Dealing with feature interactions for prismatic parts in STEP-NC


DOI: 10.1007/s10845-008-0144-y

Cite this article as:
Mokhtar, A., Xu, X. & Lazcanotegui, I. J Intell Manuf (2009) 20: 431. doi:10.1007/s10845-008-0144-y


Determining the precedence of machining features is a critical issue in feature-based process planning. It becomes more complex when geometric interaction occurs between machining features. STEP-NC, the extension of STEP (ISO 10303) standard developed for CNC controllers, is a feature-based data model. It represents all the geometric and topological product data minus feature interactions. In this paper, machining precedence of interactive and non-interactive STEP-NC features is discussed. Local and global precedence of machining features are defined on the basis of geometric constraints, such as geometric interaction of features and feature approach face and technological constraint such as access direction of the cutting tool. A software tool has been developed to visualize the STEP-NC part model and to generate the graphs of feature interaction and feature precedence. The output can be then used to augment the STEP-NC data in order to generate the optimal sequence of operations.


Feature interaction Feature precedence Process planning STEP-NC 



The final part


The starting workpiece, blank


Feature i

Interaction between two features


Common face of feature i, j


Top approach face for feature i


Normal vector for top approach face for feature i


Normal vector for tool access direction


Null set

ωi, j

The interacting entity of feature i, j

σP (Fi)

The common boundary of feature i and the final part

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  1. 1.Sharif University of TechnologyTehranIran
  2. 2.Department of Mechanical Engineering, School of EngineeringThe University of AucklandAucklandNew Zealand
  3. 3.RWTHAachen UniversityAachenGermany

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