The Fraunhofer Institute for Laser Technology ILT has developed a process monitoring system that can precisely measure the position and speed of the laser beam processing point on the surface. This enables deviations from the set contour and speed to be minimised and the energy input to be stabilised.
Research scientists at the Fraunhofer ILT in Aachen have developed a camera-based system which analyses the movements of the workpiece through the optical axis of the laser beam before or during processing. It does not matter whether a fixed or scanner optic is used – in both cases the system measures the movement of the processing point on the workpiece and documents deviations from the set contour during machine setup or operation.
The process monitoring system uses image sequence frequencies of up to 10kHz. In various applications, contours have been measured with a processing speed of up to 10m/min (fixed optic) and up to 15m/s (scanner optic). The deviation from a reference system was less than 3cm/min. At present the measured data is evaluated separately. While the same technology does permit real-time measurement (there are no technical barriers to this), the accuracy class of this has not yet been completely specified.
The design of the system means that it can be used in a very wide range of applications, including laser cutting and welding, soldering, drilling, ablation, micro-joining, SLM and hardening. The various modes of operation are interesting both for system integrators and for end users. On the one hand, the system can track the processing point during machine setup, enabling the planned contour to be adjusted.
On the other hand, the system permits process control during actual operation. This means not only can the processing contour be adjusted, the laser output can also be controlled to ensure an even energy input at different laser spot speeds. That is a critical factor in particular when processing thin materials. As a result, existing processes can be optimised and new processes are made possible.
In addition to application tests, the specialists at the Fraunhofer ILT provide full support for integration of the process monitoring system in their customers' systems. This includes calibration of the system and adaptation to the customer's optical equipment.