Criteria for Evaluating Laser Cutting Machine Processing Quality

During laser cutting of general materials, the relatively high cutting speed results in minimal thermal deformation of parts. The dimensional accuracy of cut components primarily depends on the mechanical precision and control accuracy of the laser cutting machine's worktable. In pulsed laser cutting, the use of high-precision cutting devices and control technologies enables dimensional accuracy down to the micrometer level.

Internationally, there remains no unified standard for evaluating laser cutting quality. To date, China also lacks specific standards for laser cutting quality, with inspections primarily relying on JIS (Japanese Industrial Standards) and WES (Welding Engineering Specifications). Standardization efforts for laser cutting are underway within CEN (European Committee for Standardization) and ISO (International Organization for Standardization). Research on ISO 9000 series quality assurance methods, primarily led by the EU, addresses laser cutting standards and standard test specimens. This includes: classification of cutting quality grades, standards for reference and processed samples, optical systems, machine types for reference samples, and beam characteristics.

For laser cutting processing, evaluating its processing quality primarily involves the following principles:

1. Smooth cutting without streaks or brittle fractures;

2. Narrow kerf width, primarily related to the laser beam spot diameter;

3. Good kerf perpendicularity with minimal heat-affected zone;

4. No material combustion, no formation of a melt layer, and no large slag;

5. Surface roughness of the cut edge, where roughness magnitude is the key metric for assessing laser-cut surface quality.

Beyond these principles, the state of the molten layer during processing and the final forming directly influence the aforementioned quality evaluation indicators.

Laser-cut surface roughness primarily depends on the following three aspects:

1. Inherent parameters of the cutting system, such as spot mode and focal length;

2. Adjustable process parameters during cutting, such as power level, cutting speed, auxiliary gas type, and pressure;

3. Physical properties of the processed material, including laser absorption rate, melting point, viscosity coefficient of molten metal oxides, and surface tension of metal oxides. Additionally, the thickness of the workpiece significantly impacts laser-cut surface quality. Generally, thinner metal workpieces yield higher surface roughness grades.

To achieve superior surface quality grades, multiple optimizations of process parameters like laser power and cutting speed are essential. Generally, materials with identical characteristics and thicknesses yield varying cut surface qualities despite sharing optimal cutting parameters. Metals with low melting points, high thermal conductivity, low molten metal viscosity coefficients, and low metal oxide surface tensions readily achieve high surface quality during laser cutting. While surface quality is easily measured during flat plate laser cutting, direct measurement becomes challenging during precision machining or cutting complex patterns. Surface quality control in such cases relies solely on optimizing experimental parameters. Therefore, to facilitate automated cutting, a correlation between external optimization parameters and surface quality grades must be established.