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 limit switch can be transmitted to the CNC either via the PLC interface (see [HLI]) or by reading the drive digital inputs directly if the used drive type supports this (see also P-AXIS-00321).

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 operated, the drive stops automatically and only accepts setpoints which move away from the limit limit. 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:

  1. Motion to hardware limit switch
  2. Reversal
  3. Axis homing either at the falling edge of the hardware limit switch or after the falling edge of the hardware limit switch and reception of the encoder zero impulse (see also P-AXIS-00084).

Homing to hardware limit switch with gantry axes

Attention

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 operated.