# Evaluation of Non-Planar Tool Interaction in Milling of Shaped Surfaces Using a Copy Milling Cutter
## 1 Introduction  
The manufacturing process of machining is a specific process mainly found in automotive and aircraft parts production, as well as plastics processing in the area of shaped cavities production. Input factors entering the machining process affect the resulting quality of the machined surface, as well as shape and dimensional accuracy, and include cutting conditions, type of choice of machine tool, type of fixture, size of the machined sample, type of tool, selected milling strategy, clamping of the part, unloading of the tool, cooling medium and, last but not least, the post-processor and the control system of the machine [1]. In the production of shaped parts, a larger portion of the process is focused on optimizing production from the point of view of productivity with regard to the quality and accuracy of production. Production optimization can be addressed by correctly selecting milling strategy, machines, etc. However, due to the production of these shaped surfaces, it is necessary to understand the behaviour of the tool in the cutting process. The milling of shaped surfaces is characterized by non-planar interactions between the tool and workpiece [2, 3]. In the case of machining free form surfaces, which are complex surfaces, it is important to select a suitable milling strategy to achieve not only efficient production in terms of time, but also surface quality in the form of dimensional and shape accuracy. Therefore, great importance is placed on appropriate finishing strategies, as well as their use [4]. Machining shaped surfaces is very time-consuming. In the industrial sector, these shapes are machined on 3-axis machines, which leads to some inaccuracies. This requires special positioning and repositioning of the workpiece for machined surfaces. Machining is only possible with a certain degree of accuracy on these machines. For general machining of surfaces, only one tool is often used, when it is necessary to consider higher machiningtime and possible errors. Undesirable effects arising during the cutting process can be eliminated using a tool with a suitable diameter. In 3-axis milling, the tool is controlled in three directions, the position of the tool relative to the general position of the surface is determined by three coordinates. In conventional milling, the diameter of the ball mill is limited by the curvature of the convex shapes. Exceeding the used diameter of the tool is most often manifested by undercutting the machined surface. Therefore, it is necessary to ensure the correct ratio between the radius of the used tool and that of the curvature of the machined surface [5]. CAx systems are widely used to simulate various production processes such as machining, forming, joining, welding, or additive manufacturing processes and other production methods [6; 7; 8; 9]. The selection of suitable strategies was implemented in the SolidCAM CAM system. With the appropriate selection of milling strategies, we can machine different types of surfaces, which is greatly helped by the simulation modes in the CAM system. Hence, the CAM system plays an important role in the field of machining parts with complex shapes, where it is not possible to use classic workshop programming containing only certain cycles intended for 2.5D milling. It is important to define the tool used to machine a complex shape (general surface), considering the maximum possible usable diameter. It is important to prevent local undercutting of the workpiece. Therefore, it is necessary to determine whether the shape of the general area is concave and saddle-like and what is the degree of curvature. This control is usually performed in CAM systems where it is possible to practically control undercutting or the collision of the tool with the workpiece [10]. The use of copying tools in the field of finishing operations has its advantages due to adaptability to changes in surface curvature.