Six common problems in laser cutting machine and how to deal with them

Laser cutting in common problems and solutions

1, cutting perforation technology

Any kind of thermal cutting technology, in addition to a few cases can start from the edge of the board, generally must be perforated in a small hole in the board. Previously in the laser stamping compound machine is used to punch a hole first, and then use the laser to cut from a small hole. For laser cutting machines without a punch there are two basic methods of perforation.

Blast perforation - the material is irradiated by a continuous laser to form a crater in the center, and then a hole is quickly formed by a stream of oxygen coaxial to the laser beam that removes the molten material. The size of the general hole is related to the thickness of the plate, the average diameter of the blast perforation is half of the plate thickness, so for thicker plates blast perforation hole diameter is larger, and not round, should not be used in the processing of parts requiring high precision, can only be used for scrap. In addition, because the oxygen pressure used for perforation is the same as when cutting, the spatter is larger.

Pulsed piercing - using high peak power pulsed laser to melt or vaporize a small amount of material, commonly used air or nitrogen as an auxiliary gas to reduce the expansion of the hole due to exothermic oxidation, the gas pressure is smaller than the oxygen pressure during cutting. Each pulse of the laser produces only small jets of particles that penetrate gradually, so the perforation time for thick plates takes a few seconds. Once the piercing is complete, the auxiliary gas is immediately switched to oxygen for cutting. This results in a smaller perforation diameter and a better perforation quality than blast perforation. The laser used for this purpose should not only have a high output power; more importantly, the time and space characteristics of the beam, so a general cross-flow CO2 laser cannot be adapted to the requirements of laser cutting. In addition, pulse perforation also requires a more reliable gas control system to realize the gas type, gas pressure switching and perforation time control.

In the case of pulsed perforation, the transition from pulsed perforation of the workpiece at rest to continuous cutting at the same speed as the workpiece should be taken into account in order to obtain a high quality kerf. Theoretically it is usually possible to change the cutting conditions in the acceleration section, such as focal length, nozzle position, gas pressure, etc., but in practice it is not possible to change the above conditions because the time is too short. In industrial production is mainly used to change the average power of the laser approach is more realistic, the specific method is to change the pulse width; change the pulse frequency; change the pulse width and frequency at the same time. The actual results show that the third effect is the best.

2, cutting processing small holes (small diameter and plate thickness) analysis of the deformation situation

This is because the machine tool (only for high-power laser cutting machine) in the processing of small holes is not to take the blast perforation, but with a pulse perforation (soft puncture), which makes the laser energy in a very small area is too concentrated, the non-processing area will also be scorched, resulting in hole deformation, affecting the quality of processing. At this point we should be in the processing program will be pulse perforation (soft piercing) way to blast perforation (ordinary piercing) way to solve. For smaller power laser cutting machine is the opposite, in the small hole processing should be taken pulse perforation in order to achieve a better surface finish. Metal processing WeChat content is good, worthy of attention.

3, when laser cutting mild steel, the workpiece burr solution

According to the work and design principles of CO2 laser cutting, the following reasons are analyzed as the main cause of burrs in the processed parts: the laser focus is not correctly positioned up and down, the need to do focus position test, according to the focus of the offset to adjust; laser output power is not enough, you need to check whether the work of the laser generator is normal, if normal, then observe the output value of the laser control button is correct To adjust; cutting line speed is too slow, you need to increase the line speed in the operation control; cutting gas purity is not enough, you need to provide high-quality cutting working gas; laser focus shift, you need to do the focus position test, according to the amount of focus shift to adjust; machine running time instability, you need to shut down the machine to restart.

4, laser cutting processing stainless steel and aluminum zinc plate, the workpiece has a burr generated by the analysis

The above situation, the first consideration of cutting mild steel burr factors, but not simply speed up the cutting speed, because the increase in speed will sometimes be cut through the plate, this situation is particularly prominent in the processing of aluminum zinc plate. This should be a comprehensive consideration of other factors of the machine to solve, such as whether the nozzle to replace, the guide movement is not stable.

5, the laser is not completely cut through the state of analysis

Analysis can be found in the following situations is the main case of processing instability: the choice of laser head nozzle does not match the processing plate thickness; laser cutting line speed is too fast, the need for operational control to reduce the line speed; in addition, special attention should be paid to the L3030 laser cutting machine cutting more than 5mm carbon steel plate when the need to replace the 7.5″ focal length of the laser lens.

6, cutting mild steel when the appearance of abnormal sparks solution

This situation will affect the quality of processing the cut section finish of the part. At this time, in the case of other parameters are normal, the following should be considered: the loss of laser head nozzle NOZZEL, the nozzle should be replaced in a timely manner. In the absence of a new nozzle replacement, the cutting working gas pressure should be increased; nozzle and laser head connection at the thread is loose. At this time should immediately suspend the cutting, check the laser head connection state, re-threaded.

7, laser cutting process when the choice of puncture point

The working principle of the laser beam during laser cutting processing is: during the processing, the material is irradiated by continuous laser light to form a crater in the center, and then the molten material is quickly removed by the working gas flow coaxial to the laser beam to form a hole. This hole is similar to the threading hole of a wire cut, and the laser beam starts the process with this hole for contour cutting, usually with the direction of the laser beam in the flight path perpendicular to the tangential direction of the cut contour of the part to be processed.

Therefore, when the laser beam begins to penetrate the steel plate to enter the part contour cutting of this period of time, its 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 tangential direction to the cutting contour of the tangent line coincident, that is, with the contour of the tangent angle of 0 °. This results in a relatively rough cut surface flowing down the cut section of the material being processed, which is mainly due to the rapid change in the vector direction of the laser beam during its movement in a short period of time. Therefore, attention should be paid to this aspect when using laser cutting to process parts. Generally, in the design of the parts on the surface of the cut section no roughness requirements, you can do not do manual processing in the laser cutting programming, so that the control software automatically generated puncture point; However, when the design of the parts to be processed cutting section has a high roughness requirements, we need to pay attention to this problem, usually need to do manual adjustment of the laser beam start position when programming laser cutting, that is, manual for the puncture point of control. It is necessary to move the original puncture point generated by the laser program to a reasonable position in order to achieve the required surface accuracy of the machined part.