System Developments

For the industrial use of remote technology for welding, cutting, ablation and perforation, Fraunhofer IWS Dresden develops software and control solutions that take into account the process and customer requirements.

Depending on the application, the control technology solutions available on the market are examined and, if necessary, own solutions are developed. The focus is on the highly dynamic control of galvanometer scanners and their integration into new or existing machines.
 

Motion Control Framework

The motion control framework forms the basis for efficient, yet adaptable software development for the realization of complex remote processing tasks. The goal of software development based on the motion control framework is to efficiently encapsulate the technological and process interrelationships so that an easy-to-use software is created for the end user. The Fraunhofer IWS does not only act as a pure software developer here, but also contributes its longstanding process competencies in the field of laser material processing to develop a user-friendly control technology solution.
 

ESL2-100 Module

The ESL2-100 module was developed by Fraunhofer IWS as a gateway between the EhterCAT fieldbus and the SL2-100 protocol. In the context of control system development the ESL2-100 module is used if

• a networking of the galvanometer scanners to a superior machine control (PLC) is necessary or
• a real-time capable influence of the scan movement has to be realized.

Since all sensors and actuators involved in the processing task can be combined in one controller, continuous, real-time and synchronous communication is possible. Due to the flexibility of the fieldbus system, the galvanometer scanners involved can be distributed and scaled almost arbitrarily.
 

Applications

• Laser treatment of grain oriented electrical steel (LMDR)
• Joining of thermoplastic fiber composites

The processing system developed by Fraunhofer IWS together with partners allows the realization of continuous processes with constant treatment conditions and at the same time highest parameter flexibility. The optical design of the processing system takes into account the process and production requirements. It consists of up to 12 individual scanners and allows the combination of up to four beam sources at lateral spot velocities of up to 300 m/s. The control of the scanners and the beam sources is based on the same system. The control of the scanners and the beam sources is synchronized to the conveyor speed. For this purpose, Fraunhofer IWS developed a control solution that automatically adapts the process parameters to the feed rate of the electric strip in order to achieve consistent processing results independent of the strip speed.

Based on many years of experience in remote machining, Fraunhofer IWS together with the company Held Systems has developed a concept that can be implemented in industry. The contiLAS principle is a double superimposed "on the fly" processing.

The remote technology allows the laser cutting process to be implemented on any cutting contours and material widths. One or more scanners can process the fabric webs. Material transport speeds of up to 25 meters per minute can thus be achieved.

In addition to flat woven fabrics, one-piece woven airbags (OPW) can also be processed. The special feature of OPW is that - woven in one piece - they have flat material on the one hand and recessed cavities on the other. In conjunction with the appropriate coating, the process ensures that the airbags trap air better.

Cutting using laser technology offers the advantage that the resulting edges fuse directly, while at the same time preventing trickling.

The challenge with OPW material is to identify where the laser needs to cut. The position of the airbags is detected by a camera system and transmitted to the control software developed by Fraunhofer IWS. Subsequently, the nominal and actual data are compared and the cutting contour is adjusted based on the recorded positions.

Modern beam sources have significantly pushed the limits of material thickness- and power-dependent cutting speeds. Novel solid-state lasers, such as fiber or disk lasers, enable significantly higher cutting speeds, especially for metals, compared to CO₂ lasers at the same output power. However, this potential cannot be transferred to contour cutting by conventional cutting machines. Especially for workpiece geometries with many directional changes, high acceleration and jerk values*) of the axes are required.

These can be realized in highly dynamic axis systems with an adapted, reduced working field. With the aid of a parallel kinematic axis structure, the masses to be moved for beam and cutting gas movement can be reduced to a considerable extent, thus significantly increasing the dynamic properties. The average machining speed can be increased or the cutting time reduced for many workpiece geometries. 

*) The jerk (m/s³) describes the change in acceleration over time (m/s²). Along with the acceleration, it is the decisive variable for increasing the average machining speed in contour cutting.

Programming / Control

Depending on customer requirements, highly dynamic axis systems can be integrated in "stand alone" operation or in an existing machine control system. Interfaces to various fieldbus systems are created through an open control platform.
 

Advantages

• Conversion of the cutting power of brilliant beam sources in contour cutting
• narrow heat-affected zones even at sharp corners and small radii
• particularly suitable for cutting thermally sensitive materials
• up to 60 % part time savings for complex component geometries
• Extension of the working area through repositioning or superimposed movements with additional axis systems