68 Fraunhofer Institute for Laser Technology ILT, www.ilt.fraunhofer.de

DQS certified by DIN EN ISO 9001, Reg.-No.: DE-69572-01

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2011

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532 µm

2

1 Beam control component for integration

with process monitoring.

2 Coaxially imaged cut gap.

task

Lasers are an established tool for cutting stainless steel sheet

and plate. Production systems with CO2 laser beam sources

have particular strengths for cutting heavier-gauge plate and

rapidly producing contours on flatbed machines. Reliable

process control for the necessary product quality, however,

requires information about the current working point of the

process. A process sensor system therefore has to provide

relevant measured variables for active closed-loop control.

Method

In the cluster of excellence at RWTH Aachen University

research scientists from Fraunhofer ILT are working on the

development of a sensor system which observes the laser

cutting process coaxially through the cutting head. From

the signals measured, variables are extracted which make

it possible to determine the working point of the process.

This information is subsequently used for self-optimization

of the cutting process.

Result

The sensor setup for CO2 laser cutting consists of two com-

ponents: an optical system with an area sensor and a system

for image processing. The optical system couples process

observation coaxially into the beam path of the laser and

projects the zone of interaction through the focusing optic

onto the sensor. By subsequent signal processing variables are

extracted which enable a conclusion to be drawn as to the

working point of the process. One of these variables is the gap

width, which as a function of further parameters permits a

conclusion to be drawn about the focus position.

For the purpose of self-optimization the signal processing

function is extended to extract numerous variables using

multiple algorithms. In combination with process modeling,

a method has thereby been established to comprehensively

determine the working point, enabling self-optimization of

the process.

applications

The process sensor equipment has been installed in an indus-

trial production system. Together with model-based analysis

of the measured variables, quality-relevant information is

extracted which is used to control the process. The system is

being transferred to other production processes on the basis

of corresponding process models.

contacts

M.Sc. Dipl.-Ing. (FH) Ulrich Thombansen

Phone +49 241 8906-320

ulrich.thombansen@ilt.fraunhofer.de

Dipl.-Ing. Peter Abels

Phone +49 241 8906-428

peter.abels@ilt.fraunhofer.de

sensors for Laser cuTTIng

1