Several key technologies of laser cutting machine are integrated technologies of light, machine and electricity.The parameters of laser beam, the performance and precision of machine and nc system in laser cutting machine directly affect the efficiency and quality of laser cutting.Especially for parts with high cutting accuracy or large thickness, the following are several key technologies:
Focus position control technique
One of the advantages of laser cutting is the high energy density of the beam.Since the energy density is inversely proportional to the area, the focal spot diameter should be as small as possible in order to produce a narrow slit.The focal spot diameter is also proportional to the focal depth of the lens.The smaller the focal depth of the focusing lens, the smaller the focal spot diameter.However, there are spatter in cutting. The lens is too close to the workpiece to damage the lens easily. The actual focal spot diameter is between 0.1~0.4mm.For high quality cutting, the effective focal depth also depends on the diameter of the lens and the material to be cut.The position of the control focus relative to the surface of the material being cut is very important.
How do you determine the focus?
1. Make the cutting head move from top to bottom, print laser beam on the plastic plate, and print the focus point with the smallest diameter.
2. Pull the plastic plate at an Angle to the vertical axis, and look for the smallest point of the laser beam as the focus.
3. Remove the nozzle, blow the air and hit the pulse laser on the stainless steel plate so that the cutting head moves from top to bottom until the blue spark is the focus.
1. Size of laser coagulation of laser generator.If the light spot is very small after the aggregation, the cutting accuracy is very high, and if the slit after the cutting is very small.It shows that the laser cutting machine precision is very high, the quality is very high.
2, Accuracy of the table.If the accuracy of the table is very high, the cutting accuracy will also be improved.So the precision of the table is also a very important factor to measure the precision of the laser generator.
3. Laser beam condenses into a cone.When cutting, the laser beam is tapered downward, and if the thickness of the workpiece is very large, the cutting accuracy will be reduced, and the slit will be very large.
4. Different cutting materials will also affect the precision of laser cutting machine.In the same case, the precision of cutting stainless steel and aluminum will be very different, stainless steel cutting precision will be higher, and the cutting surface will be smooth.
(1) Blasting perforation: after the material is irradiated by continuous laser, a pit is formed in the center, and then a hole is formed when the molten material is quickly removed by the oxygen flow coaxial with the laser beam.The size of the general hole is related to the thickness of the plate, and the average diameter of the blasting hole is half of the thickness of the plate, so it is not suitable to be used in the parts with higher requirements for the thicker plate blasting hole.In addition, because the oxygen pressure used in perforation is the same as in cutting, splash is greater.
(2) Pulse perforation: a small amount of material is melted or vaporized by the pulse laser with peak power. Air or nitrogen is commonly used as auxiliary gas to reduce the hole expansion due to exothermic oxidation. The gas pressure is lower than the oxygen pressure during cutting.Each pulse of laser produced only a small jet of particles, which went deeper and deeper, so it took a few seconds for the thick plate to perforate.Once the perforation is complete, replace the auxiliary gas with oxygen for cutting.In this way, the perforation diameter is smaller and the perforation quality is better than that of blasting.The laser used for this purpose should not only have high output power;The more important is the time and space characteristics of the time beam, so the general CO2 laser cannot meet the requirements of laser cutting.
There are three ways to change the average laser power in industrial production:
(1) Change the pulse width
(2) Change the pulse frequency
(3) Change the pulse width and frequency simultaneously
Nozzle design and flow control technology: When laser cutting steel, oxygen and focused laser beam are shot through the nozzle to the material to be cut, thus forming a flow beam.The basic requirement for airflow is that the flow rate into the incision should be large and the speed should be high, so that enough oxidation can make the incision material fully exothermic reaction.At the same time there is enough momentum to eject the molten material.
Nozzle is generally made of red copper, small in volume, and is a fragile part, which needs to be replaced frequently. Therefore, fluid mechanics calculation and analysis are not carried out.When in use, a certain pressure of gas is passed into the side of the nozzle, which is called nozzle pressure. It is ejected out from the nozzle outlet and reaches the surface of the workpiece through a certain distance. The pressure is called cutting pressure.