How to cut high-quality products in laser cutting?

In small batch production, plane laser cutting and 3D laser cutting are both indispensable means of realization. They are widely used in industries such as automobiles, sheet metal processing, and electric vehicles. They are also used in industries with short life cycles and rapid changes. Very extensive. So how to cut high-quality products in laser cutting? Take thick stainless steel as an example to analyze the settings of various elements of the cutting process.

Cutting process elements:
1. Nozzle selection

The size of the nozzle diameter determines the shape of the gas flow entering the incision, the gas diffusion area, and the gas flow rate, thereby affecting the stability of the melt removal and cutting. The air flow into the incision is large, the speed is fast, and the position of the workpiece in the air flow is appropriate, the stronger the jetting ability to remove the molten material. Under a fixed flow, different nozzle sizes, the thicker the stainless steel that monitors the air pressure, the larger the nozzle selection should be, the larger the proportional valve setting, and the larger the flow, can the pressure be ensured and the normal section effect can be cut.

2. Auxiliary gas selection and gas purity
Various auxiliary gases are often used in stainless steel laser cutting processing, such as oxygen, nitrogen, air, etc. Different gas types are used, and the effect of cutting sections is different. Oxygen is a black section, air is light yellow, and nitrogen can keep the original color of stainless steel from being oxidized. Nitrogen is a better auxiliary gas for stainless steel cutting.
Recommended oxygen and nitrogen purity:
【oxygen】
Advantages: high cutting speed, able to cut thick sheets
Purity recommendation: ≥99.999%

【Nitrogen】
Advantages: avoid oxidation of the cutting edge, so the workpiece does not need to be reworked
Purity recommendation: ≥99.995%
Test data chart of nitrogen flow rate, nozzle diameter and gas pressure

The ordinate is the gas flow test value, the abscissa is the adjustment setting for different gas pressure changes, and the different colors indicate the test conditions for different nozzle diameters. It can be seen from the graph above that the flow rate is determined by the set gas pressure and nozzle diameter, and it is linearly positively correlated.
3. Focal spot position
In order to ensure the cutting effect and protect the nozzle from damage, it is necessary to do a coaxial test before cutting to ensure that the nozzle is coaxial with the laser output beam. Test method: Attach the transparent tape to the nozzle outlet end surface, adjust the laser output power to punch, observe whether there is a center hole and the position of the center hole on the transparent tape, adjust the adjustment screw on the handle of the mirror cavity synchronously, until the laser is on The hole punched in the scotch tape coincides with the center of the nozzle. The focus is different, and the thickness, material, and quality that can be cut are also different. Different materials and thicknesses need to be adjusted to different focus. Before cutting, the actual zero focus is measured, and the test and analysis of the cutting process parameters can be carried out with the zero focus as the benchmark. The negative defocus is the main process selection direction for stainless steel cutting.

Fourth, the laser frequency adjustment, and the influence of the duty cycle on the cutting quality
The effect of frequency change on stainless steel thick plate cutting: the frequency is reduced from 500-200Hz, the cutting section effect becomes finer, and the layering is gradually improved. When the frequency is set to 100Hz, it cannot be cut and the blue light is reversed. By changing the frequency, find a better frequency range. In order to ensure a better cutting section, the number of pulses must be perfectly matched with the energy of a single pulse.

The effect of duty cycle change on stainless steel thick plate cutting:
The duty ratio of 53% is the critical value. If you continue to decrease the duty ratio, there will be traces of incomplete cutting on the lower surface. The duty ratio increases to 60%, the section becomes rough, the delamination is obvious, and the cut surface becomes yellow.

to sum up:
Seiko produces fine work. Generally speaking, the influence of nozzle height, machine tool motion parameters, motion acceleration, operating speed, material quality, etc. on the cutting results also needs to be tested and analyzed item by item. It requires laser process debugging technology and other aspiring people to actively work hard for it. Contribute to the improvement of the laser cutting process. When the laser cutting capacity reaches 130 mm or even higher, the application field will also be further expanded.