Search

Your search keyword '"Li, Chen-Jung"' showing total 21 results
Start Over Author "Li, Chen-Jung" Publication Year Range Last 50 years
21 results on '"Li, Chen-Jung"'

6. The effect of flexible-tool rotation on regenerative instability in machining

Author

Li, Chen-Jung, Ulsoy, Galip A., and Endres, William J.

Subjects
Milling-machines -- Usage, Milling-machines -- Methods, Engineering and manufacturing industries, Science and technology
Abstract

For rotating-tool machining, such as milling, line boring, and cylinder boring, the tool rotation causes the machining force on each tooth to rotate repetitively relative to the inertial coordinate frame. This is quite different than stationary-tool machining, such as turning or boring with a stationary boring bar, in which the force directions are fixed relative to the inertial frame. Although the subject of stability analysis for rotating tools has been studied extensively in milling, the process is intermittent and hence time varying, which leads to analysis methods that are either analytically approximate or employ time-domain simulation. In this paper nonintermittent machining processes that employ a rotating tool are modeled and analyzed in the rotational coordinates both to simplify the stability analysis and to permit an exact solution. Using rotating-bar boring to illustrate, the analytical results show that the stability limits for boring with a rotating boring bar are quite different from those for boring with a stationary boring bar, and the experimental validation is also provided. Furthermore, the results show a discrepancy to exist between the predicted stability limits for the exact and approximate solutions, especially at low spindle speeds. In both cases an explanation is provided based on the analysis presented. [DOI: 10.1115/1.1536657]

Published
2003

21. Tool-tip displacement measurement, process modeling, and chatter avoidance in agile precision line boring.

Author

Li, Chen-Jung

Subjects
Agile, Chatter Avoidance, Line Boring, Measurement, Modeling, Precision, Process, Tool-tip Displacement
Abstract

An agile precision line boring system is proposed to increase the flexibility of traditional line boring stations and at the same time to improve part quality. This research: focuses on precision tool-tip displacement measurement and process modeling to support this system. A new strain-gage based method is developed for precision tool-tip vibration measurement and is also validated via simulation and experiments. By placing multiple sets of strain gages, multiple modes can be taken into account to achieve high-precision measurement. Research on process modeling focuses on assessing the importance of boring-bar rotational effects (i.e., tool rotation, rotary inertia, gyroscopic moments, and mass unbalance) through regenerative stability analysis. The model developed can be easily applied to on-line detection of the tool deflection and to the analysis of system stability. Since the agile line boring station has a Mapal tool that uses the previous machined journals as intermediate supports, the boundary conditions of this tool are also considered. The developed model will be applied to the aspect of chatter avoidance. In process modeling, the rotating-frame approach is utilized to analyze system stability. In line boring (a case of rotating-bar boring), the machining forces rotate with spindle rotation and are periodic, resulting in a time-varying process model in the inertial coordinates. However, in rotating coordinates, this time-varying model is transformed to a time-invariant one that is much easier to analyze for stability leading to an exact solution rather than approximate solutions. Through this rotating-frame approach, the difference in stability between rotating-bar and stationary-bar boring (the tool-rotation effect) is examined. Experimental results are given for validation. The effect of rotary inertia and gyroscopic moments is systematically assessed by discretizing the Rayleigh beam model via the modified Galerkin's method and then normalizing the discretized model, while the effect of mass unbalance is studied by combining the results on eccentricity from literature of rotating shafts with the features of the boring process. Finally, the effect of spindle speed variation is also examined using the rotating-frame approach with the aim of improving system stability, where the spectral radius method is used to determine system stability.

Published
1999

Catalog

Books, media, physical & digital resources
See catalog results