Siemens SINAMICS S120 Getting Started page 148

Performing basic parameterization
6.3 Drive axes
The LU per load revolution should be selected as high as possible. In this way, a better
dynamic response can be achieved. If the values for p2506 are too low, this can result in
jumps when speed precontrol is activated.
For good repeat accuracy, the LU per load revolution should be selected in the ratio of 1:10
to the encoder resolution, if the encoder resolution can provide this at the required dynamic
response.
Example 1: Linear axis – spindle (encoder on the motor side)
Leadscrew pitch = 10 mm
Gear ratio i = 1 (p2505/p2504)
Target variable to be controlled: mm
Encoder resolution = 15,000 LU
10 mm distance are travelled per load revolution. According to the encoder resolution,
maximum 15,000 LU/10 mm = 1,500 LU per mm can be defined. We will select 1,000 LU per
mm (1 LU = 1 µm). 10 mm per revolution results in 10,000 per revolution:
● p2506 = 10,000 LU per load revolution
Example 2: Rotary axis (encoder on the motor side)
Gear ratio i = 44.5
● p2504 = 445 motor revolutions
● p2505 = 10 load revolutions
Target variable to be controlled: °
Encoder resolution = 364,544 LU
360° are travelled per load revolution. According to the encoder resolution, maximum
364,544 LU/360° = 1012 LU per ° can be defined. We will select 100 LU per ° (1 LU = 0.01°).
360° per revolution results in 36,000 LU per load revolution.
● p2506 = 36,000 LU per load revolution
Example 3: Modulo axis – chain drive
The chain has 250 chain links and a chain link is 0.0338667344 m long. The output wheel
has 40 teeth, i.e. 40 chain links are moved per revolution. The target positions are at a
distance of 25 chain links to one another.
Gear ratio i = 114.28 (rounded off)
Ratio of the number of teeth of the gearbox = 106,967/936
● p2504 = 106,967 motor revolutions
● p2505 = 936 load revolutions
Encoder resolution = 468,095 LU
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Getting Started, 12/2018, 6SL3097-5AG30-0BP0