During the sheet metal bending process, the friction between the sheet and the mold will not only cause scratches on the sheet surface, affecting the appearance and quality of the product, but also accelerate the wear of the mold, shorten the service life of the mold, and increase production costs. A reasonable lubrication process can effectively reduce the friction coefficient, reduce wear, and improve processing quality and efficiency.
Selecting a suitable lubricant is the basis of the lubrication process. Common sheet metal bending lubricants include lubricating oil, grease, and solid lubricant. Lubricating oil has the characteristics of good fluidity and strong cooling performance. It can quickly take away the heat generated by friction, reduce the temperature of the processing area, and reduce the adhesive wear between the sheet and the mold. For high-speed bending processing, low-viscosity lubricating oil can quickly penetrate into the contact surface between the mold and the sheet to form a continuous lubricating film. Grease has good adhesion and can form a thicker oil film on the mold surface. Even under high-pressure and heavy-load bending conditions, it is not easy to be squeezed out. It is suitable for scenes with large bending forces and slow processing speeds. Solid lubricants such as molybdenum disulfide and graphite are often used in the form of powder or coating. They can still maintain good lubrication performance under high temperature and high load conditions, and are particularly suitable for bending difficult-to-process materials such as stainless steel and high-strength steel. In practical applications, lubricants need to be selected based on factors such as sheet material, mold material, and processing parameters. For example, aluminum alloy sheets are soft and easily scratched. Special aluminum alloy lubricants with good anti-wear and anti-corrosion properties should be selected to avoid chemical reactions between the components in the lubricant and the aluminum alloy.
Optimizing the lubrication method can significantly improve the lubrication effect. Currently, the commonly used lubrication methods are smear lubrication, spray lubrication, and dip lubrication. Smear lubrication is to evenly apply the lubricant to the mold surface or the part to be bent by manual or mechanical means. This method is simple to operate, but the lubricant has poor uniformity of distribution and is suitable for small batches and low precision processing. Spray lubrication uses compressed air to atomize the lubricant and spray it onto the mold and sheet surface. It can achieve uniform and precise spraying of the lubricant, and the amount of lubricant is small, which is particularly suitable for automated production lines. Dip lubrication is to immerse the sheet or mold into the lubricant tank so that the surface can fully absorb the lubricant. This method is suitable for parts with high lubrication requirements and simple shapes. In addition, with the development of technology, the new micro-lubrication (MQL) technology has gradually been applied in sheet metal bending. It uses compressed air as a carrier to deliver a very small amount of lubricant to the processing area, which can not only meet the lubrication needs, but also reduce the waste of lubricants and pollution to the environment.
Controlling the timing and frequency of lubrication is the key to ensuring the lubrication effect. Before bending, ensure that the surface of the mold and the sheet is clean and free of impurities, and then evenly apply or spray the lubricant to form an initial lubricating film. During continuous processing, the lubricant needs to be replenished in time according to the processing speed, number of bending times and lubricant consumption. For high-speed automated bending production lines, the friction state between the mold and the sheet can be monitored in real time by sensors. When the friction coefficient exceeds the set threshold, the lubrication system is automatically triggered to replenish oil. At the same time, different bending process stages have different requirements for lubrication. For example, in the pre-bending stage, in order to make the sheet fit the mold better, the amount of lubricant can be appropriately increased; in the fine bending stage, in order to ensure the bending accuracy, the thickness of the lubricant needs to be controlled to avoid the sheet sliding due to excessive lubricant, which affects the forming size.
The synergistic effect of mold surface treatment and lubricant should not be ignored. Polishing, hard chrome plating, coating treatment, etc. on the mold surface can reduce the surface roughness of the mold and reduce the friction resistance between the mold and the sheet. When used with lubricants, the lubrication effect can be further improved. For example, after the mold surface is hard chrome plated, the hardness is increased and the wear resistance is enhanced. At the same time, the smooth surface of the chromium layer is conducive to the uniform distribution of the lubricant and the formation of a stable lubricating film. In addition, some new mold surface coating technologies, such as diamond-like coating (DLC), have good self-lubricating properties. When used in combination with lubricants, they can form double lubrication protection between the mold and the sheet, greatly reducing wear.
Establishing a quality monitoring system for the lubrication process is an important measure to ensure the stability of the lubrication effect. By regularly testing the physical and chemical properties of the lubricant, such as viscosity, acid value, flash point, etc., it is possible to determine whether the lubricant has deteriorated or failed, and replace unqualified lubricants in time. At the same time, surface roughness meters, microscopes and other equipment are used to detect scratches on the sheet surface and the degree of wear on the mold surface, analyze the problems in the lubrication process, and adjust the lubricant type, lubrication method or process parameters in a targeted manner. In addition, simulation tests can be used to study the friction and wear laws between the sheet and the mold under different lubrication conditions, providing data support and optimization solutions for actual production.
Under the trend of green manufacturing, the development of environmentally friendly lubrication processes is particularly important. Research and develop biodegradable lubricants to reduce environmental pollution; adopt closed-loop lubrication systems to achieve lubricant recovery, filtration and reuse, and reduce production costs and resource consumption. For example, water-based lubricants use water as the main carrier, are environmentally friendly and have good cooling performance, and are gradually being used in sheet metal bending. At the same time, optimizing lubrication process parameters and reducing the amount of lubricant used are also important ways to achieve green lubrication. By accurately controlling the pressure, flow rate and injection time of spray lubrication, the lubrication effect can be guaranteed and the lubricant can be saved to the maximum extent.
By rationally selecting lubricants, optimizing lubrication methods, controlling lubrication timing, coordinating mold surface treatment, establishing a quality monitoring system, and developing environmentally friendly lubrication processes, it is possible to effectively reduce sheet surface scratches and mold wear during sheet metal bending processing, improve product quality and production efficiency, and promote the sheet metal processing industry to develop in a high-quality, green direction.
