Facetime: LASER MECHANISMS INC.’s MIKE LEE discusses advancements and new challenges for robotic laser cutting with Modern Metals

August, 2023- Facetime: LASER MECHANISMS INC.’s MIKE LEE discusses advancements and new challenges for robotic laser cutting with Modern Metals

Q:Can you provide a brief history of robotic laser cutting?

A: A fiber laser’s flexible fiber optic cable was a natural match for manipulation by an industrial robot. The first fiber-delivered robotic cutting cells emerged in the late 1980s, but they had a severe limitation. Height sensing is a critical feature for all laser cutting of metals to maintain a constant standoff of the cutting nozzle to the material. Laser cutting heads with height-sensing nozzles provided the signals to a flat-sheet cutting machine’s Z-axis to position the head accordingly. Early attempts to mimic the same with a robot found that robots were not capable of the short, quick standoff control moves. The solution came in the form of adding this motion axis to the cutting head. Not only did this provide the precise motion but also had the advantage of a low moving mass —a critical design feature. The breakthrough of a robotic cutting head led to multiple installations of robotic cutting systems. By 2002, the bloom was coming off the rose, however. A few factories had shut down their laser cutting operations and others were experiencing unacceptable downtimes and extremely high consumable costs. Consequently, the design of the robotic cutting head was re-evaluated from top to bottom. Notable improvements included eliminating all external cables and hoses and making access to consumable items simple and tool-less. One major automaker reported savings in the millions of dollars in the first year, just on consumables alone. A second wave of new installations followed. Now, 20 years later, it is time to once again plan and implement for the next generation of robotic laser cutting systems.

Q:What are some of the upcoming changes for robotic laser cutting?

A: In its efforts to manufacture lighter vehicles for better fuel economy, the automotive industry turned to alternative materials such as high-strength steels, cut efficiently only by lasers. In fact, automotive engineers began to base their part designs with an understanding of laser cutting. Most recently, manufacturers have transitioned to fabricating more vehicle body panels out of aluminum, leading to new cutting parameters and a significant advantage in using shop air instead of nitrogen as the cutting assist gas. Many nonmetals, plastics and composites are also incorporated, which are best cut by CO2 lasers, but CO2 lasers are not fiber-delivered. However, “articulated arms,” a series of tubes joined by rotatable knuckles containing mirrors, provide a flexible delivery system for CO2 lasers, similar to fiber delivery. Most recently, the ability for articulation by industrial robots has been refined, leading to production cells cutting bumpers, dashboards and other nonmetal components.

Q:Describe some of the challenges encountered when robotic laser cutting.

A: A recent development allows the detection of even the slightest capacitance in many nonmetals and the ability to extrapolate it into a usable signal. Robotic laser cutting heads are now able to detect the surface position of composites, polymers, glass and many other materials. Another challenge is cutting small features. Just as robots are incapable of the precise short, quick moves required for height sensing, they are also limited on the trepanning of small features—generally anything smaller than 5 millimeters. Efforts to add high-speed stages to the end of a robot failed as the inertia destabilized the robot’s axes of motion. Early systems were limited to mounting the trepanning head to a stable structure with the robot presenting and manipulating the material under the cutting head. For some applications, this was acceptable, but it was not an ideal system configuration. A breakthrough development in counter-balancing solved the problem, adding three additional axes to the robot controller for precise motion on small features. This expands the capability to previously unattainable small features, and cutting is now three times faster with three times better accuracy, piercing is quicker and cut quality of materials with various thicknesses is greatly improved.

Q:Are there any new features or capabilities for robotic laser cutting that customers are asking for?

A: Absolutely. The ability to cut different thickness of material requires the capability to change the focus spot size and/or move it up or down. Initial designs for applications labs provided a manually operated external adjustment. Subsequently, the development of a programmable version targeted production applications. Customer requirements have led to additional features of the cutting head such as slug detection and part mapping. In addition, the power rating of robotic cutting heads has increased to 6 kW. As laser manufacturers continue to develop more capabilities, robotic laser cutting will continue to innovate and grow.

Mike Lee, sales engineer, has been with Laser Mechanisms, Novi, Michigan, for nearly 20 years. He works directly with leading system builders and specializes in the integration of robotic laser processing.