The influence of cutting assist gas and pressure on the laser cutting of lumber products

Abstract

The laser cutting characteristics of pine, spruce, aspen, Douglas fir, plywood, medium density fibreboard (MDF), and oriented strand board (OSB) of several thicknesses were determined, using a 1600 Watt Carbon Dioxide laser cutting system. In all cases, the wood thickness was large compared to the depth of focus produced by the focusing system. The maximum cutting speed that produced acceptable cuts under a given set of processing conditions was found. For some woods, the maximum speed was proportional to the laser power. When cutting several woods of thickness 19 mm, however, an increase in laser power would not result in a proportional increase in cutting speed. In cutting of plywood, an increase in laser power would result in a greater than proportional increase in cutting speed.The effect of different cutting gases and cutting gas pressure was investigated. The use of oxygen as a cutting assist gas invariably resulted in a charred lower surface. The use of nitrogen as a cutting gas allowed a faster cutting speed than the use of compressed air in cutting the 19 mm Douglas fir and pine. However, in cutting of 32 mm thick OSB and plywood, the use of compressed air as a cutting gas allowed a slightly higher cutting speed than the use of nitrogen. The cut quality increased with increasing pressure of compressed air. The reason that the benefit in using compressed air was relatively minor was attributed to the oxygen supply in the compressed air being sufficient to contribute to the cutting of the upper part of the kerf.In the cutting of 19 mm thick samples of pine, aspen, spruce, and medium density fibreboard (MDF), the cutting rate was inversely proportional to the density of the wood; that is, slower speeds were required to cut the denser woods. Spruce plywood and Douglas fir, however, cut at slower speeds than would be expected from the inverse proportionality relationship. For several woods, the effect of lens focal length on cutting speed was investigated. Cutting of 19 mm thick MDF with a 190 mm focal length lenses was slower than with a 127 mm focal length lens; for thicker wood samples, however, cutting speed was greater with the longer focal length lens.The laser cutting characteristics of pine, spruce, aspen, Douglas fir, plywood, medium density fibreboard (MDF), and oriented strand board (OSB) of several thicknesses were determined, using a 1600 Watt Carbon Dioxide laser cutting system. In all cases, the wood thickness was large compared to the depth of focus produced by the focusing system. The maximum cutting speed that produced acceptable cuts under a given set of processing conditions was found. For some woods, the maximum speed was proportional to the laser power. When cutting several woods of thickness 19 mm, however, an increase in laser power would not result in a proportional increase in cutting speed. In cutting of plywood, an increase in laser power would result in a greater than proportional increase in cutting speed.The effect of different cutting gases and cutting gas pressure was investigated. The use of oxygen as a cutting assist gas invariably resulted in a charred lower surface. The use of nitrogen as a cutting gas allowed a faster cu...