micromachines Article Simulation-Based and Experimental Investigation of Micro End Mills with Wiper Geometry Timo Platt * , Alexander Meijer, Torben Merhofe and Dirk Biermann   Citation: Platt, T.; Meijer, A.; Merhofe, T.; Biermann, D. Simulation-Based and Experimental Investigation of Micro End Mills with Wiper Geometry. Micromachines 2021, 12, 496. https://doi.org/10.3390/ mi12050496 Academic Editor: Xichun Luo Received: 1 April 2021 Accepted: 23 April 2021 Published: 27 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁl- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Institute of Machining Technology (ISF), TU Dortmund University, D-44227 Dortmund, Germany; alexander.meijer@tu-dortmund.de (A.M.); torben.merhofe@tu-dortmund.de (T.M.); dirk.biermann@tu-dortmund.de (D.B.) * Correspondence: timo.platt@tu-dortmund.de Abstract: One of the major advantages of micromachining is the high achievable surface quality at highly ﬂexible capabilities in terms of the machining of workpieces with complex geometric properties. Unfortunately, ﬁnishing operations often result in extensive process times due to the dependency of the resulting surface topography on the cutting parameter, e.g., the feed per tooth, f z . To overcome this dependency, special tool shapes, called wipers, have proven themselves in the ﬁeld of turning. This paper presents the transfer of such tool shapes to solid carbide milling tools for micromachining. In this context, a material removal simulation (MRS) was used to investigate promising wiper geometries for micro end mills (d = 1 mm). Through experimental validation of the results, the surface topography, the resulting process forces, and tendencies in the residual stress state were investigated, machining the hot work tool steel (AISI H11). The surface-related results show a high agreement and thus the potential of MRS for tool development. Deviations from the experimental data for large wipers could be attributed to the non-modeled tool deﬂections, friction, and plastic deformations. Furthermore, a slight geometry-dependent increase in cutting forces and compressive stresses were observed, while a signiﬁcant reduction in roughness up to 84% and favorable topography conditions were achieved by adjusting wipers and cutting parameters. Keywords: micromilling; wiper; material removal simulation; surface roughness; cutting force; AISI H11 1. Introduction Micromachining offers great advantages over conventional machining processes re- garding achievable manufacturing precision and surface integrity. In principle, micro- machining refers to the scaling of conventional machining processes into the micrometer range [1]. However, since certain inﬂuencing factors, such as the material microstructure, are not arbitrarily scalable, size effects arise that signiﬁcantly distinguish micromachining from conventional machining [2,3]. Micromilling in particular offers the possibility of machining a wide variety of materials and shapes. Even very hard materials, e.g., hardened tool steels, can be machined to a high manufacturing quality. While the achievable surface quality of conventional milling often requires the use of post-processing, micromilling can accomplish the shape production and surface ﬁnishing in one process step [4]. Further pro- cess steps, such as grinding and polishing, can be avoided in order to shorten the process chain and thus the cycle time of the production. This offers the possibility for tool and mold manufacturing to produce dies and punches with a high degree of quality. However, due to the ﬁligree tools (d ≤ 1 mm) and the low values for cutting parameters, high process times occur when machining larger components, which limits the application of the processes. Increasing the feed rate can reduce the process times in conventional machining processes and thus the production costs, however, with a regular tool design, it leads to a nega- tive inﬂuence on the surface ﬁnish and thus on the production quality [5,6]. Despite the Micromachines 2021, 12, 496. https://doi.org/10.3390/mi12050496 https://www.mdpi.com/journal/micromachines