In case of gear machininig by continous mode, the milling tool runs along teeth profile, from tip circle down to diameter that it is necessary to warrant.

For usual teeth dimensions the lenght of this path is about 2 - 2,2 x normal module.

In case it is possible to fit Feed value along X in order to have constant feed value along the profile, ( (fig.15A) (fig.16A) ) according to:

thus:

active maching time for a path-lenght s= 2,2 * module may be calculated by:

and for the whole gear, consisting in Z teeth cut in L/p levels:

In case feed on profile Frel = 150 mm/nin and p = 50 mm will be:

For example, with (Frel=150 p=50) mn=30 z=28 L=500 will lead to 123' = 2,05 h for each flank , thus 4,10 h for whole facewidth, that might reduce to about 2,50 in case of double tool.

By using an HM insert hob diam 360 mm , with cutting parameters: Vt=110 n=97 a=1,25 L=500+250=750 we have about 173'=2,90 h for whole facewidth.

This may seem a good result, but if you consider all remaining service activities (handling, insert change, offset, controls etc) and the cost of tool and inserts, I think to may say that milling is anyway a convenient way of machining.

Don't forget that 1 only milling cut may remove much more material stock than a HM skyving unit action.

Machining time in multi-plane mode will be a little higher than in continous mode, because there are more many not-cutting movements and some paths are partially covered each other.

Only a real test may show the difference, and I extimate machining time in multi-plane mode might be about 1,2 * continous mode time.