Analysis of micro-lubrication cutting technology

Cutting fluid is usually used during metal cutting. The cutting fluid mainly plays the role of cooling, lubrication, chip removal and rust prevention in the cutting process, which helps to improve the durability of the tool, reduce the thermal deformation of the workpiece, and ensure the surface quality of the workpiece. However, the large use of cutting fluid has also caused many negative effects, which not only led to a significant increase in production costs, but also brought enormous potential harm to the environment and human health.

High-speed cutting is a major process technology for high-performance machining and has been widely used in aviation, mold, automotive and other industries. Because the high-speed rotation of the machine tool spindle (8000 ~ 60,000r / min) will produce centrifugal high-speed, high-pressure airflow around the tool, relying on conventional methods to increase the flow rate of cutting fluid and reduce the temperature rise of cutting can not achieve the desired effect. The use of effective cooling and lubrication conditions can effectively reduce the cutting temperature, improve the cutting friction state, and inhibit tool wear, which is the main technical way to further improve the processing efficiency. At the same time, a variety of environmentally friendly new green cutting technologies have emerged in the field of metal cutting, such as dry, liquid nitrogen cooling, spray cooling, air cooling and micro lubrication cutting. Wait.

Minimal quantity lubrication cutting <br> <br> MQL (Minimal Quantity Lubrication, MQL) cutting means is pressurized gas (air, nitrogen, carbon dioxide, etc.) with a very small amount of the lubricating oil mixed vaporized form micron-sized droplets, ejection A cutting method for effective lubrication to the processing area. The amount of cutting fluid is generally only 0.03 ~ 0.2L / h (conventional wet cutting amount is 20 ~ 100L / min), can effectively reduce the friction between the tool and the workpiece, the tool and the chip, to prevent bonding, extend the tool Life expectancy and improved surface quality. MQL has obvious application advantages and wide application range. The research on MQL at home and abroad contains almost all cutting processes, such as drilling, milling, turning and grinding.

MQL technology combines the advantages of both dry and conventional wet cutting: On the one hand, MQL reduces the amount of cutting fluid to a very small amount, which not only significantly reduces the cost of cutting fluid, but also uses a highly natural synthetic degradation. Ester as a lubricant minimizes the environmental and human hazards of the cutting fluid. On the other hand, compared with dry cutting, MQL introduces a cooling lubricant to greatly improve the cooling and lubrication conditions of the cutting process. The wear between the workpiece and the chip is significantly reduced, helping to reduce cutting forces, cutting temperatures and tool wear. This kind of cutting technology, also known as semi-dry cutting, has great prospects under the influence of green environmental protection in the 21st century.

MQL oil mist system

The system structure of MQL is mainly composed of oil mist supply system, nozzle and lubricating oil.

MQL liquid supply system

There are two main types of MQL liquid supply systems: one is an external liquid supply system; the other is a built-in type. The built-in liquid supply system is integrated inside the machine. The mixture of lubricating oil and compressed air is introduced into the machining area through the inner hole of the machine tool spindle and the built-in conveying pipe of the tool. It is easier to cool the lubricating oil mist supply. However, this method puts new demands on the spindle structure and often limits the maximum number of revolutions of the spindle. The external liquid supply system is designed separately, and the structure of the oil mist supply is simple, and it is almost unnecessary to modify the machine tool. The lubricating oil and compressed air are mixed by the mixing device outside the machine and can be taken out by a plurality of nozzles to act on the tool and workpiece in the machining area. However, when the diameter of the machined workpiece changes greatly or the tool is changed, the position of the original nozzle must be corrected manually or through other auxiliary positioning systems to achieve correct positioning of the nozzle axial, radial and angular. In external oil mist supply, there are still technical difficulties for specific processing methods such as drilling. With the current technology, the lubricating oil mist can only achieve a lubrication with a length to diameter ratio of about 2 to 3 in the processing zone. Similar problems exist with milling of deep hole members.

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