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Couplings and Clutches
The revolution toward using highly dynamic digital drives
with high-speed, accurate AC servo and induction motors has dramatically
changed machine design and coupling performance.
Currently, machines are made to be smaller, smoother and faster. In
addition, smaller motors, with or without planetary gearboxes, let them
achieve the speed, torque and precision previously accomplished using
larger, full-speed (2,000-3,000 rpm), analogue AC servo-motors.
Conventional coupling design is incompatible with the performance levels
of today’s machines. Gear-type couplings exhibit backlash and with
repeated positioning in both directions, have high wear and replacement
rates. Jaw-type couplings are suitable for pumps and hydraulic drives,
but are too soft for highly dynamic drives.
The disc type, with low inertia and high stiffness, is preferred over
the jaw and gear types for servo-controlled machines. However, its use
is limited to machines with small coupling requirements. On larger
applications with frequent reversing, the screw connecting the disc to
the clamps will experience backlash and eventual wear.
Small step motors or encoders make cost-effective use of aluminium,
helical split-beam couplings. However, this coupling type isn’t
torsionally stiff enough to handle applications requiring load reverses.
A stainless-steel version improves stiffness, but its high inertia uses
up most of the torque on small motors, leaving little to move the load.
A wide range of new coupling designs allows every type of industrial
machine to experience advanced, servo-quality machine and drive
protection. New capabilities include the following:
- Zero backlash
- Low inertia
- High torsional stiffness
- Long life with no wearing parts
- Compensation for axial, radial, and angular misalignment
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