4. Servo Adjustment
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(2) Unbalance torque compensation
If the load torque differs in the positive and negative directions such as with a vertical axis or slant
axis, the torque offset (SV032 (TOF)) is set to carry out accurate lost motion compensation.
<Setting method>
Measure the unbalance torque. Carry out reciprocation operation (approx. F1000) with the axis to
be compensated and measure the load current % when fed at a constant speed on the NC servo
monitor screen. The unbalance torque at this time is expressed with the following expression.
Unbalance torque (%) =
(+ feed load current %) + (– feed load current %)
2
The unbalance torque value above is set for the torque offset (TOF).
If there is a difference in the protrusion amount according to the direction, make an adjustment with
LMC2. Do not adjust with TOF.
Assume that the load current % was −40% in the + direction and −20% in the –
direction when JOG feed was carried out at approx. F1000. The unbalance torque is as
shown below, so −30% is set for TOF.
−40 + (−20)
2
= −30%
No. Abbrev.
Parameter
name
Explanation Setting range
SV032 TOF Torque offset Set this parameter when carrying out the lost motion compensation.
Set the unbalance torque of vertical axis and slant axis.
–100 to 100
(Stall [rated]
current %)
POINT
Even when TOF is set, the torque output characteristics of the motor and load
current display of the CNC servo monitor will not change. Only the
characteristics of the LMC compensation function are affected.
(Example)
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