
4.SELECTING A MOTOR DESCRIPTIONS FOR FANUC AC SERVO MOTOR β series B-65232EN/03
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(6) Data to be provided by FANUC
(a) Input multiply ratio, command multiply ratio, and flexible
feed gear ratio
The NC set values required for moving the machine tool at
the least input increment values are entered in these blanks.
The relation among these values as illustrated below.
Command multipl
Error
register
Flexible
feed gear
In the above figure, each ratio is set so that the units of the
two inputs (a and b) of the error register are the same. The
β pulse coder uses a flexible feed gear as standard. So,
CMR is normally set to 1. When other than 1 is to be set for
CMR, contact FANUC for details.
For the flexible feed gear (F.FG), the ratio of the number of
position pulses required per motor shaft revolution to the
number of feedback pulses is set.
The set value is obtained as follows:
F.FG=(Number of position pulses requiredper motor shaft
revolution)/1,000,000
NOTE
The maximum permissible value for both the
numerator and denominator is 32,767. So, the
fraction should be reduced to its lowest terms,
after which the resultant numerator and
denominator should be set.
Example)
Suppose that the NC uses increments of 0.01mm,
the machine travel distance per motor shaft
revolution is 8 mm, and pulse coder βA32B is
used.
F.FG=(8/0.01)/1,000,000=800/1,000,000=1/1250,
CMR=1