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1. Knife holder 2. Backing plate 3. Retaining iron 4. Additional chip remover 5. Bolt 6. Insert blade Mechanically fixing the carbide blade
Table The distance from the cutting edge of the cemented carbide insert to the backing plate (the amount of protrusion) mm Depth of cut
Mm Feeding amount (mm/r) <0.5 <0.8 <1.2 <6 5 ~ 7 8 ~ 10 12 ~ 14 <10 7 ~ 8 9 ~ 11 13 ~ 15 <15 - 11 ~ 13 15 ~ 16 Grinding Carbide inserts should be noted that the carbide inserts are placed in the shank grooves and secured with bolts and a wiper plate. The length of the blade protruding from the cutter bar should not exceed 1 to 1.5 mm. The backing plate is to be placed in front of the blade. When placed, the chips can be spiraled out. The distance or protrusion measured from the center of the blade depends on the size of the chip section. The amount of sticking should not be less than the value listed in the table on the right. Otherwise, the chip will hit the chip conveyor violently, which will cause the cutting part of the turning tool to break and even break the cutter bar. When cutting, replace blunt or broken blades in time. The blade must be cleaned of swarf from the shank. The advantage of this type of cutter structure is that: when there is an error between the cutter block and the cutter body, grinding can be performed to ensure the assembly accuracy; the pressing bolt is located on the flank face and is not easily damaged by the chip. The plate tool holder is more suitable for heavy-duty cutting, because it greatly increases the stiffness of the blade in the direction of force. After increasing the cutting amount, it will not produce large vibration, which is conducive to the improvement of production efficiency and processing quality. 4 Selection of cutting amount The cutting depth in the roughing stage of heavy turning can reach 50mm on one side, the corresponding cutting speed is about 10m/min, and the feed amount is 1.5mm/r. Since the rough machining stage takes the removal margin as the main processing purpose, the cutting depth should be increased in order to increase the cutting efficiency in accordance with the principle of determining the machining allowance in machining. Due to the large cutting depth during heavy cutting, the cutting force is large, and the corresponding cutting speed is generally selected to be 10 to 15 m/min, and the feed amount is 1 to 2 mm/r. With such a cutting amount, the surface roughness of the workpiece is relatively poor and can only reach Ra12.5 to Ra6.3. The roughness value can be increased by the rolling method to meet the requirements of the subsequent processing. 5 Conclusions Compared with ordinary turning, heavy-duty turning is different from the theoretical calculation. At present, many processes and tool data for heavy-duty turning are based on ordinary machining. This is not entirely applicable, and therefore more in-depth discussions are needed.
Cemented Carbide Introduction Turning is the main process of mechanical manufacturing process. Especially in the heavy-duty machining manufacturing industry, the size of the workpiece structure can be regarded as a huge one. The weight is as high as 60 to 80 tons, or even hundreds of tons. The heavy-duty horizontal turning diameter of the processing equipment reaches 6m, and the heavy-duty vertical-vehicle can reach 10m. Compared with ordinary machining, heavy-duty turning machining has a large depth of cut, a low cutting speed, and a slow feed rate. The machining allowance is 35 to 50mm on one side, combined with poor workpiece balance in the cutting process, uneven machining allowance distribution, and vibration caused by some components of the machine tool such as unbalance, which causes the processing of the dynamic imbalance process to consume a lot of maneuvering Time and auxiliary time. Therefore, the processing of heavy parts, improve productivity or the utilization of machinery and equipment, must increase the thickness of the cutting layer and the amount of feed, we must consider the cutting amount and the choice of tools, improve the tool structure and geometry, the strength characteristics of the tool material Take into consideration in order to increase the amount of cutting and significantly reduce the maneuvering time. 1 Selection of tool materials The cutting tool materials commonly used in cutting include high-speed steel, hard alloy, cubic boron nitride (CBN), and ceramics. Heavy-duty cutting depth can reach 30-50mm in general, and the balance is uneven. The surface of the workpiece has a hardened layer. The tool wear in the roughing stage is mainly in the form of abrasive wear: the cutting speed is generally 15 to 20m/min, although the speed value is in the product The area of ​​occurrence of talomas, but the high temperature enough to cut the point of contact between the swarf and the rake face is in a liquid state, which reduces the friction and suppresses the formation of the built-up edge. The choice of tool material is resistant to wear and impact. Ceramic tools have high hardness, but low bending strength, poor impact toughness, and are not suitable for heavy-duty turning. CBN has the same problem. Carbide has a low friction coefficient, which can reduce the cutting force and cutting temperature during cutting, greatly improve the tool durability, and is suitable for high hardness materials and heavy-duty turning rough machining. Cemented carbide is classified into tungsten cobalt (YG), tungsten cobalt titanium (YT) and tungsten carbide (YW). When processing steel, YG cemented carbide has good strength and toughness, but its high temperature hardness and high temperature toughness are poor: Heavy-duty turning workpieces have large plastic deformation, severe friction, and high cutting temperature. Therefore, YG is rarely used in heavy-duty turning. Carbide. YT type hard alloy has high hardness and wear resistance, high heat resistance, anti-bonding diffusion ability and anti-oxidation ability. It is a commonly used tool material for heavy-duty turning and is suitable for processing steel materials. However, during low-speed turning, the uneven cutting process will cause the toughness of the YT alloy to be poor, resulting in chipping: especially when machining some high-strength alloy materials, the durability of the YT carbide decreases rapidly and cannot meet the requirements for use. In this case, YW tools or fine-grain, ultrafine-grain alloy tools (such as 643) should be used. The fine-grained alloy has good wear resistance and is more suitable for processing chilled cast iron products, and its efficiency can be improved by more than 1 time compared with YW-type tools. The use of carbide tools to increase the turning speed of heavy-duty machining is one of the keys to improving productivity, and it is also a favorable factor for shortening the production cycle time. In the process, several strokes are taken to remove large margins, each time the depth of cut is small, and the cutting speed of carbide cutting tools can greatly improve the cutting speed. 2. Selection of tool angles During heavy-duty turning rough machining, forging scales, cracks, spade pits, casting inclusions, and pores on the outer surface of the workpiece can easily cause the tool to break. Therefore, a reasonable tool angle should be selected. Under heavy-duty machining conditions, a very thick swarf is to be removed for rough machining. The turning tool usually uses an anterior angle of g=8° to 12°, and ordinary g=15°. Cutting edge inclination l=10° to 18°. If the rake angle is reduced, that is, the cutting angle is increased, the strength of the cutting edge can be increased to some extent. It should be pointed out that reducing the rake angle increases the cutting force, but when the g changes from 15° to 10°, the cutting force increases very little, while the increased working rake angle and wedge angle improve the sharpness of the cutting edge and Tool tip strength 3 Especially when the workpiece is heavy and the rotary load has an impact, the cutting edge's blade inclination l=10° to 18° creates the most favorable cutting conditions, and therefore, the impact force is applied during cutting. Leaving the knife tip prevents the tip from breaking. At the same time, in the main cutting edge is open about 1mm wide negative chamfer, R2mm about the tip radius to improve the impact resistance of the blade, but the tool installation angle must be adjusted according to the actual situation. 3 Selection of tool structure The cutting allowance is large during the roughing stage and the rigidity of the tool is required to be high. In general, the overall tool stiffness is good, but the structure is cumbersome and difficult to assemble and disassemble: The machine tool can be disassembled flexibly, and the dynamic stiffness can also meet the processing requirements. The tool material selection and clamping structure of the machine tool is very important for machining accuracy. In actual machining, it is found that the eccentric pin clamping and the head compression are not suitable for heavy roughing because the process system during roughing process has large vibration and often causes pressure. Loosening of the tightening mechanism leads to damage of the blade: the pressure-inducing structure also often causes damage to the compact due to the impediment of the outflow of the chips. The manufacturing precision of the machine tool is also very high, because even if the error is small, it can make the positioning mechanism into a bearing mechanism. Because the cutting force during the heavy cutting process is very large, it is easy to damage the tool. After actual machining verification, the tool with the structure shown in the figure below is more suitable for rough turning of heavy turning.