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PLC User's Manual - Positioning Control Edition
Built-in Positioning Functions
4 Before Programming
4.6 Setting of Various Items on Servo Amplifier (Drive Unit) Side
B - 68
4.6.2 Setting of Electronic Gear (For MELSERVO Series)
Use the electronic gear of the servo motor to set the transfer distance per pulse.
For details on the electronic gear setting, refer to the manual of the servo motor or servo amplifier, and set an
optimum value depending on the application.
Setting example 1:
To set the transfer distance per pulse to 10 µm (if the machine uses a ball screw):
Machine specifications
Set the electronic gear as follows:
CMX = 8, CDV = 1
In this case, when the main unit outputs the maximum output
pulse frequency (100 kHz), the servo motor rotational speed
will be as follows:
It is necessary to reduce the pulse frequency on the PLC side in order to reduce the servo motor rotational
speed so that it is less than the rated rotational speed.
*1. Y002 (pulse output destination) cannot be specified when the 14-point or 24-point type FX
3G PLC is
connected.
*2. Devices related to Y003 (pulse output destination) are only valid if two FX
3U-2HSY-ADP adapters are
connected to the FX
3U PLC.
Servo amplifier MR-C Series
Rated rotational speed of servo motor 3000r/min
Lead of ball screw (Pb) 10mm (0.4")/rev
Reduction ratio (mechanical gear) (n) 1/2
Resolution of servo motor (Pt) 4000PLS/REV
Pulse output destination device Maximum speed setting device
Y000 D8344,D8343
Y001 D8354,D8353
Y002
*1
D8364,D8363
Y003
*2
D8374,D8373
f0 : Command pulse frequency [Hz]
(Open collector system)
CMX: Electronic gear
(numerator of command pulse
multiplying factor)
CDV : Electronic gear
(denominator of command pulse
multiplying factor)
N0 : Servo motor rotational speed [r/min]
0 : Transfer distance per pulse [mm]
Servo motor
Pt = 4000 (PLS/REV)
n
Pb=10[mm](0.4")
n=NL/NM=1/2
NL
NM
=
0
×
n
×
P
b
Pt
1/2
×
10
4000CMX
CDV
= 10
×
10
-3
×
=
1
8
×
CMX
CDV
N
0
=
60
Pt
×
f
0
=
1
8
×
60
4000
×
100000
= 12000r/min > 3000r/min (Rated rotational speed of servo motor)