The occurrence of burrs during laser cutting not only affects the precision and appearance of workpieces but also increases the cost of subsequent grinding processes. Achieving burr-free processing requires collaborative control from multiple dimensions such as equipment parameters, material characteristics, and process optimization. The specific methods are as follows:
1. Precisely Match Laser Parameters to Control Energy Output
The rationality of laser parameters is crucial for avoiding burrs. Firstly, the laser power must be adapted to the material thickness: insufficient power will result in incomplete cutting of the material, leaving un-fused metal as burrs; excessive power may cause over-melting of the material, and the cooled liquid metal will form nodular burrs. For example, when cutting low-carbon steel with a thickness of 1-3mm, the power is usually set at 1500-3000W, while for thick plates of 5-10mm, the power needs to be increased to 3000-6000W.
Secondly, adjust the cutting speed and frequency: too slow a speed will prolong the laser irradiation time on the material, expand the heat-affected zone, and easily cause burrs on the edges; too fast a speed will lead to incomplete cutting. Generally speaking, thin plates are suitable for high speed and high frequency (e.g., for 1-2mm steel plates, the speed is 10-15m/min, and the frequency is 5000-10000Hz), while thick plates require lower speed and lower frequency (e.g., for 8mm steel plates, the speed is 1-3m/min, and the frequency is 1000-3000Hz).
In addition, optimize the focal position: a too-deep focus will disperse the energy, resulting in uneven width of the upper and lower parts of the cut and easily leaving burrs at the bottom; a too-shallow focus will cause excessive melting of the surface. When cutting metals, the focus should usually be 0.5-1mm below the material surface, and for non-metallic materials, it can be appropriately shifted upward.
2. Reasonably Select Auxiliary Gases to Enhance Slag Removal Effect
Auxiliary gases play a role in blowing away slag and cooling the workpiece during laser cutting. Their type, pressure, and flow directly affect burr formation. For ferrous metals such as carbon steel, oxygen is preferred as the auxiliary gas: oxygen can react with the metal oxidatively, release additional heat to assist cutting, and at the same time, high-pressure oxygen can quickly blow away slag to reduce residues. However, the oxygen pressure needs to be controlled, generally between 0.3-0.8MPa. Too low pressure will result in incomplete slag removal, and too high pressure will easily cause excessive oxidation of the cut edge, forming burrs.
When cutting non-ferrous metals such as stainless steel and aluminum alloys, inert gases such as nitrogen should be used: inert gases can prevent material oxidation and blow slag out of the cut by virtue of high pressure. The nitrogen pressure is usually higher than that of oxygen (0.5-1.2MPa), especially for thick plates. It is necessary to ensure a stable gas flow to prevent slag retention due to pressure fluctuations. In addition, the diameter and distance of the gas nozzle also need to match. A too-small nozzle diameter is prone to pressure loss, and a too-large one will cause gas diffusion. It is recommended to select a nozzle with a diameter of φ1.5-3mm according to the material thickness, and keep the distance between the nozzle and the workpiece at 0.5-2mm.
3. Preprocess Materials to Reduce the Impact of Inherent Defects
The state of the material itself is the basis for burr-free processing. Ensure the raw material surface is flat and free of oxide layers: for rusty or scale-covered metal plates, the oxide layer will absorb part of the energy during laser cutting, resulting in uneven cutting temperature and easily causing burrs. Before processing, the oxide layer can be removed by grinding, pickling, etc., or plates with qualified surface quality can be selected.
Control the material thickness tolerance: if the thickness deviation of materials in the same batch exceeds 0.1mm, it will be difficult for the laser energy to act on the material uniformly. The thin parts are prone to over-melting, and the thick parts are prone to leaving burrs. Therefore, it is necessary to select high-quality materials with small thickness tolerance and conduct spot checks on the plate thickness before cutting. In addition, for coated materials (such as galvanized plates), it is necessary to confirm in advance whether the coating is high-temperature resistant to avoid burrs formed by the coating burning or melting and adhering to the cut.
4. Regularly Maintain Equipment to Ensure Stable Operation
The good condition of the equipment is the prerequisite for continuous burr-free processing. Clean the focusing mirror and nozzle: if the surface of the focusing mirror is contaminated with dust or metal spatter, it will cause the laser energy focus to shift and reduce the cutting ability; nozzle blockage will affect the flow rate and pressure of the auxiliary gas, weakening the slag removal effect. It is recommended to wipe the focusing mirror with a special cleaning agent before operation every day, and disassemble the nozzle for dredging and cleaning every week.
Check the accuracy of the guide rail and transmission system: wear of the guide rail or looseness of transmission components will cause the cutting head to deviate from the running track, resulting in inclined cuts and thus burrs. It is necessary to regularly lubricate the guide rail, check the tightness of transmission components such as gears and belts every month, and ensure that the cutting head moves smoothly and is positioned accurately. In addition, regularly calibrating the laser optical path to ensure the verticality of the laser beam and the accuracy of the focal point position is also an important measure to avoid burrs.
5. Process Optimization for Special Materials
For highly reflective materials (such as copper and aluminum alloys) or high-hardness materials (such as titanium alloys), targeted processes need to be adopted. When cutting highly reflective materials, green or blue laser generators (with higher absorption rate for short-wavelength lasers) can be used, and the cutting speed can be reduced and the peak power can be increased to reduce incomplete cutting caused by energy reflection. When cutting high-hardness materials, the pulsed laser mode can be adopted to instantly pierce the material through high-frequency pulses, avoiding thermal deformation and burrs caused by long-term action of continuous lasers.
In conclusion, achieving burr-free processing with laser cutting machines is a systematic project. It is necessary to accurately adjust parameters, optimize auxiliary processes in combination with material characteristics, and do a good job in equipment maintenance to obtain smooth and flat cuts while ensuring cutting efficiency.
--Rayther Laser Jack Sun--