Siemens sinumerik 840D sl Function Manual page 512

Detailed description
2.1 Function description
Laser cutting technology is used as an example for the detailed description of the "clearance
control" functionality .
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.
Special functions: Clearance Control (TE1)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
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