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4 Servo Adjustment
MITSUBISHI CNC
(2) Setting and adjusting LMC compensation type 3
LCM compensation type 3 can be used to accommodate quadrant projection changes that accompany
feed rate and circular radius changes which could not be accommodated by LCM compensation type 2.
In this case, on a machine model where the travel direction is reversed, the effect caused by torsion or
expansion and contraction on the machine system are also considered in addition to the friction, with
compensation occurring in accordance with the changes in the cutting conditions.
Adjust Compensation parameter (SV016, SV041), a basis of compensation, while measuring roundness
at low speed. Then adjust viscous coefficient (SV086) while measuring roundness at high speed.
LMC compensation type 3 parameter adjustments should be made while measuring an electrical end
position FB waveform by the NC sampling function.
<Adjustment method>
[1] Turn the NC side machine error compensation (pitch error compensation, relative position
compensation or backlash compensation) OFF.
(Even if SV113/bit7=1 is applied, the machine error compensation can be ignored.)
[2] Set servo function selection 5 SV082/ bit=1. (The LMC compensation type 3 will start).
[3] Set a value double the friction torque to the lost motion compensation 1 (SV016). The SV016
setting value will be used for compensation in the positive and negative directions when the lost
motion compensation 2 (SV041) is 0.
[4] Set the initial value, SV016 x 200 to the lost motion compensation viscous coefficient (SV086).
[5] Perform a roundness measurement at such speed as radius R=100mm and feedrate F=1000mm/
min and adjust SV016 value.
[6] Set SV041, when changing the compensation amount in the direction for compensation. The
setting of the compensation direction is shown below with the setting of CW/CCW in the NC
parameter. If compensating only one direction, set –1 to the side not to be compensated.
[7] Perform a roundness measurement at such speed as radius, R=100mm and feedrate, F=5000mm/
min. (Select a condition to be used for the actual cutting according to the machine's specification.)
Adjust viscous coefficient (SV086) by increasing and reducing it approx. ±500 gradually to have
minimum quadrant protrusion.
[8] After adjusting SV086, verify its accuracy by performing roundness measurement at low speed
again.
[9] At this time, if requiring to improve the accuracy further, adjust the spring constant (SV085) in
increments of about 50 while performing the machine roundness measurement at low speed.
Compensation point CW CCW
A X axis: SV041 X axis: SV016
B Y axis: SV016 Y axis: SV041
C X axis: SV016 X axis: SV041
D Y axis: SV041 Y axis: SV016
+Y
-Y
+X-X
A
T
he X axis command direction
c
hanges from + to -.
D
The Y axis command direction
changes from + to
-
.
B
The Y axis command direction
changes from - to +.
C
T
he X axis command direction
changes from - to +.