Open-Architecture CNC Closes Servo Loop In Software

Manufacturing Data Systems Inc. (MDSI) was founded by Charles Hutchins and Bruce Nourse—twice. The first time was in 1969 in Ann Arbor, Michigan. The company developed Compact II, an NC programming language that quickly became one of the most widely used in the metalworking industry. The original MDSI was eventually acquired by Schlumberger and merged with Applicon and the MDSI name was subsequently abandoned.

In 1989, Hutchins and Nourse reunited as partners to found a new company which would eventually adopt the MDSI name, allowing them to claim that the new MDSI shares both a common name and a heritage with the original company. (Technically, of course, the new MDSI is an entirely new and different company, and is neither a successor to, nor affiliated in any way with, the original MDSI, Schlumberger, or Applicon.)

The Big Idea behind the new company is open architecture for CNCs (computer numerical controls) on machine tools. What makes this Big Idea different from other Big Ideas about open-architecture CNCs is that openness is seen from two distinct angles. They see openness as a new approach to connecting a machine to its control device, on one hand. On the other, they see openness as a new approach to connecting a machine tool to the rest of the shop or factory via an integrated network.

So Hutchins and Nourse set out to develop a common machine control that would provide management with real-time data needed to make informed decisions about how best to manage the manufacturing process. It was clear the personal computer (PC) would provide the low-cost computing platform needed to support an integrated manufacturing environment. The vision was that machine tools would no longer be isolated islands of automation but would become on-line peripheral devices controlled in real-time by PCs on the company-wide network. Unbundled software systems, not special electronic hardware, would control machines and production just as PCs control other operations of a manufacturing business.

Their concept of physical and functional integration of factory equipment with enterprise-wide computing systems requires an "open, modular architecture control" on the machines. To this way of thinking, existing proprietary hardware-based controls are the antithesis of openness needed for fully integrated systems. The product conceived to accomplish this vision is what MDSI has named OpenCNC. This product was intended to be the machine control software that would one day serve as the software foundation upon which their vision for the factories of the future could be realized. After four years of development, the OpenCNC software was ready for factory testing in August, 1993.

What sets this approach apart from other approaches to open architecture is that OpenCNC is a completely software-based CNC control. It is designed to eliminate end-user dependency on proprietary hardware—including PC motion control cards. According to the company, the servo-loop is closed entirely in software running on a single Intel processor on a standard Intel motherboard.

All of the servo motion control algorithms traditionally performed on the motion control card are a part of the software that executes on this standard Intel processor in the PC. OpenCNC is optimized for real-time processors, which the company says enables them to avoid using specialized digital signal processors favored by some open-system vendors.

OpenCNC is currently being used in production on a variety of machine tools, including two- through five-axis machining centers; two- and four-axis single- and multi-spindle lathes; dual-station grinders with integrated part handlers; and three-axis gear hobs.

According to Jim Fall, MDSl's vice president of marketing, companies are showing strong interest in OpenCNC for both retrofit of existing machine tools and new machine tools. "A lot of manufacturers have machine tools that can still make good parts, but they're saddled with obsolete, unreliable or dead controls," he explained. "The implementation of OpenCNC allows companies to extend the useful productive life of their machine tools."

One machine tool builder working with MDSI is The Monarch Machine Tool Company (Cortland, New York)[now Genesis Worldwide]. Robert Skodzindsky, Monarch's vice president and general manager, says his company has a strong interest in control flexibility for machining centers. Monarch currently offers different proprietary controls with various machining center models, but is investigating open architecture CNC such as MDSl's control software.

Mr. Skodzinsky said that both current and future owners of Monarch equipment could benefit from having a broad range of control options. With thousands of Monarch CNC machining centers still operating after twenty or more years in the field, he said, it makes sense to investigate open-architecture retrofitting.

At a recent trade show, Monarch's new PMC V-750 was shown with OpenCNC. This machining center performs operations traditionally handled by three types of machining centers: vertical, horizontal and universal. An infeeding column serves as the Y axis, while a vertical X-axis table creates a hole where the compound table is normally located, allowing large parts to be mounted on the vertical face.

According to Charles Hutchins, solving the short-term needs of reducing CNC costs and improving overall machine tool reliability is important but the larger benefit comes from providing a bridge to integrate the factory floor. "The ultimate goal," Hutchins explained, "is to enable open access to manufacturing data throughout the enterprise. Certainly, manufacturers want a more open solution for controlling their manufacturing by leveraging the information generated by machine tools throughout the business."

Mr. Hutchins continued, "Machine controls, apart from their value as controllers of machine tools, have the potential of being collectors of critical manufacturing information, from cycle times and feed rates to setup and SPC data. Manufacturers need this information—in real-time without operator intervention—if they're going to continuously improve their processes to increase quality, lower costs and reduce time to market.

"People in the industry are saying that a real-time distributed manufacturing information system is on the horizon," Mr. Hutchins said. "We believe it's much closer." He believes that OpenCNC is the type of control that manufacturers need to collect and distribute information throughout the enterprise, noting that such controls are already driving machine tools in production on the plant floor.