# Calibration of a Hybrid Machine Tool from the Point of View of Positioning Accuracy
## 5 Conclusions  
Improvements in machine tools in the 21 st century are carried out in several directions. One of the most important is improving their mechanical structure through the search for solutions that are adaptable to specific application areas. By applying reconfigurable building principles and non-linear kinematic forms, solutions are realized where, in addition to an adjustable workspace, variable kinematic and dynamic characteristics of machine tools are obtained with a whole series of advantages and disadvantages compared to machine tools with serial kinematics. In such conditions, the analysis of the accuracy of the realized movements and the definition of the methodology of its determination following the valid standards represents an essential step towards a unique process of calibrating machines that considers the differences in the kinematic structure. Testing the accuracy of positioning and calibration of the hybrid machine tool described in the paper is a step in this direction. It represents an introduction to the formation of a unique methodology for testing the volumetric accuracy of machine tools, which takes into account the machine tool's kinematic characteristics, in addition to the components' characteristics. Based on the obtained results, it can be concluded that the application of bidirectional error compensation on all three external axes of the O-X slide of the machine tool provides the complete elimination of discrete damage to the lead screw spindle and sliders as well as the gap in the nut. By analyzing the systematic errors that occur with machine tools, applying this error compensation method eliminates the need to decompose errors into individual errors and eliminate them with discrete values. Positioning accuracy results obtained after the calibration process fully correspond to machine tools with open-loop control and applied stepper motors. They can even be considered very good, except for the Y axis, where the error is somewhat more significant due to construction reasons (on one side of the gantry is the driving element, and on the other is the sliding, driven element). The research conducted on the results presented in the discussion indicates the influence of the stopping time, the feedrate movement speed, and the movement method during measurement. The standards determine all these influential parameters but without recommendations on when and how to choose them according to the machines' kinematic structure, purpose, and working conditions, which directly impact the calibration process. In addition, the results of such research create prerequisites for the application of Edge computing technologies to compensate for errors in real time, which is a continuation of the presented research. Conceptualization, S.T. ; methodology, S.T., M.Z. and S.Z. ; software, S.T. ; validation, M.Z. and A.B. ; investigation, S.T. and S.Z. ; resources, S.T. ; writing--original draft preparation, S.T. ; writing--review and editing, Z.D. and S.Z. ; visualization, A.K., S.T. and S.Z. ; supervision, M.Z. All authors have read and agreed to the published version of the manuscript. This research has been supported by the Ministry of Science, Technological Development and Innovation through projects \"Scientific and Artistic Research Work of Researchers in Teaching and Associate Positions at the Faculty of Technical Sciences, University of Novi Sad\", grant number 451-03-65/2024-03/200156, \"Integrated research in macro, micro, and nano mechanical engineering\", grant number 451-03-65/2024-03/200105 and \"Research project of the Institute Lola Ltd.\", grant number 451-03-66/2024-03/200066. Not applicable. The data presented in this study are available in the article. We appreciate the anonymous reviewers' and editorial team members' suggestions and comments. Thanks for the support of the fund projects mentioned above. Conflicts of Interest: Author [PERSON] was employed by the company Research and Development Institute Lola Ltd.