
B-65150E/04 3. α SERIES PARAMETER ADJUSTMENT
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3.4.5 Rapid Traverse Positioning Adjustment Procedure
(1) Overview
The fine acceleration/deceleration function applies a filter to each axis
in the servo software to reduce a shock associated with
acceleration/deceleration. By combining the fine
acceleration/deceleration function with feed-forward, high-speed
positioning can be achieved in rapid traverse. This section describes
rapid traverse positioning adjustment.
(2) High-speed positioning by a combination of fine acceleration/deceleration
and feed-forward
(Rapid traverse positioning when fine acceleration/deceleration is
not used)
A servo loop not performing feed-forward has a delay equivalent to a
position loop gain. The time required for positioning after completion
of distribution from the CNC is four to five times the position gain time
constant (33 ms for 30 [1/s]) (133 to 165 ms for a position gain of 30).
In normal rapid traverse, rapid traverse linear acceleration/deceleration
(Fig. 3.4.5 (a)) is used, so that acceleration changes to a large extent at
the start and end of acceleration. However, since feed-forward is not
used, acceleration change is made moderate by a position loop gain,
and a shock does not occur.
If a low linear acceleration/deceleration time constant is set for high-
speed positioning, and a high position gain and feed-forward are set,
the time required for positioning is reduced, but a shock occurs. In this
case, a shock can be reduced by setting rapid traverse bell-shaped
acceleration/deceleration (optional function) (Fig. 3.4.5 (b)).
Fig. 3.4.5 (a) Rapid traverse linear
acceleration/deceleration
Fig. 3.4.5 (b) Rapid traverse bell-shaped
acceleration/deceleration
Rapid traverse linear time constant (T1) only
Rapid traverse bell-shaped
acceleration/deceleration (T1+ T2)
T1
Feedrate
Time
Acceleration change is
large, so a shock tends
to occur. Feed-forward
cannot be applied.
Feedrate
Time
Acceleration change is
reduced.
T1 + T2