Laser cutting machine has many advantages, very suitable for large-scale batch production, used to process sheet metal parts can greatly improve labor productivity, has the advantages of high precision processing parts, short processing cycle, processing process without replacing the stamping mold can be processed arbitrary complex parts. At present, metal laser cutter is being introduced into the factory by more and more processing manufacturers. In the process of laser cutting sheet metal, various problems are often encountered. This paper mainly introduces six common problems and solutions.
1. Over-burning phenomenon
The metal laser cutter generates a large amount of heat when processing the sheet metal. Normally, the heat will spread along the cutting surface to the sheet metal. Laser cutting machine in the processing of small holes, the outside of the hole can be fully cooled, single hole inside the hole part, the heat can diffuse space is small, heat diffusion is not too concentrated and caused by over-burning, hanging slag, etc. In addition, in the case of thick plate cutting, the accumulation of molten metal on the surface during the perforation process and the high heat accumulation required to cut the thick plate can disorder the auxiliary gas, resulting in heat increase and thus over-burning. There are four solutions as follows:
1). Add cooling point at the corner or use loop-cut function
Laser cutting has a corner or sharp Angle plate is easy to occur in the corner or sharp angle over-burning phenomenon, so that it forms a round, affecting the yield. Thus You can add a cooling in the corner points, pause and blow in the corner, which can effectively avoid burnt. It can also use the loop-cutting function to reduce the cutting speed to avoid overheating caused by excessive heat increase.
2). Adopt nitrogen cutting
When cutting metal, gas is needed to assist, different gases have different characteristics. As an inert gas, nitrogen does not produce chemical reactions when cutting. When cutting aluminum alloy or stainless steel using nitrogen cutting, nitrogen cutting is to rely on laser energy melting, nitrogen and the material itself will not occur chemical reaction, so in the cutting will not occur over burning phenomenon. In addition, the melting point area temperature is low and nitrogen cooling, protection, to ensure that the material in the cutting reaction is smooth, uniform, cutting end face smooth and uniform, low surface roughness, and no oxide layer. It is easy to see hanging residue at the bottom of nitrogen. Therefore, it is necessary to adjust the gas to the conditions of high auxiliary gas pressure, low frequency pulse and peak output.
3). Prevent oxidation reaction
When using fiber laser cutting machine to process aluminum alloy and stainless steel, the auxiliary gas used is nitrogen or air. In the cutting process will not occur edge burning, but because of the high temperature inside the hole, the inner hanging slag phenomenon will be more frequent. In this case, burrs and slag can be reduced by increasing the pressure of the auxiliary gas.
4). Use high-power lasers
High power laser cutting and bright surface cutting technology are used to process carbon steel. This technology can achieve the finished product with bright surface and no burr, effectively avoid the phenomenon of over-burning, and improve the yield.
2. Analysis of the deformation of cutting holes
High-power laser cutting machine in the processing of small holes, the use of pulse perforation (soft puncture), so that the laser energy in a small area is too concentrated, the non-processing area is burnt, resulting in the deformation of the hole, affect the quality of processing. At this time, we should change the pulse perforation (soft puncture) to the blasting perforation (ordinary puncture) in the processing program to solve the problem. On the contrary, for the laser cutting machine with less power, pulse perforation should be adopted in the small hole processing to obtain better surface finish.
3. Solution to burr of work-piece
According to the work and design principle of CO2 laser cutting machine, the following reasons are analyzed to cause the burr of the work-piece: the upper and lower position of the laser focus is not correct, need to do the focus position test, according to the offset of the focus to adjust; The output power of the laser is not enough. It is necessary to check whether the laser generator works normally. If so, observe whether the output value of the laser control button is correct and adjust it. Cutting line speed is too slow, need to increase the line speed in the operation control; Cutting gas purity is not enough, need to provide high quality cutting gas; Laser focus offset, need to do the focus position test, according to the focus of the offset to adjust; The machine is unstable when it runs for a long time. It needs to be shut down and restarted.
4. The laser does not cut through completely
After analysis, it can be found that the following situations are the main cases of machining instability: the choice of laser nozzle and machining plate thickness does not match; Laser cutting line speed is too fast, need to operate control to reduce the line speed; In addition, it should be noted that the 7.5 "focal length laser lens needs to be replaced when laser cutting machine cuts the carbon steel plate above 5mm.
5. Solution in cutting low carbon steel abnormal spark
This situation will affect the parts of the cutting section finish processing quality. At this time in the other parameters are normal, should consider the following situation: when there is a laser head loss, an in-time replacement will be necessary. In the case of no new replacement, should increase the cutting work gas pressure; The thread at the connection between the nozzle and the laser head is loose. At this time, stop cutting immediately, check the connection state of the laser head, and reset the thread.
6. Selection of puncture point during laser cutting
Laser cutting processing laser beam working principle is: in the process of processing, the material after continuous laser irradiation in the center of the formation of a pit, and then by the laser beam coaxial working air flow will soon remove molten material to form a hole. This hole is similar to the threading hole of linear cutting, and the laser beam takes this hole as the starting point for contour cutting. Normally, the routing direction of the flying optical path laser beam is perpendicular to the tangent direction of the cutting contour of the processed part.
Therefore, the laser beam began to penetrate the steel plate to enter the part contour cutting this period of time, the cutting speed in the vector direction will have a great change, that is, the vector direction of 90° rotation, from perpendicular to the cutting contour of the tangent direction to coincide with the cutting contour, that is, the Angle with the contour of the tangent is 0°. This will be processed in the cutting section of the material left relatively rough cutting surface, which is mainly in a short period of time, the laser beam in the moving vector direction changes quickly to. Therefore, in the use of laser cutting parts should pay attention to this aspect of the situation. In general, in the design of parts on the surface cutting fracture without roughness requirements, you can do not do manual processing in the laser cutting programming, so that the control software automatically produce puncture points; However, when the design of the cutting section of the parts to be processed has high roughness requirements, we should pay attention to this problem, usually need to make manual adjustment of the starting position of the laser beam in the laser cutting program, that is, manual control of the puncture point. It is necessary to move the puncture point generated by the laser program to a reasonable position in order to meet the requirements of surface accuracy of machining parts.
Common Problems and Solutions in Sheet Metal Laser Cutting
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