Micromachining of hardened hot-work tool steel: effects of milling strategies

Abstract

Recently, micro-milling has been one of the most important technologies to produce miniature components, because optional geometrical structures can be machined with a high material removal rate. In terms of conventional dimensions, dynamic milling definitely signals the direction of development in modern technologies: dynamic milling results in higher productivity, better thermal circumstances, and increased tool life. The current paper gives a summary of the possible applications of dynamic milling tool paths in the case of micromachining. The major problems of this technology are the issue of minimum chip thickness and relatively large tool deformation. Different milling strategies, i.e. up milling and down milling, will be compared in detail. A systematic series of experiments were performed in order to generate data for the investigation. A special measuring system was established to perform related data collection. The experiments were carried out on a 5-axis micromachining centre using a tool steel workpiece with a hardness of 50 HRC. Based on the results of the experiments, the force components and the vibrations were also analysed at different radial depths of cut and different feed per tooth values, where productivity was also an important factor. It was found that dynamic milling can be applied in micro sizes, too. It is concluded that in the case of small contact angles, setting as high a feed per tooth value as 23.52 μm is also justified. During the investigation, optimal cutting parameters were also determined within the applied parameter range, these are ae = 34.80%, fz = 8.28 μm, and the use of the down milling strategy.

AISI 8740 çeliğinin frezelenmesinde kesme gücü, özgül kesme enerjisi ve yüzey pürüzlülüğü karakteristiklerinin belirlenmesi

“…Deneylerde, aynı V f değerlerinde zıt-yönlü frezelemeye göre eş-yönlü frezelemede %2 ile %15,5 arasında daha düşük Pc değerleri elde edilmiştir. Literatürden eş-yönlü frezeleme işlemlerinin aynı koşullardaki zıt-yönlü frezeleme işlemine göre daha düşük kesme kuvveti, dolayısıyla daha düşük Pc değeri, gerektirdiği bilinmektedir [34,35]. f z değerinin artması ile P c düşmüştür.…”

“…Bunda temel sebep, Şekil 4'te görüldüğü üzere eş-yönlü frezeleme işlemlerinde zıt-yönlüye göre daha düşük P c ihtiyacıdır (p s =P c /Z w ). Esasen bu durum frezelemedeki kesme mekaniğinden kaynaklanmakta olup, eş yönlü işlemede kesme kuvvetleri zıt yönlü işlemeye göre daha küçük değerlerde oluşmaktadır [1,34,35]. Şekil 5'te düşük f z değerinde V f 'nin artışı ile p s değerlerinin düştüğü, yüksek fz değerinde ise tam tersi bir ilişki olduğu görülmektedir.…”

A fogásmélység hatása a mikroméretű forgácsleválasztás dinamikai sajátosságaira

“…A kísérleteket egy VHTC 130 típusú öttengelyes megmunkálóközponton hajtottuk végre, 500 µm átmérőjű, kétélű, AlTiN bevonatos, sarokrádiuszos (50 µm) keményfém mikromaróval. A gyártói ajánlást, a korábbi tudományos kutatómunkáinkat, valamint a gép maximális fordulatszámát figyelembe véve 90 m/min forgácsoló sebességet alkalmaztunk a vizsgálatok során [16][17][18]. Az élenkénti előtolást -szintén korábbi kutatásainkra alapozva -8 µm-re választottuk [16][17][18], mivel ez mind a szakirodalom, mind a saját vizsgálatok alapján meghaladja a hmin értékét [8,19].…”

A review on micro-milling: recent advances and future trends

“…In the captured images, the tool can be in any positions, and the algorithm can evaluate it correctly. This is based on the fact that the size of the tool (which perpendicular to the cutting edges of the tool) does [4], [33], [38], [46], [48], [51], [54], [83], [88], [89], [122], [133], [144], [164], [165], [166], [167], [168] AISI 1015: [169] AISI 1018: [125] AISI 1040: [77] AISI 1050: [37] AISI 4340: [119], [139], [170] AISI P20: [20], [145], [164] S960QL: [171] NAK80: [123], [172], [173], [174] AISI A2-annealed: [175] 42CrMo4: [167] X13NiMnCuAl4-2-1-1: [146] SK2: [176] Hardened steels AISI H13: [2], [30], [42], [72], [80], [164], [177], [178], [179],…”