Initial Situation and project task

In 2001, ILV (Ingenieurbüro für Lasertechnik und Verschleißschutz) headquartered in Schwalbach, Germany, has developed a high-quality DC scanner system for laser welding machines. This innovative scanner can be used for subsequent setup changes to welding machinery and is able to replace 90°-bending mirrors of standard welding optics with parabolic focussing mirror.

If the scanner unit is not active the scanner mirror will be used like a standard bending mirror; there will be no need for dismounting the scanner unit in this case.

For this scanner system, a professional control unit, being able to cope with harsh industrial working conditions and to control and monitor the mirror unit was required. In addition to that, PLC control of the system should be implemented, so that the scanner could be integrated into complex facilities with superior control systems.

Furthermore, the system should provide an external power control, offering the opportunity to design, store and recall individual power waveforms.

NOFFZ was charged with the development of an overall hardware and software concept and with the design of a first prototype. After extensive testing and optimization of this prototype, the final version of the controller should be produced at NOFFZ as a small batch series.

Implementation and challenge

The project could be split into two major tasks: Development of a control system for the mirror unit and Implementation of an external power control. Both tasks have been implemented by means of an individual microcontroller, exactly meeting the demands of each task.

One microcontroller is responsible for all problems being related to the task of monitoring and controlling of the mirror unit. It generates a control signal for the mirror’s movement and detects if a sensor indicates breakage of the mirror’s spring. The controller evaluates all signals being generated by temperature sensors inside the scanner unit indicating the temperature of the mirror and its motor.

The scanner’s mirror is driven by an AC motor and oscillates at a specified frequency. Oscillation amplitudes are properly adjusted according to the demands of the specific welding application. Usually, a sine-signal is used for motor control, but it is also possible to use impulses, triangle or saw tooth waves at a frequency range of 3Hz … 1000Hz. The signal’s frequency directly influences the oscillation of the mirror. The signal can be adjusted with the accuracy of one per-mille. An external or internal offset of maximum +/- 50% can be added to the signal.

The second microcontroller is responsible for the external power control. This control unit generates an additional signal, which can be parameterized by means of 32 values (up to 50Hz) or 16 values (up to 1000HZ).

The user control interface consists of 2 LC displays, providing operating parameters and menu control. Four status LEDs indicate operational readiness and possible faults; a matrix keyboard can be used for user input. The control unit comprises a D-Sub25 connector, allowing for the connection to a remote-System such as a PLC.

The whole electronic circuit is integrated into a chassis, which is suitable for industry applications according to common standards.

Conclusion

Since its successful development and evaluation period, the control unit for the DC scanner has been produced at NOFFZ.

Since the implementation of the first control unit in 2001, the controller has been enhanced continuously and has been equipped with state-of-the-art components. The series, being currently produced at NOFFZ, belongs to its third generation, which is reflecting the great and overall success of the product.