Calculation of cut-in profile cutters using KOMPAS 3D V8 graphic software

Abstract

Owing to progress in continuous path machining of profiled parts on lathe machines with numerical program control, application of profile cutters for cutting parts of the rotary-body type has shrunk. However, there is no alternative to such cutters when cutting parts with a complex profile (step junctions with kinks and short segments of straight lines, circular arcs, and other curves) that cannot be produced by continuous path machining. Profile cutters have a number of additional advantages: a long service life, which is possible thanks to a large number of resharpening cycles; the exact profile of a part is ensured for the same initial setting with a resharpened cutter during its entire service life; and the possibility to use one cutter instead of several sequentially operating cutters machining segments of a complex profile that require coordinated setting during initial configuring, resharpening, and replacement, thus, resulting in a reduced number of changeovers and toolheads required for automatic lathe machines. All of these advantages can only be realized if cutters are automatically designed by a computer program removing the problems related to the selection of a cutter’s design that correspond to the specific features of a part’s profile surface. The variety of profile-cutter designs is explained by the following factors: the different location of the profiled surface on a part (internal, external, end face), the different location of the cutter with respect to a part owing not only to the previous reason but also due to additional turns and tilts needed to increase the back rake angle, the different shapes of the profiled flank surface of cutters (prismatic, spiral, or body of rotation), and the different positions of a cutter’s face surface (below profile cutters with a flat face surface are considered). The latter feature ensures obtainment of optimal front rake angles and easy installation of the cutter on a machine. When designing a cutter, to diminish the spread of the back rake angle, it is desirable to have not only those points of the cutting edge (CE) that are located on the height of a part’s axis and below it (but not higher) but also to ensure a possibly small range of the heights of the CE points. In addition, when machining conic segments of a profile for a part where strict linearity of the generatrix is required, the cutter face has to cross the surface of such a segment along the generatrix. In a standard approach, for each such specific case, an algorithm for calculation of the cutter profile is created (which is called the adjustment calculation); however, such algorithms are not always available, so a designer often has to develop the required algorithm independently. The solution to this problem usually consists of obtaining a sequence of formulas derived on the basis of geometric relations. If a more universal calculation program integrated in modern graphic packages is developed, method [1] is more convenient. This method, which is called the coordinate one, includes the following steps. 1. The position of a cutter’s front face is set in the part’s coordinate frame Σ p ( X p , Y p , Z p ) (Fig. 1) using a reference point, a reference line (through which the front plane passes), and the face angle set in the plane perpendicular to the cutter’s base 1 or in the part’s faceend plane (for prismatic cutters with back slope of the frame), i.e., the cutter face is set in the standard way. The cutter’s front face is oriented by the designer (program user) regardless of the cutter’s position.