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3. Characteristics
3 - 8
3-2-2 Magnetic brake
CAUTION
1. The axis will not be mechanically held even when the dynamic brakes are
used. If the machine could drop when the power fails, use a servomotor with
magnetic brakes or provide an external brake mechanism as holding means
to prevent dropping.
2. The magnetic brakes are used for holding, and must not be used for normal
braking. There may be cases when holding is not possible due to the life or
machine structure (when ball screw and servomotor are coupled with a timing
belt, etc.). Provide a stop device on the machine side to ensure safety.
3. When operating the brakes, always turn the servo OFF (or ready OFF). When
releasing the brakes, always confirm that the servo is ON first. Sequence
control considering this condition is possible by using the brake contact
connection terminal (CN9) on the servo drive unit.
4. When the vertical axis drop prevention function is used, the drop of the
vertical axis during an emergency stop can be suppressed to the minimum.
(1) Motor with magnetic brake
(a) Types
The motor with a magnetic brake is set for each motor. The "B" following the standard motor
model stands for the motor with a brake.
(b) Applications
When this type of motor is used for the vertical feed axis in a machining center, etc., slipping
and dropping of the spindle head can be prevented even when the hydraulic balancer's
hydraulic pressure reaches zero when the power turns OFF. When used with a robot, deviation
of the posture when the power is turned OFF can be prevented.
When used for the feed axis of a grinding machine, a double safety measures is formed with
the deceleration stop (dynamic brake stop) during emergency stop, and the risks of colliding
with the grinding stone and scattering can be prevented.
This motor cannot be used for the purposes other than holding and braking during a power
failure (emergency stop). (This cannot be used for normal deceleration, etc.)
(c) Features
1) The magnetic brakes use a DC excitation method, thus:
• The brake mechanism is simple and the reliability is high.
• There is no need to change the brake tap between 50Hz and 60Hz.
• There is no rush current when the excitation occurs, and shock does not occur.
• The brake section is not larger than the motor section.
2) The magnetic brake is built into the motor, and the installation dimensions (flange size) are
the same as the motor without brake.
(d) Considerations to safety
1) Using a timing belt
Connecting the motor with magnetic brakes and the load (ball screw, etc.) with a timing
belt as shown on the left below could pose a hazard if the belt snaps. Even if the belt's
safety coefficient is increased, the belt could snap if the tension is too high or if cutting
chips get imbedded. Safety can be maintained by using the method shown on the right
below.
Dangerous!
Safe!
Timing belt
Ball screw
Top
Bottom
Load
Motor
(No brakes)
Brake
Ti
ming belt
Ball screw
Top
Bottom
Load
Motor
Brake