ã€China Aluminum Industry Network】 Aluminum alloy is a general name for aluminum-based alloys. By adding copper, silicon, magnesium, zinc, manganese, and alloying elements such as nickel, iron, titanium, chromium, and lithium, it maintains the advantages of pure aluminum and light weight. At the same time, its "specific strength" can surpass many alloy steels and become an ideal structural material. It is widely used in machinery manufacturing, transportation machinery, power machinery and aerospace industries. Aircraft fuselage, skin, compressor and other common aluminum alloys are used to reduce their own weight. Typical uses include aircraft engines and diesel engine pistons, aircraft engine cylinder heads, jet engine impellers, aircraft structural rivets, propeller blades, missile components, wheel hubs, storage containers, sheet metal processing, deep drawing or spinning concave vessels, Welding parts, heat exchangers, printing plates, nameplates, reflectors, etc.
On the other hand, with the development of science and technology and the increasingly sophisticated, integrated and miniaturized cutting-edge products, the number of micro-hole processing is increasing, and the requirements for processing quality are also increasing. Although there are many processing methods for processing micro-holes, such as laser beam, electron beam, ion beam, and EDM, it is still widely used at home and abroad, and the practicality is still strong. [1]
Aluminum alloy has relatively low strength and hardness, little wear on the tool, high thermal conductivity, and low cutting temperature. Therefore, the aluminum alloy has good machinability, and is suitable for easy machining and is suitable for cutting at higher cutting speeds. The spindle speed during high-speed drilling is usually 10,000 r/min or more. However, the melting point of the aluminum alloy is low, and the plasticity increases after the temperature rises. Under the action of high temperature and high pressure, the interface friction of the chip is very large, and the chip fused easily to the blade and stick the knife. The fused material will also cause the blade edge to be lost when it is impacted by the subsequent processing [2]. The above-mentioned machinability of the aluminum alloy makes it difficult for micro-hole drilling. This is because drilling is one of the harsher cutting conditions. Drilling small holes, especially holes with a diameter of 1 mm or less, not only concentrates all the difficulties in drilling, but also has a cutting condition that Drilling is even worse. Specifically embodied in the following aspects [3-4].
(1) The stiffness of the micro drill bit decreases sharply with the decrease of the aperture and the increase of the borehole length ratio. In order to make up for the insufficiency of the micro drill bit stiffness, the drill core thickness of the micro drill bit is relatively large: the ratio of the core thickness of the drill with a diameter greater than 1 mm to the drill diameter is usually less than 0.2, and the micro drill bit is generally 0.3 to 0.4. If the core thickness is large, the width of the horizontal cutting edge is shallow and the spiral groove is shallow, and the drilling conditions deteriorate. When entering the drill, the horizontal edge will cause the drill tip to move on the working surface, destroying the positioning accuracy of the drill, and the wider the horizontal blade, the more serious the swimming will be. When drilling, the chisel edge is in the secondary rake cutting state. The wider the chisel edge, the greater the cutting resistance and the greater the load on the drill bit.
The function of the spiral groove of the drill bit is mainly chip, chip evacuation and introduction of cutting fluid. Shallow spiral groove, the chip capacity is poor, difficult chip removal, scraping and scraping of the surface has been processed seriously, affecting the surface quality, and easy to cause chip clogging, while the cutting fluid is difficult to reach the cutting area, cooling lubrication is very poor. The exit burr is closely related to the axial cutting force, while the axial drilling force mainly comes from the chisel edge. The wider the transverse edge, the greater the axial drilling force and the more serious the exit burr.
(2) The twist drill belongs to a cutter with a relatively complicated structure. In order to reduce the friction between the guide portion and the hole wall, a standard twist drill has a narrow edge at the guide portion, and an inverted cone is formed from the outer round toward the tail to form a comparative Narrow secondary backface and secondary side angles greater than 0°.
For the application of a wide range of high-speed steel micro twist drills, in order to improve its stiffness, strength, and ease of manufacturing considerations, generally no edges and inverted cones, forming a larger sub-back angle of 0 ° of the Vice Vice-blade face and 0 ° Vice Deflection, so the drilling part of the drilling process and the hole wall friction.
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