Metal Laser Cutting: Principles and Influencing Factors

The processing effect of laser cutting is affected by various parameters, some of which depend on the technical performance of the laser itself, and others are adjustable variable parameters.

This article focuses on sharing the process elements related to the beam and focus in laser cutting, analyzing their core impact on the cutting effect, and helping to optimize the laser cutting process and improve processing efficiency and quality.

Laser Cutting Principle

Laser cutting is a precision processing technology that focuses a high-power laser beam on the surface of laser cutting metal part, melts or burns the workpiece material, blows away the slag with cutting gas, and forms a kerf through the movement of the cutting head on the workpiece surface, ultimately realizing the separation of the workpiece.

Laser Output Power and Mode

Laser Output Power

Laser output power is the core parameter determining the processing performance of a laser cutting machine, directly affecting cutting efficiency, kerf quality and processing range. Generally speaking, the thicker the workpiece, the higher the required laser output power.

In the cutting scenario of plates with the same material and thickness, the higher the laser output power, the faster the cutting speed, the smoother the cutting end face, and the higher the processing efficiency.

However, it should be noted that when the laser output power is determined, the cutting speed must be accurately matched with the material and plate thickness to achieve the best cutting effect — too fast cutting speed will lead to uneven kerf and incomplete cutting, while too slow speed will cause excessive melting of materials and widening of kerf, affecting processing accuracy.

Laser Output Mode

The beam quality distribution of lasers is mainly divided into two types: Single Mode and Multi Mode. The core difference lies in the distribution form of beam energy density: single-mode laser has only one concentration point of energy density, while multi-mode laser has two or more concentration points of energy density.

In laser cutting applications, the quality of the focused spot directly determines the cutting accuracy and end face effect. The core diameter of the single-mode laser is relatively thin, and the beam quality is better than that of the multi-mode.

The energy distribution is Gaussian, with the highest energy density in the center, and the three-dimensional shape is similar to a sharp round mountain peak; the core diameter of the multi-mode laser is relatively thick, the beam quality is slightly inferior to that of the single-mode, the energy distribution is more uniform, the three-dimensional shape is similar to an inverted cup, and the edge steepness is much higher than that of the single-mode.

There is no distinction between single-mode and multi-mode; they are only suitable for different scenarios: single-mode is more suitable for precision cutting of thin plates, and multi-mode is more suitable for efficient cutting of thick plates. Both are core configurations of fiber lasers. Just as a car is suitable for road driving and an off-road vehicle is suitable for mountain driving, the choice between single-mode and multi-mode depends on the actual processing needs of the end customer (such as plate thickness, processing accuracy requirements, etc.).

Laser Cutting Focus Size, Focal Depth and Focus Position

Focus Size and Focal Depth

During the process of laser cutting metal parts, focus position, focus size and focal depth are key process elements affecting cutting effect and processing efficiency. Workpieces of different materials and thicknesses need to be matched with corresponding parameter settings.

After the beam is focused by a short-focus focusing lens, the spot diameter is small, the focal depth is short, and the power density at the focus is extremely high, which is suitable for high-speed cutting of thin materials, effectively improving cutting accuracy and reducing kerf error; after being focused by a long-focus focusing lens, the focal depth is long and the spot diameter is relatively large. As long as sufficient power density is ensured, it can be adapted to thick plate cutting, taking into account cutting efficiency and kerf quality.

How Laser Cutting Focus Position Affects Cutting Surface Finish

The reasonable setting of the focus position is the core to ensure the cutting quality of plates with different thicknesses:

When cutting thin plates, the focus is usually set on the workpiece surface, which can realize high-speed precision cutting and reduce material waste;

When cutting thick stainless steel plates, the focus needs to go deep into the plate, with a depth of about 1/3—1/4 of the plate thickness, in the negative defocus range, which can ensure cutting penetration and avoid uneven kerf;

When cutting thick carbon steel plates, the focus needs to be set above the workpiece surface, and as the plate thickness increases, the focus is farther away from the plate surface, in the positive defocus range, which can reduce slag residue and improve the smoothness of the cutting end face.

Summary

Laser output power and mode determine cutting efficiency and applicable thickness range, while focus size, focal depth, and focus position directly influence kerf quality, surface finish, and dimensional accuracy. By scientifically matching power, speed, and focus settings according to different materials and thicknesses, LVMA can achieve higher cutting precision, improved stability, and better overall processing efficiency.