When selecting the main cutting fluid (such as cutting oil), it should be transported to the area where oil film can be generated on the friction surface. Conversely, if the coolant selected is based on cooling (such as water-based cutting fluid), the cutting fluid should be brought close to the edge of the tool. Under these conditions, the pressure method is usually used to force the cutting fluid into the cutting area, thereby taking away the heat generated by the tool, the workpiece, and the chip due to friction and deformation.
Continuous application of cutting fluid is better than intermittent application of cutting fluids. The intermittent application of cutting fluid will generate thermal cycles, resulting in cracks and chipping of hard and brittle tool materials (such as carbide tools). The intermittent use of cutting fluid not only shortens the tool life, but also makes the work surface rough.
Another benefit of the correct use of cutting fluid is the effective removal of chips, which also contributes to longer tool life. If the nozzle of the cutting fluid is properly placed, the chip flutes of the milling cutter and the drill bit can be prevented from being chipped or chipped by the chips. For the machining of some large workpieces, or the powerful cutting and grinding of large feeds, two or more rows of coolant nozzles are used so that they can be sufficiently cooled, which will help improve the processing efficiency and ensure the processing quality.
First, cutting fluid cooling manual filling method
Solid or paste lubricant can use the brush, brush to apply or dripping lubricant to the tool or workpiece (mainly tapping, die set thread). Recently, hand-held liquid dispensers have also been developed. The lubricant is atomized by pressure and sprayed on the tool and the workpiece. On machines without a dosing cooling system, manual dosing is an effective method if the number of drilling or tapping is small. When two different types of machining are to be performed on the same machine tool, manual oil can be used in combination with the overflow cooling system on the machine tool.
Second, cutting fluid cooling overflow method
The most common method of using a cutting fluid is an overflow method. The low-pressure pump is used to drive the cutting fluid into the pipeline and exit the nozzle through the valve. The nozzle is installed near the cutting area. The cutting fluid flows through the cutting area and then flows to different parts of the machine tool. It is then collected in the oil pan and then returned from the oil pan to the cutting fluid tank for recycling. Therefore, the cutting fluid tank should have a sufficient volume to allow time for the cutting fluid to cool and cause fine chips and abrasive particles to settle. Depending on the type of machining, the volume of the cutting fluid tank is approximately 20-200L, and the individual machining is even larger. For example, deep hole drilling and strong grinding, the cutting fluid tank can reach 500-1000L or more. A coarse filter should be provided in the oil pan to prevent large cuttings from entering the cutting fluid tank and a fine filter at the suction port of the pump.
For machine tools such as grinding, swarving, deep hole drilling, and deep hole boring, because the surface quality of the machined workpiece is high, finer grinding debris, grinding wheel particles, and cutting particles must be removed. Filter paper for filtration. The use of filtration equipment can avoid excessive contamination or excessive metal particles in the cutting fluid, helping to keep the cutting fluid clean and prolong the service life of the cutting fluid. Modern automated machine tools are generally equipped with cutting fluid filtration, separation, and purification devices. The overflow method allows the cutting fluid to continuously flow to the cutting area and wash away the chips. The flow of the cutting fluid must be larger in order for the tool and workpiece to be submerged by the cutting fluid.
In addition to providing proper cutting fluid to the cutting area, there must be enough cutting fluid to prevent abnormal temperature rise. In deep hole drilling, if the cutting fluid tank is too small, the temperature of the cutting fluid rises quickly. When the oil temperature exceeds 60Â°C, the cutting cannot continue, so the deep hole drilling machine is generally equipped with a large cooling oil tank.
The distribution of the cutting fluid flow directly affects the efficiency of the cutting fluid. The nozzle should be positioned so that the cutting fluid is not thrown away from the tool or workpiece due to centrifugal forces. It is best to use two or more nozzles, one to send cutting fluid to the cutting area, and the other to assist in cooling and flushing away the chips. Turning and boring require the cutting fluid to be sent directly to the cutting area so that the cutting fluid covers the cutting edge of the tool and the workpiece to provide good cooling.
Practical experience shows that the cutting fluid has an inner diameter of at least three quarters of the width of the turning tool. For heavy-duty turning and boring, a second nozzle is required to feed the cutting fluid along the underside of the tool. The cutting fluid supplied by the lower nozzle can be smoothly fed between the tool and the workpiece without being blocked by the cutting, which contributes to the lubrication at low speed. When horizontally drilling and reaming, it is best to feed the cutting fluid through the inner hole of the hollow tool to the cutting area to ensure that the cutting edge has enough cutting fluid and flush the chips out of the hole. Because the spiral groove of the drill bit (to discharge chips) plays a role of discharging the cutting fluid from the cutting zone, even if it is a vertical drill, the cutting fluid entering the cutting zone is very few. Only the hollow drill bit can solve this problem.
Third, cutting fluid cooling high pressure method
For some processing, such as deep hole drilling and hole drilling, high pressure (0.69-13.79MPa) cutting fluid system is often used for oil supply. Deep-hole drilling uses a single-edged drill, similar to boring, except that the inside of the drill has access to cutting fluid. Hole drilling is a drilling method that drills a cylindrical hole in the workpiece but leaves a solid cylinder. When the tool enters the workpiece, the drilled solid cylinder passes through a hollow cylindrical cutter head, and a pressure pump is used to send the cutting fluid around the cutter, forcing the cutter to flow out of the center of the cutter. The cutting fluid used for hole drilling must have good extreme pressure and anti-sintering properties, the viscosity should be very low to allow free flow around the tool, and it should have good oiliness to reduce the tool and workpiece, tool and chip Friction coefficient. The main problem with deep hole drilling is how to maintain sufficient cutting fluid flow in the cutting area. One approach is to use a drill flutes as a path for cutting fluid. The cutting fluid pressure is 0.35-0.69 MPa. The rotating seal sleeve flows into the drill bit and then directly into the cutting zone. The cutting fluid flowing out of the holes helps to remove the swarf. In deep-hole drilling, the use of oil hole drilling is a big improvement compared with flooding method, and the bit life and productivity have been greatly improved. The high pressure method helps the cutting fluid reach the cutting area and is sometimes used on other machine tools. Grinding makes high-pressure nozzles conducive to the washing of the grinding wheel.
Fourth, cutting fluid cooling spray method
The cutting fluid can be sprayed onto the tool and the workpiece in the form of airborne oil mist. The cutting fluid flows through a small nozzle and uses compressed air at a pressure of 0.069-0.552 MPa to disperse the cutting fluid into small droplets and spray it into the cutting zone. In this case, the water-based cutting fluid is better than the oil-based cutting fluid because oil mist of the oil-based cutting fluid pollutes the environment, which is unhealthy and easy to integrate with larger oil droplets. The spray method is best suited for machining with high cutting speeds and low cutting areas (such as end mills). Use a cutting fluid with good cooling performance. The tiny droplets come in contact with hot cutting tools, workpieces, or cuttings and can quickly evaporate away. Spray cooling eliminates the need for splash plates, oil pans, and return pipes. It uses only a small sphere and the workpiece is dry. Even a little oil can easily dry.
The spray method has the following advantages:
1, the tool life is longer than dry cutting;
2. It can be used to provide cooling when no overflow system is available or not suitable;
3, cutting fluid can reach other methods can not be reached;
4. Between the workpiece and the tool, the flow rate of the cutting fluid is higher than the overflow method, and the cooling efficiency is calculated with the same volume of cutting fluid, which is many times higher than the overflow method.
5, under certain conditions can reduce costs;
6. The cut workpiece can be seen. The disadvantage of the spray method is that the cooling capacity is limited and also requires ventilation.
There are three ways to spray the device:
The principle is the same as that of a household sprayer. The principle of the thin waist tube is mainly used. The compressed air sucks the cutting fluid out of the liquid tank and is mixed and atomized in the air flow. It has a tube of compressed air and another tube of siphon cutting fluid and is connected to a mixing joint, which is suitable for the spraying of low viscosity cutting oils and emulsions.
2, pneumatic type (Pressure method)
The principle is that the cutting fluid is installed in the sealed liquid cylinder and pressurized with 0.2-0.4 MPa of compressed air. When the electromagnetic valve is opened, the cutting fluid is pressed out and mixed and atomized with the compressed air flow through the mixing valve. This device is suitable for spraying water-based synthetic liquids and emulsions, but the aqueous solution and emulsion must not contain fatty oils or suspended solids. Atomization mixing ratio can be adjusted by mixing valve and pressure regulator.
3, jet type
The principle is to pressurize the cutting fluid with a gear pump and spray it directly into the compressed air flow through the mixing valve to atomize it. This device is suitable for atomizing transparent cooling water and low viscosity cutting oils. Spraying can be applied to end milling, turning, automatic machining, and CNC machining. Spray device with solenoid valve control is suitable for tapping and reaming on CNC machine tools.
Fifth, cutting fluid cooling cooling liquid cooling method
There are many types of cooling liquid cooling methods. For example, nitrogen, argon, carbon dioxide, and other gases can be compressed into liquids and placed in cylinders. Fluorine gas can be compressed into liquid by mechanical means. When used, it is discharged. After being regulated, the nozzle is directly injected into the cutting zone. , Cooling tools, workpieces and swarf by gasification and heat absorption. This method has a very good cooling effect and is applicable to the machining of hard-to-machine materials such as stainless steel, heat-resistant steels, and high-strength alloy steels, and can greatly improve the tool durability.
For large and medium-sized mechanical processing plants, where possible, consideration should be given to the use of a concentrated circulation system to supply cutting fluid for multiple machine tools, but each machine tool must use the same cutting fluid. Several grinders can handle abrasive debris with a linked conveyor system. The concentrated treatment of fine chips and abrasive debris wetted by the cutting fluid can reduce manual processing and improve working conditions.
The concentrated fluid supply system allows the factory to better maintain the cutting fluid. The cutting fluid is concentrated in a large pool. Regular sampling inspections and regular replenishment of raw liquid or water according to the inspection result facilitate the control of the cutting fluid concentration. The number of sampling inspections can be reduced so that more items can be inspected and the quality of the cutting fluid in use can be guaranteed. Compared with many separate multi-fluid feed systems that are separately installed, the maintenance cost of the cutting fluid is reduced and the cost is relatively reduced.
The main advantage of the centralized supply system is that it can be processed by centrifugation. It can effectively remove slicks and metal particles in the cutting fluid, and also remove half of the bacteria in the cutting fluid (because the bacteria is easy to float in the cutting fluid. At the interface with the metal particles).
Continuous removal of these contaminants, regular inspection of the quality and based on these inspections, the planned use of additives or the addition of stock solutions are important factors that make the centralized system very effective in extending the service life of the cutting fluid. This also reduces the waste liquid treatment of the water-soluble cutting fluid.
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