Calculating The Switching Instants; Switching Frequency And Switching Position Distance - Siemens SINUMERIK 840D sl Function Manual

TE8: Cycle-independent path-synchronous switching signal output
16.2 Functional description
16.2.3

Calculating the switching instants

In order for the switching to be as precise as possible at the switching positions calculated,
the control calculates the positional difference between the actual position of the geometry
axes involved and the switching difference in every position controller cycle.
If the positional difference is less than 1.5 position controller cycles, the control converts it into
a temporal difference taking into account the current path velocity and acceleration rate of the
geometry axes.
With the temporal difference specified, a hardware timer is started, which triggers the
switching signal at exactly the instant calculated in advance regardless of the position
controller cycle.
16.2.4

Switching frequency and switching position distance

Maximum switching frequency
The maximum switching frequency is: 1 signal edge change per IPO cycle
Note
Special case: IPO cycle time = position controller cycle time
In this case, the maximum switching frequency is:
1 signal edge change per 2 IPO cycles
Minimum switching position clearance
The minimum possible distance between the switching positions placed one above the other
depends on:
• The duration of an IPO cycle
• The feed rate
The theoretically possible minimum distance can be determined from these dimensions as
follows:
Example:
For IPO cycle times of 2 ms and position controller cycle times of 1 ms as well as a feed rate
of 20000 mm/min, the theoretically possible minimum distance between switching positions
one above the other is limited to:
20000 mm/min * 2 ms = 0.667 mm
652
Function Manual, 09/2011, 6FC5397-2BP40-2BA0
Special Functions