Каталог Dormer Pramet фрезерование 2021 - 2022 - страница 704

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AXIAL ANGLERADIAL ANGLE b ap b 1 ap ap 9 CHOICE OF TOOL Milling Cutter Geometry 0° + - + - 0° + - - + When choosing a tool, it is necessary to take many criteria into ac- geometry perform the best, while tools with positive - positive geom- count. One of the primary requirements is that the place of first etry will be the most problematic. Another criterion is chip removal. contact between the cutting wedge and the workpiece lie further Negative - negative tools push the chip into the work surface (towards away from the tip and the cutting edge. That, however, is dependent the workpiece) while positive - positive tools do the opposite, leading on the basic geometry of the cutting wedge i.e. angles GAMO – go, the chip away from the work surface, i.e. away from the workpiece. LAMS – ls, KAPR – kr , as well as the mutual position of the mill- It is thus an optimal compromise to combine negative and positive ing cutter and the entry edge of the workpiece. The following figure angles. shows individual milling cutter geometries (or rather, the combina- tions of radial and axial angles) at some of the most adverse engage- ment conditions (i.e. when the axis of the milling cutter is in line with the edge of the workpiece). At the bottom of the figure is a depiction of the indexable insert with an indication of the area where the in- sert makes first contact with the workpiece. The figure shows that in such adverse engagement conditions, tools with negative - negative Entering Angle hDKAPR = 90° KAPR = 75° hD1 KAPR = 45° h D2 b2 f f f hD = f hD1 = 0,97f hD2 = 0,71f kc = 1,00 kc1 kc = 1,01 kc1 kc = 1,09 kc1 kc/b = 1,00 kc/b1 = 0,98 kc/b2 = 0,77 When choosing the entering angle for face milling, you should, Finally, it is important to emphasise that the lower the entering angle, among other things, account for the power and rigidity of the ma- the thinner the chip and the longer the engaged section of the cutting chine (size and type of tool holder), its dynamic capabilities and maxi- wedge, which is important with regard to heat dissipation and the mum depth of removal. For instance, if you have a high-performance distribution of force across the edge of the insert. Also worth men- (50 – 100 kW) machine at your disposal with an ISO 50 tool holder and tioning is the change in the direction of the resultant cutting forces, you cut at high depth, your first choice should be a milling cutter with which, in simplified terms, can be visualised as perpendicular to the an entering angle between 90° – 58°. On the other hand, if you have a edge. (Decreasing the entering angle increases the passive compo- low-power machine (up to 10 kW) with an ISO 40 (HSK 63) tool holder nent of the cutting force leading into the spindle and decreases the and you expect to cut at 2 – 3 mm depth, you should choose a tool active radial component of the cutting force). with an entering angle of 45° – 10° (i.e. HFC) or with round inserts. It would thus be an ideal compromise to choose a tool with an entering angle of 45°, which can also handle higher depths of cut and, when compared to a tool with an entering angle of 90°, can cut at the same depth at up to 30 % higher feed and at approximately the same load. 703