Servomotors are handy for Kuka's robots

The MCS range of servomotors is used for the hand axes of the KR2004 robot manufactured by the Kuka Company of Ausberg, Germany.

Todays servo drive systems must be able to meet very exacting requirements.

A graduated range of high performance servomotors is essential to allow optimised matching between the load, the motor and the drive.

Lenze has used new technology to create a range of synchronous servomotors with maximum torque and higher dynamics.

The MCS range is available in five frame sizes with a spread of torques from 0.5 to 190Nm, manufactured with an innovative new production technique called SEpT - single element pole technology.

Evidence of the exacting standards of performance and durability achieved in the MCS range is their selection for the hand axes of the KR2004 robots manufactured by the Kuka Company of Ausberg, Germany.

Kuka is Germany's leading robot manufacturer and is number three in the world.

Its customers range from Audi to Volvo, and include almost all European automotive manufacturers.

MCS motors are integrated in the hand axes of the KR2004, which can carry up to 200kg - for example a typical load for an automotive fully automated welding system.

The motors had to be powerful, compact and resistant to harsh conditions, particularly including vibration.

Lenze developed SEpT technology as an improved way to construct the coils within servomotors.

Unlike conventional stators, the copper wire is not fed through a narrow opening in the slot.

Instead the pole is wound individually and directly.

Considerably more copper fits into the stator using this clever solution.

This means the motor is more compact and so the power density is higher.

At the same time, the poles are wound very tightly further increasing the power density and achieving excellent resistance to vibration.

These individual coils are matched with a new generation of high-energy magnets.

Constructed from neodymium-iron-boron material (NdFeB), they are highly resistant to corrosion and demagnetisation, even at high temperatures.

Using SEpT technology combined with high-energy magnets, Lenze has created a practically distortion-free sinusoidal working field in the motor.

An important part of the design process was simulation using finite element method, or FEM.

This numerical calculation process is normally used to calculate the stresses and deformations of complex geometrical structures.

Here the method was used to optimise the density of magnetic flux between the rotating magnets on the motor and the stator with its individual coils.

The result is the motor runs extremely smoothly because there is no disruption from a distorted field.

In the UK customers have commented on how smooth the running is at low speeds.

This is most noticeable at low speeds where conventional motors show "cogging", that is uneven torque as the motor rotates from pole to pole.

The MCS motors with SEpT technology run close to zero speed with a smooth torque output.

Further benefits from the optimised magnetic flux paths are increased efficiency as less flux is lost, and once again higher power density.

Lenze introduced the MCS range with SEpT single element pole technology to the market in 2004.

The main benefits from the distortion free, purely sinusoidal working field are increased torque at a given physical size, and excellent smooth running.

The higher levels of power density can also allow the designer to choose a motor with reduced inertia and so increase the performance of his system.

All models are designed for long life with large bearings and long lasting temperature resistant grease.

In addition the SepT technology allows the wires in the windings to be mechanically absolutely fixed.

The result is high resistance to shock and vibration because the wires in the coils cannot move against each other.

The MCS range has as standard five frame sizes with bodies from 60 to 190mm square.

However this range is extended to 28 models by variation in length and speed.

In each frame size up to four different body lengths are offered by varying the length of the stator and rotor.

Changes in rated speed are achieved by internal construction of the poles, and typically range from 4000 to 6000rev/min on small motors to 1400 to 3000rev/min on the larger models.

The end result is a choice from nominal torques between 0.5 and 51Nm with peak torques available between 2.4 and 190Nm.

The overload capacity varies from model to model and is typically between 3 and 6 time the nominal torque.

For the machine designer, this all means a wide choice so that the optimum motor in terms of torque, speed and inertia can be selected for highest machine performance.

The options available for the MCS motors make the task of the system specifier easy.

As well as motors only, MCS can be supplied as geared motor in helical, bevel and planetary configurations.

The connection between motor and gearbox is direct without requiring a shaft coupling, saving on size and cost but particularly avoiding the potential of extra inertia, torsion under load and wear in reversing applications.

Standard on the motors is a built-in temperature sensor and insulation to temperature class H.

Permanent magnet brakes can be specified and most frame sizes have two brake options to give a choice of brake torque.

Feedback to the controller can be done by low cost and robust resolvers, or with sincos absolute encoders for better accuracy.

With the new SEpT technology, Lenze has created a range of synchronous servomotors with a step forward in terms of performance.

The MCS range is already proven in arduous applications and achieves particularly long life.

The breadth of the range together with comprehensive options makes possible the choice of the best motor for the machine task.

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