Before using the laser cutting machine to process any material, the distance between the focus of the laser cutting machine and the cutting material must be adjusted first. Different focus positions often lead to different final machining effects of different cutting materials. If the focal length cannot be adjusted correctly, it may even lead to damage of cutting materials, waste and even serious production accidents. How to adjust the focus of laser cutting machine for different materials?

Focus position of laser cutting machine

Laser cutting machine

Classification of laser cutting machine focus:

The distance between the laser focus of the laser cutting machine and the surface of the cutting part is usually called the positive focus, while the focus position below the workpiece is usually called the negative focus.

Schematic Diagram of Laser Cutting Machine Focus

Importance of laser cutting machine focus:

The change of focus position of laser cutting machine is the key to change the size and focal length of light spot on the surface and inside of the plate. The thickness of the light spot, the width of the crack, and the size of the heating area are all affected by the focus position of the laser cutting machine, which ultimately affects the size of the cutting seam and the slag removal ability of the processing materials.

Application of positive focus:

When the laser cutting machine is used for carbon steel oxygen cutting, it is suitable to use the positive focus. The bottom of the workpiece is cut more than the top, which is conducive to slag removal. The oxygen will participate in the full oxidation reaction at the bottom of the workpiece. Within a certain focus range, the larger the active focus is, the larger the size of the surface light spot is, the more sufficient the preheating and heat supplement around the cutting seam is, and the smoother and brighter the carbon steel cutting surface is.

For the thick stainless steel plate processed by optical fiber laser cutting machine, the positive focus cutting is adopted, which is stable in cutting, conducive to slag removal, and not easy to reverse the blue light.

Application of negative focus:

When the laser cutting machine is used to process the workpiece, the negative focus is used because the focus is far away from the cutting surface and the cutting point is larger than the cutting point on the workpiece surface. The cutting air flow is required and the temperature is sufficient.

When cutting stainless steel, it is suitable for negative focus cutting. The cutting surface is uniform and the cutting surface is good.

Before cutting, the perforated plate has a certain height. The negative focus is used to ensure the minimum size and maximum energy density of the perforation. The deeper the perforation, the greater the negative focus.

Zero focus cutting:

The cutting focus is on the workpiece surface. Generally, the focus close to the cutting surface is relatively smooth, and the surface lower from the cutting focus looks rough. This condition is mainly used for continuous laser cutting of thin plates, and peak power evaporation of pulsed laser cutting of metal foils.

The selection of laser cutting focus is not determined by the cutting plate (stainless steel, carbon steel), but by the cutting method (oxidation cutting, melting cutting).

The laser cutting machine needs to adopt different focus modes for different working parts. Because the adjustment parameters of the laser head focus position are different, the user can choose the appropriate focus cutting mode according to the different effects on the positive and negative focus in stainless steel and carbon steel processing, and combine their own processing requirements to make it more powerful.