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Research Papers

Aggressive Spiral Toolpaths for Pocket Machining Based on Medial Axis Transformation

[+] Author and Article Information
Nuodi Huang

School of Power and Mechanical Engineering,
Wuhan University,
Wuhan 430072, China
e-mail: huangnuodi@126.com

Roby Lynn

George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332
e-mail: roby.lynn@gatech.edu

Thomas Kurfess

Mem. ASME
George W. Woodruff School
of Mechanical Engineering,
Georgia Institute of Technology,
Atlanta, GA 30332
e-mail: kurfess@gatech.edu

1Corresponding author.

Manuscript received July 21, 2016; final manuscript received January 3, 2017; published online January 30, 2017. Assoc. Editor: Xiaoping Qian.

J. Manuf. Sci. Eng 139(5), 051011 (Jan 30, 2017) (8 pages) Paper No: MANU-16-1400; doi: 10.1115/1.4035720 History: Received July 21, 2016; Revised January 03, 2017

High-speed machine tools typically provide high spindle speeds and feedrates to achieve an effective material removal rate (MRR). However, it is not possible to realize the full extent of their high-speed capabilities due to the sharp corners of toolpaths which are introduced by conventional machining strategies, such as contour- and direction-parallel toolpaths. To address this limitation, spiral toolpaths that can reduce the magnitude of sudden direction changes have been developed in previous researches. Nevertheless, for some pockets, the average radial cutting width is significantly decreased while the total length of the toolpath is significantly increased as compared to contour- and direction-parallel toolpath. In this situation, spiral toolpath may take more machining time. To overcome these drawbacks, an aggressive spiral toolpath generation method based on the medial axis (MA) transformation is proposed in machining pocket without islands inside, which refers to no additional material inside the counter. The salient feature of this work is that it integrates the advantages of both conventional contour-parallel machining strategy and the existing spiral toolpath machining strategy. The cutting width at each MA point is determined based on the diameter of the locally inscribed circle (LIC) of the MA point and the topological structure of MA. A distance-constrained contour determination algorithm is utilized to calculate the toolpath for each pass. Finally, a circular arc transition strategy is used to transform all the isolated passes into a spiral toolpath. Experiments are conducted to show the effectiveness of the proposed method.

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References

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Figures

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Fig. 1

Pocket machining toolpaths: (a) zigzag path, (b) one-way path, (c) contour parallel path, and (d) spiral path

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Fig. 2

Basic elements of the MA of a pocket

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Fig. 3

Structure of MA circulation loop

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Fig. 4

Toolpath generation process: (a) isolated passes and (b) spiral toolpath

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Fig. 5

Architecture of proposed approach

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Fig. 6

Update pass number for MA points: (a) before update and (b) after update

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Fig. 7

Algorithm to determine pass number

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Fig. 8

Toolpath optimization at tip area

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Fig. 9

Tangent points between local circles and envelope curve

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Fig. 10

Toolpath for each pass

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Fig. 11

Contour determination with distance constraint

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Fig. 12

Smoothed toolpath for each pass

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Fig. 13

Connection strategy between adjacent passes

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Fig. 14

Generated spiral toolpath by proposed method

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Fig. 15

Spiral toolpaths generated by proposed and existing methods

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Fig. 16

Demonstrations of developed method in case 3

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Fig. 17

Combination strategy of adjacent passes: (a) cam package and (b) proposed method

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