Indramat (Rexroth, Bosch) MDD/MHD Encoder Removal

There are several types of encoders used on the Indramat MDD/MHD series motors. Please see the section for the encoder type you are working on.  The removal procedure is very much the same across all encoder types. It consists of removing the encoder center bolt and encoder mounting bolts, dropping a small spacer into the encoder shaft, then using a slightly larger "jack bolt" that mates with the larger internal threads of the encoder shaft and pushes the encoder off of the motor's tapered shaft. There are a few minor differences for each type.    

Original Large Diameter Encoders

(Heidenhain ECN/RCN 212, EQN/RQN 224, and Stegmann SCS/SCM70)

The procedure below describes the oldest Hiedenhain and Stegmann types with larger diameter encoders. These encoder shafts often have a keyway, and the motor shaft usually has a soldered key to match. Even if the motor shaft key gets broken off, the encoder can still be easily installed and aligned using our software.  

1. Remove the 4 encoder housing bolts and the 5mm encoder shaft retaining bolt.           
   

2. Insert a 35mm x 3.5mm nail spacer into the empty encoder shaft. Then thread in the slightly larger 6mm jack bolt.
   
   
   

3. Lock the motor shaft and tighten down the jack bolt.
   
   
   
4. The encoder should come off the taper with minimal torque.

Intermediate Encoders (Heidenhain ECN/RCN 413 and EQN/RQN 425

1. Remove the ribbon cable cover plate and detach the ribbon cable. Then remove the encoder's center bolt and any mounting bolts holding it down. These intermediate encoders come with several mounting options. Most are simple to see their removal, the more difficult being these locking ring types. Simply loosen the hex bolt pictured below, which will contract the encoder mounting ring. Once loose, the encoder should spin freely on the shaft, though still locked to it. After motor repairs are finished, make sure to tighten this bolt to secure the encoder's position. 

2.  As in the steps above for the original encoders, insert the spacer into the empty encoder shaft, then insert the larger jack bolt to gently push the encoder off the motor's tapered shaft. Notice the shaft on these intermediate encoders has threads that go all the way to the end of the encoder shaft, like older models. The encoder shaft is also likely keyed. In this case the spacer is not as crucial as in the modern encoders, but we still recommend using it so as not to damage the motor shaft side. 
 




Modern Encoders (Heidenhain ECN/RCN1313 and EQN/RQN1325) 

1. Slide back the black wire cover and carefully remove the delicate ribbon cable. Take care with this cable as they are old and prone to failure (cracking). If the encoder is not testing well through the motor feedback plug (TI-5021), make sure to try connecting directly to the encoder (TI-5076) as these ribbon cables are often an issue. 

2. Loosen the hex bolt pictured below, which will contract the encoder mounting ring. Once loose, the encoder should spin freely on the shaft, though still locked to it. After motor repairs are finished, make sure to tighten this bolt to secure the encoder's position. 

3. As in the steps above for the original encoders, insert the spacer into the empty encoder shaft, then insert the larger jack bolt to gently push the encoder off the motor's tapered shaft. Notice the shaft on these newer encoders does not have threads that go all the way to the end like older models. If you do not use the spacer, then your jack bolt will bottom out too early and you risk damaging the internal threads or even breaking the jack bolt off in the encoder shaft if too much torque is used. It should not take much torque to press the encoder off the motor shaft.