The SICK Stegmann Hiperface SEK/SEL series encoders are bearing-less inductive encoders. The lack of internal bearing can make the removal and installation process slightly more complicated. Part of the encoder shaft and disc housing are made of plastic, and it is susceptible to break if not careful with removal.
Encoder Removal
The removal process is simple enough, as shown below from the SEK/SEL 37 manual:
Block the motor drive shaft. Open the cover (1) using a screwdriver (Fig. A).
With the supply voltage disconnected, withdraw the stranded cable set (9+10).
Undo the screw (7). Undo the 2 M3 screws (6). The encoder can be removed.
A common issue from removing these encoders is that the shaft of the encoder can get stuck inside the motor shaft. and when you go to finally remove the encoder, it can break the plastic shaft as shown below. If you feel any resistance when removing the encoder, proceed slowly. You can try gentle pressure on the inside of the encoder shaft to try and brake the friction with the motor shaft.
Encoder Installation
Installing the encoder should be fairly simple. From the encoder manual, referencing the picture above:
Block motor drive shaft. Open the cover (1) using a screwdriver if required (Fig. A).
Carefully push encoder (2) onto the motor shaft. Ensure that the center collar (3) of the encoder locates cleanly with the center of the motor and that the tapered shaft (4) is inserted straight into the taper of the motor shaft. Rotate the encoder until the holes of the encoder fixing lugs (5) are positioned over the fixing holes of the motor plate. To ensure that the encoder housing seats correctly, fasten it to the motor bearing plate by alternately tightening the 2 M3 screws (6). Tighten the screws (7).
Caution!
The thread in the motor shaft must be free from dirt, grease and burrs.
The taper must be free from dirt and grease.
One of the common issues when installing these encoders is setting the alignment. The SEK/SEL encoders have the lowest incremental resolution of all Hiperface encoders at only 16ppr (64 counts). This makes the Electronic Alignment tool much less accurate. You may notice the electrical angles are set far off from the angle you entered, especially on motors with a high number of poles. You can un-check the "Preserve Phase" box which will provide better results, but you need to know if the corresponding drive is OK with an error in the Phase Offset field. Rexroth drives requires the encoder to be aligned with "Preserve Phase" box checked. It's best to leave the phases preserved if you are not sure.
If the encoder is used on a Rexroth MSK series motor, then the better option is to use the Rexroth MSK Memory Programming test to write a new angle into the memory data that matches your current alignment. For all other motors, they can be aligned correctly by using a combination of mechanical adjustment and electronic alignment. Simply try aligning the encoder using the electronic commutation tool. If the angle is off then remove the center bolt from the encoder, jiggle the disc into a slightly new position, then re-tighten and try electronic alignment again. Eventually the disc will be in a good position where the electronic alignment should fall within our 3 degree tolerance.
Video of the electronic alignment process:
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