Siemens SINUMERIK 840D sl Function Manual page 456

TE1: Clearance control
11.1 Brief description
Laser cutting
During laser cutting, a divergent parallel laser beam is directed across a fiber-optic cable or
via a mirror to a light-collecting lens mounted on the laser machining head. The collecting lens
focuses the laser beam at its focal point. Typical focal lengths are from 5 to 20 cm.
The position of the focal point in relation to the workpiece is an extremely critical process
parameter in laser cutting operations and must be kept constant within a tolerance of ≤ 100
µm.
The distance between the focal point and the workpiece, which is also a key process variable,
is usually measured by means of a high-speed capacitive clearance sensor. The analog
output voltage of the clearance sensor is approximately proportional to the distance between
the sensor and the workpiece surface.
The output voltage of the clearance sensor is transmitted as a digital input value via an
analog I/O module to the control where, in the event of deviations from the setpoint clearance,
it generates an additional velocity setpoint for the machining head motion axes.
System overview (840D)
An overview of the system components required for clearance control in conjunction with
SINUMERIK 840D is provided in the following diagram.
Figure 11-1
456
System components for clearance control with SINUMERIK 840D
Function Manual, 09/2011, 6FC5397-2BP40-2BA0
Special Functions