Page 195 - Gear Technology Solutions

DW12Z = SLTW-p/Z * [WAME/(p/ZC)] (8)

The gear axis set-over DW12Z does not consider the slot width increase due to
the cutter point radius difference (2 • DRCOW). The V-H machine settings for both
flanks are independently calculated and use an EX-vector which is derived from
the individual radii RWIB and RWOB in a zero-based setup where the tip of the ra-
dius vectors in both cases point at the horizontal center line of the generating gear
(see Figure 6). This would result in a zero-slot width in case of WAME = 0. There-
fore, the equation for DW12Z only computes the difference between the desired
slot width SLTW and the slot width produced by the blade spacing angle WAME.

The following nomenclature is used in the equations:

WAME… blade spacing angle
SLTW… final slot width angle
SLCT… slot width produced by unequally spaced blades in cutter
SCST… stock allowance angle for set-over from convex flank cutting to
concave flank
DRMAX… maximal radius difference to allow for set-over stock allowance
DRCOW… radius difference in reference point 52 for desired length crowning
RWIB… inside blade reference radius (see Figure 2)
RWOB… outside blade reference radius (see Figure 2)
ZC… number of cutter starts
Z… number of coupling teeth
RM… generating gear mean radius

13.7 Practical Results

The calculation of face hobbed couplings is done in the standard Cyclocut™ soft-
ware. Although the input data are quite different from the input data for a Cy-
clocut™ bevel gear pair, the same input screen in the UNICAL™ software is used.
The Cyclocut™ program recognizes the coupling by the additionally entered de-
dendum angle. Basic settings are calculated employing the double V-H method for
both coupling members. The length crowning is realized with a determined radius
difference between the outside and inside blades according to equations (1)
through (7) and the set-over amount is adjusted according to equation (8). Profile
crowning is realized simply with curved blade cutting edges.

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