The structure and principle of a double tooth bar indicates that the horizontal horizontal lathe of the horizontal lathe generally adopts the mercerized bar drive to meet the machining precision and transmission requirements, while the numerical control lathe generally adopts the ball screw transmission structure. The double-jaw drive described in this paper is now applied to the large horizontal lathe of CNC horizontal lathe, which changes the structure of the traditional large tool post longitudinal movement. The double-jaw drive is a structure in which a precision helical toothed bar is engaged with two helical gears. The two helical gears mesh with the dental bar at the same time. According to the principle that the helical gear can transmit the axial force, the structure adopts one oblique axis. The gear is fitted with a helical gear having a helix angle opposite to that of the oblique shaft gear. Two transmission chains are transmitted from the III axis to mesh with the helical toothed bars (the gear transmissions after the III axis are both helical gears), and the two axes that are meshed with the helical teeth are adjusted by the axial adjustment of the III axis. The gear rotates in the opposite two directions to achieve a gap-free transmission between the gear and the toothed rod.
2 superior tooth bar drive superior ball screw and double bar drive transmission data. According to the data analysis, the application of double-toothed bar gear in CNC machine tools is superior to ball screw: (1) The traditional ball screw drive has high requirements for environment and maintenance, in order to ensure the protection and maintenance of ball screw. Convenience often complicates the structure of the machine tool and causes a lot of trouble for the assembler; the double-rod structure does not need to be considered, as long as the lubrication is guaranteed.
(2) The ball screw structure is limited in length, because the longer the ball screw is, the more difficult it is to ensure the installation accuracy of 0.02 mm, and the ball screw straightness will have an impact on the life of the ball screw pair; The rod structure does not have these problems. As long as the installation accuracy is 0.14 mm, the bed can theoretically be infinitely long, and the gear can be worn to achieve the gapless transmission through the adjustment of the III axis.
(3) The reduction of the double-claw drive is larger than that of the ball screw. It is optimized by the gearbox and has a maximum speed reduction ratio of 97, which also increases the cutting force and stability of the machine. The ball screw is limited by structure, and the ball screw speed reduction ratio is very low. In order to increase the speed reduction ratio, not only the reduction gear box is complicated, but also the screw with large outer circle and large screw moment, and the protection and length. The requirements have also increased accordingly.
(4) From the perspective of economy, the double-rod structure is superior to the ball screw. Due to the difference in the length of the machined workpiece and the structure of the machine tool, the ball screw required for each machine tool is different. It needs to be customized by the manufacturer according to the design drawings. It is not only expensive but also has a long ordering period. The general ordering period is 10 months. The price is about 20,000 yuan / m. Most parts of the double-toothed bar structure are processed by themselves. The main purchased parts are helical toothed bars. The ordering period is 4 months, and the price is about 10% cheaper than the ball screw.
In summary, the superiority of the double-jaw structure in the numerical control horizontal lathe is higher than that of the conventional ball screw.
3 double tooth bar in the practice of production and adjustment and application (1) double bar structure in the practical assembly installation and commissioning is quick and convenient. Firstly, when adjusting the gap between the gear and the tooth bar in the final assembly, ensure that the clearance is within 0.14 mm, then lift the III shaft with the tooling, and loosen the expansion sleeve of the two helical gears that mesh with the helical toothed bar. Adjust the direction of the gap according to the direction of the III axis, rotate the two helical gears so that the helical tooth surface is close to the tooth surface of the tooth, and then expand the expansion sleeve of the two helical gears. Finally, the III shaft tooling is removed, and III is removed. Axial down adjustment to eliminate the gap between the gear and the bar.
(2) After the gap of the double-rod structure is adjusted, the back gap can be within 0.05 mm in the open loop state. Through data comparison, the structure of the double-jaw drive reflects its practical value and economic benefits. At present, in addition to the special requirements of users, the CNC heavy-duty horizontal lathes are all made of double-jaw drive transmission structure, which not only reduces the production cost, but also shortens the production cycle, which brings economic benefits to the enterprise and deserves extensive promotion and application. .
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