Abstract: The advantages and disadvantages of the hobbing machine's measurement and control refinement technology are analyzed. A mechanical cam refinement scheme based on precision measurement is proposed, which has good promotion value. The principle and implementation method of this scheme are introduced in detail.
Gears produced in large quantities are generally processed by roll-shave-twisting. If the hobbing machine has large errors, the quality of the gears will be difficult to guarantee. To this end, people continue to explore simple and effective hobbing machine error correction compensation technology, so that the old machine tools have been refined.
First, measurement and control refinement technology
This solution works with real-time testing and real-time correction. A sensor (raster, etc.) is mounted on each of the hobbing tool holder and the table, and a test system is formed with a computer (single-chip microcomputer); and a stepping motor is mounted on the differential shaft to form a control system with the computer. Measurement and compensation control is performed while the machine is machining motion. According to the measured transmission error, the computer converts the corresponding number of driving power pulses, so that the stepping motor drives the differential shaft to rotate, so that the working table obtains an additional compensation movement opposite to the transmission error, which can correct the machine tool error and improve the workpiece processing. The purpose of precision.
The advantage of this scheme is that the working mode is flexible and the number of teeth is convenient; the disadvantages are: (1) high cost, each machine tool transformation needs a full set of inspection and control system; (2) poor reliability, to ensure that the complete system is accompanied by production all the time. It is almost impossible to carry out long-term errors, which is almost impossible in the harsh environment of the workshop; (3) the installation, location and shielding of sensors and the like are troublesome. Therefore, such a scheme has not been popularized in production.
Second, mechanical refinement technology
This kind of scheme adopts one-time test, and the eccentric cam is processed according to the test result, and the transmission chain is added to correct the transmission error. The advantage is that each modified machine tool only adds 1 to 2 cams, the cost is low, the work is reliable, simple, and maintenance-free; the disadvantage is that the flexibility is poor, and each refinement can only target one or a few teeth. Gears, if you want to change the number of teeth, you must retest and redo the cam. Therefore, this method is suitable for use in large-volume, low-volume gears such as automobile and motorcycle gear manufacturers. The specific implementation of this program has the following forms.
1. Two-way double eccentric gear. An eccentric wheel is cut into two, and the eccentric amount is designed according to the error values ​​of the positive and negative directions of the modified axis. In the forward and reverse motion test, select the phase under the instrument monitoring, mark it, find the best position of the error compensation and tangentially misalignment, and turn a distance to ensure that the forward and reverse rotation motions are only carried by one gear. At the same time, a certain backlash is ensured, and finally the two teeth are fixed to the shaft by pins. Thus, the two eccentric gears actually occupy the original gear position. This device solves the error correction of the motion in the forward and reverse directions.
2.e round eccentricity correction. As shown in the figure below, some machines start from the gear behind the hob until the differential mechanism has a total of 1:1 gear ratios. In this case, their respective errors are combined into a single error of the same frequency, as long as The e-round is machined to eccentricity and can be offset by instrumental testing to find the phase.
Hobbing machine drive chain diagram
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