7 years ago
motor turning the workpiece that was sychronised to the
rotations of the hob used a series of belts and pulleys to up
the speed of the hob so that a sufficiently high rate of pulses
could be had to drive the stepper motor from an optical disc
Now, those of us with an interest in amateur radio will know of
the technique of using a PLL to resolve FM.
Now, the rate of variation of audio is several orders of
magnitude higher than the variations in speed of a cutter
when it is subject to the force of cutting, so it seems
to me that a PLL synchronised to an optical disc right
on the hob axis, without the multiplying effect of the
pulleys and belts, should do the same trick?
What is needed is to divide down in the first instance
so that the workpiece is turning at the same RPM as
the hob, and then divied down agin for the number of teeth.
This, of course, is for straight-cut spur gears for the division
ratios for helical-cut gears are a nightmare altogether, and
a second stepper motor is needed in any case for the feed.
(I refer to my widely-available spreadsheet, "Hobnail" that
calculates gear ratios for mechanical hobbing machines)