A Unique Methodology for Chatter Stability Mapping in Simultaneous Machining

[+] Author and Article Information
Nejat Olgac

Mechanical Engineering,  University of Connecticut, Storrs, Connecticut 06269-3139olgac@engr.uconn.edu

Rifat Sipahi1

Mechanical Engineering,  University of Connecticut, Storrs, Connecticut 06269-3139


Currently at Université de Technologie de Compiègne, France under Chateaubriand Bourse.

J. Manuf. Sci. Eng 127(4), 791-800 (Feb 15, 2005) (10 pages) doi:10.1115/1.2037086 History: Received June 18, 2004; Revised February 15, 2005

A novel analytical tool is presented to assess the stability of simultaneous machining (SM) dynamics, which is also known as parallel machining. In SM, multiple cutting tools, which are driven by multiple spindles at different speeds, operate on the same workpiece. Its superior machining efficiency is the main reason for using SM compared with the traditional single tool machining (STM). When SM is optimized in the sense of maximizing the rate of metal removal constrained with the machined surface quality, typical “chatter instability” phenomenon appears. Chatter instability for single tool machining (STM) is broadly studied in the literature. When formulated for SM, however, the problem becomes notoriously more complex. There is practically no literature on the SM chatter, except a few ad hoc and inconclusive reports. This study presents a unique treatment, which declares the complete stability picture of SM chatter within the mathematical framework of multiple time-delay systems (MTDS). What resides at the core of this development is our own paradigm, which is called the cluster treatment of characteristic roots (CTCR). This procedure determines the regions of stability completely in the domain of the spindle speeds for varying chip thickness. The new methodology opens the research to some interesting directions. They, in essence, aim towards duplicating the well-known “stability lobes” concept of STM for simultaneous machining, which is clearly a nontrivial task.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Orthogonal turning process

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Figure 2

Functional block diagram of chatter regeneration

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Figure 3

Typical stability lobes and constant stability margin lobes

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Figure 4

Conceptual depiction of simultaneous face milling. (a) Workpiece coupled. (b) Machine tool coupled.

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Figure 5

Block diagram representing the simultaneous machining

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Figure 6

(a) Uniform pitch. (b) Variable pitch.

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Figure 7

(a) Stability regions for 4mm axial depth-of-cut, with four-flute cutter milling on Al 356 (kernel: thick red, offspring: thin blue, stable zones: shaded). (b) Chatter frequencies (exhaustive) (rad∕s) vs. the kernel (τ1,τ2).

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Figure 8

(a) Comparison of CTCR (circle) and ((33), Fig. 2) (square) for pitch ratio=1. (b) 11/7.

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Figure 9

Chatter stability chart in delay domain

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Figure 10

Chatter stability lobes




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