bnp-b2365(eng)b.pdf - 第222页

4. Servo Adjustment 4 - 23 (1) Unbalance torque and frictional torqu e Machine unbalance torque and frictio nal torque measurement s are required before the LMC compensation can be set. Ho wever, the horizontal axis unba…

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4. Servo Adjustment
4 - 22
4-3-5 Improvement of protrusion at quadrant changeover
The response delay (caused by dead band from friction, torsion, expansion/contraction, backlash, etc.)
caused when the machine advance direction reverses is compensated with the lost motion compensation
(LMC compensation) function.
With this, the protrusions that occur at the quadrant changeover in the DBB measurement method, or
the streaks that occur when the quadrant changes during circular cutting can be improved.
The following three compensation types are available for lost motion compensation (LMC compensation).
[1] LMC compensation type 1
This is a backward compatible (for older models) compensation type. Either type 2 or type 3 should
be used on new models.
[2] LMC compensation type 2
Performs servo internal PI control response delay compensation for the frictional torque reversing
condition that occurs during servo reverse travel. Reverse response delay is compensated with
adding the torque command set by parameter when a speed and direction change occurs.
LMC compensation type 2 adjustments should be performed with reference to the following items.
(1) Unbalance torque and frictional torque
(2) LMC compensation type 2 setting and adjustment
(3) Lost motion compensation timing adjustment
(4) Adjustment at feed forward control
[3] LMC compensation type 3
In addition to frictional torque influence, this type compensates torsion and expansion/contraction
influences in the machine system in which compensation amount is changed by travel speed. A
mechanical system viscosity coefficient setting further enhances the compensation accuracy even
if the travel speed is changed. Adjustment requires a machine end roundness measurement.
LMC compensation type 3 adjustments should be performed with reference to the following items.
(1) Unbalance torque and frictional torque
(2) LMC compensation type 3 setting and adjustment
Circle cutting path before compensation
Compensation
Cutting
direction
DBB: Double Ball Bar
Circle cutting path after compensation
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