Description
The “Move to fixed stop” function can move an axis to a fixed stop and exert a defined contact pressure on the fixed stop.
The function is selected by an axis-specific command in the NC program. In addition, the axis must be moved by a path motion or a single axis motion (see [PROG//Independent axes]). Motion to the fixed stop is referred below as ‘approach block’.
After the “Move to fixed stop” function is activated:
- the CNC reduces the permitted torque in the drive and
- also switches off other monitoring functions such as the position lag monitor (see [FCT-A1]) in the CNC and in the drive.
The motion to approach the fixed stop is executed at reduced torque. The CNC then automatically reduces axis acceleration. During the approach motion the CNC monitors the position lag of the axis and increases it when the stop is reached. As soon as the specified limit is overshot:
- the CNC stops the axis,
- discards the block distance to go and
- changes to the next NC line.
As long as the axis is stationary at the fixed stop, the drive continues to apply the specified torque on the fixed stop. While the axis is moving towards the fixed stop or when it reaches the fixed stop, it may not be reprogrammed in the NC program. However, the parameters may be changed at any time, e.g. torque limit.
While the axis is stationary at the fixed stop, the CNC monitors the actual position. As soon as the actual value leaves a specified tolerance window, the CNC issues error message P-ERR-70548.
When the “Move to fixed stop” is switched off, the setpoint is tracked on the actual position of the axis. At the same time, the torque limit is cancelled and the monitoring functions are re-activated, e.g. position lag monitor. Together with the switch-off command, a path motion should always be specified for the axis to move away from the fixed stop.
If the fixed stop was not detected at the end of the motion block, the CNC issues error message P-ERR-50886. Output of the error message can be suppressed by the axis parameter P-AXIS-00716 or by the keyword ERR_NOT_DETECTED.
Prerequisites
“Move to fixed stop” can be used:
- For SERCOS and CANopen drives which support a maximum torque limit. Normally they are the drive objects S-0-0092 for SERCOS and 0x6072 for CANopen.
- For path or spindle axes which were replaced in the path compound.
- If the backward motion memory is not switched off in the controller, i.e. a value greater than 0 is specified for the NC channel in the start-up parameter P-STUP-00033.
Restrictions
If the “Move to fixed stop” function is active for an axis, the following commands and actions are not permitted for this axis:
- The axis may not be reprogrammed in the NC program.
Otherwise the CNC issues error message P-ERR-21967. - The axis may not be released.
Otherwise the CNC issues error message P-ERR-21970. - No actual position may be requested for the axis.
#CHANNEL INIT [ACTPOS].
Otherwise the CNC issues error message P-ERR-21964. - Tracking mode may not be activated for the axis.
Otherwise the CNC issues error message P-ERR-70549. - Drive releases may not be reset for the axis.
Otherwise the CNC issues error message P-ERR-70546.
Behaviour at CNC reset
After a reset the CNC issues error message P-ERR-70549 if:
- moving to fixed stop was interrupted by a CNC reset,
- the fixed stop is not detected and
- the parameter P-AXIS-00715 has the value 1.
The “Move to fixed stop” is then deselected.
However, if the fixed stop was already detected at CNC rest, the function "Move to fixed stop" remains active. If the parameter P-AXIS-00717 is set with the value 1, the CNC issues the warning message P-ERR-70550 during the CNC reset.
Behaviour at program end
If the function "Move to fixed stop" is not deselected before the end of the NC program, the function remains active after program end. No automatic deselection takes place.