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Six problems and solutions of metal laser marking machine

by:Leadtech Coding     2022-05-08

1. Cutting perforation technology

Any thermal cutting technology, except for a few cases, can start from the edge of the board, generally a small hole must be perforated on the board. Previously, on the laser stamping compound machine, a punch was used to punch a hole, and then a laser was used to start cutting from the small hole. For laser cutting machines without punching devices, there are two basic methods of perforation:

Blasting perforation - the material is irradiated by a continuous laser to form a pit in the center, and then the material is irradiated by a continuous laser. A stream of oxygen coaxial with the laser beam quickly removes the molten material to form a hole. Generally, the size of the hole is related to the thickness of the plate. The average diameter of the blasting perforation is half of the thickness of the plate. Therefore, the diameter of the blasting perforation for thicker plates is larger and not round. It should not be used on parts with high machining accuracy requirements. on waste. In addition, because the oxygen pressure used for perforation is the same as that for cutting, the splash is larger.

Pulse perforation - a pulsed laser with high peak power is used to melt or vaporize a small amount of material. Air or nitrogen is often used as an auxiliary gas to reduce the expansion of the hole due to exothermic oxidation. The gas pressure is higher than that of oxygen during cutting. low pressure. Each pulsed laser produces only a small jet of particles, which gradually penetrate deeper, so the perforation time for thick plates takes a few seconds. Once the perforation is complete, immediately change the assist gas to oxygen for cutting. In this way, the diameter of the perforation is smaller, and the perforation quality is better than that of blasting perforation. The laser used for this purpose should not only have high output power; more importantly, the time and space characteristics of the beam, so the general cross-flow CO2 laser can not meet the requirements of laser cutting. In addition, pulse perforation also needs a more reliable gas circuit control system to realize the switching of gas type, gas pressure and the control of perforation time.

In the case of pulse piercing, in order to obtain high-quality cuts, the transition technology from pulse piercing when the workpiece is stationary to constant velocity continuous cutting of the workpiece should be paid attention to. Theoretically speaking, it is usually possible to change the cutting conditions of the acceleration section, such as focal length, nozzle position, gas pressure, etc., but in practice, it is unlikely to change the above conditions because the time is too short. In industrial production, it is more realistic to mainly use the method of changing the average laser power. The specific methods are changing the pulse width; changing the pulse frequency; changing the pulse width and frequency at the same time. The actual results show that the third effect is the best.

2. Analysis of the deformation of small holes (small diameter and plate thickness) during cutting process

This is because the machine tool (only for high-power laser cutting machines) does not process small holes when machining small holes. The method of blasting perforation is adopted, but the method of pulse perforation (soft perforation) is used, which makes the laser energy too concentrated in a small area, and burns the non-processing area, causing deformation of the hole and affecting the processing quality. At this time, we should change the pulse perforation (soft perforation) method to the blast perforation (ordinary perforation) method in the processing program to solve it. For the laser cutting machine with lower power, it is just the opposite. When processing small holes, pulse perforation should be adopted to obtain better surface finish.

3. The solution to the burr on the workpiece when laser cutting low carbon steel

According to the work and design principle of CO2 laser cutting, the following reasons are found to be the cause of the workpiece. The main reason for the burr: the up and down position of the laser focus is not correct, the focus position needs to be tested and adjusted according to the offset of the focus; the output power of the laser is not enough, it is necessary to check whether the laser generator is working normally, if it is normal, observe the Adjust whether the output value of the laser control button is correct; the cutting line speed is too slow, and the line speed needs to be increased during operation control; the purity of the cutting gas is not enough, and high-quality cutting working gas needs to be provided; the laser focus is shifted, it is necessary to Do the focus position test and adjust it according to the offset of the focus; if the machine tool runs for too long, it needs to be shut down and restarted.

4. Analysis of burrs on workpieces when laser cutting stainless steel and aluminum-zinc-coated sheets

For the above situation, first consider the factors of burrs when cutting low carbon steel, However, the cutting speed cannot be simply accelerated, because sometimes the plate cannot be cut through when the speed is increased, which is particularly prominent when processing aluminum-zinc coated plates. At this time, other factors of the machine tool should be considered comprehensively, such as whether the nozzle needs to be replaced, and the movement of the guide rail is unstable.

5. Analysis of laser incomplete cutting through state

After analysis, it can be found that the following situations are the main situations that cause processing instability: the selection of laser head nozzle and the processing plate Thickness does not match; the laser cutting line speed is too fast, and operation control is required to reduce the line speed; the nozzle induction is inaccurate and the laser focus position error is too large, and the nozzle induction data needs to be re-detected, especially when cutting aluminum.

6. Solutions for abnormal sparks when cutting low carbon steel

This situation will affect the quality of the cutting surface finish of the parts. At this time, when other parameters are normal, the following conditions should be considered: the loss of the laser head nozzle NOZZEL, the nozzle should be replaced in time. In the case of no new nozzle replacement, the cutting working gas pressure should be increased; the thread at the connection between the nozzle and the laser head is loose. At this time, the cutting should be suspended immediately, the connection status of the laser head should be checked, and the threads should be re-threaded.

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