The integration of advanced digital servo control and high-repetition rate fiber lasers delivers exceptional laser marking performance. This technology combines precise digital state space control with a "low-order mode" pulsed fiber laser, enabling fast and accurate marking for automated production lines that demand high throughput and minimal maintenance. The key benefit of this system lies in its compatibility with high-speed scanners, ensuring consistent and high-quality results even at rapid speeds.
At the heart of the digital servo controller is a high-speed digital signal processor (DSP), which handles all necessary calculations for torque, speed, or position control of the motor. The controller uses a high-resolution analog-to-digital converter (ADC) to interface with control and feedback signals, such as motor current, voltage, and encoder position data. Parameter tuning is automatically extracted and stored digitally, eliminating the need for manual adjustments and reducing issues caused by analog drift or component aging. Advanced algorithms like model-based predictive control can also be implemented using the DSP, improving overall system responsiveness and accuracy. These models are derived from the state space equations of the scanner motor's motion, along with observed variables like current and voltage. By predicting the movement of the laser scanner in advance, the system ensures optimal power usage and precision.
Compared to traditional laser technologies like Nd:YAG, Nd:YVO4, and CO2 lasers, pulsed fiber lasers offer superior performance, particularly in terms of beam quality (M² value). This makes them ideal for high-precision applications where consistency and clarity are critical.
In testing, a digital laser marking system was evaluated using a Cambridge Technology DC2000 digital state space servo, a 6230 scanning galvanometer, and a 20W fiber laser from SPI. The system operated at a 125 KHz repetition rate and was tested on stainless steel plates. The performance was compared against an optimized analog system driven by a CTI 671 analog servo. Both systems were fine-tuned for optimal pattern quality, considering parameters like laser power, marking speed, delay times, and more.
Figures 1a and 1b illustrate the marking patterns produced by the digital and analog systems, respectively. The complex design included hatching, prongs, spirals, and varying line lengths, making it an effective test of system performance. The digital system completed the task in 25.6 seconds, while the analog system took 52 seconds. Further reducing processing time would compromise quality, so we conclude that the digital system improves marking speed by 200% for moderately complex patterns.
Another test compared the response of the digital and analog servos during acceleration and deceleration. When both systems marked at 10 Kmm/sec, the digital system showed a much shorter acceleration phase (around 310 µm) compared to the analog system (around 2600 µm). This indicates that the digital system’s torque control is more efficient and responsive, supporting the earlier findings about its superior speed and performance.
In a third experiment, we analyzed the angular response of the scanning galvanometer under both digital and analog control. The digital system closely followed the input command, while the analog system exhibited distortion due to bandwidth limitations. This further highlights the advantages of digital state space control in maintaining accuracy and consistency.
In conclusion, the digital state space servo-driven fiber laser system significantly outperforms traditional analog systems in speed, accuracy, and reliability. For manufacturers looking for cost-effective, low-maintenance, and high-output laser marking solutions, this technology offers substantial economic benefits and long-term value.
Jiangsu Zhongyi Tools and Riggings Co., Ltd. , https://www.zy-rigging.com