FAULT INSPECTION OF SHAFTS AND GEARS WHILE REPAIRING FARM MACHINERY REDUCTION MECHANISMS TO ASSURE THE QUALITY OF CONNECTIONS

The fault inspection of the main parts of gearboxes aims to determine their technical condition and assess the degree of wear of the working surfaces and the possibility of their further use. In the process of fault inspection, parts are usually sorted into three groups: fit, unfit (irrepairable reject) and requiring repair (recoverable reject). The parts are separated into particular groups based on the measurement results of controlled parameters obtained using selected optimal measuring instruments (a micrometer, a caliper, an indicator, etc.). The authors have carried out a study of the dimensions of new and worn parts forming the 040H7/k6 "shaft-to-gear bushing" connections used in farm machinery gearboxes. It has been found that the hole size defect amounts to 12.45%, and the shaft size defect is 8.69%. The study has revealed that the greatest wear of the holes reaches 0.082 mm, about 19% of gears are subject to replacement during repair due to their enlarged internal diameter, the shafts wear out to 0.12 mm, and about 23% of the shafts are defective. The authors have shown that a new connection has a transitional fit, as evidenced by the presence of both gaps and tightnesses, the latter prevailing. The reject is 0.91% to the left of the fit tolerance and 0.47% - to the right. This indicates that all new holes and shafts can be allowed for assembly, including those that turned out to be defective, but the resulting connection will be practicaly defectless. When connections are formed from worn parts, more than 25% of defects are due to the largest gap; therefore, fault inspection and continuous monitoring are necessary in this case. The article shows that the inspection analysis of parts in case of defects must be carried out taking into account the quality assurance parameters of the connection assembly.

fault inspection, gearbox, part, wear, fit, control, measuring instruments

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