Why lasers are used for cutting
Although Lasers have many purposes, we just use them to cut metal plates. On mild steel, stainless steel, and aluminum plate, the laser cutting process is highly accurate. It yields excellent cut quality, a very small kerf width, and a small heat affect zone, this makes it possible to cut very intricate shapes and small holes in the material.
You may already know that the word “LASER” is an acronym for Light Amplification by Stimulated Emission of Radiation. But how does light cut through a steel plate?
How it works
The laser beam is a column of very high-intensity light with a single wavelength or color. In the case of a typical CO2 laser, that wavelength is in the range of Infra-Red light according to the light spectrum. This light is invisible to the human eye. The beam is only about 3/4 of an inch in diameter as it travels from the laser resonator, which creates the beam, through the machine’s beam path. It may be bounced in different directions by a number of mirrors, or “beam benders” before it is finally focused onto the plate. The focused laser beam goes through the bore of a nozzle right before it hits the plate. It is here where the beam is met with compressed gas, such as oxygen or nitrogen, to protect the welding point.
Focusing the laser beam can be done by a special lens, or by a curved mirror. This takes place in the laser cutting head. The beam has to be precisely focused so that the shape of the focus spot and the density of the energy in that spot are perfectly round, consistent, and centered in the nozzle. By focusing the large beam down to a single pinpoint, the heat density at that at the pinpoint is extreme. Think about using a magnifying glass to focus the sun’s rays onto a leaf, and how that can start a fire. Now think about focusing 6 kilowatts of energy into a single spot, and you can imagine how hot that spot will get.
The high-power density results in rapid heating, melting, and partial or complete vaporizing of the material. When laser cutting mild steel, the heat of the laser beam is enough to start a typical “oxy-fuel” burning process, and the laser cutting gas will be pure oxygen, just like an oxy-fuel torch. When laser cutting stainless steel or aluminum, the laser beam simply melts the material, and high-pressure nitrogen is used to blow the molten metal out of the kerf.
On a CNC laser cutter, the laser cutting head is moved over the metal plate in the shape of the desired part, thus cutting the part out of the plate. A capacitive height control system maintains a very accurate distance between the end of the nozzle and the plate that is being cut. This distance is important because it determines where the focal point is relative to the surface of the plate. Cut quality can be affected by raising or lowering the focal point from just above the surface of the plate, at the surface, or just below the surface.
There are many, many other parameters that affect cut quality as well, but when all are controlled properly, laser cutting is a stable, reliable, and very accurate cutting process.
CO2 lasers are tried-and-tested industrial lasers, durable, and robust. Their cut edge quality is so high that for the most part, they do not need rework. The 10.6 μm wavelength produces burr-free edges which have very low surface roughness and are immediately ready for further processing.
Winchester Metals has become a proven leader in the laser cutting market in the Northern Shenandoah Valley and beyond. We now have two lasers in our facility with two shifts of capacity:
The Trumpf Trulaser 1030 will laser cut up to a half-inch thick carbon steel as well as up to one quarter-inch thick aluminum and stainless steel. The table can accommodate up to a 5 ft x 10 ft sheet or plate. The Trulaser 1030 is a CO2 CNC laser cutting machine for processing flat metal sheets. The tool used for this purpose is the laser beam, which is guided by mirrors to the laser cutting head. The machine works according to the principle of flying optics: the workpiece remains in place and the cutting head moves. The laser consists of the beam generator and the HF generator.
The beam generator of the Trulaser C02 laser consists of two coaxially aligned electrode tubes. Inside the tubes, the beam is reflected by two mirrors and travels around the inner tube. The entire system is diffusion- cooled. A small gas cylinder attached directly to the jet generator supplies the laser gas mixture.
The Amada LC 2012 Punch/Laser can handle up to one quarter-inch thick in carbon, aluminum or stainless steel. The laser portion of the C1 features the AMADA/Fanuc AF2000i-B LU2.5 resonator with 2.5 kilowatts of cutting power. The laser head moves in the Y-axis via a direct drive servo mechanism for maximum speed and accuracy. The laser head is also isolated from punching vibration to help maintain beam integrity and cut quality. A cartridge-type lens assures simple and fast lens changes when required. The resonator is located on a frame designed to reduce floor space requirements and to provide isolation from punching vibration.
The punching portion of the C1 is based upon the highly successful AC-series of 22-ton servo drive turret punch presses. The servo drive not only offers punching speeds of up to 370 hertz per minute on 1-inch centers but is also more efficient than hydraulic punch drives, requiring no pump or chiller.
The Winchester Metals team is eager to help assist you with all of your laser cutting and punching needs, give us a call today and we will help you get your project going.