Siemens SINUMERIK 840C - Manual (Page 731)

07.97 10 Axis and Spindle Installation
10.4.4 Reference point approach
This function is started by
• G74 from the part program (with internal triggering of G200 for this axis at the end of
referencing) or
• pressing of the direction key enabled for referencing by the user in the reference point
approach mode.
The block-stepping conditions with G74 are the same as with conventional referencing. As
soon as the function has been initiated, either the axis or the measuring system must be
moved, for example by hand or by an auxiliary drive, so that the reference cam and the zero
mark are passed.
When the zero mark is reached, the absolute system is set according to MD 240*, 244* and
the constant offset of 2000 position control increments (not with C axes to spindles). A con-
ventional NC-controlled reference operation provides the same result.
In order to be able to execute the function, servo enable must also be set for an axis in follow-
up mode.
10.4.4.5 Setting reference dimension by a PLC request
(SW 4 and higher)
The PLC request ”Set reference dimension” permits to bring an axis to the ”Axis referenced”
state at any position without explicit referencing operation:
This function cannot be executed unless the axis is at standstill.
Corresponding data:
NC MD 1824*, bit 5 ”Setting reference dimension allowed”
NC MD 1824*, bit 3 ”Set absolute system to reference dimension”
NC MD 240*, ”Reference point value”
NC MD 244*, ”Reference point offset”
NC MD 396*, ”Absolute encoder offset”
NC MD 564*, Bit 1 ”Reference point offset negative”
Signal: ”Set reference dimension”, (DB 32, DW K+2, bit 14)
Signal: ”Reference point reached”, (DB 32, DW K+0, bit 12)
Significance of this function:
• Set absolute system to MD 240* (depending on MD 1824*, bit 3)
• Enable leadscrew error compensation, IKA compensation
• Enable SW limit switch monitoring
• Set "Reference point reached" bit, (DB 32, DW K+0, bit 12)
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SINUMERIK 840C (IA)