit interdependence, alongside additional factors impacting the mechanical properties of the product.