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Research Papers: Design for Manufacture and the Life Cycle

Automatic Reasoning for Defining Lathe Operations for Mill-Turn Parts: A Tolerance Based Approach

[+] Author and Article Information
Wentao Fu

Department of Mechanical Engineering,
The University of Texas at Austin,
Austin, TX 78712
e-mail: wentao.fu@mail.utexas.edu; fu_wentao@cat.com

Ata A. Eftekharian

Department of Mechanical Engineering,
The University of Texas at Austin,
Austin, TX 78712
e-mail: ata.eftekharian@gmail.com

Matthew I. Campbell

School of Mechanical, Industrial, and
Manufacturing Engineering,
Oregon State University,
Corvallis, OR 97331-6001
e-mail: matt.campbell@oregonstate.edu

Tolga Kurtoglu

Automation for Engineered Systems,
Intelligent Systems Laboratory,
Palo Alto Research Center,
Palo Alto, CA 94304
e-mail: tolga.kurtoglu@parc.com

All experiments in this paper were implemented on a desktop computer with AMD 3.2 GHz processor and 6 GB of memory.

1Corresponding author.

2Present address: Caterpillar Inc., 1901 S 1st St, Champaign, IL, U.S. 61820.

Contributed by the Design for Manufacturing Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received October 17, 2013; final manuscript received August 4, 2014; published online October 20, 2014. Assoc. Editor: Rikard Söderberg.

J. Mech. Des 136(12), 121701 (Oct 20, 2014) (10 pages) Paper No: MD-13-1468; doi: 10.1115/1.4028275 History: Received October 17, 2013; Revised August 04, 2014

With the increase in computer-controlled hybrid machining (e.g., mill-turn machining), one needs to discern what features of a part are created during turning (i.e., with a lathe cutter) versus those created by milling. Given a generic part, it is desirable to extract the turnable and nonturnable features in order to obtain feasible machining plans. A novel approach for automating this division and for defining the resulting turning operations in a hybrid process is proposed in this paper. Given a mill-turn part, the algorithm first identifies the dominant rotational-axis in order to quickly generate the axisymmetric “as-lathed” model. This model is then subtracted from the original part to isolate the nonturnable features. Next, the as-lathed model is translated to a label-rich graph, which is fed into a grammar reasoning algorithm to produce feasible turning sequences. During the turning process planning, the knowledge encapsulated in the design tolerances is used to guide the generation of feasible turning sequences. Two case studies are provided to explain the details of our algorithm. One of the suggested turning plans is compared with a manually proposed plan from an expert machinist and the results show the optimality of our plan in satisfying the prescribed tolerances.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

A sample part with nonturnable features

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Fig. 2

(a) The identified curved edges and (b) their axial normal vectors for the part in Fig. 1

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Fig. 3

A unit circle with nonuniform radial vectors

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Fig. 4

(a) The sampled cross sections of the part in Fig. 1 and (b) the union of all the cross sections

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Fig. 5

(a) The revolving face and the rotational axis and (b) the as-lathed model

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Fig. 6

(a) The decomposed turnable features and (b) nonturnable features

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Fig. 7

A test summary of more complex parts

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Fig. 8

Graph grammar reasoning flowchart

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Fig. 9

The CAD drawing of the part shown in Fig. 5(b)

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Fig. 10

The tolerance graph generated from the 2D drawing in Fig. 9

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Fig. 11

The generalized angle α of the parallelism tolerance

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Fig. 12

The screenshot of the first rule

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Fig. 13

The screenshot of the setup graph

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Fig. 21

A traditional turning sequence for the part shown in Fig. 5(b)

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Fig. 20

The suggested turning sequence for the part shown in Fig. 15(a)

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Fig. 19

The setup graph for the part in Fig. 15(a). The internal arcs a5 and a6 are deleted.

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Fig. 18

The updated tolerance graph for the part shown in Fig. 15(a)

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Fig. 17

The initial tolerance graph for the part shown in Fig. 15(a)

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Fig. 16

The CAD drawing of the as-lathed model in Fig. 15(a)

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Fig. 15

A complex part with interacting feature

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Fig. 14

The suggested turning sequence for the part shown in Fig. 5(b)

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