The broaching tool is a machining tool in which a plurality of teeth are arranged in the direction of the axis by a blade and a tooth, and the broaching process is characterized in that a workpiece having a complicated shape can be machined with high precision. Because the broach is a valuable tool, tool durability has a greater impact on production costs.
In addition, broaching is a finishing process that requires strict surface roughness of the workpiece. When broaching, the cutting resistance is large, the chipping is not easy, the cooling condition is poor, and the surface of the workpiece is easily scratched, so the lubricity and the venting performance of the cutting fluid are required to be good. There is a special broaching oil for sulfur-containing extreme pressure additives in China.
Drilling with a general twist drill is a rough machining. It is difficult to remove the chips during drilling. The heat of cutting is difficult to be exported, which often causes the edge of the blade to anneal, which affects the service life of the drill bit and the machining efficiency. The use of good cutting fluid can extend the life of the drill several times or more, and the productivity can be significantly improved.
Extreme pressure emulsion or extreme pressure synthetic cutting fluid is generally used. Extreme pressure synthetic cutting fluid has low surface tension, good permeability and can cool the drill bit in time, which is very effective for prolonging tool life and improving machining efficiency. For difficult-to-cut materials such as rust-producing steels and heat-resistant alloys, low-pressure extreme pressure cutting oils can be used.
7.deep hole drilling
Deep hole drilling (gun drilling) is a deep hole processing technology developed in recent years. Conventional deep hole machining (also deep to aperture ratio greater than 5) requires multiple processes such as drilling, boring, roughing, and grinding to produce holes with higher precision and lower surface roughness. The new process uses a special-structured tool and a high-pressure cooling lubrication system that simplifies the above-mentioned multiple processes into one continuous pass to achieve considerable depth and high surface roughness. This process is highly efficient and has significant economic benefits.
The deep hole drilling cutting fluid with excellent performance is one of the key technologies of deep hole drilling. The deep hole drilling cutting fluid must have the following properties.
Good cooling, eliminating heat generated by deformation and friction, and inhibiting the formation of chips.
Good high temperature lubricity, reducing the friction and wear of the blade and the support, ensuring that the tool maintains a good lubrication state at high temperatures in the cutting zone.
Good permeability and chip evacuation enable the cutting fluid to penetrate into the cutting edge in time and ensure the smooth discharge of the chips. Therefore, the deep hole drilling cutting fluid is required to have high extreme pressure and low viscosity.
For high-speed cutting machining, oil-based cutting fluid will produce large oil smoke, pollute the environment, and due to insufficient cooling, it will often cause surface burn on the workpiece, affecting the processing quality, and the tool wear will also be intensified. Strong extreme pressure water-based cutting fluid, such as water-based synthetic cutting fluid containing sulfur or phosphorus extreme pressure additive or high concentration extreme pressure emulsion, can overcome oil pollution during high-speed cutting, processing quality and tool wear are better than oil The base cutting fluid is good. However, for the original hobbing and gear shaping machines, measures must be taken to prevent water from entering the rotating part to avoid malfunction of the machine.
Shaving processing requires high surface quality. In order to prevent the sticking knife, cutting oil containing active extreme pressure additive can be used, and fine chips are generated by shaving. In order to make the chips easy to be washed off, it is better to use low viscosity cutting oil. If the chip separation is not smooth, the quality of the processed surface will deteriorate.
Grinding results in high dimensional accuracy and low surface finish. When grinding, the grinding speed is high and the heat is large. The grinding temperature can be as high as 800-1000 or even higher. It is easy to cause surface burn on the workpiece and surface crack and workpiece deformation due to thermal stress. The grinding wheel is passivated and the abrasive grains fall off. And the abrasive chips and grinding wheel powder are easy to splash, falling on the surface of the part and affecting the processing precision and surface roughness. When processing the toughness and plastic material, the grinding debris is stuck in the gap of the grinding wheel working surface or the grinding debris and the processing metal are sintered. On the surface of the grinding wheel, the grinding wheel loses the grinding ability. Therefore, in order to reduce the grinding temperature, rinse off the grinding debris and the end of the grinding wheel, and improve the grinding ratio and the surface quality of the workpiece, it is necessary to adopt a good cooling performance and cleaning performance. Cutting fluid for lubrication and rust resistance.
High-speed grinding: Grinding with a line speed of more than 50 m/s is usually called high-speed grinding. As the line speed of the grinding wheel increases, the grinding temperature increases significantly. From the test, the grinding temperature (working average temperature) when the grinding wheel linear velocity is 60m/s is about 50% to 70% higher than 30m/s; when the grinding wheel linear velocity is 80m/s, the grinding temperature is 60m/s. It is 15% to 20% higher. After the linear speed of the grinding wheel is increased, the number of abrasive grains participating in grinding per unit time increases, the friction effect is intensified, the energy consumption is also increased, the surface temperature of the workpiece is increased, and the possibility of burns and cracks on the surface is increased, which requires It is solved by a coolant with high-efficiency cooling performance. Therefore, in high-speed grinding, ordinary cutting fluid cannot be used, and high-speed grinding fluid with good penetration and cooling performance can be used to meet high-speed grinding with a line speed of 60 m/s. Process requirements.
Strong grinding: This is an advanced high-efficiency grinding process. For example, in the high-speed and powerful grinding process, the grinding wheel with a line speed of 60m/s has a feed rate of about 3.5~6mm per minute. The removal rate can be as high as 20~40mm33/mm·s. At this time, the friction between the grinding wheel and the workpiece is very severe. Even under high pressure and large flow rate and condition, the surface temperature range of the workpiece in the friction zone is 700~1000. If the cooling condition is not Well, the grinding process is impossible. In the powerful grinding of the work type, the synthetic grinding fluid with excellent performance is improved by 35% compared with the emulsion, the grinding ratio is increased by 30% to 50%, and the normal grinding time is extended by about 40%. The power loss is reduced by about 40%, so the performance of the coolant has a great influence on the grinding effect during strong grinding.
Grinding of diamond grinding wheel: This is suitable for grinding of hard materials such as cemented carbide, ceramics and glass. It can be coarsely ground and finely ground. The surface is not cracked or notched, and a lower surface can be obtained. Roughness. In order to prevent excessive heat generation during grinding and premature wear of the grinding wheel, obtaining a lower surface roughness requires continuous and sufficient cooling. Due to the high hardness of the workpiece, the grinding fluid should mainly have cooling and cleaning performance, keep the grinding wheel sharp, and the friction coefficient of the grinding fluid should not be too low, otherwise it will cause poor grinding efficiency, surface burn and other adverse effects. A chemical synthesis liquid based on inorganic salts is used as the grinding fluid. When grinding, a small amount of polyethyl alcohol can be added as a lubricant to improve the surface quality of the workpiece. For parts with high machining accuracy, low-viscosity oil-based cutting fluids with good lubrication properties can be used.
Thread, gear and lead grinding: This type of grinding places special emphasis on the quality and dimensional accuracy of the machined surface after grinding. Generally, grinding oils containing extreme pressure additives are preferred. These oil-based grinding fluids are lubricated due to their lubricating properties. Well, the grinding heat can be reduced, and the extreme pressure additive can react with the workpiece material to form a low shear strength iron sulfide film and a ferric chloride film, which can reduce the wear of the abrasive grains and the cutting edge and smooth the grinding. get on. In order to obtain better cooling and cleaning properties, the cutting fluid should ensure fire safety. It is advisable to use grinding oil with low viscosity and high flash point.
The honing processed workpiece has high precision, low surface roughness, small particle size of iron powder and whetstone powder during processing, and is easy to be suspended in the grinding fluid, causing blockage of the oil stone hole, affecting the processing efficiency and destroying the processing quality of the workpiece surface. The cooling lubricating fluid is required to have good penetration, cleaning and sedimentation performance. Water-based coolants have poor sedimentation properties for fine powders and are generally not suitable for use. Oil-based grinding fluids with high viscosity are also unfavorable for sedimentation of powders. Therefore, mineral oils having a viscosity of about 2 to 3 mm 2 /s (40) are generally used to add a certain amount of inactive sulfurized fatty oil as a honing oil.