SICK Stegmann CNS/SRS/SRM Encoders with Threaded Rear Shaft: Removal and Installation

Overview

SICK Stegmann has legacy encoders which have a threaded rear shaft and a pressure fit, collapsible front shaft. In this article we cover the removal and installation process to safely service motors that have these encoder types equipped. 

Removal

Block the motor's drive shaft to prevent rotation. Undo the electrical encoder connections. The encoder likely has a split compression shaft as shown above. It is only held into the motor shaft by pressure and sometimes a little glue. To safely remove the encoder, a custom tool is needed.  SICK Stegmann does not offer any such removal tools for this type.  We use this custom-made slide hammer to safely tap them out. The mating tool threads onto the rear encoder shaft, and the slide weight moves over the rod to gently tap out the encoder. You could also design a simple T-handle that threads on the encoder shaft and allows you to pull straight out but that will require more care to remove safely. The original installation can use glue to help bind the shafts, and that requires a bit more force to break their bond.  

Installation

That following steps are from the Stegmann manual, but the general idea is fairly simple. You lock the motor, preset the encoder alignment, then press the encoder into the motor shaft. The Hiperface models encoders can be electronically aligned afterwards, but you must take extra care with physically aligning the shafts on the CNS incremental types. 

Stegmann suggest using a tool to press the encoder in but this can be done by hand. They mention an "activator and adhesive" be used on the mating shafts. We are not familiar with either product they use.   

"Block the customer's drive shaft (motor's shaft) to prevent rotation. Use a screw pressing tool onto the B-side encoder shaft end (2). Spray activator onto the encoder shaft (1) and into the hole of the drive shaft. Thinly apply adhesive onto the encoder shaft (1). Plug encoder shaft (1) in drive shaft (3) and continuously press, with the pressing tool, up to the stop (10). Do not hit with a hammer or similar tool!"

These encoders often have a rubber boot on them to prevent ingress when installed. Make sure that the encoder's rubber boot is in tact and makes a proper seal with the motor housing and contact plate.