# The Influence of Automated Machining Strategy on Geometric Deviations of Machined Surfaces
###### Abstract
The most used form of deviation for controlling the milling process and checking the machine tools is the flatness [8]. A key issue in flatness measurements is the definition of an appropriate reference plane [16]. Ideally, all points of the measured plane are in one plane [23]. The different types of tolerances show the allowed errors. Considering the errors, the most often used tolerances are the dimensional tolerance, the surface roughness, the shape, position and orientation tolerances (geometric tolerances). [PERSON] et al. [24] investigate the dependency between roughness and flatness measured by 12 methods of point sampling strategies. The results show that the evaluated parameters are dependent. [PERSON] et al. [25] studied the influence of surface roughness on parallelism and perpendicularity in milling. The results from the experiment show that surface roughness affects the parallelism and perpendicularity errors, thus confirming the results of [PERSON] [24]. [PERSON] and [PERSON] [26] state the impact of milling machines (milling machine and CNC machining center) on flatness and surface roughness. The results are represented with values of parameters and with the topographical distribution of deviations. [PERSON] et al. [27] evaluate dimensions and geometric tolerances on different types of measuring machines--optical, roundscan, contour measuring machine, CMM and computed tomography. The results clearly show the strengths and weaknesses of measuring devices. The most versatile device is the coordinate measuring machine. Modern CNC machines or new cutting tool designs provide many possibilities for improving the accuracy of the workpiece surface. In practice, we often encounter the optimization of the machining process, in which, for example, by changing the depth of cut, changing the feed rate, or analyzing the orientation of the workpiece, it is possible to achieve a change in the flatness of the part [28]. [PERSON] et al. [29] present in their research the impact of machining direction on surface flatness. The result show that length of the face milled section affects the values of flatness deviations; the flatness deviation grows with machining length. Various contributions examining the flatness of machined surfaces after milling have proven their justification in choosing the right machining strategy for surface quality [30]. [PERSON] and [PERSON] [31] investigate the effect of machining parameters on surface roughness and flatness. For the prediction of machining parameters, the results were analyzed by ANOVA. The error of predicted surface roughness was up to 11% and flatness 7%. [PERSON] et al. [32] evaluate the suitability of a coordinate measuring machine to measure the circle radius, position of the center and roundness. For element creation, different fitting methods and numbers of measuring points were used. The authors state that the uncertainty of CMM is the limiting factor. There are always certain differences between the designed and realized properties that occur during the production process. They are caused by changes in various parameters, such as the machine tool, material, human factors, measuring devices or process parameters. The number of factors affecting the deviation can be reduced by quality control and by the planning of the production process. The acceptable level of deviations is defined as the tolerance of dimensions and geometry. During the measurement with a coordinate measuring machine or any other suitable measuring device, the measuring strategy defines the number of recorded points and the created element [33]. [PERSON] and [PERSON] [34], in three types of milling machines, investigated flatness, perpendicularity and parallelism. The results show that the cutting tool and machine rigidity affect the values of form and shape errors, and the flatness of vertical and horizontal planes is affected by the depth of cut. Additionally, the machine tool, the direction of milling and the position of the surface also affect geometric errors.