STEP/XML Based Macro Data Representation for Parametric CAD Model Exchange

There is tremendous need in collaborative design today for the integration of heterogeneous CAx

systems. This general practice has serious shortcomings like design discontinuity, limited

parallelisation, loss of information, and conversion errors. To overcome these shortcomings,

macro-parametric approach (MPA), which is a history-based method of parametric CAD model

exchange, has been proposed. The macro-parametric approach is a way to achieve compatible

CAD model exchange amongst a variety of mutually incompatible CAD systems. CAD models can

be exchanged in the form of a macro file that comprises a sequence of modeling commands. A

standard macro file that contains a set of event-driven commands can transfer the designer intent

such as parameters, features and constraints.

Currently, STEP (STandard for the Exchange of Product model data) as an international standard

(ISO-10303, Industrial automation systems and integration - Product data representation and

exchange) for the computer-interpretable representation and the exchange of product model data

is widely used. STEP is becoming the ‘lingua franca’ in the area of modelling and exchanging

product data. One remaining problem of the using STEP as a neutral format is that it does not

retain parametric information such as the designer intent but only the pure boundary representation

(B-rep) of the CAD model. The B-rep model without parametric information presents difficulties for

engineering changes and it may also lead to an unexpected distortion of shape.

This research aims to investigate an exchange method that uses STEP/XML (extensible mark-up)

technology to express a set of standard modeling commands extracted from CAD models created

by Autodesk InventorTM, to enable the same CAD models are readable and shareable with other

CAD application systems.