web
You’re offline. This is a read only version of the page.
close
Support Portal

FAQ

What is the difference between static and dynamic shaft movement at encoders and motor feedback systems

Article No: KA-10543
Version: 1.0
Subject to change without notice
Related Products
absolute encoders
incremental encoders
motor feedback systems

Table of Contents

Static radial shaft movement of the drive element

The static radial shaft movement is the inaccuracy of the encoder mounting. It is caused, when the shaft is not exactly between the mounting holes. This inaccuracy is called static, because it is not changing by turning the shaft. At the DFS60, the maximum value could be +-0,3mm.

Dynamic radial shaft movement of the drive element

The dynamic radial shaft movement is the inaccuracy of the shaft. This is caused due of a runout tolerance of the shaft. This inaccuracy is called dynamic, because we get it during the rotation movement of the shaft. At the DFS60, the maximum value could be +-0,1mm.

Static axial shaft movement of the drive element

The static axial shaft movement is caused of temperature expansion of the shaft or a wrong mounting. This force act static of the encoder, because it is moving very slowly (temperature), or it is not moving (wrong mounting). The force changes not with a movement of the shaft. At the DFS60, the maximum value could be +-0,5mm.

Dynamic axial shaft movement of the drive element

The dynamic axial shaft movement describes a fast or short movement of the shaft. E.g. an axial movement of the shaft at the startup of the motor because of a helical gear or a tolerance of the ball bearing of the motor. At the DFS60, the maximum value could be +-0,2mm.

General

You can combine the 2 values. But the single value must be inside it’s limit. E.g.: If the shaft is shifted about 0,3mm and the shaft is wobbling about +-0,1mm. Then the shaft is moving in a range from +0,2mm to + 0,4mm.

Additional information about the axial movement in a motor

A motor has 2 ball bearings.

  • The "A side" is where the motor is connected to the application
  • The "B side" is where usually the encoder is mounted

One ball bearing is mounted "fixed" and one ball bearing is mounted "floated"
The reason to do this, is to compensate the axial movement due to temperature change in the motor's shaft.
If the "fixed" ball bearing is on the "A side" or on the "B side" depends on the kind of motor, the application or the motor manufacturer.

Depending on the position of the fixed ball bearing, we also have to struggle with the axial movement in the encoder.


How big is the movement due to temperature?
→ from cold to hot, the movement is: each 100mm shaft length it is 0.1mm

Due to the fact, that the ball bearings have a kind of lash, we also have a kind of dynamic movement.
→ the ball bearing lasch is about 0.1mm (depending on the size of the ball bearing)
Keywords:
mounting, mechanic, radial, axial
Create request