Before blanking, the distance between laser focusing and cutting materials must be determined. Different focusing positions often lead to different cutting fineness, different bottom slag, or even inability to cut; Different cutting workpieces and materials often lead to different focusing positions of laser cutting machines. Before discussing the choice of the focus position, let's first look at the positioning method of the focus position.

As we all know, laser cutting is to focus the laser beam into a point through the focusing lens, which is the "focus". Then the metal panel illuminated by the focus will be melted and broken down by high energy to form a metal cutting tool.

There are two main ways to locate the focus position of laser cutting, namely, bevel burning method and direct burning method.

To use the inclined plane burning method, you need to prepare a board first, and then tilt the board by about 10 degrees. The cutting head is set at point A. The height of point A to the focusing mirror is 20mm smaller than the focal length of the focusing mirror. Enter the system to set the cutting head, and move it horizontally and continuously along the x or y axis for 230mm. At the beginning, the laser outputs 200W continuous laser. When the cutting head stops moving, the laser also stops. It can be seen from the burning trace of the board, From width to width, take the narrowest trace as the focus position and record it. The measured distance from the wood plate at this position to the lens is the actual laser beam focus position.

Another method is direct burning. This method is mainly operated manually. It also uses a board to tilt 85 degrees, raise the cutting head 1.5 times the focal length from the worktable, and then continuously output a 200W laser beam, which moves horizontally and quickly to the board below the focusing lens. This is almost the same as the oblique burning method. The final focus position can be determined by referring to the last step of the oblique burning method.

After knowing the location method of the focus position, let's look at the selection method of the focus position. We usually refer to the distance of the upper surface of the workpiece processed by the focal length as the focal length of the upper and lower parts of the workpiece. The focus position above the workpiece is generally called positive focus, and the focus position below the workpiece is generally called negative focus. Changing the focusing position means changing the size of the light spot, which increases the focusing distance, thickens the light spot and widens the gap, thus affecting the heating area, focusing distance and slag discharge.

Positive focus cutting means that the cutting focus is on the workpiece and the cutting focus is on the material. When the carbon steel is cut by oxygen positive polymerization, the cutting width of the lower cutting surface is larger than that of the upper cutting surface, which is conducive to slag discharge. The oxygen reaching the lower cutting surface participates in the full oxidation reaction. In the range of focal length, the larger the positive focus amount, the larger the spot size of the plate surface is; and the more sufficient the preheating and heat source supplement, and the smoother and cleaner the carbon steel cutting surface is. The 10000 watt pulsed laser is used to cut thick stainless steel plates. The positive focus cutting is more stable, conducive to slag removal, and not easy to produce blue light.

Negative focus cutting means that the focus of cutting is on the workpiece. Because the focus is far away from the cutting surface, the cutting width is larger than the cutting width of the workpiece, and the required cutting air flow is large enough and the temperature is high enough. When cutting stainless steel, the negative focus cutting effect is good, the cutting surface has even lines, and the section is good. Before cutting, because the perforation has a certain height, negative focusing can minimize the spot size on the hole location and maximize the energy density. The greater the hole depth, the better the negative focusing effect.

Zero focus cutting, that is, the cutting focus is the surface of the workpiece. The cutting surface near the focus is usually smooth, while the surface away from the focus is rough. The invention is mainly applied to continuous thin sheets laser cutting, and pulse laser cutting high peak power evaporation foil.

The selection of the cutting point in the laser cutter does not depend on the material of the cutting plate (stainless steel and carbon steel), but on the cutting method (oxidation cutter and melting cutter).

The laser cutting machine requires different focusing methods for different workpieces. Due to the different focusing positions and adjustment methods of different types of cutting heads, when cutting stainless steel and carbon steel, users can choose appropriate focusing methods according to the different focusing effects and their own processing needs, so as to give full play to the performance advantages of laser cutting equipment!

About HGTECH: HGTECH is the pioneer and leader of laser industrial application in China, and the authoritative provider of global laser processing solutions. We have comprehensively arranged laser intelligent equipment, measurement and automation production lines, and smart factory construction to provide overall solutions for intelligent manufacturing.