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5. Spindle Adjustment
5 - 27
5-3-2 Adjusting the acceleration/deceleration operation
(1) Calculating the theoretical acceleration/deceleration time
Each theoretical acceleration/deceleration time is calculated
for each output range based on the spindle motor output
characteristics as shown on the right. Note that the load
torque (friction torque, etc.) is 0 in this calculation expression,
so the acceleration/deceleration time can be known as a
rough guide, but this calculation result differs from the
acceleration/deceleration time of the actual machine.
(a) Maximum motor output during
acceleration/deceleration: Po
During acceleration/deceleration operation, the motor
can output at 120% of the short-time rating. Thus, the
motor output Po in the constant output range during
acceleration/deceleration follows the expression below.
Po = (Short-time rated output) × 1.2 [W]
(b) Total load inertia: J
all
The inertia of the total load which is accelerated and decelerated follows the expression below.
J
all
= (Motor inertia) + (motor shaft conversion load inertia) [kg•m
2
] (Caution 1)
The acceleration/deceleration time until the rotation speed "N" to be required is calculated for
each motor output range as shown below, using the values obtained in (a) and (b).
(c) Acceleration/deceleration time for constant torque range: t1···0 to N [r/min] (0≤N≤N1)
(For N>N1, apply N=N1 and also calculate t2 or t3.)
1.097 x 10
-2
x J
all
x N1 x N
t1 =
Po
[s] (Caution 1)
(d) Acceleration/deceleration time for constant output range: t2···N1 to N [r/min] (N1<N≤N2)
(For N>N2, apply N=N2 and also calculate t3.)
1.097 x 10
-2
x J
all
x (N
2
- N1
2
)
t2 =
2 x Po
[s] (Caution 1)
(e) Acceleration/deceleration time in deceleration output range: t3···N2 to N [r/min]
(N2<N≤N3)
1.097 x 10
-2
x J
all
x (N
3
- N2
3
)
t3 =
3 x Po x N2
[s] (Caution 1)
Based on the above expressions, the acceleration/deceleration time: t from 0 to N3 [r/min] is:
t = t1 + t2 + t3 [s] (Caution 2)
CAUTION
1. Note that the inertia (J) is a quarter of "GD
2
".
Ex.) When "GD
2
" is 0.2 [kg･m
2
], the inertia is "0.2 ÷ 4 = 0.05 [kg･m
2
]".
2. If the AC input power voltage to the power supply is low, or if the input
power impedance is high, the acceleration/deceleration time may be long.
(Especially, the acceleration/deceleration time of the deceleration output
range may be long.)
Output [W]
Output characteristics for
acceleration/deceleration
0
N1
N2
0
N3
Po
Rotation speed [r/min]
Short-time rating
×
1.2
Constant
output range
Constant out
p
ut ran
g
e
Deceleration
range