Heidenhain: Scale Drum with centering collar (TTR ERM 2400 Series)
Scale drum with centering collar for an incremental built-in encoder with magnetoresistive scanning

The robust ERM modular magnetic encoders are especially suited for use in production machines. Their large available inside diameters, their small dimensions and the compact design predestine them for:

C axis on lathes

For years, the ERMs have been the preferred encoders for C axes on lathes.
Besides their high resistance to contamination, the large inside diameters are
also important to allow bar material to be machined without limitations.
Because of this design arrangement, the graduation of the ERM is usually on a much larger diameter than the workpiece. Position errors of the encoder therefore affect workpiece accuracy to a correspondingly reduced degree.

Rotary and tilting tables

Rotary tables and tilting axes require encoders with high signal quality for position and speed control. Encoders with optical measuring standards, for example the RCN series, fulfill these requirements in an ideal way. For medium accuracy requirements magnetic modular encoders can also be used. Due to their small signal period of 200 µm, the ERM 2200 encoders feature particularly low position error within one signal period and therefore permit relatively high axis speed stability. In addition, the typical advantages of magnetic modular encoders, such as tolerance to contamination and large inside diameters, are very helpful in this application.

Spindles on milling machines

Spindles are among the key components of machine tools and significantly influence their function. The spindle properties are determined by design, drives and bearing systems, but also the encoders make a decisive contribution to performance. They have to permit high rotational speeds and be sufficiently sturdy. Speeds of over 40 000 rpm are no problem for the ERM 2900. In addition they fulfill the requirement for compact dimensions.

If milling and turning operations are to be performed on one machine, increased requirements for spindle accuracy are the result. On complex workpieces, certain machining movements can be performed only through the interaction of feed axes and spindle positions. For example, when manufacturing a thread, a single-point tool needs to assume a defined angular attitude. Here the ERM 2400 encoders with 400 μm signal period come into use. They have better accuracy behavior and, for example, 600 lines on an outside diameter of 75.44 mm. This is significantly more than gears with comparable dimensions.