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TECHNOLOGY REVIEWS

Challenges and Choices in the Specification and Implementation of the STEP-NC AP-238 Standard

[+] Author and Article Information
Martin Hardwick

Department of Computer Science, RPI, Troy, NY 12180

David Loffredo

 STEP Tools, Inc., 14 First Street, Troy, NY 12180

J. Comput. Inf. Sci. Eng 7(3), 283-291 (Jul 10, 2007) (9 pages) doi:10.1115/1.2768090 History: Received August 21, 2006; Revised July 10, 2007

STEP-NC AP-238 is the result of a ten-year effort to replace the RS274D (ISO 6983) M and G code standard with a modern associative language that connects CAD design data to CAM process data. STEP-NC builds on previous work to develop a neutral data standard for CAD data and uses the modern geometric constructs of that standard to define device-independent tool paths, and CAM-independent volume removal features. This paper describes four key factors, or challenges, that had to be addressed to extend STEP-NC AP-238 functionality beyond that offered by other CNC standards. The four factors are difficulties inherent in all CAD/CAM integration projects and can be summarized as follows: the information complexity of geometry, the volume of attributes defined for manufacturing processes, the difficulties of integrating models that span CAD and CAM, and the requirement for easy implementation. We describe an advanced CNC application that uses these four factors and show how STEP-NC AP-238 enhances CNC machining and measurement.

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Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Some limitations of the RS274D Standard

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Figure 2

STEP definitions for point and B-spline curve written in EXPRESS

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Figure 3

EXPRESS-G description of the STEP-NC process model

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Figure 4

Design to manufacturing pipelines

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Figure 5

STEP AP-238 mapping for working step to operation relationship

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Figure 6

New implementation architecture

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Figure 7

Architecture of the tolerance application

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Figure 8

(a) Toleranced part and probing operations, (b) colors for individual probe results and complete features, and (c) probing results for a particular hole feature

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