ACTUAL MINIMAL LENGTH OF ENTRY AND EXIT PARTS OF THE WORM GEAR CUTTERS WHEN PROCESSING HELICAL WHEELS

For the efficient operation of worm gear cutters (WGC), it is necessary to know their minimal lengths of entry and exit parts. The lengths of entry and exit parts of the WGC less than the minimum admissible values are impossible due to the creation of defects of gear wheels along the teeth profile. If the lengths of entry and (or) exit parts of the WGC are more than the minimum admissible values, the cutting power resource of hobs will not be used to a full degree, i. e. possible maximal period of their durability will not be ensured. The review and analysis of data on the recommended minimal lengths of entry and exit parts of the WGC when hobbing helical wheels presented in reference literature showed that the values of these lengths at equal initial data are different in different information resources. Data presented in reference literature need to be added and updated taking into account both the direction and size of axial feed and the directions of teeth helical curves of a hob and a wheel. The author describes the technique of determining the minimal lengths of the entry and exit parts of the worm gear cutters using the computer simulating modeling of the kinematics of the process of hobbing WGC cylindrical gearwheels, which results reliability is proved by the previous investigations. The author found eight possible options of hobbing helical wheels, specified four not mirrored variants and defined the regularities of influence of the module, number and angle of wheel teeth inclination and axial feed size on the minimal lengths of the entry and exit parts of the hobs, determined the influence of axial feed direction on these lengths. The regression equations to calculate minimal lengths of entry and exit parts of hobs taking into account the module, the number and inclination angle of wheel teeth and the axial feed size were obtained for not mirrored variants of hobbing helical wheels.