3-start Spiroid Gear Set

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The flanks and the root surfaces are computed. The IGES file contains geometrical information about the contact. Moreover, the model file contains both, forward and backward drive contact surfaces. Forward is when the gear in top view rotates CCW.To make the root surfaces is somewhat difficult, because the motion of the hob tip is almost along the flank surfaces. Therefore is the connection of the root surfaces to the flank surfaces has no sharp intersection, resulting in non-exact partition curve. Nevertheless, it is to see that the concave flank (backward drive) has a kind of an undercut, typical for face gears of this kind. I designed the gear quite wide to demonstrate the multiple contact places. In praxis this is not usual, because due to pitch errors contacts over three are uncertain. If you see the contact surfaces in relation to the gear flanks, you will recognise that there is almost no loss of contacts on the flanks due to the undercuts. A bit more on the backward flank. The asymmetric arrangement is typical for one-directional drives, the convex curved flank of the gear should have contact with the steep flank of the worm. This is the case if this worm rotates left, causing the gear to rotate CCW in the top view. The circular arc meridian section profile of the worm ( to be seen in the IGES file) is called CAVEX (TM) profile, invented by Prof. Niemann at the Munich Institute of Technology decades ago, has benefits for building the lubrication film between the teeth. Using the profile the gears teeth are somewhat "fat", good when the gears are made of plastics. To grind a tapered CAVEX worm is tricky, however. The grinding wheel's position must be 3-D changed along the worm axis and the wheel needs to be simultaneously dressed by a CNC controlled dressing diamond. Cylindrical CAVEX worms are much easier to grind.