Specifications

Chapter 8 Adjustment
8–17
(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 (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 CNC
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
Unit Explanation Setting range
SV032 TOF Torque offset Stall % (rated
current %)
Set this when carrying out lost motion compensation.
Set the unbalance torque amount.
–100 to 100
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. Both the LMC
compensation and collision detection function are affected.
(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 (DDB 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 msec at a time, to find the timing that the
protrusion and compensation position match.
Before timing delay compensation After timing delay compensation
(Example)
A
fter
compensation
Cutting
direction