Siemens SINUMERIK 840C - Manual (Page 834)

11.92 12 Functional Descriptions
12.7.2 Description of the spindle modes
Example:
• Spindle/C axis with double-track encoder
• One motor for both modes (one setpoint output)
• In this example, the actual values from the two encoder tracks show the same direction of
rotation, which means that MD 564*, bit 2 and MD 520* bit 1 have to have the same
setting. The values for the sign in front of the setpoints are taken from these settings.
• If this is not the case (direction of rotation of spindle and C axis not the same), positioning
with M19 will be incorrect after switching from C axis to spindle operation.
• Where opposite directions of rotation are required for C axis and spindle, "Resynchronize
spindle" (DB 31, DW K +2, bit 0 and bit 3) must be triggered after switching back to
spindle operation via the PLC and before repositioning with M19.
Procedure for ”parked” axis
The spindle-specific signal SPINDLE SYNCHRONIZED is cancelled when the PARKING AXIS
signal is reset, although it is an essential precondition for the selection of the C axis mode.
So, if the PARKING AXIS signal is cancelled in the C axis mode, the C axis must be explicitly
referenced (e.g. with G74).
If the signal is cancelled in the spindle mode, the C axis can be referenced automatically when
the spindle is synchronized. The following can be employed:
1. Program an M function for selecting the C axis mode.
2. Decode an M function in the PLC user program.
3. Employ user program control:
• Move the spindle to a position near the zero mark (IS:PLC SPINDLE CONTROL and
POSITION SPINDLE).
• Cancel the signals PLC SPINDLE CONTROL and PARKING AXIS (couple up the C
axis encoder first if necessary).
• Re-synchronize the spindle. There are several alternatives, e.g.:
–
Pass the zero mark at basic speed (IS:PLC SPINDLE CONTROL and INITIALIZE;
ascertain direction of rotation with IS:SET ROTATION CW).
• Cancel the signal PLC SPINDLE CONTROL and set the signal INITIATE C axis MODE.
4. Machining with the C axis
The advantage of this method is that machining with the C axis can begin sooner because a
defined axis position is reached quickly.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50 12–59
SINUMERIK 840C (IA)