Continued integration among CAD, CAM, and CNC software will make tomorrow's machine tools smarter, faster, and more accurate.
Today's digital exchange of part data between CAD and CAM consists primarily of nominal geometry and not the part specifications necessary for automated manufacturing.
The STEP-NC format contains all the manufacturing information required to machine a part.
Even though many software manufacturers tout their "interoperability," end users are still dealing with disconnects among their CAD, CAM, and CNC systems. But this is quickly changing. In the not-too-distant future, industry-wide collaboration between software and CNC vendors will lead to more-complete data being shared throughout the design-through-manufacturing cycle. This, in turn, will lead to intelligent machine tools that process quality parts in less time.
Fortunately, over the years, integration and data sharing ( interoperability) between CAD and CAM products have come a long way. For instance, industry-standard file formats, such as the Initial Graphics Exchange Specification (IGES), are better supported, letting CAD geometry reliably transfer between CAD and CAM systems. Industry is also developing new standards, like the International Standards Organization's (ISO) Standard for the Exchange of Product Model Data (STEP), to meet expanding interoperability requirements.
In addition, both CAD and CAM systems typically use solid-modeling kernels such as Parasolid and ACIS that not only allow transparent exchange of solid-model data, but also consistent interpretation of the data. And software libraries, which support reading geometry contained in native CAD-file formats, allow CAM systems to access CAD data without requiring the CAD software. Because of these advances, today's manufacturers expect to be able to flawlessly read CAD geometry from almost any source.
Today's jobshops typically shop for CAD/CAM software by either purchasing from a single-source supplier or building a solution from a number of best-in-class CAD and CAM products. Which they choose is often determined by price, dataintegrity concerns, and flexibility to deal with a variety of customer file formats. But the best solutions lend themselves to the following product/process flow:
- Design CAD — used by the product design engineer.
- Manufacturing CAD — employed by manufacturing engineers and CNC programmers to program parts designed by someone else.
- CAM — defines machining strategies, order of operations, and the tooling used. It also generates machine-specific CNC programs.
- CNC machine tools — run these programs to cut parts.
Today, designers use CAD to create new products. They then send the CAD file (wireframe or solid models, for example) to the manufacturing departments or jobshops. This CAD data, called a "nominal" model, gives CAM users the final geometry of the parts, but it does not include geometric dimensions, tolerances, or surface-finish information. Thus, the solid model contains the geometry but not all the information necessary to machine a part.
Unfortunately, design and manufacturing groups still communicate product-specification data through engineering drawings. Where CAM system functions could be boosted is by integrating the product specs with the solid model from the CAD system. As is, the CAM system doesn't have all the information it needs. Hence, CAM users still have to import CAD geometry into their CAM systems and then read blueprints to completely understand what is to be machined.
A similar disconnect occurs between a CAM system and a CNC. G-code, currently the state-oftheart in CNC-program format, tells machine tools exactly where and how to move. But the machines never really make these perfect "nominal moves." In reality, they just comes "close enough." That's because the physics of a CNC machine requires a small tolerance — in deviating from a corner, for example — so that the machine doesn't come to a complete halt after every move.
Sophisticated CNCs handle axisservo acceleration and deceleration while following toolpath motion. But G-code from the CAM system does not specify tolerances or tell the CNC whether it is roughing, finishing, or cutting a surface or a solid. If it did, CNC manufacturers could build machines that cut parts faster, while still holding tolerances.
In addition, if CAM systems knew the accel/deaccel curves for specific machines, how controllers calculated path deviations, and how fast they processed blocks of G-code, they could better optimize toolpaths and accurately model tool motion and run times. In fact, having a complete understanding of a specific-machine tool's configuration — including tools loaded in its tool changer and tolerances it can hold —would let a CAM system further tailor developing manufacturing strategies for faster run times and improved part quality.
Such opportunities cannot easily be acted upon by any single product vendor. That's because the CAD product must include geometric dimensions and tolerances with other part-specification data and provide a way to access it. The CAM software, in turn, has to do something useful with this data. And information communicated from the CAM system to the machine tool must contain enriched data that lets the CNC intelligently process it.
Through a collaboration similar to that between CAD and CAM vendors, CAM software and CNC manufacturers will build next-generation capabilities to take advantage of this extended data. However, collaborations can be tough to realize.
Fortunately, the U.S. Government provides grants and funds programs for improving technologies. For instance, it supports projects for next-generation technologies such as STEP-NC. This ISO data format should extend CNC's data-input format well beyond Gcode. Though still in the early stages of definition, STEP-NC shows much promise in providing process data to machine tools.
At the same time, various industry groups are working together to promote the development of nextgeneration machine tools.The Open Modular Architecture Controller (OMAC) consortium is defining a control architecture that integrates components from multiple sources, not just single-source, proprietary solutions. OMAC is also defining a standard human-machine interface for controllers. This will give a common interface for operators moving from machine to machine. Finally, the Smart Machine Platform Initiative (SMPI) project is defining a next-generation machine tool smart enough to ensure that the first cut part is correct.
But this smart machine tool needs more than just G code to realize the vision of a correct first part.
GIBBS AND ASSOCIATES CELEBRATES ITS 20'TH
Gibbs and Associates celebrated its 20th Anniversary during IMTS 2004 by giving its customers and other booth visitors special pins created for the occasion. A company representative reports the commemorative pins were a hot item.
Since 1984, Gibbs and Associates has been a developer of CAM software for CNC machining supporting two through five-axis milling, turning, mill/turning, multitask simultaneous machining, and wire EDM.
Bill Gibbs, president and founder recalls, "When I saw the first graphical interface, I was hooked. I remember laying awake nights thinking it would be fun to create CAM software with an easy-to-use interface. This resulted in the company's first product, the Gibbs System. Today, we develop GibbsCAM with the same commitment to usability."
Gibbs believes in empowering the NC programmer, machinist, and manufacturing engineer, not eliminating them. He says, "We don't want GibbsCAM software to be perceived as expert-friendly. We want it to be machinist-friendly."
Today, Gibbs and Associates prides itself on being a provider of tools that it claims are intuitive, graphically interactive, visual, associative, and enjoyable to use — "powerfully simple, simply powerful" is Gibbs' guiding philosophy.
SHOPPING FOR CAD/CAM
Today, companies typically shop for CAD/CAM software in two different ways — either purchasing from a single-source supplier or building a solution from a number of best-in-class CAD and CAM products. Products such as CATIA, Pro/ENGINEER, and Unigraphics are single-source suppliers, often called "process-centric," integrated CAD/CAM. Their advantage is that all parts are integrated, so all have direct access to the data — this integration eliminates potential data loss from data translation. The downside is all-encompassing systems tend to be more expensive, as well as limiting the buyer to the single solution. Concerned about data integrity, large corporations often pick one-source systems.
Buying best-in-class gives users flexibility in selecting components, much like a component stereo, best fitting their needs and preferences. Small companies typically purchase best-in-class. They first select a best-in-class CAD system, such as SolidWorks or Solid Edge. Then, they pick a best-inclass CAM system compatible with their CAD choice. Job shops normally receive designs from a wide variety of CAD systems, so they usually select a CAM system supporting the broadest range of formats, allowing them to get data from many sources.
Mr. Gibbs is president and founder of software developer Gibbs and Associates in Moorpark, Calif.