While manufacturers prize operational flexibility, the reality on the production floor traditionally falls short. For example, consider part fixtures, those dedicated, inflexible devices that clamp and locate parts to be machined, says Lamb Technicon's Philip S. Szuba, director of research and new product development. Traditionally each part size and shape requires a special fixture.
"If an automotive company wants to build a manufacturing system to machine a particular cylinder head, conventional practice is to design a work-holding fixture specifically for that one part," Szuba says. "At a cost of $40,000 to $50,000 each, these dedicated fixtures pose both operational and strategic constraints on production flexibility and profitability.
"Consider that for a manufacturing system making hundreds of thousands of parts per year, multiple dedicated fixtures, maybe a hundred or more, would be needed."
The demand escalates as parts are refined or redesigned, Szuba says. On today's production floors it's a given that any change to a part obsoletes the fixture intended to hold it during processing.
"Any time you retool a line, you're generally discarding all your tooling and all of your fixtures."
To combat this, Lamb Technicon, Warren, Mich., has developed the Intelligent Fixturing System (IFS), a solution that is flexible enough to accommodate part families. The technology was patented in 2001, and manufacturers in the auto industry are using prototypes of it. (Lamb Technicon declined to name the companies using the prototypes.)
Szuba says Lamb Technicon's IFS technology will benefit a user's process, product and even business strategy.
In terms of the process, IFS will accommodate families of non-identical parts instead of being specifically limited to a part of one shape and size. Intelligent Fixtures automatically reconfigure themselves to hold any member of a predetermined part family, Szuba says.
"The customer that would buy one of these systems can run multiple parts with the fixture in an automated fashion," he says. "The operator only needs to load the parts on a very simple conveyor, and the IFS takes care of the rest. The operator doesn't even need to know what he put into the system because a vision system takes care of the identification."
The technology also removes a design constraint from parts destined for fixturing. "Conventional fixtures require that part designs include features -- fixed, mechanical locating holes or pads -- whose only purpose is to assure proper contact with the fixtures," Szuba explains. "With IFS technology such features no longer need to be designed into the parts." From an enterprise management viewpoint, Szuba sees the flexibility of IFS contributing to increased business potential by enabling new competitive strategies.
"With IFS, an automaker can more easily and inexpensively switch to machining the engine that [customer] demand dictates. After all, yesterday's market forecasts are not always accurate. Also without manufacturing flexibility, it's impossible to participate in the trend toward mass customization. Adding production flexibility will help the automakers accelerate the switch from make-to-stock to make-to-order."
Szuba notes that manufacturing experts consider the dedicated nature of fixturing the main barrier to the implementation of truly flexible machining systems for automotive parts. He says completely flexible machining systems will enable automakers to start producing vehicles with low-volume demand (less than 50,000 annually).
Lamb Technicon's largest customer segment is the auto industry, but the company says its new technology also will benefit the entire machine tool industry and other sectors that use machine tools or perform processing requiring fixturing.
"No longer will it be necessary to schedule production equipment to produce [machine] the fixture locating features on parts. By eliminating the need for those nonfunctional locating features, users of the Intelligent Fixturing Technology should find it possible to get by with fewer machines or increase output by reassigning production time.
"For automakers, per-vehicle savings could range from $30 to $50, depending on the power-train option."
He estimates annual industry savings from $450 million to $750 million based on an annual domestic production of 15 million vehicles (both cars and trucks). For machine tool users alone, Szuba estimates annual fixturing cost easily exceeds $600 million -- for both new and existing equipment.
The basis of Lamb Technicon's system is a flexible clamping system incorporating a unique "bed-of-nails" device that allows parts to be held in any orientation. "Bed-of-nails" describes a series of air-actuated pins in the fixture that conform to the external shape of the part. The clamping cycle concludes with the IFS mechanically locking the pins against the part. What makes the device unique is the very high static stiffness, its compactness and the ability to be applied to harsh machining environments, says Szuba.
With the IFS technology the position of a part is not determined with great precision either before or during the clamping cycle. However, after a part is secured, a part location system precisely locates the part. With the difference between the actual and desired position of the part known, a micro-positioner works with the machine tool control to correct misalignments. Lamb Technicon's challenge was to integrate all those elements into a fixture configuration station. Here the fixture is configured automatically to service whichever member of a predetermined part family is presented to the machining system.
Research activity in devising flexible fixturing systems predates the work of Szuba and Peter M. Beecherl, assistant manager of research and new product development. Previous efforts in designing and developing flexible fixturing for either small batch manufacture or mass production scenarios fall into two groups-modular fixtures and conformable fixtures, says Beecherl. Modular fixtures originated in the post-war era and consist of a library of elements such as V-blocks, toggle clamps, and locating blocks. Their flexibility lies in their ability to be reconfigured either manually or by a robotic device.
However, the modular fixtures have no intrinsic ability to adapt to different sizes and shapes of parts within a part family. In addition, the time necessary for reconfiguration is long, and modular fixtures generally lack stiffness. Consequently, modular fixtures appear to be more suited to a job shop environment than mass production, says Szuba.
Beecherl says examples of the conformable type are found in the aerospace industry where low melting-point metal is used to enclose turbine blades and produce well-defined surfaces for part location and clamping for grinding operations.
Lamb Technicon's research on flexible fixturing began in 1996, says Beecherl. The company established a concept and applied for government funding through the National Institute of Standards and Technology's (NIST) Advance Technology Program. Recognizing the broad-based potential for U.S. manufacturing, NIST provided funding of $2 million. NIST's rationale: The technology could benefit any high precision, discrete parts-making operation. Beecherl stresses that the technology's potential isn't limited to metal cutting or even processes involving metal.
With the NIST-supplied funding, Lamb Technicon subcontracted sub-systems of the IFS to a university consortium called the Machine Tool Agile Manufacturing Research Institute. The participants: The University of Illinois-Urbana/Champaign, Georgia Institute of Technology, Pennsylvania State University, and the University of Michigan.
Lamb Technicon also partnered with Mitutoyo America Corp., Aurora, Ill., to incorporate shop-hardened coordinate measuring machine technology for part location. The company plans to display the system at next September's IMTS 2002 (The International Manufacturing Technology Show) in Chicago.
