Crossed helical gears are helical gears that are mounted on crossed axes. The shaft angle is usually Σ = 90 degrees. In contrast to the line contact shown in cylinder worms, paired with globoid worms, crossed helical gears only contact at one point. With increasing load, the point of contact between the worm and the helical gear is expanding to a contact ellipse. In the helical gearing, the meshing line runs tangentially to the base circle, angular in space. So, the contact situation has to be tested in 3-D.
With the 3-D variant skin model, the contact pattern characteristics of the crossed helical gears and worms with enveloping worm wheels can be simulated in KISSsoft. Collisions or interference in the crossed helical gear are recognizable by the changed form course of the compression ellipse. Unlike the highly-limited elliptical contact pattern of crossed helical gears, an identical worm geometry paired with a globoid worm leads to a wider range over the entire tooth extending contact pattern.