The smart factory can only work if machines and parts operate increasingly independently and communicate with each other via the network. This would not be possible without progressive digitalization and a high degree of flexibility. This is why servo drives have become indispensable in networked and flexible production environments. With the help of digital interfaces for motor-controller communication, important parameters such as position, speed, vibration or temperature can be transmitted. Motor and system manufacturers always focus on issues such as cost and space reduction, simple implementation and maximum performance.

Hengstler, a manufacturer of industrial counting and control components, has now introduced the new Acurolink interface. According to Hengstler, this guarantees a saving of at least 50 percent of the plug-in space, reduced set-up costs and a high level of machine safety. The entire motor feedback communication is realized via two hybrid cables specially developed by the Lapp Group.

Hengstler calls its technology Single Cable Solution. This is a combination of the high-performance Acuro AD37 encoder and the new Acurolink open interface. Hengstler has been involved in the development and production of encoders since 1983. "These many years of experience and the close cooperation with well-known customers during the pilot project phase ensure that the Single Cable Solution has the potential to create a new industry standard," says Adrian Benz, Team Leader Marketing Communication at Hengstler.

Gaining space and losing weight

The servo motor feedback encoder series from Hengstler is designed for the most demanding applications.

The data protocol of the electrical interface meets the SIL3 requirements according to IEC 61508, Cat. 3 PLe according to EN ISO 13849. The encoder contains both an internal temperature sensor and a separate connection for the motor's winding temperature sensor, making it possible to record this information directly in the encoder. A standardized "Electronic Data Sheet" (EDS) in the encoder stores specific encoder data and can be retrieved at any time. Motor and drive data can be stored in an internal OEM memory in the encoder itself. Acurolink offers great advantages, especially for compact servomotors. The provision of motor power and motor feedback signals via a single-cable solution significantly increases efficiency. The space saving and lower weight are particularly noticeable in larger systems.

Low-capacity cables with a small cross-section

The Lapp Group has developed two hybrid cables precisely matched to the digital interface: The Ölflex Servo FD 7DSL and the Ölflex Servo 7DSL. With this solution, both power and data are transmitted via a common cable. This also applies to the signals from other sensors, such as the temperature sensor, which are integrated into the digital motor feedback protocol. The FD variant is equipped with a highly durable PUR sheath and is therefore ideally suited for use in guide chains. If, on the other hand, the cable is used in fixed installations, the more cost-effective PVC version can be used. Polypropylene (PP) is used throughout as the conductor insulation material. This meets the demand for low-capacity cables and minimizes the problem of interfering leakage currents on the braided shield. In addition, smaller wall thicknesses can be realized with PP than with PVC.

Typical cable structure: 3 black power cores, GN/GE protective conductor, optional control pair with shielding braid (black), signal pair with aluminum-clad foil and shielding braid (white/blue). (Image: Lapp)

The lower wall thicknesses in the insulation also reduce the outer diameter. Up to 20 percent can be saved with PP compared to PVC. "We can also contribute our expertise to cables for torsion applications and offer types that meet the demanding requirements," says Lucas Kehl, Head of Product Management Cables at Lapp. As data is also transmitted in the hybrid cable, electrical parameters such as characteristic impedance, damping values, but also capacitance, inductance and resistance values as well as propagation times and wave impedances in the defined frequency range are of great importance. For Acurolink, for example, the characteristic impedance is specified as 110 ±10 Ω.