Technical Difficulties And Solutions For Laser Cutting Of Thick Plates

With the continuous development of industrial manufacturing technology, laser cutting has been widely used in the field of metal processing due to its advantages of high precision, high efficiency and non-contact processing. However, laser cutting technology faces many challenges when cutting thicker plates. This study aims to systematically analyze the technical difficulties encountered in the process of laser cutting thick plates and propose corresponding solutions to provide theoretical guidance and technical reference for industrial practice.

Laser cutting technology has experienced a continuous development from low power to high power and from thin plate to thick plate. At present, laser cutting has been widely used in automobile manufacturing, aerospace, ship construction and other fields. However, with the increase of material thickness, the problems of cutting quality, efficiency and cost are becoming more and more prominent, which urgently need to be studied and solved in depth.

1.The main technical difficulties of laser cutting thick plate

The primary problem faced in the process of laser cutting thick plate is the significant decline in beam quality with the increase in cutting depth. As the laser in the penetration of thicker materials will occur many times when the reflection and scattering, resulting in uneven distribution of energy density, which in turn affects the cutting quality. Studies have shown that when the cutting thickness exceeds 20mm, the focusing characteristics of the laser beam will deteriorate significantly, resulting in a wide cut on the bottom of the narrow wedge-shaped defects.

Secondly, the heat-affected zone generated in the thick plate cutting process should not be ignored. Due to the poor thermal conductivity of the thick plate, the laser energy accumulates inside the material, resulting in the expansion of the heat-affected zone, which may trigger changes in the microstructure of the material and an increase in residual stress. Experimental data show that when cutting 30mm thick carbon steel, the width of the heat-affected zone can be up to 3-5 times that of the thin plate cutting, seriously affecting the mechanical properties of the material.

Slag adhesion and cutting surface roughness increase is another important technical difficulties. In the thick plate cutting process, the molten metal is difficult to be completely blown away by the auxiliary gas, and it is easy to form a slag accumulation at the bottom of the cut. At the same time, due to the unstable energy input, the cutting surface often appears obvious streaks and unevenness. Statistics show that when the plate thickness exceeds 25mm, the roughness Ra value of the cutting surface may reach 2-3 times of the thin plate cutting.

2.The solution to the technical difficulties of laser cutting thick plate

For beam quality problems, optimizing laser parameters is the most direct solution. By increasing the laser power (usually need more than 6kW), adjust the pulse frequency and duty cycle, can improve the energy penetration depth. At the same time, the use of dynamic focusing system can realize the automatic adjustment of the focus position during the cutting process to maintain the best energy density distribution. Experiments have proved that the use of 12kW fiber laser with dynamic focusing technology can effectively cut 40mm thick stainless steel plate.

In the control of heat-affected zone, the development of new cutting head technology is crucial. The use of oscillating cutting head or beam oscillation technology can disperse heat input and reduce localized overheating. In addition, precise control of auxiliary gases (e.g., using high-pressure nitrogen or special gas mixtures) can effectively cool the cutting zone. Studies have shown that combining gas cooling and intermittent cutting strategies can reduce the heat-affected zone by more than 40% for 30 mm thick aluminum alloys.

To address the slag problem, improving the auxiliary gas system is key. Adopting a dual gas nozzle design (inner high-pressure gas to remove slag and outer protective gas to prevent oxidation) can significantly improve the cutting quality. At the same time, optimized cutting path planning and the introduction of real-time monitoring systems (e.g., visual sensors or acoustic monitoring) can detect and deal with slag buildup in a timely manner. Practice shows that these measures can reduce the slag residue rate of thick plate cutting by more than 60%.