Laser cutting is one of the most important applications of industrial lasers, along with the continuously price drop of medium and high power fiber laser source, laser cutting machine market booming in China in the last three years, laser cutting machine is gradually replacing plate cutting machine and punching machine, it is expected that high end laser cutting machine (high cutting speed, high precision, high power and large cutting format laser cutters) market will have a significant increase in the next years.
The main factors affect cutting effect
In laser cutting fabrication process, the laser beam is collimated and focused on focal point, operators need to align the laser beam at the center of nozzle and adjust the distance between nozzle and surface of the plate, normally high pressure gas used during cutting. The cutting effect mainly related to below points:
Focal point spot size
Small spot size suitable for cutting thin metal, with small kerf: Large spot size suitable for cutting thick metal, with big kerf, change focus lens to change the spot size.
The focus position can be above workpiece, on workpiece surface or under workpiece surface, the focus position decides the beam spot size on workpiece surface, power density and kerf shape, the best focus position depends on the material type and thickness.
Cutting material type and thickness is the key to dimension laser power, a higher power density normally leads to a higher cutting speed.
The cutting speed is related to laser power, material, and assist gas pressure, etc., too fast or too slow cutting speed leads to burrs and rough kerf, in extreme cases, too fast cutting speed makes the material cannot be cut through, in most of the cases, thicker material has slower cutting speed.
The diameter of nozzle determines gas flow volume and shape, small nozzle is suitable for thin sheet metal cutting as small airflow is good enough to blow molten material and residue out of kerf, similarly, large nozzle is suitable for thick plate cutting.
Gas purity and pressure
The purity and pressure of gas will affect cutting effect, when fusion cutting with nitrogen, 99.995% above nitrogen required to prevent kerf oxidation, when flaming cutting with oxygen, 99.6% above oxygen required for a burr-free kerf. Normally thick steel sheet requires a higher nitrogen pressure, but when flaming cutting, thick steel plate needs a low oxygen pressure.
What is a good cutting effect
Though laser cutting equipment needs to cut different metal materials and produce different shapes of workpiece, the cutting effect could be evaluated by below factors:
Laser cut edge reveals a grooved striation, a fine striation with shallow depth means a low surface roughness and good cutting quality, the cutting surface roughness depends on material type, thickness and laser cutting procedure, normally thin metal plates cutting have a good surface quality and to cut with nitrogen has a lower surface roughness than to cut with oxygen.
Laser beam divergence when away from focus, the kerf widened toward the top or bottom according to focus position, this way, the cutting surface and the sheet metal surface are not perpendicular, normally better beam quality and thinner workpiece leads to better perpendicularity, maintaining perpendicularity is critical when sheet metal thickness over 10 cm. Aside of workpiece thickness, perpendicularity also related to focus position when cutting.
Burr is an indicator of laser cutting quality, laser cutting produces a variety of burrs, whether it be easily removable slag or difficult to remove metal thorn, deburring need additional workload, a burr-free cutting effect can be achieved by optimizing the cutting laser parameters.
Laser cutting is thermal cutting, the rapid heating during cutting process induces workpiece deforming, workpiece deforming during laser cutting should be minimized especially in thin metal cutting or precision parts cutting, normally lower laser output power, shorter pulse, higher cutting speed and larger gas airflow helps to reduce parts deforming.
Maiman fiber laser cutting machines could be configured with laser power ranging from 300W, 500W,700W,1000W,1300W,1500W,2000W,4000W to 6000W, the laser cutting systems are suitable for stainless steel, carbon steel, aluminum and copper laser cutting, and they are widely used in metal plate, hardware, electronics manufacturing, automotive industry, etc.