By Thomas Burdel and Pieter Schwarzenbach
Pima North America (www.prima-na.com)
|Synchronized axis motions for micro and macro movement give Prima’s laser cutting system its ultrahighspeed capability. |
Synchronized ultrahigh-speed laser cutting machines paired with automated material handling systems are giving conventional machine tools, such as punching machines, shears and plasma cutters, a run for their money.
Shops should not hesitate to venture into “ultra speed” for the right applications, especially in demanding markets, because the cost of consumables and part production is much lower for such laser systems, while high-volume processing is attained. Plus, the cutting quality of highacceleration machines is better due to reduced overheating of materials, especially in small part features, and automation further enhances machine flexibility.
But what is synchronized ultrahighspeed laser cutting?
It came to fruition in 2005 with the introduction of two additional parallel kinematic drive axes on the laser cutting head. This effectively created two machines in one – a highly dynamic and light cutting head joined to a machine with a large work volume moving in precise synchronicity.
Algorithms coordinate the two “machines” by automatically controlling the local axes of the head and the main axes of the machine. The local axes perform micro movements, such as holes, corners, small shapes, and paths with frequent changes of direction, while the main axes carry out macro movements – contours, large shapes and the like.
These micro and macro movements happen simultaneously, like those of a human hand and arm when writing or playing a piano. The numerical control, like the human brain, synchronizes them to achieve continuous, smooth and fast movement.
This synchronized breakthrough opened up new frontiers and much higher limits in processing speeds, for example, being able to cut 1,000 holes per minute.
Since two short, linear-driven axes on the machine’s cutting head are making all the small-scale movements, as much as up to 4 in. in X and Y, there is minimal weight to move around.
Pair this with optimized linear drives and accelerations that jump as high as 6 G in actual cutting conditions. Previously, high acceleration rates were obtainable only in positioning speeds, but vibrations would diminish the cutting quality because of the heavy masses being moved around.
To augment this level of speed, other machine design features also were implemented.
These include the addition of shock compensation to the additional short travel and lightweight X and Y axes for eliminating vibrations transferred to the machine along with some proprietary CNC software. These features, combined with the new head design, doubled machine productivity compared with conventional machines, reduced power consumption, decreased wear and tear on the machine, and improved cut quality.
It’s commonly known that with increased cutting speed, cut quality often deteriorates, leading to rough edges, dross formation, vibrations and other deviations.
However, the physics of the cutting process are not altered with synchronized ultrahigh-speed laser cutting machines.
Cutting speed still depends on material, thicknesses, laser power, beam quality and focal spot size, as well as gas type, pressure and shape of the nozzle.
Higher laser power and nitrogen as a cutting gas have extended the limits for good cut quality to 800 ipm, especially for thin gauge sheet metal to 0.125-in. The difference is in higher
acceleration versus higher cutting speeds, with the machine CNC reducing cutting speeds to below programmed values to prevent a potential “overshoot” of the cutting process.
The combination of high dynamics and acceleration allows users to optimize the cutting process by maintaining the programmed cutting speed to a much greater extent. Synchronized ultrahigh-speed cutting improves cutting quality by also reducing heat load in corners and small features of complex contours.
High-speed laser cutting systems always have had the advantage of increased flexibility by being able to cut any hole diameter/shape without the need of tool changes or new tools. Lasers are not limited in the contour complexities they can handle, so they allow manufacturers to use their utmost creativity for designing better products.
With synchronized ultrahigh-speed laser cutting machines, the complex contour is easy to process, providing improved parts at a lower cost. Faster production and fewer steps in the manufacturing process are what reduce costs.
Fabricators can use such machines to their advantage with a large variety of customers whose needs are in the 0.020 in. to 1.0-in. thickness range in mild steel, aluminum and stainless steel. Although, the maximum advantage is with material thicknesses of 0.125 in. or less.
Shops that want to invest in a new laser cutting system should research the optimal ratio of light gauge to thick material and where the most profit comes from.
Synchronized ultrahigh-speed machines are faster than turret punch presses and set-up times are almost non-existent, making it possible to produce a part in half the time compared with a conventional laser or punching machine. In turn, the extra production time gained allows fabricators to take on new jobs and expand business operations in precision sheet metal markets.
In addition, new synchronized ultrahigh-speed laser cutting systems can be twice as productive as conventional systems.