STEP NC—The End Of G-Codes?

Imagine this: You call up a Web browser on the PC-based CNC at your machine tool. You go to a certain Web site. From a menu on the home page, you select one of the databases it accesses. A 3D image of a workpiece comes up. You click on an icon in the task bar and check a few parameters and default settings on a pop-up window. Then it's a click on the CYCLE START button. The spindle motor starts to whir, axes begin to move, coolant spurts out and chips are soon bouncing off the Lexan panels in the machine guarding.

According to efforts underway right now, it won't be long—a couple of years at most—before this scenario depicts how most shops will be running their machine tools. NC part programs as we've known them for almost 50 years will become passe. All that the machine tool controller will need is the digital product model represented by the 3D image on the Web page.

The CNC won't use G-codes. Everything it has to know about how to move the cutting tool is in the product model's database. There will be no need for creating a new and separate file of tool path data. Tool paths will be figured out in the CNC itself, based on the product model. That means there's no need for post processors either. Data will be formatted for execution by the machine within the CNC. And because the product model won't change, it will be available for machining "hard copies" whenever and wherever needed.

"Whenever" means as long as the product's life cycle is on-going. Twenty-five years is a typical life span for aerospace parts, for example. Neither changes in computer technology nor advances in machine tool technology over the years would affect the usability of the product model as machine tool input.

"Wherever" means anywhere an adequately equipped shop has authorized access to the product model database. With the Internet, that access is worldwide. Parts could be machined anywhere in the world through a global supply chain, with the digital product model serving as the universal "NC part program."

What will it take to make this dream come true? How much more has to be done to get there? How close are we right now?

The First STEP

The biggest step in this direction has already been taken. It's STEP, the STandard for the Exchange of Product model data, a comprehensive ISO standard (ISO 10303) that describes how to represent and exchange digital product information. STEP replaces IGES as the means by which graphical information is shared among unlike computer systems around the world. The big difference is that STEP is designed so that virtually all essential information about a product, not just CAD files, can be passed back and forth among users.

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3D Model data is not used in manufacturing because even as simple supply chain must rely on too many interface among unlike computer systems. Suppliers 1 to 4 are subcontractors and job shops. Suppliers A to D are software solution suppliers serving various applications.

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The core of the standard is a library of engineering definitions that can be assembled into various "application protocols" customized for the product models needed by particular industries and activities. A common library covers geometry, topology, tolerances, relationships, attributes, assemblies, configuration and other characteristics. New product models can be added as the need arises.

An extension to STEP has been created to cover product information related to CNC machining. This is STEP NC. STEP NC forms the basis for the scenario that caught your attention at the beginning of this article. The development effort to make STEP NC product model data usable as direct machine tool input has already progressed substantially.

In May 2000, a prototype for the sets of data required to add machining information to the product model of a test part was demonstrated. A later phase of this project will develop the machine tool controller capable of accepting this "super model" as input. The current test part is a milled workpiece. Turning and grinding are on the horizon. The "super model" demonstrated in May used an emerging Internet language called XML to add information about machining strategy, tool path planning, and tool selection. XML makes the resulting database "Internet ready'—a key requirement for global e-manufacturing.

STEP Vs. IGES

To understand STEP NC and where it's headed, a look at STEP and its relationship to IGES is the place to begin. IGES was about exchanging data and only the data contained in graphics files. STEP is about sharing data, allowing parties to work together by communicating information interactively.

IGES had its start 20 years ago when designers and engineers were turning to computers to create product designs. Instead of drawing lines and segment of circles on paper to make graphic representations of what a product should look like, they started making those lines and arcs on a computer screen. The completed design could be saved as a digital file. Although creating the original design file might take longer than preparing the engineering drawing on paper, the design file could be quickly copied, modified, printed and otherwise manipulated. These time savings more than made up for the extra time it took to prepare. Moreover, the digital nature of the design file allowed it to contain much more information in a much more flexible format.

STEP allows a single database of 3D product information to be accessed by several users regardless of the different computer platforms involved. Where several companies may be producing different parts for a complex assembly with critical tolerances, having a single shared database greatly simplifies product data managment and ensures that mating parts and subassembies can be manufactured effectively.

One big problem quickly emerged. The computer-aided design (CAD) systems used to create these digital design files were not compatible with each other. A design created on a Computervision system was meaningless to an Applicon system, for example. Companies with unlike CAD systems could not exchange CAD data.

The effort to resolve this situation got underway in the spring of 1980. Representatives of U.S. user groups, vendors and standards organizations began meeting regularly to create a neutral, non-proprietary database structure and data format for CAD files, dubbed the Initial Graphics Exchange Specification (IGES). In theory, CAD files translated into IGES could be exchanged with any CAD system that could translate IGES files into its own proprietary format.

Although IGES eventually became a workable, if imperfect, approach to exchanging CAD files, a major shortcoming with this approach became apparent right away. IGES allowed one system to communicate the lines and symbols of a computerized engineering drawing, but IGES failed to communicate the meaning of the information the drawing was intended to convey. It did not provide a reliable means by which product features could be transmitted with the geometry so that computer-based applications could "understand" the engineering drawing.

While IGES was being developed and gradually made more functional as it moved through the standards formation process, efforts to develop a true "product data exchange specification" were launched. The goal of this effort was to capture and convey "logical" information about product features and provide "physical" mechanisms for data exchange. Originally conceived as a U.S. initiative, this effort was soon seen as requiring international participation.

By 1984, this international effort to develop a Product Data Exchange Specification had been established under the auspices of ISO, the international standards making body. The goal was to define the methods for creating product data models that could be interpreted by computers. These models were intended to allow the exchange and sharing of product data in a way that the meaning of the data would not change throughout the product life cycle.

The international standards covering these product data models became known as STEP. For the last 15 years, various groups and committees (mostly comprising users rather than vendors) have been meeting regularly to develop standards for product data models. They have made considerable progress. Because the STEP standards are now sufficiently developed to cover all of the original purposes of IGES, IGES will receive no further development and refinement. STEP has officially taken its place.

By July 2000, every major and almost all minor CAD system vendors had STEP translators in the latest releases of their CAD products. Moreover, these translators have been tested for conformance and interoperability. With only a few exceptions did any of the translators fail to operate effectively. (Indeed, one of the innovative features of the STEP formation process was the early commitment to include testing procedures for assuring that STEP-compliant systems would truly function as intended. This provision may have slowed development but it appears to have paid off in the end.) In short, STEP is working. According to industry analysts, more than one million STEP enabled CAD stations are in place around the world.

Super Model Steps Out Quickly Although standards-making activities are notoriously protracted, the Super Model project has maintained an intense pace from the outset, surprising and pleasing members of the Industrial Review Board who attended a review board meeting in May. Says IRB member Gary Hargreaves, director of sales at CNC Software, Inc., "It is amazing to see the progress of the STEP Super Model project . . . going from a vision and discussions in December 1999 to something real, as shown during the May 2000 Industrial Review Board meeting just five months later. I now have tangible notes and information on how STEP NC technology can actually be implemented and supported for future CAM applications." Another member, Bob Bean, president and CEO, CADKEY Corporation, had these comments after the meeting: "It is clear that with over 30 MCAD products available in the market today (and more start-ups entering the market every day), CAD data sharing and interoperability is a major challenge both in the short term and over the long term. When one looks at the stages of product and machine design such as conceptual, initial design, analysis, outsourcing of manufacturing, changes due to manufacturability, mold design, tooling, and so on, it is apparent that 3D solid model information needs to be leveraged throughout the design cycle. The STEP Super Model project is designed to facilitate not only the early phase of product development, but the full process to production." Manfred "Whitey" Simon, a 30-year veteran of General Motors Advanced Manufacturing Engineering group was likewise encouraged: "The progress shown here is definitely in line with the scope of what is to be accomplished in a three year period. There seems to be lots of attention given to the real user interface—which is so important." The IRB meets again in November 2000 at STEP Tools' headquarters in Troy, New York.

STEP NC

Although STEP NC has not quite completed the formal standards making process, it is well into the review and approval cycle, which will ultimately settle a few remaining matters of technical detail. STEP NC defines data representing "working steps," that is, a library of specific operations that might be performed on a CNC machine tool. In keeping with the STEP concept, these working steps are generic descriptions that can be incorporated into a product model. These descriptions are not linked to a specific format or code. However, STEP NC working steps are roughly equivalent to the machining commands represented by traditional M and G codes.

STEP NC is the basis, the enabling standard that underlies the potential for using the digital product model as machine tool input. STEP NC allows a complete database of machining information to be built around it. The database, then, dictates what capabilities must exist in the machine tool controller to cut the part.

What's called for is a "super model" that includes design information such as geometry, manufacturing planning information such as form features (holes, slots, contours and so on), plus manufacturing strategy information such as tool selection, fixture location and so on.

The effort to develop the super model and make it usable as machine tool input is being spearheaded by STEP Tools, Inc. of Troy, New York. STEP Tools is a developer of data exchange software for worldwide manufacturing. Although the official name of the project is the Model Driven Intelligent Control of Manufacturing, participants are simply calling it the Super Model project. Funding is coming from the National Institute of Standards and Technology (NIST), an agency of the U.S. Commerce Department's Technology Administration. The Super Model program was formally launched as an Advanced Technology Project with an award of $2.9 million in October 1999. Participating in the program is an Industrial Review Board consisting of manufacturers, software vendors and machine control builders, government and defense agencies, and a range of small- and medium-sized job shops from the Hudson Valley in New York State.

The Super Model project has a three year time line. The target for the first year is to build a STEP and STEP NC database containing three kinds of manufacturing features, and use the database to drive a machine tool controller. The target for the second year is to build a database containing all of the features defined by the STEP NC milling schema and use that database to manufacture the STEP NC test part. The target for the third year is to produce a database for another machining process such as turning, grinding or electrical discharge machining.

Dr. Martin Hardwick heads up STEP Tools, Inc., the Troy, New York-based software development company leading the Super Model project.

The Super Model Database
The challenge for the Super Model project is to create interfaces that bring together the information defined by STEP and STEP NC. Product geometry can be defined by one STEP application protocol. Product features can be defined by another STEP protocol. Machining operations can be defined by STEP NC. However, all three types of data and others must be integrated in a complete product model database. Moreover, this database must be Internet compatible.

Starting with product geometry in the STEP format is the easy part because STEP translators are built into most CAD systems these days (and they handle 3D geometry, doing so more effectively than IGES ever did, apparently). The super model test part happened to be created in a ProEngineering workstation.

The next step in building the database is adding features to the geometry. For the sake of demonstration, STEP Tools originally used a Microsoft Excel spreadsheet to link STEP-defined feature names to the test part geometry. The Super Model program is evaluating an automatic feature recognition system being developed by Honeywell FM & T, one of the subcontractors in the program. Called the FBMach Process Planning System (FBMach is short for feature-based machining), this software reads STEP geometry and automatically determines what features, such as holes, pockets, slots, and so on, are represented by the geometry. The user interface allows these determinations to be validated before proceeding. The FBMach system is expected to be available commercially by the end of 2000. Its application to the super model test part will be demonstrated in November.

STEP NC establishes a hierarchy of workingstep supertypes/subtypes. In other words, it breaks down every machining operation into the steps required to perform the operation. These steps include actions to be taken as well as data (such coordinates of point-to-point motion) to be applied. These steps are then linked to the appropriate part model geometry to fill in the values. STEP Tools is setting up tables to match workingsteps, workingstep-methods, workingstep actions, and machined features.

According to Martin Hardwick, president of STEP Tools, the super model database is adapting a modified version of the company's ST Repository product data management software to structure the database. Each repository uses standard interfaces to import and export geometry, features and workingsteps to the tools used by CAD and CAM engineers.

A key part of STEP Tools approach to the super model database is the use of XML in its interfaces. XML, the eXtensible Markup Language, is a vendor-neutral data exchange language for passing information, not just data, across the Internet. XML allows data to be "tagged" so that software applications reading the database can identify what type of information is stored in the database and extract the data that is needed. HTML, the Hyper Text Markup Language, is a similar"metadata" language that the Web uses so that text can be displayed no matter what Internet browser happens to read it. XML offers a comparable level of interoperability. An XML standard for STEP is nearing completion. This standard will ensure that all data in a product model is "tagged" in the same way.

For the super model, XML provides a convenient means to link manufacturing strategy, tool pathing, and tool selection information to geometry, features and machining steps in the database. By sorting out data with the appropriate tags, for example, geometry identified as a hole to be drilled can be linked to operations such as rough drilling, boring and counterboring steps. Each of these steps will require that other data be extracted, such as workpiece material, surface finish requirements, and so on, to link with speed and feed tables. XML provides the tags so that the data is sorted correctly.

Ultimately, XML ensures that a CNC networked to the Internet will be able to find the information it needs from the product model database to machine a part.

At the May 2000 Industrial Review Board meeting, STEP Tools demonstrated how XML transactions had been used to complete a database for its test part, linking the required information for three different types of machined features, including a hole, a slot and a pocket.

Down To The CNC

The goal for the Super Model project is to show how these features can be cut on a machining center using the product model as the NC part program, so to speak. One of the subcontractors deeply involved is this phase of the program is Electro-Mechanical Integrators, Inc. (EMI) of Franconia, Pennsylvania. Engineers at EMI are writing new software for a Bridgeport control unit that will enable it to accept STEP NC data. (The company has considerable experience with Bridgeport control units and is the factory-authorized support and repair agency for the Bridgeport DX32 control.)

A Bridgeport V3XT milling machine like this one is being outfitted with a CNC customized with special software. This software will enable it to interpet the super model database and use the information to machine the part without a conventional G-code program.

According to Bart Stater, head programmer of EMI, this effort requires a customized command parser and command interpolator to process STEP NC. "Essentially we are creating a new CNC protocol to interpret the information in the product model in real time. This software will extract the data it needs to determine axis moves, get the specified tool, and issue commands. It will not need or use G-codes," he says. Otherwise, the I/O structure and servo system of the machine remain the same. He notes that this concept assumes that the CNC will be networked to a file server that receives and stores data, most likely through an Internet connection.

EMI is looking at two approaches to configuration of the CNC. One approach runs all of the executive software in the CNC's internal processors. Another approach uses a "PC front end" interfaced to the CNC. The PC would process the STEP NC data and spoon feed it to the CNC, filling a buffer with blocks of data on demand. This approach would ensure that the CNC is not starved for data while the product model is processed.

In November 2000, EMI is scheduled to demonstrate actual cutting of the three selected workpiece features on the test part. Although the concept could be proven with a simulation of the machining operations, cutting chips is a more convincing demonstration. "We want to show the CNC accessing the product database on the Web, finding the features to be machined, then generating commands to drill the hole, mill the slot and machine the pocket," Mr. Stater insists.

STEP Tools is also working with the Lawrence Livermore National Laboratories, where a STEP NC interface is being developed for the OMAC (Open Modular Architecture Control) project. Additional shopfloor tests and demonstrations of STEP NC are set to take place at a production machining facility operated by General Dynamics Land Systems in Scranton, Pennsylvania. A pilot project at the Jet Propulsion Laboratory is also in the proposal phase awaiting funds.

Art To Part

Those three words sum up the promise of STEP NC and the Super Model project.

From a shop floor viewpoint, art to part means the intermediate steps of creating an NC program are eliminated. Most of those intermediate steps necessitated a transformation of product data, causing data files to proliferate. Part geometry had to be translated, reconstructed or edited. The edited, translated or reconstructed geometry had to be processed to generate tool paths. Tool path files had to be post processed to suit the requirements of the machine tool and control unit combination. Postprocessed files were often edited on the shop floor. In short, one piece of part geometry begot hundreds by the time the part was actually cut from metal.

With STEP and STEP NC, the digital product model database replaces all of the other product data files otherwise created to make the part.

From a design and engineering viewpoint, art to part means that design and manufacturing can be managed with a single database. Just as data files need not proliferate down the supply chain, they need not proliferate across the manufacturing organization. Product data can be shared between products, between corporate divisions and between applications. The Internet will make this sharing of data global and virtually instantaneous.

This concept of art to part does make G-code programming obsolete. But this traditional form of programming for machine tools was already on its way out. Advances in CAM software make G-codes less and less visible to programmers and machine operators.

This concept also implies that CAD and CAM will have a different relationship than they did in the past. Dr. Hardwick believes that product models will originate in CAD, with STEP enabling a high degree of collaboration between designers and engineers. Feature recognition will be applied at this level as manufacturing engineers define the manufacturing process that becomes part of the product model. "At this point, the process data will be ready for any machine tool but will allow for important local parameters to be defined when it gets to the machine," he predicts. Selecting cutting tool, setting feeds and speeds and so on will be handled at the machine tool on the shop floor.

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The super model solution seeks to replace hundreds of product data managment files with one database from which data may be shared via the Internet. The translators, editors, converters and postprocessors require to exchange or reformate product files are unnecessary.

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These CAM functions become the domain of intelligent controllers with on-board CAM software. This software will generate the movements necessary to make the parts after the appropriate parameters have been set on the CNC. "The on-board CAM software is there to do the last minute custom tool path generation using selections made by the operator," Dr. Hardwick says. Intelligence built into the software stops the operator from making mistakes or using less than optimum settings. "It's a huge opportunity for the CAM industry. This software will be a required component of all future CNCs," Dr. Hardwick contends.

Vision

With the development of STEP NC, what's happening is not simply the re-shaping of CNC. It is the reshaping of manufacturing. And in the vision that is emerging, the CNC machine tool will be more important than ever.

STEP - Internet Links

1. STEP-NC
   www.steptools.com/library/stepnc
   STEP-NC is a worldwide effort to extend STEP to define data for NC machines. These pages include an overview of the project, and the specification.
   
   
2. Interoperability Success Stories: STEP
   http://www.mel.nist.gov/msid/sima/daratech
   Boeing Commercial Aircraft, Boeing CSTAR, Delphi Automotive Systems, Lockheed Martin
   
   
3. STEP Glossary of Terms and Acronyms For The Technical at Heart
   http://pdesinc.aticorp.org/Glossary.htm
   This link provides definitions for commonly used terms in the context of STEP.
   
   
4. PDES, Inc.
   http://pdesinc.scra.org
   An International industry/government consortium accelerating the development and implementation of STEP. Worldwide news of STEP including press releases and announcements
   
   
5. Lockheed Martin Releases News on STEP implementation
   http://www.mel.nist.gov/msid/98whatsn/3-4-98.htm
   As part of its ongoing effort to foster product affordability, Lockheed Martin Tactical Aircraft Systems (LMTAS), in Fort Worth, Texas, recently implemented an international data exchange standard known as the Standard for the Exchange of Product Model Data, or STEP, on its F-16, F-22, Joint Strike Fighter, F-2 and KTX-2 programs.
   
   
6. Automotive Interoperability Cost Study
   http://www.mel.nist.gov/div826/msid/sima/99ovwvis
   What is the economic cost due to lack of interoperability in the automotive supply chain? Conservatively, One Billion Dollars Per Year! Conducted with NIST Strategic Planning and Economic Assessment office in March 1999. This slide presentation is easy to use and study.
   
   
7. Publication: STEP the Grand Experience
   http://www.mel.nist.gov/msid/99whatsn/10-1-99.htm
   The Manufacturing Engineering Laboratory of the National Institute of Standards and Technology is proud to announce its book publication, "STEP the Grand Experience."
   
   
8. Fundamentals of STEP Implementation [PDF]
   http://www.steptools.com
   This white paper walks you through a the initial stages of a typical STEP implementation project. You will need an Adobe Acrobat viewer to read this.
   
   
9. STEP - Information Sources
   http://www.nist.gov/srd/astm/astm-ym/tsld016.htm
   http://www.tc184-sc4.org
   SOLIS a repository of STEP working material on the Web.
   
   
10. Investigating the STEP Data Standard at No Cost
    http://www.steptools.com/translate
    For those who are interested in exploring the STEP Data standard, STEP Tools, Inc. offers a free Online Data Translation Service. CAD users wanting to convert 3D data to and from STEP part files will find a variety of translation options, including popular graphic data formats. To date, over 8000 data translations have been performed online.
11. European STEP-NC Project
    http://www.step-nc.org/
    This site is the hub for the European Perspective of STEP.

Steel Strikes Back

One of the things that the steel industry has done over the past several years is to aggressively position itself vis-à-vis competitive materials. Not only is this being done on a company-by-company basis, as new materials are developed, but also through coordinated efforts, specifically those of the Automotive Applications Committee of the American Iron and Steel Institute (www.autosteel.org). The objective is not to simply react to what other material suppliers are doing, but to take a proactive approach in proving to vehicle and component manufacturers that, although the proffered approach is different materials for different applications, chances are the material they’re most interested in seeing being deployed happens to be ferrous. And more specifically, of the steel variety, as opposed to iron.

When you’re building an engine that produces 505-hp, like the Corvette Z06 LS7, what would you use for the crankshaft other than forged steel?

Consider Cranks. Consider, for example, that the move toward cast iron crankshafts starting in the 1970s raised some considerable concern because the material that was losing out in this switch happened to be steel. Yet as Dave Anderson, director, Bar and Rod Programs, AISI, points out, GM’s Buick Div., which is looking for performance and improved NVH for its vehicles, is using engines fitted with forged steel crankshafts under the hoods of its latest vehicles, the Lucerne and the LaCrosse. Specifically, the 275-hp 4.6-liter Northstar V8 in the Lucerne and the 255-hp, 3.6-liter V6 in the LaCrosse both have forged steel crankshafts. Because of the rigidity of these cranks, there’s little vibration, which helps Buick achieve the sort of “QuietTuning” that it is seeking. In addition to which, there is the performance aspect of the steel cranks, too. So a great example here is found under the hoods of two Cadillac performance models, the STS-V and the XLR-V, both how which have the 4.4-liter supercharged Northstar V8, which produces 443-hp for the XLR-V and 469-hp for the STS-V.

And as an example where the steel crankshaft really performs is under the hood of the Z06 Corvette, which uses the 7-liter, 505-hp LS7 hand-built V8 engine. 4140 steel is used.

Anderson points out that if diesel engines grow in popularity for light vehicles, then the number of forged steel crankshafts will grow accordingly, as the higher compression ratios of that type of engine necessitates the use of steel cranks.

Although the Pontiac Solstice is a low-volume vehicle and even though it has some seriously formed body panels, it isn’t made of plastic. It’s steel. The panels are made with a sheet hydroforming process. The hydroforming not only allows the steel panels to achieve shapes that one ordinarily doesn’t associate with steel (e.g., look at the clamshell hood), but it has lower tooling costs than is the norm when it comes to producing steel parts. Shown here is the ’07 GXP model.

Strength & Durability. Another material that steel is staring down under the hood is powdered metal, which, Anderson admits, has the larger proportion of connecting rod applications under the hoods of cars built in the U.S. However, he points out that the preponderance of engines built for European and Asian applications have forged steel con rods, primarily because, Anderson says, “forged components are stronger and more durable.” Those engines tend to operate at comparatively higher rpms, which puts stress on the con rods, which means that strength and durability are paramount. While he acknowledges that there may be a weight advantage to using powdered metal, “If the con rods are redesigned”—for forged steel—“then they can be lower in weight than powdered metal.” He also explains that while there is also a cost advantage for powdered metal, “the cost differences are coming down because of near-net shape forging.” The use of a material like C-70, which is a crackable steel (which allows the cap to be separated from the rod without requiring machining of the mating surfaces for subsequent reattachment) has been shown to allow weight and manufacturing cost reductions for connecting rods. (It should be noted that the aforementioned LS7 engine doesn’t use steel for its connecting rods—they’re forged titanium.)

Trapping Emissions. Another area where steel has lost significant ground that it is working to recover is in the production of fuel tanks. Here the alternative material is plastic, which is light and easily formable. So the AISI organized the Strategic Alliance for Steel Fuel Tanks (SASFT) initiative, which examined the ways and means to regain some of what has been lost to blow-molded products. One of the concerns with steel has been that of corrosion. So SASFT undertook a two-year corrosion test program to assess both internal and external corrosion potential. According to the results of the study, the steel tanks are good for “up to 20 years,” which means that they meet the California Air Resource Board (CARB) 15-year durability requirement. Chuck Potter, AISI senior automotive consultant, also points out that when it comes to evaporative emissions—a key concern for vehicle manufacturers that are looking to meet CARB’s Partial Zero Emission Vehicle (PZEV) requirements—a single layer of steel can get the job done versus multiple layers of plastic. And while on the environmental front, there is another issue related to gas tanks: What happens at the end of life? Potter says, “Steel is 100% recyclable. Plastic tanks get thrown into land fills.” Certainly that is a consideration for the environmentally minded.

Steel Steps On Aluminum The original aluminum pedal set for the Lotus Elise and Exige may have a high-tech look, but the new lightweight steel pedal box (inset) swaps cables for drive-by-wire electronics, has better pedal feel, and needs less space. (Photos courtesy of General Motors) In a move sure to confound many, Lotus Cars has switched from extruded aluminum pedals in its Elise and Exige models to a hybrid system that uses solid steel pedal arms and extruded aluminum pads. Unlike the previous latticework design, the new lightweight pedal box has an integral mounting point for the drive-by-wire throttle electronics. In addition, Lotus took the opportunity to reduce the brake pedal ratio, improve the feel of the throttle and brake, and reposition the pedals for easier “heel-and-toe” downshifts. These items, Lotus engineers say, would have been more costly and difficult to do with the aluminum pedal arms due to their comparative lack of stiffness.

Although plastic had previously had advantages as regards to both weight and formability for fuel tanks, Potter says that advanced high-strength steels are competitive on both counts.

Another application that steel once had 100% of the market for is wheels. Now steel accounts for less than 50%, with aluminum being the material of choice when it comes to styled wheels. Steel hasn’t disappeared, but has been pretty much relegated to the low trim levels for vehicles. However, what some wheel manufacturers are doing is using steel for creating a base and then adding trim (including plastic), plating, or painting, thereby producing comparatively lower-cost wheels with a higher-cost appearance. Applications of these wheels range from the Ford F-150 to the Lincoln Navigator.

Body Building. So far as the body-in-white goes, steel is strong. Yes, Potter and Anderson both admit that vehicle manufacturers are always looking at alternatives like aluminum and composites, but that steel continues to hold the advantage. Not wanting to lose and then regain as steel has in the aforementioned applications, the steel industry is working hard at creating new materials—Anderson says, with tongue perhaps only partially in cheek, “Steel is old and has been around for a long time. We’re looking to change its name—ferro-alloy.” Something that sounds sexier. But from the technical point of view, the materials that are being promulgated by the industry are advanced high strength steels (AHSS). These are materials with a yield strength greater than 550 MPa. Included in this are materials with improved formability—dual phase and transformation induced plasticity (TRIP) steels—and those with increased tensile strength, crush resistance, and energy absorption—complex phase and martenstic steels. One of the advantages that Potter cites for steel versus, say, aluminum, is that there is a greater familiarity in the auto industry as regards steel, especially when it comes to manufacturing with the material. He admits that the higher mechanical properties and the microstructures of the AHSS materials are different than what has historically been the norm means there must be some adjustments and precautions when it is used in place of the traditional HSS materials, “it doesn’t take wholesale manufacturing equipment changes.” Upgrades to dies (springback is greater for the AHSS materials) and different welding parameters are likely to be necessary, but those are comparatively minor.

One vehicle that makes the steel people exceedingly happy is the Pontiac Solstice. Although the vehicle “borrows” the hydroformed frame rails from the Corvette (i.e., it has the same underlying architecture as the ‘Vette, not the same rails), it doesn’t borrow the plastic body panels. It has a steel body—even though one might think that with clam shell hood plastic would be a natural. (Sheet hydroforming is used instead of plastic molding.) “Plastic used to assume the low-volume advantage,” Potter says. “It’s interesting that we can now say that there’s a low-volume scenario with steel.” The Solstice and platform partner Saturn Sky are going to account for about 20,000 units per year (a number which is likely to go up with demand).

Plastics: The Return of Body Panels?

Although there might be some people who think that in the light of the fact of the relative lack of success of the SMART vehicle lineup and the fact that the company that made plastic cars comparatively cool, Saturn, is moving toward steel with alacrity, don’t count plastics out for body applications, not by a long shot. In fact, according to Derek Buckmaster, global market director, Exterior Body Panels & Glazing, GE Plastics (www.geplastics.com; Bergen op Zoom, The Netherlands), new materials developments are showing solutions vis-à-vis one of the key problems that plastics seem to present, which is the coefficient of thermal expansion (CTE). Buckmaster explains that the problem is a simple one. That is, most body structures are steel. Steel has a CTE of around 1.9. Most plastics, on the other hand, he says, have a CTE between 5 and 10. “If you’ve got plastic exterior panels and it is a hot day, the gaps may no longer exist, and that’s not a good thing,” he says with understatement. “That has been known to happen. I know of an OEM in Japan that built a prototype vehicle with plastic doors, and they literally couldn’t get in on hot days.”

Although otherwise a study in aluminum the BMW 6 Series features plastic fenders in order to achieve the design intent.

So the issue is one of lowering the CTE for plastics. And Buckmaster says that they’re working on two different materials for body panels that have reduced CTE. One of them is what they’re calling “HMD” or “high modulus ductile.” He explains, “Say you have a polycarbonate—one of the best materials in terms of impact resistance, or ductility—and you want it to be stiffer. You would typically put glass fibers in it. But the glass fibers cause it to become brittle. So you always have this trade-off between a stiff material and an impact resistant material.” Enter HMD technology. Rather than adding glass, they are adding a nano material. He says that exactly what the material is is proprietary, but he does admit that it is not a nano-clay, which has been used in some automotive applications (e.g., the 2002 GMC Safari and Chevy Astro vans had a running board with a nano-talc material included in the TPO base; see: http://www.autofieldguide.com/columns/1001mat.html). This material, Buckmaster says, “sets up a secondary structure within the plastic itself and builds a nano-scale skeleton that stiffens the material without losing the impact resistance. It is very different to how you would use glass fibers to stiffen a polymer matrix.” Depending on the resin used, Buckmaster advises that the CTE can be reduced by as much as 50%.

This development is moving toward production, he says. “We’re launching a PCPBT [polycarbonate polybutylene terephthalate] material, Xenoy, with the HMD technology. We’ve already done trials with Krauss-Maffei”—a machine manufacturer—“and BMW and have seen some terrific results. There are a couple of car manufacturers looking at it.” He predicts that within the next 24 months there will be parts produced with the HMD technology. “It’s precisely about reducing the gaps and improving the coefficient of thermal expansion on the vehicle.”

While the HMD technology is for injection molded parts and is suitable for components including door skins and fenders, there is another material technology that lends itself to the production of horizontal panels including hoods and roofs. This is a “high performance thermoplastic composite,” of “HPPC.” Ordinarily, composite materials are glass or carbon fibers in a matrix of a thermoset, an epoxy or a polyester material. The materials are combined, then put in an autoclave, where they are subjected to high temperatures and high pressures. While the part produced tends to have excellent engineering properties, as a practical manner, the cycle times are such that production part applications are exceedingly limited. However, according to Buckmaster, because the HPPC uses a thermoplastic base rather than a thermoset, with continuous glass fibers as the stiffening material, part production is expedited because what’s involved is melting the thermoplastic, molding, and cooling it down again. The cycle time is much shorter than is the case with conventional composites. “Because HPPC is glass-filled and the fibers are continuous, you don’t get that sagging you used to get in the past,” Buckmaster says, referring to the fact that historically large horizontal plastic panels have either been avoided or ribbed on the underside because of this tendency to sag. “We tend to have the same stiffness as a piece of aluminum sheet.”

With a vehicle as tough as the H3 one would think that the body would have ferrous materials abounding. But the deep drawn fender forms necessitated the use of plastic.

Buckmaster suggests that within the next year there will be production parts produced with HPPC. But does this mean that there could actually be a return to plastic skins on cars? Probably not on a wholesale basis. Buckmaster admits that one of the issues that they’re faced with when dealing with OEMs is that of an installed base of metal stamping machines: How can plastic parts production be justified if the machinery sits idle?

Perhaps part of the answer to that question simply goes to the design advantages that Buckmaster says plastics can provide. He explains that typically, if OEM designers want to save weight they consider aluminum, but then pay a cost penalty. What’s more, he says, “Typically, because aluminum’s ductility is not as good as steel, they’re limited in the depth of draw that they can pull on a sheet metal pressing. So that means you have to go to more expensive tooling and be gentler on the aluminum sheet or”—and here’s where the other shoe drops, as you might expect—“you can move to a polymer material.” He provides a solid example of a case where aluminum is used—but so is plastic for the fundamental formability: The BMW 6 Series. “Look at the body-in-white of that vehicle,” he says. Although the majority of body panels are aluminum, the front fenders of the vehicle are made of Noryl GTX. “They would have done it with aluminum if they could have,” Buckmaster claims, “but with the styling design—the curvature and the depth of draw—it wouldn’t be possible.” (The decklid is an SMC composite.)

Another example that he cites regarding the importance of formability is one that is probably more unexpected than that of a sleek coupe: The fenders on the 2006 HUMMER H3. “They’re a complex, deep-drawn shape that are not possible to make with steel or aluminum,” Buckmaster suggests. The fenders, produced with Noryl GTX resin, are said to be the first thermoplastic fenders on a North American truck platform.

STEEL Improves C-Class Structure

When it came time to reengineer the most popular model in the Mercedes-Benz lineup, engineers focused on making the body-in-white stronger, safer, yet lighter. These seeming contradictions (i.e., don’t stronger and safer mean heavier?) forced the team to reevaluate its material choices to meet this challenge, and resulted in a surprising outcome: Approximately 70% of all the steel panels on the body shell of the 2008 C-Class use high-strength steel alloys; a rate Mercedes says is unprecedented for a passenger car. Engineers also used ultra high-strength steel in 20% of the body shell to enhance durability and safety. Together, their expanded use provides unexpected weight savings and improved body rigidity. “We have managed to put an end to the weight spiral,” said Thomas Weber, head of Mercedes research and development. “In the body shell alone, intelligent use of high-strength steels has produced a weight savings of 17.6 pounds.” Torsional resistance also improved by 13% when compared to the outgoing model.

The 2008 Mercedes-Benz C-Class uses ultra- and high-strength steels to provide a structure that is lighter, stiffer and safer than the previous model.

Svelte Safety
Beyond the weight and stiffness benefits, Mercedes also touts the safety benefits of using ultra- and high-strength alloys. Development engineers were able to enlarge the crumple zones through the use of the materials, resulting in improved energy flow and occupant protection. The structure on which the engine, steering, front axle and transmission are mounted, is constructed from high-strength steel and is extended forward, forming an additional impact plane at the lower section of the vehicle, allowing it to act as part of the front deformation zone. The use of high-strength steel also improved deformation and energy absorption characteristics. Ultra high-strength steels and panels of varied thickness are used in the construction of the occupant cell. The main floor structure is comprised of three steel sheets laser-welded together with the thickest sections forming the center tunnel backbone. Continuous floor side members, constructed from steel with reinforced inner sections, provide added protection. Hot-formed, ultra high-strength steel in portions of the B-pillars absorbs large forces and transfers them to the main body side structure in a side impact. The pillars are made up of three formed steel layers with a large, reinforced area that extends to the upper belt deflector point. High-strength steel plates with reinforcements are placed in the frame, waistline and bumper levels of the door. At the rear, the side members are comprised of continuous, closed box sections with defined material thickness at various points that enables the structure to absorb large energy forces. An ultra high-strength bolt-on steel cross member is manufactured via a flexible rolling process that allows the thickness to vary—the outer edge thickness is greater than the inner section—for better impact load management. As a final touch, Mercedes engineers made the steering rack from high-strength steel, which cut 1.7 lb from the steering system.

Plenty of automotive engineers are taking advantages of the comparatively new steels. The 2008 Mitsubishi Lancer utilizes high- and ultra-high-strength steel in its body-in-white, improving torsional rigidity by 56% and bending rigidity by 50% over the previous model. Engineers use the ultra-high-strength 980 MPa alloy for constructing the rocker panel between the A- and C-pillars, resulting in improved side-crash performance. High-strength 590 MPa alloy makes up the B-pillar, roof joints and cross-car structure, adding to the safety credentials.

All Machine Tools Are Not Created Equal

There are almost as many machine tools as there are potential and actual users combined. Each builder has its own niche (or niches) and adds its own "flair" to the machine, making it that much different from the competition. To try and name every builder and every machine here would be impossible, yet a valiant attempt will be made to break everything down and let you know what to expect from a range of machine tools, from verticals to horizontals to universals.

Trend: Controls

While every builder goes to great lengths to make its machines unique, there are a couple of things happening out there that can be labeled "trends." The first of which is the evolution of controls from tape reader to full-out PC. Most, if not all, machine tool makers feature controls that are dubbed "PC-based" or "PC-compatible." A recent survey of those involved in control technology see industrial PCs completely overtaking the control market in the next few years. In fact, many companies have already begun creating "open architecture" controls, meaning that the user can configure the controls to exactly their specifications. Others have gone one step further, putting all capabilities into software, so that nearly any hardware will do, because the control is actually the software. Either way, users had better be pretty computer savvy, and had better be prepared to become more so.

Another trend seeping into the realm of controls is Windows NT. Most hardware and software providers are banking on the fact that Bill Gates will take over the machine control market also, and are converting to a Windows NT environment. Short of this, they may offer Windows NT as an option, and let you decide.

Combining these two technology directions leads to an exciting possibility for the future: networkability. While many controls are plugged into user local area networks (LANs), few have yet to be reliably brought into the realm of the World Wide Web. Once the issues of reliability and security are cleared up, Tier 1 and Tier 2 suppliers will further tighten up the supply chain, transferring CAD/CAM data from the design department at one company directly to a machine at another.

Some Specifics

Out of all of the newer control technologies out right now, the slickest looking features are coming from combining mega-capable hardware with creative software solutions that help boost machine capabilities. For example, the BostoMatic BDC 3200X CNC from Boston Digital Corp. (Milford, MA) uses software algorithms, 32-bit VME bus architecture, and multiple microprocessors to enable the processing of 1,100 five-axis blocks per second. While achieving such high speeds is something else, the control gets slicker when you consider that no preprocessing is required, even on the most data-intensive part programs. Contour optimization software and user-programmable servo parameters round out the 3200X's features.

Creative Technology Corp.'s (Arlington Heights, IL) Creative Evolution is a PC-based control that Defiance Machine & Tool Co., Inc. (Maryland Heights, MO) counts on to give its small machining centers a few extra punches. A look-ahead feature scans for corners, and automatically adjusts speed and feedrate to prevent gouging and provide rounder corners. The system also provides automatic chamfering, canned milling and Z-axis cycles, mirror-image programming, and an on-screen text editor that includes global program modification.

Trends: Spindles

Used primarily to machine EDM electrodes, the Defiance VTX line of tabletop machining centers gets a lot of its precision and capability from its control and specially designed software from Creative Technologies.

There's something fishy going on with spindles. Everyone is talking about self-balancing, high-speed spindles, but no one we've found will talk specifically about them. Several machine tool companies are "looking into" the development of these units, but mum's the word until they're ready to launch the product. Of course, there are some self-balancing spindles out there already, but they are incredibly expensive, and are really still in the R&D stage of things. It should be interesting to see what develops in the next few months.

Some Specifics

The tilting head spindle configuration from Mandelli is designed to provide precise machining under tough conditions. This particular tilting head is used to machine various car components at Ferrari's plant in Maranello, Italy.

In the mean time, there are some tangible advances being made in regard to spindle technology. One that stands out is the tilting head configuration at Mandelli (Rockford, IL). While tilting head spindles add a fifth axis, they tend to be too delicate to stave off vibration and other accuracy inhibitors. Taking that into account, the company's engineers have developed a high-torque spindle that can handle heavy-duty cutting applications, but without sacrificing accuracy. Combining that with the standard Sinumerik 840D control from Siemens, this system can really cook through some mold and die applications.

Trends: Toolchangers

As with the rest of the machine, toolchangers have gotten more sophisticated. Some systems are capable of tool condition monitoring, reporting data back to the control; and many ATCs feature a load cell that monitors whether the tool is present, and transfers tool length data to the control as the tool is mounted to the spindle. Manufacturing cells and flexible systems now use one toolchanging system for several machines, saving space, time, and money. A robotic system patched into the machine's control moves tools from machine to machine as needed.

Some Specifics

Changeover times range from 10 seconds in cells and systems, to 1.5 seconds in some of the smaller horizontal machines. Capacity ranges from 12 tools to hundreds. Shank type depends on the spindle. A system from Mikron Corp. (Monroe, CT) uses rotary magazines with 12 positions each. This lets users set up tool sets for specific jobs, and switching from job to job only means lifting out one magazine and replacing it with another. The system is expandable up to 40 positions.

Trends: Feed & Speed Rates

With most vertical machines, the magic number seems to be 787 ipm rapid feeds in the Z-axis and around 1,100 ipm in the X and Y axes when you're talking vertical machining. Horizontals are capable of faster speeds, hitting around 1,100 to 1,400 ipm.

Some Specifics

Going fast isn't just a function of the spindle and the cutting tool anymore. Machine tool builders are using software to get things moving faster. Makino (Mason, OH), for example, has a software function called "rapid traverse bypass." It determines where the spindle needs to be, allowing rounded corners on rapid paths to get it there. Enshu U.S.A. Corp. (Elk Grove Village, IL) uses a programming algorithm to provide fast, synchronized tapping with forward control. According to Enshu, the algorithm works even for extremely small diameters.

Trends: Work Changing

To speed up automated pallet changeover, most companies are incorporating shuttle control into the programming of the machining system's control. Here again, the configuration of the changer is going to be up to the user.

Some Specifics

The Flexline manufacturing system from Chiron is packed with a lot of time and money saving features, but one of the more interesting ones is a part changing system that uses robotic arms to perform changeover in about 10-seconds.

Five-axis machining for under $200,000? Yep. The HS-1R 5AX horizontal from Haas Automation, Inc. (Oxnard, CA, seen here performing porting operations on a cylinder head, features X,Y, Z travels of 24 x 20 x 22 in., respectively, and a standard extended table measuring 15 x 40 in. All of the bells and whistles are integrated into this machine: full five-axis control, a 7,500-rpm spindle powered by a 15-hp motor, rapid traverse rates of up to 710 ipm, a 24-pocket toolchanger, and a chip auger that automatically senses loads to prevent jamming.

One of the more unique (and quick) workpiece changeover systems comes from Chiron America, Inc. (Charlotte, NC). Its flexible transfer lines employ a rail-guided robot moving from station to station, and back to a load/unload station. Moving at 8,000 ipm, the robot zips from machine to machine, and changes parts in around 10 seconds. An optional part magazine allows unattended operation for long periods of time.

Trends: Construction

Ribbed, cast iron, Meehanite, even concrete. The base material and construction of machining centers are both common and different. Not to say that machine tool builders have lost their creativity in this regard. Quite the contrary. Builders are left with the dubious task of making machines that have as large a work envelope as possible while maintaining rigidity, while damping vibration, while not taking up too much room. You get the picture.

Some Specifics

Looking again at Mikron Corp., its machines feature a cast structure in a portal design. Two portal supports are fixed on the base, and the transverse beam accommodates the cross slide. The Z-axis runs on top of this. According to the company, the symmetry of the design naturally minimizes vibration.

Clearly, the machine tool industry is extremely competitive, and builders work very hard to stay one innovation ahead of its competition. If they all stay on the track they're on, users will be machining parts in France from their living rooms in Ohio before we know it.

Things to Know About Cam Grinding

The changing shape and composition of camshafts are challenging those responsible for surface finishing. As a result, an increasing number of cam-grinding operations are being performed with cubic boron nitride (CBN) superabrasives and technologically advanced conventional abrasives.

Camshaft grinding requires instantaneous changes in wheel-work contact length and material removal rates. In camshaft grinding, the arc of the contact between the wheel and the camlobe changes continuously as the base circle, flanks and nose are ground (see illustration). The arc of contact can be represented by means of the equivalent diameter (De) and can be calculated:

De = Ds x Dw Dw ± Ds with: Ds is the wheel diameter Dw is the work diameter + is to be used when Ds > Dw - is to be used when Ds < Dw

A large equivalent diameter represents a longer arc of contact between the wheel and work material. So the arc of contact is large as the wheel passes over the flanks and becomes smaller as the nose and base circle are ground.

As the De increases, more abrasive particles come in contact with the work material. This reduces the force acting on each grain, and makes the ploughing and sliding interactions more dominant. This is usually observed as increased grinding power or force for the same grinding condition.

In camshaft grinding, as the De is larger while grinding the flanks, higher power will result if the radial infeed and work speeds are maintained the same as when grinding the nose or base circle. This can result in unacceptable thermal damage on the lobes. In order to avoid this problem, the work speed is generally reduced as the wheel grinds the flank portions. This reduces the rate of material removal and helps lower the grinding power.

Take Care

The equivalent diameter in camlobe grinding.

Camlobe grinding is a complex variant of cylindrical grinding. When raw camshafts are manufactured—by casting in sand or shell molds (cast iron), forged or machined from barstock (steel)—roughly 0.02 to 0.12 in. of stock is generally available for grinding. After the lobes and journals are induction hardened, the journal bearings are ground, usually on a centerless or cylindrical grinder. Since the camshaft is supported on workrests, with the journals as a reference during camlobe grinding, it is important that the journals be ground properly because any imperfections will be translated to the camlobes during lobe grinding.

Although the necessary surface finish on the lobes and journals is usually provided by the grinding, they are often lapped with fine-grit abrasive belts. Lapping after grinding has been found to be effective in reducing initial friction during the engine break-in period.

New Profiles

During the past decade, camlobes with a re-entrant profile have been gaining popularity because this design helps increase engine torque and horsepower and reduces emissions. In re-entrant camlobes, the ramps are concave instead of a straight line; this helps in opening and closing the valves much faster.

Also, the use of roller bearings at the interface with the camshaft in place of flat tappets has reduced friction, permitting higher engine speeds. However, the sharp line contact results in significant increases in contact stresses, which can exceed 250,000 psi. These high stresses can result in spalling and accelerated camlobe wear. So depending on the magnitude of the contact stresses, camshafts of different construction are used.

For lower contact stress applications, induction hardened or chilled nodular cast iron may be acceptable.

For contact stresses of 250,000 psi and above, steel cams can provide the most-reliable solution.

Composite Approaches

Composite camshafts of medium- and high-alloyed powered metal lobes mounted on a hollow tube are popular as they have the capacity of withstanding high contact stresses and offer improved tribological properties. Composite camshafts can be 50% lighter than cast iron or steel shafts; can have lobe material tailored to the application; and they can have lobes molded to near-net shape, which means that the amount of grinding stock, and consequently grinding time, are both reduced.

The requirements to have high-strength, low friction and minimal wear have prompted Japanese researchers to consider ceramic camlobes.

Camlobes are usually machined to final shape by grinding with bonded abrasive wheels containing aluminum oxide or CBN. Usually, one lobe is ground at a time, although in order to improve productivity, machines using multiple abrasive wheels are available. With this equipment, two wheels are mounted on a one-piece precision-balanced hub to grind two lobes at a time. But this approach can be used only if the lobes being ground simultaneously have similar lift profiles.

Abrasive Belts

Another approach to improve cycle time is using machines with abrasive belts. This was developed in Italy in 1977; it was successfully implemented by GM engineers only in the early 1990s. In these machines, the abrasive belt is pressed against the workpiece by a cylindrical contact shoe that, together with the belt, replaces the curved surface of the grinding wheel. These multiple-belt cam grinding machines can grind all lobes simultaneously for cycle time reduction.

Another advantage offered by these machines is in the grinding of re-entrant camlobes. Grinding of re-entry type cam profiles with grinding wheel requires that smaller diameter wheels be used. This restricts the life of the wheel, making its use less cost-effective. With abrasive belts, the curvature of the belt can be controlled by changing the contact shoe diameter, so re-entry lobes of high negative curvature can be easily ground.

Higher Speeds

The current trend to reduce cycle time involves grinding at high wheels speeds. Machine builders in Europe and Japan are marketing high-speed cam-grinding machines with wheel speed capability of up to 200 m/sec. High grinding wheel speeds offer the advantage of longer wheel life, lower forces, and high removal rates. Higher metal removal rates at higher wheel speeds reduce cycle time.

A variation of the high-speed approach involves high wheel speeds, large depth of cuts, and low work speeds. This approach is similar to High Efficiency Deep Grinding (HEDG) and is essentially high-speed, cylindrical, creep-feed grinding.

Another approach uses a high-speed grinder with a pair of wheel heads. One wheel head uses a brazed, single-layer CBN wheel and is used to rough grind the lobes very aggressively. The other wheel head uses a small-diameter vitrified CBN wheel for finishing the lobes. This approach has been successfully used to grind re-entry type camlobes.

Vitrified bonded aluminum oxide wheels are still popular for grinding camshafts, but most CNC machines are now shipped with superabrasive wheels.

CBN & Beyond

The hardness, thermal conductivity and chemical inertness of CBN
have made it an abrasive of choice for production grinding of ferrous and aerospace alloys. Several bond systems—resin, metal, glass, and brazed—are available with CBN. Among these, the glass, or vitrified, bond system has proven to be the most popular. These bonds are rigid, free-cutting and have good form-retention. In addition, the porosity in these bonds can be controlled for more chip clearance and better coolant application at the grinding zone. Vitrified bonded wheels are easy to true and do not require additional dressing procedures.

The inherent brittleness of the vitrified bond system contributes to the self-sharpening action during grinding, but the brittleness also makes the wheels susceptible to chipping and breaking if used improperly.

One answer to this problem is a segmented wheel design, where individual segments are cemented to a steel or aluminum oxide core. Benefits include:

•Easy replacement of damaged sections
•Safety at high wheels speeds—up to 150 to 200 m/sec.
•Properties of individual segments can be measured and monitored so there is consistency along the wheel periphery and from wheel to wheel.
•Special wheel adapters can be resegmented and reused after the CBN layer has worn out.

There is also a ceramic aluminum oxide abrasive that's making an impact in cylindrical grinding operations. This elongated, high-aspect ratio abrasive can make a difference in high speed grinding of cast-iron camlobes. They provide high removal rates compared to a vitrified CBN wheel. The lower cost and single-point truing capability compared to CBN could make them excellent alternatives.

Tools of the Trade: Machining

TURN, TURN, TURN

The amount of things that you can do with turning may be surprising. At least that’s the sense one gets from spending time talking to the people at Fuji Machine America Corp. (Vernon Hills, IL). If there is any question of the company’s bona fides in relation to the work that it is doing in the auto industry, this should dispel it: According to company information, 64% of the lathes used by Toyota in Japan are from Fuji (the parent company is based in Chiryu City, Japan), and apparently there is a good working relationship between engineers from both companies such that there are mutually beneficial developments, developments that eventually make their way into commercial availability.

One of the ways that additional flexibility is being achieved in systems, including those built by Unova Manufacturing Technologies, is through the utilization of robots even for large-parts handling (note: this picture shows a system being tested; the actual installation doesn’t employ wood for purposes of fixturing).

Consider, for example, a camshaft cell that is available, one that meets “automation level C” within the Toyota Production System ranking of automation (ranging from A, fully automatic to D, which is essentially a standard CNC machine). In the “C” configuration, there is manual part load/unload and then fully automatic within-machine part handling. The camshaft cell makes use of a CE-30 mill and centering machine and a GN-30TTS four-axis turning machine. The CE-30 has double turrets for workpiece facing and centering; it can handle parts from 300 to 550 mm long. Then it is passed on to the GN-30TTS, which has two slides above the centerline of the bed. Through the use of CNC tailstocks, the machine is capable of handling various shaft lengths. A hybrid chuck grips the ends of the shaft wherever appropriate for the specific turning operations performed (e.g., edge- or mid-section turning).

Whereas a traditional crankshaft line is typically configured with Op. 10: centering; Op. 20: turning; Op. 30: turning; Op. 40: pin broach/mill; Op. 50: gauging, Fuji has a flexible alternative. Instead of dedicated equipment, there is the ability to change to other crank configurations in a reasonable amount of time. For Op. 10, the centering machine is replaced with a machining center (model YM-40) that performs facing on both ends and center drilling. Op. 20 is performed with a two-turret lathe (model GN-51TTS); the steps here including machining the front shaft OD and counterweight ODs, and facing the journals. The part orientation is reversed for Op. 30 (a double-hand gantry loader is used to transfer parts between machines); at Op. 30 there’s machining the rear shaft OD, threading, and journal finishing. Op. 40 is where there is some awfully clever turning performed (in fact, there is a patent pending). Here a GN-51TWS lathe is employed: it is capable of turning the eccentrics because the machine has adjustable offsets in the eccentric chucks that mean that off-center turning can be performed. Compared with the traditional dedicated broach/mill with special ring cutter, this alternative employs less expensive tooling and an overall lower investment cost. As for Op. 50, Fuji offers a variety of gauging alternatives, from a C-gage to laser.

CONSIDER THESE BENEFITS:
• Cycle time: improved 10%
• Machine cost: reduced 25%
• Total manufacturing cost: reduced 60%
• Machine space requirement: reduced 30%
• Power consumption: reduced 50% In addition to which, environmental concerns are greatly reduced.

Those are the sorts of benefits that can be achieved by utilizing hard turning in place of grinding for a variety of workpieces, ranging from gear blanks to wheel hubs. One of the big issues that can be overcome through the use of a turning machine in place of a grinder is the fact that the form tools ordinarily required for tapers, radii and chamfers aren’t necessary for hard turning equipment. Rather, because these machines can be programmed, tools can be rapidly oriented where required.

About that environmental issue: the folks at Fuji point out that this process can be performed without coolant, so the grinding sludge that’s characteristic of the alternative operation isn’t generated. Turning can have big benefits.

MAINLY MILLING

It wasn’t all that long ago that it seemed as though high-speed machining (as in milling) was all the rage—or at least something that consumed a lot of rhetoric. People were fascinated by the possibility of spinning spindles at high rates, rates in excess of 25,000 rpm at minimum, in order to remove metal more rapidly. And there were discussions of how this would lead to manifold benefits. The technology was pioneered in the aerospace industry, where the workpiece material tends to be aluminum. As the auto industry began its transition to aluminum blocks, heads, transmission housings, etc., it seemed like a natural transition to make: If the aero guys were running quite quickly on aluminum, then why not do it in powertrain plants?

Well, there were some issues encountered, notes Richard A. Curless, director of Research & Development, Unova Manufacturing Technologies (UMT), a division of Unova, Inc. (Fundamentally, UMT combines the capabilities and products of Lamb Technicon and Cincinnati Machine.) For example, consider the nature of machining in the aerospace industry. There are large workpieces (e.g., wing spars) that are milled and contoured. These operations are long, as plenty of material is removed from the billets (as Dr. Phil Szuba, director of R&D for Lamb products at UMT, points out, they’re removing about 90% from a billet to end up with a spar), so working with a high spindle speed can be exceedingly helpful. But Curless notes that in auto, “There’s a lot of starting and stopping.” As in: Drill. Stop. Tap. Stop. One of the burgeoning characteristics of more and more automotive parts is that they are being cast to a near-net shape, which requires comparatively less metal removal. It is one thing to keep a high-speed spindle running for a long time, generating lots of chips, a la aero. It is entirely another to put them through the sort of duty cycle that goes on in auto. Which can lead to the need to change spindles more frequently than would be liked, for, as Curless notes, one of the key issues in automotive machining is uptime, with particular attention being paid to mean time to repair (MTTR). So, according to Szuba, a spindle speed in auto of 16,000 rpm is fairly common (achieved through the use of grease-pack bearings that provide reliability), as compared with the 30,000 to 40,000 rpm that might be run in aero. What’s more, given the faster pace of car making as a whole compared with the number of aircraft built, the fundamental focus is not merely on the speed of the spindle, but on the entire cycle time. Which includes the time required to load and unload parts.

This mill can be deployed in machining centers as well as mill-turn machines for serious cutting.

Although there is a natural assumption to think something along the lines of “Machines/Metal,” Curless points out that electronics developments—both in terms of software for parts programming and optimization, as well as vector drives and high-speed servos—are having a huge effect on the nature of machine tools and their capabilities. Speaking of the former, Curless notes that there is greater modularity of the equipment, which leads to the sourcing of components from a variety of sources (e.g., components for a machine, say way systems, might come from any number of countries, ranging from Japan to Switzerland). And speaking of contributions of things like the drives, servos and controls, he points out that the traverse rates of machines have been marching forward at a considerable rate during the past several years, going up to around 80 m/min today, with an acceleration of at least 0.5 G being almost an expectation.

One of the characteristics that is keenly sought by both OEMs and suppliers alike in terms of machining capability is flexibility, the former’s interest deriving from the heavy investment in major machine lines, and the latter being concerned with the consequences of losing programs. While this has been a discernable trend for the last few years, Szuba says the extent to which this is occurring is somewhat surprising, as in even performing applications like gundrilling crankshaft oil channels on flexible CNC machines rather than on dedicated pieces of equipment.

Flexibility in machine operation is one thing. Making it easy for an operator to take advantage of it is another. This cylindrical grinder addresses both.

A DIFFERENT GRIND

Those who have a need to (1) perform cylindrical grinding, both internal and external, and (2) find themselves doing so on various parts should be interested in the capabilities of the Studer S151cnc, which has a swing diameter of 350 mm and a between-centers grinding length of 350 mm. There are two independently programmed grinding spindles on the turret head so that there is the ability to rough and finish grind in a single setup. Because changing from one part to another means a whole lot more than adjusting workholding, the machine has a Fanuc 16i digital control loaded with Studer Pictogramming, which is a step-by-step approach for operator programming. The machine is available from United Grinding Technologies (Miamisburg, OH).

TOUGH CUT

Need to mill some heavy metal—as in steel, stainless steel, or even heat-resistant super alloys? Check out the CoroMill 390 long-edge milling cutter from Sandvik Coromant (Fair Lawn, NJ), which features a hardened-steel cutter body (in diameters from 40 to 200 mm) and handles 18-mm long inserts. The cutter can mill depths up to 3.9-in. and can provide 90° corners.

Designed and engineered for use by automotive suppliers who need a sizable machining center at an economical price.

BIG BUT FAST

Although the a81 horizontal machining center is big—it has a 630-mm square pallet, a standard 50-taper spindle (capable of 10,000 rpm), a payload capacity of 1,500 kg, and X-, Y-, Z-axis travels of 900 x 800 x 900 mm—it is a quick machine, as well. That is, it provides a rapid traverse rate of 60 m/min, as well as the same speed for the feedrate. There’s a 40-tool magazine that works in conjunction with an automatic toolchanger that handles tools with a 1.7-sec. tool-to-tool time. Yet the a81 from Makino (Mason, OH) has a comparatively compact footprint: 3,460 x 5,370 mm.

DOUBLE UP

By putting two spindles on a single base and by providing plenty of tools, productivity in turning can be realized.

Optimal working space is a fundamental characteristic of the TWIN 42 turning machine from Gildemeister Group (DMG America; Schaumburg, IL), as it has, as its name implies, twin spindles. In addition, the machine has 12-station turrets for handling a good variety of tools, all of which can be driven. The machine has a turning diameter of 42 mm and can handle 580 mm between centers. Four-axis machining can be performed on either of the spindles or there can be simultaneous two-axis machining on both spindles. In addition, there is the capability of automatically transferring a workpiece from one spindle to the other, thereby providing the means to do full processing without manual intervention.

Simple addition for improved production from small Haas lathes.

UP OUTPUT

For those of you who have a small lathe from Haas Automation (Oxnard, CA)—such as the SL-10 turning center—and are looking to up your production, check out the new Barr-100, pneumatic, automatic bar feeder that the company has developed for its small machines. It can handle bars up to 1-in. diameter. When used in the pneumatic mode, 6-ft. long bars can be automatically loaded. This additional productivity is cost-effective: the Bar-100 has a retail price of $2,995.

Machining: Tools for the Trade

What's It Called? The ANS-3100P from FUJI Machine America (Vernon Hills, IL; www.fujimachine.com).

What Is It? A hard turning lathe.

Configuration? It's a modular machine that features one spindle, one turret, and a four-axis swing arm robot for part handling.

Key Specs? The spindle has a 20-hp motor. The turret has eight positions. A Fanuc control is deployed.

Considerations? Hard turning can work as an alternative to grinding. The machine is built as a module, so the potential for lines to be created out of several is there (especially given the deployment of robotic automation).

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What's It Called? The EWB-AL aluminum tooling system from BIG Kaiser Precision Tooling (Elk Grove Village, IL; www.bigkaiser.com).

What Is It? Ultra lightweight automatically balanced precision boring heads for diameters ranging from 3.937 to 8.000 in.)

Key Specs? The tooling system uses two different heads to cover the entire diameter range. It is designed for cutting speeds up to 6,600 sfpm. There's micrometric adjustment via dials that are graduated in 0.0005-in. increments as well as a Vernier scale that permits setting to 0.0001-in./diameter.

Considerations? Several. Because these heads are made of a hard-coated high-tensile aluminum, their weight is one-third that of steel, then when you add other tooling elements (e.g., extenders) that are also aluminum, the total tooling weight can be half of that of ordinary tools, which is an aid during automatic toolchange procedures. (The hard coating, incidentally, helps extend tool life.) The balance that is provided by the adjustment is particularly important for boring at high speeds with polycrystalline diamond (PCD) or cubic boron nitride (CBN) tools, especially as this facilitates improved surface finish.

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What's It Called? The Variaxis 730 5X five-axis vertical machining center from Mazak Corp. (Florence, KY; www.mazakusa.com).

What Is It? A machine with a 150º tilting table that allows simultaneous five-axis machining without the need for re-fixturings or additional machines.

Key Specs? There is a 50-taper spindle. Maximum spindle power is 40 hp and 387 ft-lb of maximum torque. The top speed: 10,000 rpm. The table on the standard single-pallet machine measures 24.8 x 19.7 in. The rapid traverse rate in the X, Y, and Z axes is 1,575 ipm. The standard tool magazine holds 30 tools. The control is via the conversationally programmed Mazatrol Fusion 640M CNC.

Considerations? Mazak brought out its first generation Variaxis machine in 1999, and has been pursuing continuous improvement since that's so far culminated in this machine. Because it has a 50-taper spindle, it can better perform heavy-duty roughing ops on castings and forgings. Compared with the 40-taper version of the machine, cycle time reductions of 24% on duplicate parts have been realized. Another improvement area is environmental: the amount of air consumed during machining is reduced 50%, a grease lube system reduces waste oil by 57%, and coolant life is boosted by 50% because there are no tramp oils from the linear guide lube system.

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What's It Called? Servo and Spindle High-Response Vector Software Version 4.(HRV4) from GE Fanuc Automation Americas (Charlottesville, VA; www.gefanuc.com).

What Is It? HRV4 is as its name implies servo and spindle software that takes advantage of the abilities of the mechanisms they control such that high-speed and high-precision machining can be preformed. In this case, they're talking about the nanometer level of interpolation.

Key Specs? The DSPs used today allow blazingly fast servo feedback data, so the Servo HRV4 closes the current loop in 31.25 µs, the velocity loop at 62.5 µs, and the position loop at 250 µs. The Spindle HRV4 uses a dedicated spindle process to achieve a 12 kHz PWM frequency.

Considerations? Why not make the most of your GE Fanuc servos' and spindles' abilities with the latest software from GE Fanuc?

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What's It Called? The VF-6SS vertical machining center from Hass Automation (Oxnard, CA; www.haascnc.com).

What Is It? A vertical designed for high-volume operations (or when exceedingly low cycle times are required: the “SS” in the designation stands for “Super Speed”).

Key Specs? It has a standard 30-hp 12,000-rpm inline direct-drive 40-taper spindle. The machine travels are 64 x 32 x 30 in. High-pitch ballscrews and high-torque servos combine for rapids of 1,200 ipm Y and Z and 900 ipm X. There is a 24-pocket side-mount automatic toolchanger that makes changes in 1.6 seconds. Other features are an automatic chip auger and a programmable coolant nozzle.

Considerations? Speed is good, but at the end of the day (or machining operation to be more specific), quality matters. This is one reason why the direct-drive spindle setup is important. That is the system is designed to minimize vibration and heat, both of which can have negative effects on surface conditions. In addition, noise is reduced, which certainly improves the conditions for the machine operators.

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What's It Called? The FH-SX horizontal machining center from Toyoda Machinery USA (Arlington Heights, IL; www.toyoda.com).

What Is It? A machine that's designed—specifically via the design of the column—to provide the sort of rigidity required to cut steel and other ferrous materials like a boxway-style machine yet provide the kind of speeds more characteristic of a high-speed machine—i.e., 20% faster than a boxway machine.

Key Specs? Features a 50-taper, 40-hp, 6,000-rpm spindle that's flanked by a ballscrew and motor on each side so as to double the driving force on the Y axis. TheFH550 SX version has a work area that's 29.53 in. X, 31.5 in. Y and 33.46 in. Z. The rapid traverse rate in all three axes is 2,362 ipm, and the acceleration is 0.7 g. The pallet size is 21.65 x 21.65 in. The machine offers a linear positioning accuracy of ±0.00012 in. and a linear repeatability of ±0.00008 in.

Considerations? When don't you need a combination of speed and accuracy in machining?

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What's It Called? The NVG 1500 DCG vertical machining center from Mori Seiki (Irving, TX; www.moriseiki.com).

What Is It? A compact machining center that is designed to be able to achieve high-speed, high-precision machining operations.

Key Specs? The machine is just 33.5-in. wide and has an overall footprint of just 17.2-ft2. Designed for small-part production, including such things as electrodes, it has a maximum spindle speed of 24,000 rpm. The travels are 150, 150, 200 X, Y, Z, respectively, and the rapid traverse is 15,000 mm/min. It handles HSK E32 tools. Tool change chip-to-chip is 3.5 seconds. The cutting speed is 15,000 mm/min. The machine is capable of providing a roundness of 0.8 µm, which is ordinarily achieved with the assistance of a lathe, not only a machining center.

Considerations? The machine uses the “Driven at the Center of Gravity” approach that Mori Seiki has pioneered, which essentially means that the company deploys two parallel ballscrews along the spindle axis so that vibrations are minimized. This leads to high precision. In the case of this machine, the precision is further assured through the use of minimizing thermal displacement by passing coolant through the motor bracket.