THE DEFINITION OF INITIAL AND FINAL ADJUSTMENTS OF WORM GEAR CUTTERS WHEN PROCESSING HELICAL WHEELS

For the efficient operation of worm gear cutters (WGC), it is necessary to know their initial and final adjustments against the processed wheel workpiece. It is shown, that at equal initial data, the values of initial and final adjustments of WGC are different in different information sources, and the concepts of initial and final adjustments of WGC define ambiguously the relative position of a hob and a wheel workpiece. To understand definitely what part of WGC is spoken about, it is necessary to use the concepts of minimum lengths of entry and exit parts of WGC instead of the concepts of initial and final WGC adjustments. The shortening of the entry and exit parts of hobs to be less than the minimum admissible values is impossible due to the creation of defects of gear wheels along the teeth profile. If the lengths of entry and (or) exit parts of hobs 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. Using the method of computer simulation modeling of the kinematics of the process of hobbing by the WGC, when hobbing up and down with the axial feed, the authors defined the minimum lengths of WGC entry and exit parts when hobbing helical wheels with the module of 3 mm, teeth inclination angle of 30° and the teeth number equal to 20, 45 and 90 pieces. The authors proved experimentally the reliability of the results gained by the computer simulating modeling and their essential difference from the data given in reference books. The study identified the essential influence of the direction of axial feed (up or down) on minimum lengths of WGC entry and exit parts when hobbing helical wheels.