bnp-b2365(eng)b.pdf - 第223页
4. Servo Adjustment 4 - 24 <Adjustment method> Perform the final adjustment, carrying o ut the NC sampling measurem ent (DBB measurement) or actual cutting. If the compensation amount is insuffi cient, increase L M…
4. Servo Adjustment
4 - 23
(1) Unbalance torque and frictional torque
Machine unbalance torque and frictional torque measurements are required before the LMC
compensation can be set. However, the horizontal axis unbalance torque is necessarily "0".
Carry out the reciprocating operation (approx. F1000) with the measured axis, and the load
current % value during constant-speed feed is measured at the NC servo monitor screen. The
unbalance torque and frictional torque at that time are expressed by the following formulas.
Unbalance torque (%) =
(+ feed load current %) + (- feed load current %)
2
Frictional torque (%) =
(+ feed load current %) - (- feed load current %)
2
Assume that the load current % was -55% in the + direction and -25% in the - direction
when JOG feed was carried out at approx. F1000. The unbalance torque and frictional
torque are as shown below.
Unbalance torque (%) =
(-55) + (-25)
2
= -40%
Friction torque (%) =
(-55) - (-25)
2
= 15%
(Example)
(2) Setting and adjusting LMC compensation type 2
<Setting method>
[1] Set the servo function selection 1 (SV027)/bit 9. (The LMC compensation type 2 will start).
[2] Set unbalance torque to the torque offset (SV032).
[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 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.
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
The X axis command direction
changes from + to -.
D
The Y axis command direction
changes from + to -.
B
The Y axis command direction
changes from - to +.
C
The X axis command direction
changes from - to +.
4. Servo Adjustment
4 - 24
<Adjustment method>
Perform the final adjustment, carrying out the NC sampling measurement (DBB measurement) or
actual cutting. If the compensation amount is insufficient, increase LMC1 or LMC2 by 5% at a time.
Note that if the setting is too high, biting may occur.
No. Abbrev. Parameter name Explanation Setting range
SV016 LMC1 Lost motion
compensation 1
Set the compensation amount based on the stall (rated) current of the motor.
The standard setting is double of the friction torque. Setting to "0" means the
compensation amount is zero.
-1 to 200
(Stall [rated]
current %)
SV041 LMC2 Lost motion
compensation 2
Set this with SV016 (LMC1) only when you wish to set the lost motion
compensation amount to be different depending on the command directions.
Set to "0" as a standard.
-1 to 200
(Stall [rated]
current %)
SV032 TOF Torque offset This setting is specified when using lost motion compensation.
Set the unbalance torque of vertical axis and inclined axis.
-100 to 100
(Stall [rated]
current %)
F E D C B A 9 8 7 6 5 4 3 2 1 0
aflt zrn2 afse ovs lmc omr zrn3 vfct upc vcnt
bit Meaning when "0" is set Meaning when "1" is set
8 Set the compensation amount with SV016 (LMC1) and SV041 (LMC2).
9
lmc
00: Lost motion compensation stop 10: Lost motion compensation type 2
01: Lost motion compensation type 1 11: Setting prohibited
SV027 SSF1
Servo function
selection 1
POINT
1. Set SV082/bit1=0 when using LMC compensation type 2.
2. When either parameter SV016: LMC1 or SV041: LMC2 is set to 0, the same
amount of compensation is carried out in both the positive and negative direction
with the setting value of the other parameter (the parameter not set to 0).
3. When the protrusion amount varies according to direction, use LMC2 to adjust it.
For compensation in one direction only, set "-1" at the parameter (LMC1 or LMC2)
for the direction in which compensation is prohibited.
4. Even if a TOF is set, the motor's torque output characteristics and the load current
displayed at the NC servo monitor will remain unchanged. Only the LMC
compensation is affected.
5. The value set based on the friction torque is the standard value for LMC
compensation. The optimum compensation value changes with the cutting
conditions (cutting speed, cutting radius, blade type, workpiece material, etc.). Be
sure to ultimately make test cuts matching the target cutting and determine the
compensation amount.
Optimum Compensation 0 Too high
4. Servo Adjustment
4 - 25
(3) Adjusting the lost motion compensation timing
If the speed loop gain has been lowered from the standard setting value because the machine
rigidity is low or because machine resonance occurs easily, or when cutting at high speeds, the
quadrant protrusion may appear later than the quadrant changeover point on the servo control. In
this case, suppress the quadrant protrusion by setting the lost motion compensation timing
(SV039: LMCD) to delay the LMC compensation.
<Adjustment method>
If a delay occurs in the quadrant protrusion in the circle or arc cutting as shown below in respect to
the cutting direction when CNC sampling measurement (DBB measurement) or actual cutting is
carried out, and the compensation appears before the protrusion position, set the lost motion
compensation timing (SV039: LMCD).
While measuring the arc path, increase LMCD by 10 ms at a time, to find the timing that the
protrusion and compensation position match.
Before timing delay compensation After timing delay compensation
No. Abbrev. Parameter name Explanation Setting range
SV039 LMCD Lost motion
compensation timing
Set this when the lost motion compensation timing does not match. Adjust
while increasing the value by 10 at a time.
0 to 2000
(ms)
When the LMCD is gradually raised, a two-peaked contour may occur at the motor FB position
DBB measurement. However, due to the influence of the cutter diameter in cutting such as end
milling, the actual cutting surface becomes smooth.
Because satisfactory cutting can be achieved even if this two-peaked contour occurs, consider the
point where the protrusion becomes the smallest and finest possible without over compensating
(bite-in) as the optimum setting.
Cutter center path
A
ctual cutting surface
Cutting direction
Quadrant changeover point
Point of LMC compensation execution
Cutter diameter
A
fter
compensation
Cutting
direction