| Abstract [eng] |
Automatic assembly systems plays vital role in automating production process. They directly affect production efficiency and quality of the goods. According to the statistical analysis, 30-60% of the tasks in most of the industries branches are assembly operations. Part assembling time takes 35-40% of all manufacture time. Around 33% of all assembly operations are peg to bush assembly operations. Because of that, assembly operation has big potential in reducing manufacture time by improving assembly methods and installing automatic part assembly systems and devices. This work investigates a new approach of passive vibratory part alignment method using elastic vibrations. In this method bush placed on the assembly plane and is free to move in a narrow space. Another component (peg) fixed in a gripper, which has piezoelectric vibrator in it. Vibrator presses upper end of the peg. Peg and a bush also pressed to each other with a predetermined force. Piezoelectric vibrator generates high frequency harmonic excitation to the peg and creates elastic vibrations of the peg in longitudinal and lateral directions. The lower end of the peg moves in elliptical shape trajectory. Because of the friction force between the components, bush moves to the part alignment direction. Parts successfully assembled after the alignment occurs. This passive alignment method allows assembling parts with circular and rectangular cross-section with no chamfers and at their axial misalignment of few millimetres, or makes it possible to use low accuracy robots Detailed analysis of scientific papers about widely used part alignment methods in a now days industry was done. Vibrations of the peg’s tip while he is in a contact with bush were investigated. Nature of the peg’s vibrations, their relationship to the excitation signal amplitude and bush-to-peg pressing force were determined. Part alignment experiments have been done with circular and rectangular cross-section pegs using their elastic vibrations. Influence of excitation and mechanical system parameters to the alignment efficiency and reliability were determined. Mathematical model of circular part alignment when the peg excited in axial and transversal direction were composed. Excitation signal and mechanical system parameters for the stable and reliable part alignment at impact and non-impact modes were determined. |
