After the process is determined, it is very important to design the drill. Because from the perspective of the part structure, to machine the circular plane A, the arbor must be allowed to open the beam of the I-beam, otherwise it will interfere. However, it is not possible to feed from the lateral direction with a large diameter boring drill. This is because the diameter of the circular plane A of the part is not only limited in size but also concentric with the bolt hole, so the feeding mode can only be vertical. However, the diameter of the facet A exceeds the size of the narrow beam, and the feeding mode of the tool is restricted. In addition, due to the small size between the upper and lower beams and the influence of the transition arc, the space is very limited, which adds great difficulty to the tool design and processing. General factories use the national standard form of boring to process.
2 Process analysis during the drilling process with the national standard structure
When using the standard structure boring, the shank boring is first fed from the traverse to the two beams, and then the front guide column is inserted into the boring from the small hole of the B side. This installation process is troublesome. Moreover, the accuracy of one installation is poor, because the operator has difficulty in looking from the bottom to the top. In general, the installation state cannot be observed. The operation process is not only time-consuming, but also labor intensive, and the production efficiency is greatly affected. The hard work of the operator is self-evident. Why must it be installed from the bottom up? Because it has been said above, the space between the two beams of the workpiece is too small. If the guide column is first loaded into the cutter body, the tool lateral direction can no longer enter the machining space, and the machining process cannot be realized. Due to the limitation of space, the length of the cutting part of the boring drill is already very small, the surface to be machined is the blank surface, and the surface is inclined, and the strength of the cutter body is poor. Therefore, due to the structure limitation, it can only be installed upward from the lower hole.
Due to the above various conditions, the design of the guiding column structure is basically fixed, and the guiding column and the cutter body are connected by a tapered hole. The size of the cone can only be smaller than the diameter of the bolt via to ensure installation, so that the cone size is smaller due to the smaller via. This type of boring drill has become a bigger problem during its use. First of all, due to the welding process, the end face of the boring drill first contacts the arc of the workpiece, and then contacts with the inclined surface, the radial force of the cutter is unbalanced, and the vibration phenomenon is serious, causing the guide column to fall out from the cutter body. Even if it does not fall out, because the guide column is thin and the strength is not enough, it can not withstand the shearing force and cutting force in the vibration process (intermittent cutting), the breaking phenomenon and the knifeing phenomenon continue to occur, the product quality cannot be guaranteed, and the tool is scrapped. The frequency is extremely high, which increases the cost a lot. Due to the small connecting hole of the guide column cone, the machining difficulty in the tool manufacturing process is much improved, and the machining precision is not easy to guarantee, the tool cost is also increased a lot, and the precision of the matching with the guide column is lowered, so that it cannot be used normally. These conditions have seriously affected the rationality of the product process and the requirements of productivity. It is necessary to change the tool structure and design a new type of boring machine for processing the shape.
3 new structure boring design ideas and design process
For the structural characteristics of the product and the problems in the processing process, the standard tool structure of the processing facet A can not meet the requirements of the process and product quality, and the design principle of the new structure must be in the premise of ensuring the product process requirements. Next, overcome various shortcomings in the use of the standard structure of the tool. Under the guidance of this kind of thinking, we broke the convention and carried out a major reform of the boring structure, and designed a new structure boring with reasonable structure, convenient use and excellent cutting performance.
The boring is performed by integrally forming the arbor with the front guide, and the cutting portion is separately connected to the arbor by the inner tapered surface. It can be seen that when the tool is in use, the cutter bar is installed in the spindle hole of the machine tool, and the cutter body is placed into the groove of the workpiece from the side of the workpiece, and the taper surface of the cutter bar and the cutter body is naturally centered, so that the front guide portion and the processed portion are processed. The bolts are matched by the holes, and the machine tool spindle is locked. Under the action of the pin, the cutting force is transmitted to the cutter body, thereby achieving the cutting purpose. This process is obviously much more simplified than the standard structure drilling process, the workers are simple to operate, the labor intensity is reduced, the labor productivity is greatly improved (generally increased by 35 times), and the economic benefits are multiplied.
In order to further promote the boring of this structure in the production, the various parts of the boring structure design process are described in detail below.
1) The design of the shank should first consider the diameter of the neck of the shank. It is the radius from the side of the small beam of the I-beam to the center of the bolt hole H (see). At the same time, the tolerance of the forging blank and the interference without interference are considered. Is the maximum radius of the arbor. Its length is determined based on the cutting stroke drawing. The large end diameter of the connecting rod of the shank and the cutter body is in principle the same as the diameter of the diameter portion, because the H size is generally small, and the strength of the shank is considered to be the best. The diameter of the small end of the cone is determined according to the diameter of the front guide, which is generally 12 mm larger than the front guide to ensure sufficient cooperation between the cutter and the cutter body. The length of the cone is determined according to the actual size of the cutter body. Why is the shank and the body to be fitted with a cone? This is because the axial force is achieved by the tapered surface when the boring is fed. It is better and more reliable than other transmission methods, and the centering accuracy of the cone is high. As long as the inner and outer cone contact surfaces reach 60%, it can meet the matching requirements, and the larger the contact surface is, the larger the contact with the straight hole is, the advantage is that it does not have radial clearance, which not only improves the machining accuracy, but also reduces The vibration source improves the smoothness of the process.
The guide column adopts integral with the cutter bar, which solves the difficulty of observing and difficult to operate due to the installation of the standard structure from the machined hole during use, and overcomes many disadvantages caused by the guide column falling out of the cutter body during use. . Since the connecting cone with the cutter body is developed to a large diameter based on the guide column, the original large diameter of the cone becomes a small diameter, the strength is improved, and the shearing force is increased after the area of ​​the shearing surface is increased. The possibility of breaking the guide column is reduced, the large ripple caused by vibration during the cutting process is eliminated, and the product quality is effectively guaranteed.
In the manufacturing process, the cutter bar consists of a set of concentric bodies due to its Morse cone, neck, positioning cone and guide column. The precision grinding can guarantee its accuracy at one time, and the process is very good.
2) Tool body design The thickness of the tool body is first determined. It is limited by the space of the I-beam. Generally, it should not be too thick. The thickness or dimension should be determined by calculation or drawing. The outer diameter of the tool body of the hardware tool is determined according to the required size and accuracy of the product. Geometric parameters and tool body materials are determined based on the material being processed. The inner cone size is determined by the shank cone and limits the length of the shank cone. The cutter body should make a torque groove, the width of which is determined according to the diameter of the cutter pin. The depth should ensure that the cutter bar and the cutter body are matched, and the pin and the groove bottom have a large gap to avoid the problem that the cone cannot be matched. Other parameters Determined according to the specific circumstances.
4 Conclusion
It can be seen from the above structural analysis that the new structure of the boring drill solves various problems in the fixed plane of the standard structure boring and processing of the axle plate. The structural rationality, manufacturing process and ease of use are much better than the standard structure. Great improvement. After the actual production test, the new structure has fully met the technical requirements of the product, the product quality has been guaranteed, the labor intensity of the workers has been greatly reduced, the production cost has been reduced, the labor productivity and economic benefits have been greatly improved, and the processing of similar parts is the most. Good structural form.
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