Use of hardware limit switch as reference switch (P-AXIS-00329)
P-AXIS-00329 | Use of hardware limit switch as reference switch | |
Description | If a hardware limit switch of an axis is used as reference switch, this parameter has to be set to 1. The state of the hardware limit switch can either be transferred to the CNC via the PLC interface with the control unit “lr_mc_control.reference_cam“ (see [HLI]) or by reading the drive digital inputs directly if the used drive type supports this (see also P-AXIS-00321) is inactive. | |
Parameter | kenngr.ref_cam_is_limit_switch | |
Data type | BOOLEAN | |
Data range | 0/1 | |
Axis types | T, R, S | |
Dimension | T: ---- | R,S: ---- |
Default value | 0 | |
Drive types | ---- | |
Remarks | Using a hardware limit switch as reference switch is only possible if the drive amplifier does not go into an error state if the hardware limit switch is actuated. | |
When the hardware limit switch is actuated, the drive stops automatically and only accepts command values which move away from the limit switch. The deceleration used to brake the drive must be set in the drive. Since the drive only executes CNC motion commands conditionally when a hardware limit switch is operated, position lag and window monitoring are deactivated for NC-controlled homing to the hardware limit switch.
The sequence is then as follows:
- Motion to hardware limit switch
- Reversal
- Referencing the axis either on the falling edge of the limit switch or the falling edge of the limit switch followed by the zero pulse of the encoder (see also P-AXIS-00084).
Homing to hardware limit switch with gantry axes
Attention
Homing to hardware limit switch with gantry axes is only possible if the hardware limit switches of all gantry axes (master and slave axes) are mechanically located at the same position.
In other words, if the gantry system was aligned straight and moved to the hardware limit switches, they would operate all the switches simultaneously.
As opposed to NC-controlled homing to homing switches, homing to hardware limit switches causes a relative motion of the axes to each other during the homing operation. This is because the axes stop automatically when the hardware limit switch is operated and no longer execute the controller motion commands. The relative motion of the axes to each other increases proportionally to the difference in the positions of the hardware limit switches of the individual axes.
The sequence described above for a single axis is executed for each gantry system axis. In addition, the gantry system moves away from the hardware limit switches at the end of homing until all the switches are no longer actuated.