Micro milling of areal material measures-Study on surface generation for different up and down milling strategies

摘要

Ball end micro milling is a suitable process for the manufacturing of freeform surfaces and therefore appropriate for the manufacturing of material measures according to ISO 25178-70.In previous studies of the authors,ball end micro milling of areal material measures with specified microstructures was experimentally investigated and the influence of the cutting parameters,as well as the influence of the control dataset parameters and the tilt angle were systematically analyzed.The influences of the surface generation strategy(up or down milling)and the chosen tool path on the surface quality of the manufactured structure are investigated experimentally in this study.For this purpose,a full factorial experimental design is created in which two different areal material measure geometries(ACS and AFL as described in ISO 25178-70)are examined applying two different tools in two different surface generation strategies(up or down milling).In addition,two different cases per surface generation strategy are tested:the tool is retracted in the milled groove(case 1:reverse movement with engaged tool)or the tool is lifted between two paths(case 2:reverse movement without tool contact).On the basis of these two cases it is possible to evaluate how the repeatability of the z-axis(case 1)or the smaller short-wavelength roughness due to the second cut(case 2)influences the surface quality of the milled structure.In addition,a meander-shaped tool path is tested as reference:the tool moves alternately in up and down milling direction without lifting from the workpiece.The meander-shaped tool path is the most time-efficient and was applied in previous studies.As a result,information on the influence of the milling strategy on dimensional accuracy and surface roughness is provided.The quality of the manufactured surfaces is compared both quantitatively(based on areal surface texture parameters)and qualitatively(measured topography compared to nominal geometry).