The STEP Standard - ISO 10303

STEP Data Exchange Standard Moves Into Implementation Phase

By Martin Hardwick
President, STEP Tools, Inc.

As STEP approaches maturity and major CAD systems developers refine their support, product data transfer is moving into a new phase. Most CAD vendors have now released effective STEP interfaces for the exchange of solid data while many major CAD users have successfully begun implementation of the technology. A trend towards data sharing is opening up the potential for on-demand delivery of product information that will help to facilitate the virtual enterprises and the supply chain. Finally, the growth of a development infrastructure that includes mature programming toolkits has greatly simplified the path towards STEP implementation. As a result, STEP appears to be developing an unstoppable momentum as the international standard for definition of physical and functional product characteristics.

What makes STEP different from earlier data exchange standards such as IGES and DXF that despite their wide usage have engendered a considerable degree of user frustration? The immediate advantage of STEP is its effective support for the exchange of solid modeling data. The long-range advantage is that STEP provides support for complete product life-cycle data exchange including design, manufacturing, application, maintenance and disposal. This aspect of STEP makes the standard suitable, not just for IGES-style data exchanges, but also for implementing an integrated product information database that is accessible and usable to all the organizations and individuals involved in supporting a product over its lifetime.

The long-range advantage is that STEP provides support for complete product life-cycle data exchange including design, manufacturing, application, maintenance and disposal.

Application Protocols

STEP also provides a unique ability to be customized and expanded to serve the needs of specific applications while maintaining consistent core standards. This feature comes from the way STEP is organized into Application Protocols (APs), unique sets of entities chosen for a specific product, process or industry. For example, there are APs tailored to the automotive, aerospace and shipbuilding industries, as well as one for the sheet metal die design process. Each AP is a formal document describing a portion of the lifecycle of a product, called the Application Activity Model (AAM); the pieces of product information that are needed for these activities, called the Application Reference Model (ARM); and an information model that describes everything in the ARM using a library of pre-existing definitions. This information model is written in the EXPRESS language, an object-oriented language that is an important part of the STEP standard.

A number of trends in the manufacturing environment are driving STEP implementation today. The first is the shortage of skilled labor. Many companies want to develop custom software to simplify manufacturing processes, but are concerned that changing to a different proprietary system will render their efforts obsolete. STEP can provide the stable data format that will allow a custom system to communicate with whatever tools may be adopted in the future. Manufacturing firms are also placing increased emphasis on outsourcing in order to focus on core competencies which increases the strategic importance of the supply chain. STEP implementation can increase supplier involvement by improving both the quality and accessibility of product data.

Increased Rate of Change

Another factor tending to speed STEP implementation is the increased rate at which both products and processes are tending to change in today's highly competitive environment. STEP can simplify the implementation of new products and processes by providing a stable interface through which new components or methods can interface with each other. This makes it possible for any part of the whole to be changed at will without affecting the other parts. One last factor, perhaps the most important of all, that is driving STEP implementation is customer demand. Most of the leading manufacturing firms have already adopted STEP and are encouraging their suppliers to follow their lead. With suppliers taking on a greater role in the design process, the exchange of STEP data makes it possible for OEMs to capture component and subassembly information without the expense of the supplier purchasing the CAD systems used by each of its customers.

The assistance that STEP can provide in responding to a fast-changing environment is illustrated by the process planning system developed by Raytheon Electronic Systems, Tewksbury, Massachusetts. It greatly reduces the time required to produce process plans for missile components. The software first converts a CAD model into a STEP-based form feature product model. A knowledge-based system uses rules to select the appropriate machining process and resources to machine the product features. The time to create AS-IS and TO-BE visual aids, one of the most tedious tasks in process planning, is dramatically reduced because the software generates a solid model of the workpiece after each operation. Development time was reduced by an order of magnitude by using easily modified libraries to work with STEP data.

STEP can simplify the implementation of new products and processes by providing a stable interface through which new components or methods can interface with each other.

Development Tools

The preceding example illustrates the impact a new generation of development tools that dramatically reduce implementation time have already had on the proliferation of STEP. Four primary categories of tools are generally available.

  1. Information modeling tools that provide rapid definition of product models using the EXPRESS language that forms the basis of STEP.

  2. Development tools that simplify the process of interfacing STEP geometry to existing database formats by providing editors, conformance tools, EXPRESS compilers and schema definition tools and interfaces to other common product modeling formats such as IGES and to programming languages such as C++ and Java.

  3. Management tools that help facilitate the exchange process by providing visualization, translation, verification and data repair functionality.

  4. Tools to publish CAD data in STEP format to the web to help reduce dependence on particular hardware platforms or CAD systems and reduce data communications costs.

While nearly all major CAD vendors have offered STEP interfaces for some time, it is just recently that the quality of these interfaces have improved to the point that practical exchange of solid models between different systems has become a relatively painless chore. The capabilities of today's STEP translators already surpass that of the same systems' IGES interfaces, not only in their expanded scope, but also in the quality of their performance. The achievement of this milestone was easily apparent in a recent benchmark test of STEP interfaces conducted by the ProSTEP Association located in Darmstadt, Germany.

The benchmark comprised more than 250 test runs using complex solid models including assembly models. The same group of components and assemblies was modeled in each of the nine systems and translated to STEP. Then, an attempt was made to read all of the STEP data files with each of the CAD systems. The majority of the transfers were successfully completed without any loss of data. Assembly data exchange was successfully accomplished with five on the nine translators. The system most successful in the test, Unigraphics, imported STEP files from eight of the nine systems without any data loss.

The UNIGRAPHICS STEP interface was implemented using ST-Developer.

Faster Interfaces

While some CAD vendors have complained of the expense of implementing STEP interfaces, it's interesting to note that Unigraphics, the vendor whose interface showed up very well in the ProSTEP benchmark, cut months from the time needed to provide STEP functionality by making use of pre-existing development tools. Unigraphics Release 12 put Unigraphics at the forefront of STEP implementation by providing full support for conformance classes 1, 2, 4, 5 and 6 under the AP-214 and AP-203 protocols. Constructing an implementation from scratch would have taken additional months for development and further time for false starts and shaking out the development process. STEP implementation was streamlined by using a development environment that provides pre-built and easily modifiable libraries of STEP functions.

The drive towards STEP implementation is being aided By new development tools, improved CAD interfaces and recognition of the value of a data sharing model.

An increased emphasis on data sharing, as opposed to data exchange, has also played a part in the acceleration of STEP implementation. Data exchange refers to the neutral file approach by which part geometry is translated from one system to another. Data exchange is typically initiated by the data provider, involves a transformation to a neutral file format, requires the existence of redundant copies of the data file and occurs at a discrete point in time. The STEP standard provides an excellent platform for conventional data exchanges. An increasing number of implementers, however, are looking beyond data exchange to a data sharing approach that provides a much higher level of communications. Data sharing is characterized by the receiver of data initiating the transaction, involves the existence of a single master data copy, and takes place repetitively as needed by the user of the data.

Data Sharing

Data sharing clearly offers a more powerful model for communicating product information both with an organization and between customers and vendors. This model provides a better fit with today's short product life cycles and the high level of differentiation that characterize today's market. The availability of product information on a demand basis makes it much easier for manufacturing to stay current with design revisions. The natural progression for the data sharing approach is, as you might expect, to make product data available over the World Wide Web. Web publishing of product data makes it possible to provide the ultimate in a user-friendly interface while reducing data communications costs to the lowest possible level.

Data exchange and data sharing through the STEP standard is clearly an idea whose time has come.

For example, General Dynamics is developing a data-sharing based system to share STEP data with business partners over the web. Key capabilities of the system include extracting data from CAD systems, converting the geometry to Java classes, providing product models to STEP-compatible CAD systems and viewing the model geometry in a web browser. The system is being designed to share product data with partner companies helping to develop the Navy's new generation of attack submarines. Development time for the project is being reduced by an order of magnitude by using pre-built and easily modifiable libraries to create, destroy, access and update STEP data.

Data exchange and data sharing through the STEP standard is clearly an idea whose time has come. While IGES does a good job of transmitting geometry, STEP goes considerably further by providing the ability to digitally express and share all useful product information throughout a product's life cycle. The drive towards STEP implementation is being aided by new development tools, improved CAD interfaces and recognition of the value of a data sharing model. The increased use of this technology by both large and small vendors should make STEP a near-universal standard as we move into the next millenium.