The purpose of the work was the study of regularities in the cylindrical surface formation at prototyping. To achieve the task there were developed sketches of two parts of “cylinder” type. According to the sketches in the CAD medium there were formed two 3D computer parts. The next step to achieve the task was the conversion of the designed and created para-metric 3D part in STL format. The printing was carried out in two product lines: the cylinders of the first prod-uct line were printed at the maximum rate of the formation (Vform=12.7mm/h) and at the maximum layer thickness (Slayer=100 mkm), and cylinders of the second product line – at Vprint=5 mm/h; Slayer=50 mkm. The parts were printed according to the method of rapid protopyping (RP) – photopolymer light curing (Direct Light Projection –DLP) on Envision Ultra 3SP plant. Material – high-temperature photopolymer resin HTM 140. Heatresistance of this material makes 140°C. As a result of the research there was revealed a vivid saddle-shaped form in printed cylinders. The reason of a hidden defect lies in a high rate of printing and also in a layer thickness. It should be excluded that the reason of an error can be electronic mistakes during a 3D conversion of an object from CAD medium into STL format.