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Plugging into STEP NC - Emphasis: CNC - CAM software firms offer programs for CNC machines

Mark Albert

CAM software companies are offering software programs that allow their users to read STEP-NC files info their existing CAM software to generate the tool path and output for specific CNC machines. These "plugins" make many of the benefits of STEP-NC available to the average machine shop today.

The concept behind STEP NC is simple. It enables a product model database to serve as direct input to a CNC machine tool. No separate files of tool paths. No G or M codes. No post processors.

This is a radically different approach to CNC programming. It has far-reaching implications for the emerging possibilities of "e-manufacturing." Recent developments, however, promise to make it easier for CNC machine shops to make the transition to this technology Without scrapping existing machine tool and CNC programming technology, shops now have a way to implement key aspects of STEP-NC.

Several leading CAM software companies have made it possible for STEP NC files to be used with their own software. This makes their users ready to participate in supply chains that are turning to global data exchange standards to streamline the flow of digital information over the Internet.

According to STEP Tools, Inc. (Troy, New York), a leading supplier of STEP software toolsets for application software developers, design firms and manufacturing companies, STEP NC offers significant savings to machine shops and their customers. The company estimates that, by fully implementing STEP NC, machine shops can reduce the time it takes to get jobs onto their machines by 35 percent if they can seamlessly read the 3D product geometry and manufacturing instructions of their customers. Likewise, original equipment manufacturers can reduce the time they spend preparing data for their suppliers by as much as 75 percent if they can seamlessly share the design and manufacturing data in their databases.

STEP Tools also estimates that STEP NC will reduce machining time for small- to mid-sized job lots by as much as 50 percent because STEP NC compliant CNC units will be capable of optimizing speeds and feeds with very little intervention from CNC programmers or machine operators. This factor could make it easier and safer to program high speed and five-axis machines, the company says, making it more likely that they will be used for small- to mid-sized job lots.

STEP NC In A Nutshell

STEP NC is an extension to STEP, the STandard for the Exchange of Product model data. STEP is the international standard that specifies a neutral data format for digital information about a product. STEP allows this data to be shared and exchanged among different and otherwise incompatible computer platforms. STEP NC standardizes how information about CNC machining can be added to parts represented in the STEP product model.

By using STEP NC to capture instructions on what steps to follow for machining the part, the "producability" of this part would not be affected by the availability a certain brand of control unit, programming system or post processor. Figure 1 compares the key features of STEP NC to current conventional approaches to creating CNC machine tool input.

If equipped with a STEP NC compliant CNC, any suitable machine tool could be designated to make the part. Because a product model database can be made accessible through the Internet, this designated machine tool could be linked to this global network virtually anywhere on earth. For manufacturing enterprises participating in a highly competitive global supply chain, this kind of flexibility is crucial. With the Internet acting as a global DNC system, the world becomes one big job shop.

Step Rather Than Leap

The availability of STEP NC software plug-ins for CAM software puts STEP NC within the reach of many shops. Currently, plug-ins are available for Gibbs CAM from Gibbs and Associates (Moorpark, California) and for Mastercam from CNC Software (Tolland, Connecticut). A plug-in for Esprit from DP Technology(Camarillo, California) will be completed soon. With these plugins (or "add-ins," as they are also called), a shop can take in a customer's STEP NC files and produce parts on existing CNC equipment.

A full implementation of STEP NC would involve equipping machine tools with CNCs customized with special software. This software enables the CNC to interpret the STEPNC data directly and use the information to machine the part without a conventional G-code program. This software is currently under development.

Machine tools with PC-based open architecture control systems may be able to install this software to upgrade to STEP NC compatibility rather effectively. The conventional input/output (I/O) structure and the servo system of the CNC machine do not need to be modified under STEP NC.

Of course, a great many perfectly serviceable CNC machines are not candidates for STEP NC operation. Likewise, legacy data in the form of existing G-code part programs must be preserved. Shops are understandably reluctant to jeopardize these resources, even as they move toward STEP NC in future planning. The new plug-ins make it unnecessary to make a full leap to STEP NC. Essentially, a STEP NC plug-in provides a bridge between conventional CNC programming and the product-model-as-input approach of STEP NC.

A STEP NC plug-in converts a STEP NC file into the data structures of an existing CAM system. Once converted, the data can be used to generate tool paths the way the CAM software would process part geometry derived from a CAD file or other source.

The resulting output would also need to be postprocessed to produce machine-specific CNC code.

One key advantage to this approach is that the shop can promote its capability to accept STEP NC files. Knowing that the supply chain is populated with these manufacturing resources will encourage OEMs and large prime contractors to implement STEP NC. Ready access to job shops with STEP NC adds to the' incentive for OEMs to adopt STEP NC as a means integrate machining instructions in the STEP product model database. As demand for STEP NC-enabled job shops grows, job shops will find it easier to justify the investment for full STEP NC implementation, which gains them all of the advantages of this streamlined approach to CNC operations.

The plug-in strategy reflects the wisdom of STEP NC developers and supporters. It tends to break the "you-first" syndrome that has stymied other standard-making initiatives. Creating momentum behind the implementation of STEP NC will speed the introduction of affordable STEP NC products to benefit both job shops and their customers.

Plug-In Demo

How a plug-in enables a conventional shop to use STEP NC files was demonstrated in February 2002, at the Industry Review Board meeting for the Model Driven Intelligent Control of Manufacturing (MDICM) project. The MDICM project, chartered to develop and deploy a digital input standard for CNC machines and awarded to STEP Tools, Inc. as the main contractor, is funded by the National Institute of Standards and Technology (NIST), an agency of the U.S. Commerce Department's Technology Administration. STEP NC is that digital exchange standard.

The Industrial Review Board--consisting of representatives from manufacturing companies, CAD/CAM software vendors, machine control builders, government and defense agencies and job shops (all stakeholders in the effort to streamline machining and manufacturing)--operates under the contract to help make sure the project truly meets its needs in a practical, realistic way.

The demonstration was held at Experimental Machine Tool & Plating Company in Troy, New York. This shop specializes in precision machining of complex workpieces in small lots, often on a prototype basis. With four CNC machining centers and four CNC lathes, it typifies the advanced job shop serving the aerospace and defense industry. The nearby Watervliet Arsenal is a frequent customer.

In the demonstration, the shop read a STEP NC-formatted file into its GibbsCAM programming system using the plug-in for this software. The plug-in converted the STEP NC information into GibbsCAM data structures and then used GibbsCAM to generate the necessary tool path and output machine specific code. The part, shown on page 80, was then machined in aluminum on the shop's Mon Seiki MV-65 machining center.

The demonstration also made use of GibbsCAM's Cut Part Rendering functionality to validate the machining process, and the Reporter functionality to generate corresponding process documentation. See Figure 2.

Because this is the final year of the 3-year ATP contract, demonstrations of STEP NC technology are vital to illustrate STEP NC's viability, raise general awareness of STEP NC and move STEP NC "from science fiction to within the horizon of realization," to borrow words from STEP Tools.

Clicking To STEP NC

A review of the online STEP NC resource can be seen at www.stepnc.com. STEPTools is offering a downloadable version of its plug-in technology for GibbsCAM and Mastercam. The plug-ins are not initially available for production use. However, interested manufacturers can view and test-drive the technology as it is continuously improved in the coming years. The technology will benefit greatly from Phase One implementers who will use it to begin the process of integrating STEP-NC into their manufacturing programs and supply chain. This core group of companies will be breaking new ground in machining, and ultimately these advancements will be felt throughout the NC community.

For more information about GibbsCAM from Gibbs and Associates, call (800) 654-9399, enter 37 at www.mmsinfo.com to visit Online Showroom, or write 37 on tire reader service card.

For more information about Mastercam from CNC Software, call (860) 875-5006, enter 38 at www.mmsinfo.com to visit Online Showroom, or write 38 on the reader service card.

For more information about Esprit from DP Technology, colt (805) 388-6000, enter 39 at www.mmsinfo.com to visit Online Showroom, or write 39 air tire reader service card.

To contact STEP Tools, Inc., call (518) 687-2848 or visit www.steptools.com.

Find these related articles on the Web:

STEP NC--The End Of G Codes?

This article explains the background of STEP NC and puts this development into the perspective of today's Web-enabled manufacturing.

Feature Recognition--The Missing Link To Automated CAM

The role of STEP NC in emerging approaches to push-button CNC programming is explained here.

For the link to these articles, visit www.mmsonline.com/articles/070203.html

RELATED ARTICLE: Key Features Of STEP NC.

STEP NC describes "what" not "how"

* Make this geometry from this stock

* By removing these features

* In this order

* With this tolerance

* And with tools that meet these requirements

The old standard described "how"

* Move tool to this location

* And so on for millions of commands

Data For Inside And Outside

"For the [manufacturing] enterprise, STEP NC allows the same data to be used by the external and internal supply chains," writes Martin Hardwick, president of STEP Tools, Inc., in a recent white paper on automatic programming of CNC machines.

Dr. Hardwick explains that, with STEP NC, all the data required to make apart is included in one AP-238 file. (Under the ISO STEP standard, STEP NC is designated as AP-238. It is an "application protocol," one of the sets of definitions for data related to a particular industry or type of product such as, in this case, machined parts.)

An AP-238 file contains the part geometry, geometric dimensions and tolerances of the finished part, along with the manufacturing features, the tooling and the material. Thus, Dr. Hardwick points out, STEP NC means that STEP now covers the capability of both IGES (CAD exchange files) and RS 274D (conventional G and M code CNC programs) in one specification. In the past, if a part were to be made in-house, a company sent an RS 274D program to its shop floor. If the part was to be farmed out to a job shop, the company sent out an IGES file. Whether the part is made inside or outside, STEP NC allows manufacturing to be driven from the same database.

It is simpler for a CAM system to produce AP-238 data than RS 274D data because AP238 data does not require the data to contain machine tool specific tool paths, Dr. Hardwiek notes. Any system that currently produces RS 274D data can produce AP-238 data if it understands manufacturing features. He sites Unigraphics, CATIA and Pro/Engineer as examples of such systems and predicts that these systems will be enhancedsothatAP-238 data is available from them.

AP-238 datagives designers and engineers the assurance that the digital information about machining critical components remains in a viable database and will be available for manufacturing those components throughout the product's life cycle. This contrasts with the conventional approach wherein the digital information about machining a part is locked up in RS 274D data. This data may reside only with an external supplier such as the job shop contracted to machine the parts.

Likewise, this data may be valid only as long as that shop has the original or compatible resources used to generate it. Changes to these resources-the CAM software is no longer supported, the machine tool or its control unit are replaced, for example--are likely to occur before the product's life cycle expires, thereby jeopardizing the availability of machined parts critical to the product.

STEP NC protects machining data as a key manufacturing asset. As long as the company has its database of STEP NC files, the parts can be manufactured regardless of what happens to the external or internal supplier.