Mitsubishi Electric MELDAS MDS-B Series Instruction Manual page 27

(2) Unbalance axis load force
When operations (1) to (8) are for an unbalance axis, calculate so that the following forces are
required in each period. Note that the forward speed shall be an upward movement.
Period Load thrust calculation method
(Amount of acceleration thrust) +
(1) (Kinetic friction force) + (Unbalance
force)
(Kinetic friction force) + (Unbalance
(2)
force) + (Cutting force)
(Amount of deceleration thrust) +
(3) (Kinetic friction force) + (Unbalance
thrust)
(Static friction force) + (Unbalance
(4)
force)
− (Amount of acceleration thrust) −
(5)
(Kinetic friction force) + (Unbalance
force)
− (Kinetic friction force) + (Unbalance
(6)
force) − (Cutting force)
− (Amount of deceleration thrust) −
(7)
(Kinetic friction force) + (Unbalance
force)
− (Static friction force) + (Unbalance
(8)
force)
During a stop, the static friction force may constantly be applied. The static
friction force and unbalance force may particularly become larger during an
POINT
unbalance upward stop, and the thrust during a stop may become extremely
large. Therefore, caution is advised.
(3) Max. cutting thrust and max. cutting duty
If the max. cutting force and max. cutting duty (%/min) are known, the following expression can be
used for the selection conditions.
0.8 × Fs ≥ Fc ×
Fs : Motor continuous thrust
Fc : Max. cutting force during operation (N)
D : Max. cutting duty
(4) Unbalance force
For an unbalanced axis, such as a gravity axis, basically balance it with a
device such as a counterbalance. With the linear motor, the continuous thrust
is lower than the rotary motor, so if the axis is unbalanced the motor's heating
CAUTION
amount will increase. If an error should occur, the axis will drop naturally. This
is hazardous as the dropping distance and dropping speed are large.
Chapter 3 Selection
Table 3-2 Load thrusts of unbalance axes
Normally the acceleration/deceleration time constant is
calculated so this thrust is 80% of the maximum thrust of the
motor.
The signs for the amount of acceleration thrust and amount of
deceleration thrust are reversed when the absolute value is
the same value.
The holding force during a stop becomes fairly large.
(Upward stop)
The generated force may be in the reverse of the movement
direction, depending on the size of the unbalance force.
The holding force becomes smaller than the upward stop.
(Downward stop)
D
100
3–5
Explanation
(N)
(%/min)
･･･
(3-4)