Siemens SINUMERIK 840C Installation Instructions Manual page 732

10 Axis and Spindle Installation
10.4.4 Reference point approach
MD 1824* bit 5 enables this function. By means of MD 1824* bit 3 the user can define whether
only the "Reference point reached" signal is set with "Set reference dimension" or whether
the absolute system is also set to the value specified in MD 240*. MD 1824* bit 3 is active only
with the "Set reference dimension" function and has no effect on normal reference point
approach (default: setting of absolute system MD 240* active).
The request is triggered by an edge change of the axis-specific control signal DB 32, DW
K+2, bit 14 "Set reference dimension".
When the edge is positive, the "Reference point reached" status signal is first deleted (DB 32,
DW K+0, bit 12).
If the actual value system of the NC has been updated according to the the new reference
dimension (only if MD 1824*, bit 3 = 1) after subsequent deletion of the "Set reference
dimension" control signal (negative edge), the status signal "Reference point reached" is set
again as positive acknowledgement of the function. If the function could not be executed (axis
not at standstill), the "Reference point reached" signal is not set and, in addition, the axis-
specific RESET alarm 1028* "Setting reference dimension not possible" is triggered. This
monitoring function is not performed unless the axis is in position-controlled operation when
"Set reference dimension" is requested.
If position control is not active, two different cases are possible:
a) Follow-up operation/parking active:
Equal values for setpoint and actual value are set in this state. No following error is stored.
If "Set reference dimension" is requested, setpoint and actual value are set to the new
value (depending on MD 1824*, bit 3).
b) Controller enable missing:
In this state, the following error is stored. If "Set reference dimension" is requested, an
active following error is deleted (depending on MD 1824*, bit 3) and setpoint and actual
value are set to the reference dimension value (depending on MD 1824*, bit 3).
General conditions for using leadscrew error compensation, IKA:
Leadscrew error compensation/IKA does not make sense and operate properly unless "Set
reference dimension" is performed in the reference point of the axis. Otherwise, leadscrew
error compensation/IKA looses its reference to the existing machine system since leadscrew
error compensation/IKA uses the position at the moment when "Set reference dimension" is
requested as reference position.
10–42
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SINUMERIK 840C (IA)