Heidenhain further expands its inductive position measurement product line with the new ECI 4000/EBI 4000 hollow shaft encoder. This new encoder features a modular design, no built-in bearings, and a 90 mm hollow shaft. Users can use it to convert traditional belt-driven motor feedback systems into torque motors. This new encoder not only reduces the number of parts but also improves performance.
Automation levels in manufacturing enterprises are constantly increasing, and this productivity improvement relies on drive systems with higher dynamic performance and greater efficiency. Furthermore, to succeed in market competition, machinery and equipment must be designed to be more reliable, environmentally friendly, and resource-efficient. The key to meeting these requirements is electric drive technology. It offers lower noise, less wear, typically requires no maintenance, and does not sacrifice any performance.
In particular, direct-drive technology for torque motors is becoming increasingly important because it eliminates the need for other mechanical transmission components in the drivetrain. Furthermore, its power density and dynamic performance are often indispensable for meeting production demands. This necessitates a unified and high-performance complete system, including servo amplifiers for control functions, drive units, and position measurement systems as motor feedback. Heidenhain has designed and developed new high-performance position encoders for these applications: the hollow shaft rotary encoders ECI 4000 and EBI 4000 (Figure 1). These encoders set new benchmarks in the dynamic performance, reliability, and functionality of control systems, opening up entirely new applications for inductive rotary encoders.
Figure 1: Heidenhain ECI 4000 and EBI 4000 inductive hollow shaft rotary encoders, whose 90 mm diameter hollow shaft allows the encoder to be directly mounted on the motor.
Replace belt drive
For example, the new hollow shaft encoder allows torque motors to replace the belt-driven motor feedback systems commonly used to date. It also improves performance. Due to the significant reduction in the number of parts, the directly mounted new hollow shaft encoder experiences no wear during operation. A wider control bandwidth ensures a significant improvement in dynamic performance. Furthermore, the new rotary encoder is an ideal measurement system for other motors, drive modules, and machine components for which hollow shaft encoders are available.
The single-revolution ECI 4000 boasts a resolution of up to 20 bits. Heidenhain also offers a multi-revolution version of the EBI 4000. This version features a 16-bit resolution and an external backup battery. The entire system includes the readhead and induction drum. It offers exceptional performance and a total height of only 20 mm.
High-precision full-circumference scanning
Position values are read through a full circumferential scan. In this encoder, all the bars of the sensing drum (rotor) and the corresponding scan strip of the reading head (stator) acquire position signals through scanning. During operation, this rotary encoder processes two incremental scan signals with different signal periods. This scanning principle has very relaxed requirements for installation tolerances and positioning accuracy.
Positional errors occur when the rotation center of the drive shaft shifts, but this error can be largely compensated for in principle by using a full-circumferential scanning method. This important characteristic supports speeds up to 6000 rpm. Figure 2 shows the typical accuracy curves for a drive shaft with a radial eccentricity of 0.2 mm and ideal mounting. For radially positioned rotary encoders, based on geometric principles, the measurement repeatability of a single scan point under the same conditions will be significantly improved.
Figure 2: Typical accuracy curve when the drive shaft radial eccentricity is 0.2 mm (hollow shaft diameter is 90 mm)
Simple connection, reliable data transmission
The new ECI 4000 and EBI 4000 inductive rotary encoders utilize the digital EnDat 2.2 interface. The power supply voltage range is +3.6 V to +14 V. The encoder uses Heidenhain's standard plug-in encoder cable. In addition to noise-free data transmission, the EnDat 2.2 interface supports other device-related functions, such as providing temperature data from internal and external temperature sensors and standard effective digital functions for signal diagnostics. In closed-loop control mode, these operating parameters are output, allowing users to continuously monitor the encoder status. Single-turn encoders also offer an optional DRIVE-CLiQ* interface connection.
We are currently preparing for application certification of the encoder according to EN 61508 at SIL 2. The aim is to ensure the secure transmission of single-turn position information. With additional measures added to the subsequent electronic circuitry, the security of the EnDat 2.2 device can be further improved to SIL 3. Of course, the fault protection conditions required for the corresponding mechanical connection security are also part of the certification process.
This encoder can be easily installed and integrated into motor and machine tool applications. Its IP40 protection rating is one of its key features. The rotary encoder features an outer centering circle for the reading head and an inner centering circle for the sensing drum. Therefore, installation can be completed quickly without any special tools for commissioning and testing (Figure 3), allowing for immediate operation. The application-related axial misalignment tolerance between the sensing drum and the reading head is ±1.5 mm. The maximum runout tolerance of the drive shaft is also relatively large, reaching 0.2 mm. With an EnDat 2.2 interface, this encoder operates over a temperature range up to +115 °C. Therefore, according to EN 60068-2-6 standards, its vibration resistance up to 400 m/s² for the stator and up to 600 m/s² for the rotor makes it suitable as a feedback system for motors. It ensures greater robustness, making it particularly suitable for high-performance motors.
Figure 3: The induction drum (center) and the reading head (right) are aligned with the centering circle, allowing for easy encoder installation without the need for debugging or testing tools (left image: typical motor).
in conclusion
Heidenhain further expands its torque motor application product line with its new ECI 4000 and EBI 4000 inductive hollow shaft rotary encoders. These encoders set new benchmarks in key metrics for dynamic performance, reliability, and functionality in drive applications.
*DRIVE-CLiQ is a registered trademark of Siemens AG.
