Preco Subjects Laser and Galvanometer Scanhead Components to Rigorous Testing

Wayne Sommer
Vice President of Manufacturing Operations – Laser Equipment

Two of Preco’s most important core technologies are lasers and galvanometer scanheads. Since the state of the art for these technologies continues to advance at a rapid pace, Preco places a high priority on staying current with the latest developments. Preco has an ongoing program for evaluating and benchmarking the performance for both new lasers and galvanometer scanheads. Testing results are extremely valuable when it comes to selecting the best components for a particular application as well as for predicting performance results for a new application. This information, combined with Preco’s accumulated knowledge of how different material compositions respond to various laser beam characteristics, gives Preco a distinct competitive advantage in our industry.

Preco has a variety of test equipment employed to evaluate many different laser wavelengths to benchmark performance. Laser power and wavelength stability are analyzed from a cold start-up and after a warm-up period. The mode quality of the beam is evaluated, and the pulsing performance of the laser is also analyzed. We look at the temporal shape, peak power and energy per pulse at various pulsing frequencies and pulse lengths. Rise times and fall times for individual pulse are also evaluated. Each laser performs slightly differently, and much of this information is not readily available from the laser manufacturer. The net result of having this information is that it allows Preco to select the best laser for a particular material to be laser processed, whether it is cutting, scoring, perforating, ablating, heat treating or welding.

Galvanometer scanheads use mirrors mounted to high speed galvanometer motors to steer the laser beam in the X and Y directions. There are many scanhead options available today. Many models are available in either 2-axis or 3-axis configurations and with either analog or digital encoders. A 2-axis scanhead uses a flat field lens below the galvanometer mirrors to focus the beam onto the material being processed. A 3-axis scanhead uses an objective lens and a dynamic Z expander lens located before the galvanometer mirrors to precisely focus the beam anywhere in the Field of View. The Field of View (FOV) is the area, generally very close to square, that a scanhead can process with the steered beams. Preco has used 3-axis scanheads with FOVs from 4 to 24 inches and at speeds (beam moving across the FOV) of up to 800 inches per second with a 7-inch FOV. Digital encoders can provide higher encoder resolutions and better thermal stability, thereby providing better repeatability.

To evaluate the speed performance of each scanhead, the maximum jump speed and mark speed are evaluated using standard patterns. The mark, jump and polygon delay times for these standard patterns are also analyzed because they impact the total scan times for various patterns. For specific applications, Preco has done comparative testing between different scanheads to evaluate focused spot size which is also an important characteristic in predicting processing speeds. Comparative testing for repeatability and accuracy has also been done for some specific applications.

When a customer specifies a production throughput for a laser system with a galvanometer scanhead there are many parameters that affect processing speed. Having a thorough knowledge of the laser and scanhead performance characteristics, combined with Preco’s application expertise and ability to do process testing on a wide variety of systems and lasers at our facilities, gives us the best capability to accurately predict machine and process performance for a new application.