General

AXRY bearings can be equipped with inductive angle measuring systems. These are available in incremental (MI) or absolute (MA) versions, as single or multi-head systems in various accuracies.

By mounting the measuring ring directly on the bearing ring, concentricity errors with respect to the shaft (table) are minimised and thus highest accuracies of a few angular seconds are realised.

myonic only supplies the “mechanical part”, i.e. the bearing including the mounted measuring ring and thread in the outer ring for axial or radial scanning head mounting.

Advantages

myonic supplies bearing-integrated absolute and incremental angle measuring systems in cooperation with Heidenhain (AMO). Here the measuring ring is directly mounted onto the bearing. As a standard it is mounted on the inner ring as this has a fit to the shaft. The shell surface on which the measuring ring is mounted runs almost concentrically to the table centre due to exceptionally accurate myonic production tolerances. This increases the system accuracy and thus the overall accuracy of the axis. Because these measurements take place close to the workpiece, deviations through torsion or tilting are almost completely avoided. AMO measuring systems are inductive systems, i.e. no magnetic or optical components are used. AMO systems have the advantage of a high accuracy / speed, direct mounting without own bearing (no additional friction/heating and largest hollow shaft) and no encapsulation (IP67 standard) is required. The measuring unit is not magnetic and therefore completely resistant to electromagnetic interference fields.

Open system

myonic has developed the new generation of absolute measuring heads and has consciously openly designed this development. All manufacturers and users are able to procure these systems directly from Heidenhain (AMO). This guarantees that all users can access the systems without limitations. No ties to an individual roller bearing manufacturer are necessary when deciding on a measuring head.

Measuring accuracy

System accuracy:

Accuracy of the completely assembled angle measuring device only on the AXRY bearing.

Mainly influenced through:
■ The pitch accuracy of the measuring ring (±3µm or ±5µm)
■ Eccentricity error of the measuring ring (1/2 radial runout inner ring)
■ Interpolation error of the measuring head (IPF-AMO)

Total accuracy:

Accuracy of the completely assembled angle measuring device in the machine axis.

Mainly influenced through:
■ Deformation of the axis (tilting etc.)
■ Form and dimension deviations in the customer shaft and adjacent construction
■ Installation errors

The larger the bearings are, the more easily can high system accuracies be realised. Using multi-head solutions, accuracies of less than +/- 1 arcsec have been realised in practical applications. The heads are available with different input frequencies so that ultra-precision applications and high speed applications can be covered.

Available systems

Measuring systems can be mounted on most axial-radial bearings of the construction series AXRY-NGX / AXRY-NGS and AXRY-EX

The following systems are available:
■ Incremental systems (MI) as single and multi-head solutions as miniature heads with external electronics or with heads with integrated electronics.

■ Absolute systems (MA) as single and multi-head solutions as modular heads. This can be mounted axially or radially. In case of radial assembly, the measuring head is mounted on the shell surface on the outer ring of the bearing. This means that the complicated adjustment of the air gap between the head and measuring ring is no longer required.

Due to the height of the measuring ring of 10 mm incremental or 14 mm absolute, the construction heights increase for the smaller and medium bearings. Details are specified in the product tables.

Function, incremental vs. absolute systems

The measuring ring permanently mounted on the bearing contains a measuring track and a reference track. The measuring track represents the measuring embodiment, into which a high precision periodic pitch is photolithographically etched. These gradation marks or increments are counted by the head as they pass by, whereby the absolute position is unclear. On incremental systems, this is obtained through a distance code on the reference track. By travelling over 2 neighbouring reference marks, the system is able to determine the absolute position. The necessary angle is dependent on size; generally less than 30°. On absolute systems, a second absolute pitch division runs in parallel to the incremental pitch division, which continually supplies the control system with a constant, absolute position.

Connection to control system / electronics

myonic cooperates closely with Heidenhain (AMO) regarding all measuring system electronics. This enables efficient connection to very different control systems, cable outlets, cable lengths, feedthroughs etc. Prototype solutions are realised short-term. The best know-how bearers for mechanics and electronics are available from a single source.

Delivery condition

myonic only supplies the “mechanical part”, i.e. the bearing including the mounted measuring ring and thread in the outer ring for axial or radial scanning head mounting.

The bearings are prepared for mounting up to 2 measuring heads (axially or radially mountable on the outer ring). The required threads for assembly are located in the outer ring (axial and radial 2 each).

The measuring heads can be directly procured via Heidenhain (AMO).

If required, just the bearings can be supplied, appropriately prepared to hold measuring rings.