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and analysis for kinematics mechanism and is possible to use 2.3 Related efforts
in any industrial domain [17] [18].
Since the introduction of STEP in 1994, examples of how it
can be used to share data on a standard format have been
reported in scientific publications. Among the contributors,
Li et al. [10] [24] have made efforts for converting
kinematics modeling using Siemens’ NX CAD software to
the STEP format. The case study in this paper uses a similar
approach, but a new STEP generator was developed for a
different CAD tool and applied to a different machine model.

3. THE GENERAL APPROACH FOR
CONVERTING MACHINE MODELS

To extract kinematics data from a machine model defined in
a vendor-specific CAD system and integrate it with a STEP
model that contains the geometric data of the same machine
model, an application needs to be developed. Figure 2 shows
Figure 1 – An example from of the AP242 EXPRESS the general approach of how this could be done as a guideline
schema for defining kinematic joints [16] for readers with various CAx tool to follow. Section 4 will
explain the case specific settings for the case study in this
ISO is not the only standardization organization involved in paper and Figure 3 depicts the specific procedure for the case
standardizing how machine models can be represented on a study.
neutral format. Another standard that defines information
models and formats for machine tool data is B5.59 from the
American standardization organization, American Society of
Mechanical Engineers (ASME) [9]. The eXtensible Markup
Language (XML) is used for representing the specification
of machine tools (milling and turning machines). The focus
of the standard is on properties that describe capabilities and
performance of a machine tool at a specific instance of its
life cycle, e.g., in the specification or operation stage of the
machine tool. The standardization efforts made from
multiple standardization bodies indicate the importance of
this topic and a standardized solution is needed for sharing
and exchanging manufacturing resource and product models.

2.2 JSDAI

There are several available interfaces to support the
translation of machine models in a vendor-specific format to Figure 2 – The general approach for creating a complete
the STEP format, e.g., STEP Tools [19], OpenCascade [20], machine model in STEP format with both geometric and
PythonOCC [21], and Java-based SDAI (JSDAI) [22]. kinematics information
JSDAI was selected for the case study reported in this paper
because it supports most of the APs in ISO 10303 and is a A machine model may be developed in a vendor-specific
Java-based open source Application Programming Interface format with a complete description including geometric and
(API). JSDAI also supports the development of EXPRESS kinematics information; this is a foundation for us to be able
data models and their implementation in Java. It enables the to translate the complete virtual machine model to a standard
reading, writing, and runtime manipulation of object- format. Most CAx software today provides the functionality
oriented data defined according to an EXPRESS data model. to automatically export geometric information in the STEP
JSDAI provides a library that contains EXPRESS schemas format. However, a vendor-specific application (i.e., an
for most APs in ISO 10303. JSDAI uses the EXPRESS interface or adapter) is required to extract the kinematics data.
schema defined for AP 242 to represent the kinematics Examples of interfaces that support the development of such
information. applications include J-Link for PTC Creo and NX Open for
Siemens. These interfaces of vendor-specific tools enable the
JSDAI facilitates the linking of CAD, CAM, CAE, CNC, development of the STEP generator.
Product Data Management (PDM), and Product Lifecycle
Management (PLM) systems [22] [23]. After both geometric and kinematics data sets have been
extracted from the machine model in a CAx tool, the “STEP
Generator” integrates them into a complete machine model

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