AGMA 05FTM05-2005 pdf free.Computerized Design of Face Hobbed Hypoid Gears: Tooth Surfaces Generation, Contact Analysis and Stress Calculation.
3. Simulation of Face Hobbing Cutting Process: Tooth Surface Generation
According to the theory of gearing [3-4, 13], in order to get the analytical representation of gear tooth surfaces, firstly cutting process (i.e. head cutter, cutting blades and cutting machine) has to be described. It will be clear that [9], due to the complexity of FH cutting process, FH cutting blades require a more complicated representation than the ones usually illustrated in the literature (typically for FM method2. In this paper a real FH process, Gleason Tn-Ac , will be studied.
3.1. Cutting Tools: Head Cutter and Cutting Blades
As shown (Figure 1), FH head cutter carries a given number Nb of blade groups; each group contains an outer blade (OB) for cutting concave gear side and an inner one (IB) for convex side. Figure 2 reports, from two different viewing points, one blade group in a Gleason Tni-ac head cutter.
Referring, for example, to the outer blade, in order to correctly locate the blade in the head cutter, the pitch point P of cutting edge (see also Figure 3) has to be defined. The distance from this point to the head cutter center is the equal to r, the angle Lb is introduced in order to take into account that FH process, unlike FM, shows blades that are not aligned to the cutter radius. It is also evident that the blade is not perpendicular to the head cutter plane, but it is mounted at an angle rb with respect to the head cutter rotation axis. The distance from the pitch point P to the tip of the blade is measured by h.
Figure 3 shows the details of outer and inner blades. It is evident that the cutting edge lies entirely on a plane, called Rake plane, which forms an angle Ke with tool plane. It is also introduced the angle e as the angle between the vertical axis of the blade and the projection of the cutting edge on the tool plane.
Once the blade geometry has been introduced, it is possible to compute the analytical formulation of the cutting edge. Many blade profiles are available in commerce. In this paper, a complex blade shape – curved with Toprem – will be analyzed; simpler configurations as straight blade with and without Toprem or curved blade without Toprem® can be easily derived starting from the following discussion. The particular disposition of the cutting edge on the Rake plane requires to set up the reference frame S (Figure 2 and 3) and to search firstly for the analytical description of projection on XZ, plane of the cutting edge. Figure 4 shows the projection on this plane of a curved blade with Toprem the following sections, which are function of the curvilinear coordinate s, have been defined:
I) Bottom: straight horizontal segment:
II) Fillet: circular arc of radius and center at point R (XR, zp);
Ill) Toprem: inclined straight segment
characterized by the length Ly and the angle
IV) Curved blade: circular arc with radius of curvature Pr and center at point 0 (x0, zo). At pitch point P the segment tangent to the blade is inclined by an angle equal to t.AGMA 05FTM05 pdf free download.