Description

Operating mode of distance control

Distance control is integrated after interpolation and, if necessary, superimposes the programmed movement. Distance control acts independently of the interpolator's current status, and is active even when waiting for acknowledgements (e.g. M functions).

Distance control determines the actual absolute position of the workpiece surface with the aid of the motor encoder of the axis and an additional sensor. The two sensors are coupled to one another, i.e. the two sensors' values always change in mutual opposition when the axis moves.

Description 1: — Figure 1-4: Probing the workpiece surface

Calculation of deviation

With the aid of electronic probing, the deviation of the real workpiece surface from the specified set position (SET_POS) is determined in each cycle. It results from:

Deviation = sensor 1 + sensor 2 - set position (SET_POS)

= actual workpiece surface position - set position (SET_POS)

To compensate for the workpiece surface deviation, the drive position is additionally moved by the calculated offset of the distance control:

Drive setpoint = programmed setpoint (PCS) + distance control offset

Description 2: — Figure 1-5: Block diagram of distance control

Selecting and cancelling via the NC program

Distance control is activated or deactivated, or the current correction value is also frozen, via the NC program.

Example:

N10 Z[DIST_CTRL SET_POS=30] Set position 
N10 Z[DIST_CTRL ON] Selection 
…
Nxx Z[DIST_CTRL OFF] Cancellation 
N999 M30

The complete CNC syntax is described in chapter Programming.

Typical sequence

Typical sequence when activating distance control:

The tool is loaded.
X and Y axes move to machining position
Distance control is activated and the workpiece's set position is set
Z axis moves down
Sensor or probe ring reports distance
Distance control is active; thickness tolerances or position differences are compensated

Deactivating distance control:

Distance control is deactivated via the NC program
Distance control is inactive, thickness tolerances or position differences are no longer compensated, and the current offset remains active until the next position request.

Principle of operation

With distance control, deviations in the position of the workpiece surface (actual position) with respect to a specified set position can be corrected:

Description 3: — Figure 1-6: Ideal workpiece

Deviation

A deviation from the ideal workpiece surface (e.g. in the case of a thinner workpiece) is detected by the sensor (sensor 2):

Description 4: — Figure 1-7: Real workpiece without distance control

Offset compensation

After activation of distance control with SET_POS=20 mm (expected workpiece height), the offset is compensated by the distance control. As a result, there is no need to adapt the NC program (PCS position):

Description 5: — Figure 1-8: Real workpiece with distance control

	In case of an axis error, CNC reset or at program end of the NC channel, which did instruct the axis, the distance control is automatically deselected.