Siemens Direct Drives – Torque motors 1FW


Ultimate Precision with Direct Drives -

When it comes to power density, direct drives are unsurpassed. They are therefore the ideal solution when maximum dynamics and accuracy are required. In contrast to conventional motors, direct drives are integrated in the machine and transmission elements such as gearing, lead screws or toothed belts can be omitted. This arrangement ensures a high degree of control stiffness and thus a good dynamic response and excellent precision in less space.


The function, performance and accuracy of the electrical components used are the deciding factors for productivity and the quality of the output from machines and systems – not to mention the mechanical execution of the task. What's more, the drive concept also has a significant influence on the life cycle costs of a machine.


Torque motors

Torque motors are direct drives for rotary axes with which precision and force are required at relatively low speeds. Just the same as linear motors, torque motors also have a high degree of precision and dynamic performance – as well as low wear. Because their maintenance and space requirements are minimal, they are often used as an alternative to geared motors. For applications of this kind, CNC Design offers two different types of motor: 1FW3 and 1FW6.


The 1FW3 and 1FW6 torque motors are synchronous motors, which basically operate in a comparable manner to rotary synchronous servo motors. Consequently, the rotor is equipped with permanent magnets; the stator contains the motor windings. The multi-pole design of the windings endows the motor with maximum torques at low speeds. Torque motors are ideally suited for the precise operation of rotary axes when high torques is required.


Thanks to the large number of poles and because mechanical transmission elements and the associated backlash and frictional losses are dispensed with, torque motors boast the following characteristics:

·         High torque

·         Excellent rotational accuracy

·         High acceleration capability

·         Space-saving design

·         Low maintenance

·         High efficiency


The 1FW3 series of torque motors are motors in the torque range between 100 Nm and 7,000 Nm and are complete extremely compact torque motors which, mechanically speaking, needs only to be flange-mounted to the machine and the rotor connected to the machine shaft. 1FW3 complete torque motors are used, for example, in production machines for

·         Main drives for extruders

·         Worms for injection moulding machines

·         Roller drives for paper machines

·         Winders for packaging and paper machines

·         Handling and assembly systems


1FW6 torque motors are compact built-in torque motors. The high ratio between the peak and continuous torque makes this motor the ideal drive for positioning and interpolating motion. The stator and rotor are supplied as individual components and are integrated directly in the machine. Furthermore, its geometry makes it a perfect fit with all of the bearings which are generally used. Integrating torque motors into a machine is a high-precision operation. Our mechatronics experts will be happy to advise and support you in finding the right arrangement for your application and with the integration in the machine. 1FW6 built-in torque motors are used, for example, in machine tools for

·         Rotary tables

·         Swivel axes

·         Fork heads

·         Rotary indexing tables

·         Dynamic tool magazines

·         Turning spindles


Both types of motor have a large hollow bore, with which the motor can be pushed onto the machine shaft. Alternatively, media or mechanical components can be guided through the cavity in the rotor.


For speed and position control, the 1FW3 motor has a built-in shaft encoder; this must be fitted to the machine for 1FW6 motors. The torque motors are water-cooled as standard in order to achieve a high power density. This cooling method also reduces the amount of heat transferred into the machine.


Built-in synchronous and induction motors

Users who produce their own motor spindles can obtain the right built-in motor from CNC Design. These motors are characterized by their compact design, ruggedness, superior precision and accuracy. We offer three different types of built-in motors for motor spindles:

·         The 1PH2 built-in asynchronous motor is employed as a compact, standard built-in motor for turning and grinding spindles with maximum speeds of up to 10,000 rpm.

·         The "High Torque" version of the 1FE1 motor is characterized by very high torques and achieves peak speeds of 20,000 rpm.

·         The "High Speed" version of the 1FE1 motor is characterized by very fast acceleration rates and achieves max. speeds of 40,000 rpm.


The 1PH2 motor is an asynchronous motor. The rotor, which is the squirrel-cage type, and the stator, which is equipped with windings, are delivered as components, which the engineer combines to form a motor spindle that he then installs in the machine. The same applies to the 1FE1 motors. However, unlike the 1PH2 version, they are synchronous motors with a rotor that is equipped with permanent magnets.


With all these motors, water cooling is used to dissipate the heat. The position is sensed by external encoders


Because mechanical power transmission elements (belts, gears) and the resulting backlash are dispensed with, built-in motors boast the following characteristics:

·         Excellent quality of surface finish

·         High acceleration capability

·         High rigidity thanks to compact design

·         Wear-free

·         High efficiency


Our built-in motors are ideal for use in motor spindles for machine tools:

·         1PH2 motors for grinding and turning spindles

·         1FE1 motors for turning, grinding and milling spindles



Due to the high level of integration of direct drives in the machine, special attention must be paid to certain aspects of storage and cooling, that are less important when using conventional rotary servo motors. CNC Design offers not only the right direct drive for every task, but also the necessary experience and advisory expertise for supporting the user in planning the integration of the drive in his particular machine.


In addition to the standard motors described here, application-specific solutions can also be implemented on request.