Position-Time Cams - Siemens SINUMERIK 840D Function Manual

N3: Software cams, position switching signals

13.4 Position-time cams

13.4 Position-time cams
Position-time cams
The term "position-time cam" refers to a pair of software cams that can supply a pulse of a
certain duration at a defined axis position.
Solution
The position is defined by a pair of software cams.
The pulse duration is defined by the lead/delay time of the plus cam.
Machine data can be used to specify that cam pairs with "minus cam position = plus cam
position" should be processed as position-time cams.
Properties of position-time cams
● The pulse duration is independent of the axis velocity and travel direction reversal.
● The pulse duration is independent of changes in the axis position (Preset).
● Activation (rising signal edge) takes place only when the cam position is crossed.
Moving the axis position (e.g. preset) does not trigger activation.
● A lead/delay time is operative for the minus cam and causes a time displacement of the
pulse.
● Activation (ON edge) and pulse duration are independent of the travel direction.
● The cam is not deactivated if the cam position is crossed again when the cam is active
(direction reversal).
● The cam time (pulse width) is not interrupted and the cam time not restarted when the cam
position is crossed again.
This behavior is particularly relevant with respect to modulo axes, i.e. if the cam time is
greater than the modulo range crossing time, the cam is not switched in every revolution.
Settings
The following settings must be made to program a position-time cam:
● Position
The position must be defined by a cam pair with which the minus cam position is equal to the
plus cam position.
This is defined using setting data:
SD41500 SW_CAM_MINUS_POS_TAB_1
...
SD41507 SW_CAM_PLUS_POS_TAB_4.
● Pulse duration
The pulse duration is calculated by adding together the associated entries for the cam pair
in:
MD10461 SW_CAM_PLUS_LEAD_TIME[n]
SD41521 SW_CAM_PLUS_TIME_TAB_1[n]...
SD41527 SW_CAM_PLUS_TIME_TAB_4[n]
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Axes and spindles
Function Manual, 06/2019, A5E47437747B AA