Research Status of Dry Cutting Technology

Filling the coolant in the cutting process plays a very good role in reducing the cutting temperature, chip breaking and chip removal, but there are also many disadvantages. For example, maintaining a large coolant system requires a lot of money. It requires regular addition of preservatives, replacement of coolant, etc., to remove many auxiliary times. In addition, due to the harmful substances in the coolant, it is harmful to the health of workers, and the use of the coolant is also limited. For this reason, dry cutting is coming out. But again, dry cutting, as a new technology, has also brought new problems. It has caused many vague understandings. To this end, the United States Michigan Technical University (MTU) conducted a large number of research and comparative cutting tests, in-depth analysis of the use of coolant for workers' health, tool life, cutting force and torque and processing quality Impact. To raise people's understanding of new dry cutting technology.

(1) Workers' health According to a large number of investigations and studies conducted by them, the use of coolant will deteriorate the production environment, cause long-term exposure, and can infect skin diseases and bronchitis, posing a threat to workers' health and safety. Therefore, many countries have set strict environmental sanitation standards. For example, the US Environmental Protection Agency (EPA) requires that the allowable content of harmful substances in the air should be reduced from 5.0 mg/m3 to 0.5 mg/m3. And the particles (diameter size) allowed by harmful substances in the air are reduced from the original 10 μm to 2.5 μm. To achieve such a standard, it requires a high-precision coolant filtration device, an air purification device, etc., and the cost is considerable, and this disadvantage has greatly exceeded the advantages of using a coolant.

(2) Tool life The average person thinks that adding coolant to the cutting can improve the service life of the tool. However, from the MTU cutting speed of V=130m/min, the cutting test proved that the filling of the coolant cutting, due to the discontinuity of the filling process and the unevenness of the cooling degree, the tool produces irregular cold. The alternating heat changes easily cause cracks in the cutter head, which in turn causes damage to the cutter and greatly reduces the service life of the cutter.

(3) Surface roughness From the MTU's more than 100 cutting tests on the drilling process, the dry cutting without the coolant is more than twice the surface roughness of the inner hole than the filling of the coolant. Degree Ra. The cutting test conditions are: AL304 and AL390, and the tool is made of uncoated carbide drill, and the cutting parameters used in the usual drilling are selected. Therefore, the machining of parts required for the surface roughness of the inner hole should be avoided as much as possible. They also performed comparative cutting tests on the above aluminum alloy for boring. The results show that under the same processing conditions, the surface roughness of the obtained inner hole has little to do with the addition of the coolant.

(4) Cutting force and torque The drilling test by MTU on the drilling process proves (the condition is the same as above), and the coolant is added to significantly reduce the cutting force and torque acting on the drill bit. In particular, closed-cut machining has a greater impact, for example, from the cutting tests they performed on tapping. There are also deep hole machining broaching and sawing. However, they used a surface-coated carbide drill for dry cutting tests. Due to the high hardness, good cutting performance and good lubrication of the coated tool (the same effect as filling the coolant, the friction between the tool and the workpiece is reduced), so that the cutting is performed on the drill bit. The force and torque measurements are essentially the same as in the case of a coolant (except for closed machining). Similarly, a comparative cutting test was performed on the above aluminum alloy for boring. The results show that under the same processing conditions, the amount of cutting force and torque acting on the drill bit, plus or without the addition of coolant, is almost the same.

(5) Cutting heat and inner hole dimensional accuracy The MTU is used to measure the cutting temperature of the test piece in the boring test, and the cutting temperature is measured at different axial and radial positions, and the finite element is determined according to the cutting temperature. analysis. The results show that the cutting temperature rise at different positions in the inner hole of the test piece without adding the coolant, and the size of the machined inner hole will be increased. Therefore, for parts processing requiring high dimensional accuracy of the inner hole, there is a problem of whether or not to add a coolant.

From the above aspects, it can be considered that dry cutting can be completely used for non-closed cutting processing in which the dimensional accuracy of the part and the surface roughness are not high. For non-closed machining with high dimensional accuracy and surface roughness, a series of technical measures are required, such as increasing the spindle speed and reducing the feed rate, which will inevitably increase production costs. However, after calculation and analysis, these costs are exactly equal to the cost of canceling the coolant. In addition, the use of the latest manufacturing technology, such as the use of new tool materials, the use of high-speed cutting technology, etc., can completely replace the oil processing technology. Therefore, dry cutting has a good development prospect.

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