Laser cutting machine processing quality judgment standard

In the laser cutting process of general materials, the thermal deformation produced by the parts is very small due to the fast cutting speed, and the dimensional accuracy of the cut parts mainly depends on the mechanical accuracy and control accuracy of the laser cutting machine's worktable. In pulsed laser cutting process, the dimensional accuracy can be up to um level by adopting high-precision cutting device and control technology.

The quality evaluation of laser cutting has not yet had a unified standard in the international arena. So far there is no standard on laser cutting quality in China, and the main basis for testing the quality of laser cutting is JIS and WES (welding specifications). There are standardization issues concerning laser cutting in CEN (European standardization body) and ISO (international standardization body). The ISO9000 series of quality assurance methods provided mainly by the EU has studied laser cutting standards and standard specimen regulations, etc., which include: cutting quality grade classification, standards for setting samples and processing samples, optical systems, price samples of the type of machine and beam characteristics.

For laser cutting processing, the evaluation of its processing quality mainly includes the following principles:

1. Smooth cutting, no streaks, no brittle fracture;

2. Narrow slit width, which is mainly related to the laser beam spot diameter size;

3. Good perpendicularity of the slit and small heat-affected zone;

4. No material burning, no melting layer formation, no large slag;

5. The surface roughness of the cut, the size of the surface roughness is the key to measuring the quality of the laser cutting surface.

In addition to the above principles, the state of the melting layer during processing and the final molding, which directly affects the above processing quality evaluation index.

Laser cutting surface roughness mainly depends on the following three aspects:

1. The inherent parameters of the cutting system, such as spot pattern, focal length, etc;

2. The process parameters that can be adjusted during the cutting process, such as power level, cutting speed, auxiliary gas type and pressure, etc;

3. Physical parameters of the processed material, such as laser absorption, melting point, viscosity coefficient of the molten metal oxide, surface tension of the metal oxide, and so on. In addition, the thickness of the processed part also has a great influence on the surface quality of laser cutting. Relatively speaking, the smaller the thickness of the metal workpiece, the higher the cutting surface roughness grade.

To obtain a better surface quality grade, the laser power, cutting speed and other process parameters must be optimized several times. In general, for materials with the same characterization and thickness, there is an optimal set of cutting process parameters that will also result in a different cut surface quality. Metallic materials with low melting point, high thermal conductivity, small viscosity coefficient of the molten material, and small surface tension of the metal oxide are easy to obtain high surface quality when laser cutting. Laser cutting flat plate, easy to measure the surface quality, but in the fine processing or cutting some complex patterns, it is difficult to its direct measurement, only with the help of optimizing the test parameters to its surface quality control. Therefore, in order to facilitate the realization of automated cutting, the correspondence between the external optimization parameters and the surface quality level should be established.