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Design your own tools

Design your own tools

For a glimpse of tomorrow's machine tools, take a walk through any factory floor today. What you see, with a few hidden changes, is what you'll get in the future.

Fifty years from now, buying machining centers will be like buying a car. Order a standard platform, and load it with options. The actuator could be ball screws, roller screws, planetary roller screws, or linear motors. The structure might be steel, aluminum, or composites. Spindle and linear-guide bearings could use roller, ball, or hydrostatic technologies, all depending on the application. Other options may include temperature control to improve precision and repeatability, or active vibration control for reduced tool chatter and improved surface finish.

Operations such as turning, grinding, and milling will be integrated into automated manufacturing cells, machining centers, or transfer lines, much as they are today. But, according to Charles Carter, V.P., Technology, for the Association for Manufacturing Technology, technological advances will give the manufacturing machines of tomorrow increased speed, efficiency, and accuracy, and make them more user and environmentally friendly.

Fifty years from now, the only occasion for hand machining may be for highly specialized parts. Most manufacturing applications will be computer programmed. Future machine tools may all be as easy to use as Cincinnati Milacron's Acroplace fiber-placement software. "Once setup is complete, operators will select the program, and hit cycle/start," says Jay Hisset, Milacron's supervisor of software development.

Harbingers of things to come. One of the best examples of existing technology that may shape manufacturing's future is the six-legged machine, popularly known as "Hexapod." During the last twenty years, the cost of controls has come down enough so that many companies now offer hexapod-based machines. Several companies--Ingersoll, Giddings & Lewis, Hexel Corp., and Geodetic--have developed hexapod prototypes.

U.K.-based Geodetic uses hexapod technology in its head-unit design to give dexterity comparable to the human hand. And soon, a production model of Giddings & Lewis' VARIAX, will be on its way to the United Kingdom for testing in a manufacturing research project funded by the IMI (Innovative Manufacturing Initiative).

Giddings & Lewis engineers claim that their VARIAX six-legged machining center exhibits at least twice the volumetric accuracy of conventional ma-chines. The machine has no prescribed axes, no linear bearings, and no way to introduce error. Having only axial forces--tension and compression forces applied at the joints, and no bending moments on the struts--improves the rigidity ten-fold over conventional machines. "Improving the rigidity improves the accuracy," says Steven Klabunde, head of engineering and R&D at Giddings & Lewis.

New components. The hexapod design changes the fundamental geometry of the ma-chine's structure, but the drive toward higher accuracies is forcing designers of conventional machines to turn toward new structural component designs and materials to increase rigidity and damping.

For example, in the future, finished-tolerance polymer castings will offer design flexibility and lower costs for many different applications. Polymer composite castings, suitable for precision machine applications, use a liquid resin and a polymerization agent, blended with mineral aggregates such as granite or quartz. "Varying the aggregate size minimizes voids and resin content, resulting in the best mechanical properties," says Terry Capuano, president of Willoughby, OH-based Precision Polymer Casting Co.

Polymer concretes can be used to replace large metal machining-center components such as the 80,000-lb base and column of Keene, NH-based Kingsbury Corp.'s Cyber-Cell. They can also be used to increase damping of machine tools as demonstrated by work at York, PA-based Weldon Machine Tool, Inc. Its 1632 GOLD CNC cylindrical grinder is itself a harbinger of things to come.

Weldon engineers and Professor Alexander Slocum of the Massachusetts Institute of Technology employed an epoxy replicant called VibradampTM from Philadelphia Resins. The composite is injected in and around viscoelastic covered structural tubes, designed by Slocum, to improve damping on the precision grinder.

The damped structural tubes, winners of a 1994 R&D award for one of the 100 most technologically significant new products, have doubled the accuracy of Weldon's precision grinder, according to Weldon engineer Jim Flinchbaugh.

The design, used in the base of the grinder, enables engineers to highly damp a structure without imposing strict limits on the structure's geometry or materials of construction. Tests have shown that the ShearTubeTM damper can decrease amplification at resonance of a metal beam from 500 to 20.

According to Slocum, the tube design uses a thin film of viscoelastic material that dissipates energy at a rate orders of magnitude higher than most designs. And coolant can be circulated through the hollow tubes providing thermal stability for added precision.

Weldon's machine gives us a glimpse of some coming attractions in the future of machine tool design, including:

- Superior damping for greater speeds, productivity, and accuracy

- Thermal stability for high-precision repeatability

- Higher stiffness for finer surface finishes

- Easy-to-use software

- Faster controls designed for low friction and high speeds

- Self-cleaning, no-wear, hydrostatic way bearings.

Next-generation machines. Machine tools will evolve incrementally, each generation producing better parts for the next wave of machines. Consider NY-based Thomson Industries' Accumax linear roller guide, introduced in 1990. The patented crown profile raceways were waiting for the advent of CNC precision grinding. "Advances in grinder technology enabled a crowned profile raceway design," says Thomson engineer Greg Lyon. In this same way, Weldon's grinder will improve future components for the next generation of machine tools.

The days of inertia-dominated machine tools are over. Rapid traverse rates have increased from 600 ipm to more than 2000 ipm. For design engineers, this means low-inertia components for high-performance machines.

Rapid traverse rates of the future present a paradox for linear-guide designers. At first glance, increasing both the accuracy and crash resistance, while minimizing the system's mass, seem at odds. The paradox: Accurate, robust guides generally require additional elements (balls or rollers), hence increased weight. And faster guides usually have fewer elements to reduce weight. Hydrostatic bearing technology has evolved to address this paradox.

Weldon's CNC cylindrical grinder uses an improved linear hydrostatic bearing, based on a design by Slocum. The HydroGuide(TM) machine tool slide offers innovative features that cut manufacturing costs, making the technology more practical for commercial use.

The hydrostatic pad consists of two sections: a compensator and a load-bearing pad. Fluid pumped through a hole in the compensator flows outward to an annular ring, where it drains to the opposite load-bearing pad at a rate proportional to the cube of the pad-rail gap. The result: Water flows automatically to the pad with the smallest gap.

The heart of machine tools. Two spin-offs of self-compensating hydrostatic bearing technology are impacting future spindle designs. Global competition demands high speeds and accuracies for competitive manufacturing. According to Weldon's Flinchbaugh, research shows many materials, such as ceramics and advanced alloys, hold better dimensional accuracy and finishes if they are processed with high-speed techniques such as creep-feed grinding.

Better bearings make better spindles, according to Slocum. Conventional hydrostatic bearings provide high load capacity, stiffness, damping, and accuracy; but manufacturing costs are usually too high, and shear power losses are usually unacceptable at high speeds.

The HydroSpindleTM, marketed by Concord, NH-based Aesop Inc., is well suited to high-speed spindle designs. Hydrostatic circuitry, milled onto the spindle shaft's surface, meters fluid flow by collecting and channeling it to a pocket region on the opposite side of the shaft. The system's properties are optimized for any existing radial clearance. Stiffness and flow are a function of bearing gap and fluid-supply pressure, while load capacity is a function of supply pressure.

The HydroSpindle uses a picture frame pocket that leaves a central land region intact to improve damping, dynamic stiffness, and crash resistance. The design reduces turbulent shear-power losses, and water or coolant can be used for maximum thermal control and overall system simplicity.

Another spin-off impacting future machine tools is called the TurboToolTM. Also developed by Aesop Inc., the TurboTool design eliminates the tool holder by supporting the tool shaft with water hydrostatic bearings. An hydraulic turbine drives the tool at rotational speeds up to 100,000 rpm with power to 100 kW, says Dr. Kevin Watson, Aesop engineer.

"The design, a low-cost, high-performance, hydrostatic-bearing spindle, has been applied successfully in our spindle development project," says Jim Albus of the National Institute of Standards and Technology (NIST).

A key design element is the radial, self-compensating bearings, formed directly into the tool shaft. High-pressure coolant, fed directly to the radial bearings through a central pressurized annulus, gives the tool high load capacity, stiffness, and damping, according to Wasson. High-pressure coolant, fed to the rear, non-contact thrust bearing, enables the tool to support high drilling loads.

How long will engineers and factory managers have to wait for these innovations? No one can guess when they all will appear, but this much is certain: Today's factory floors embody the basic designs of things to come, and provide a working crystal ball for what lies ahead.


COMING ATTRACTIONS

- Fiber-placement systems

- Superior damping for greater speeds, productivity, and accuracy

- Thermal stability for high-precision repeatability

- Higher stiffness for finer surface finishes

- Active vibration control

- Easy-to-use software

- Faster controls designed for low-friction and high speeds

- Self-cleaning, no-wear, hydrostatic way bearings


PREDICTIONS FROM THE PAST

- Fifty years ago, Europe and Asia were looking for food and clothing after the war, not for industrial machines. And manufacturers were replacing their older machines with war surplus, making machine tool sales their lowest since the Depression, according to Charles Pollock of the Association for Manufacturing Technology.

- At the 1947 IMTS, the first since 1935, machine builders introduced the most advanced machine tools ever. Industry promoted the new capabilities these machines provided and envisioned increased productivity, raised standards of living, and new wealth for future generations. The 1947 IMTS was one of the most successful shows ever, even by today's standards, according to Pollock.

- In 1950, the Korean War broke out, and once again there was a machine tool shortage.


COMPONENTS TO WATCH

- Software control devices

- Flat-panel displays

- Field buses

- Sensors and probes

- Metrology devices

- High-speed, low-inertia actuators

- Planetary roller screws

- Linear motors

- Hydrostatic ways and spindles

- Tool holders

- Smart programmable motors

- Switched-reluctance motors


TECHNICAL HURDLES

- Designing crash/corrosion resistance into components for longer life

- Performance improvements to achieve higher speeds and accuracy

- Crash energy management with robust components and faster controls

- Temperature control for improved precision repeatability

- Open-architecture definition and implementation

- Field Bus standardization

- Modular design of bolt-for-bolt compatible components


THE ENGINEER'S ROLE

The premier machine tool companies of the future will employ engineers with knowledge in materials, process, and manufacturing, according to Peter Zuska of Farmingdale, NY-based American Laubscher Corp.

The engineer must understand molecular structures and physical properties of the materials used in manufactured products. Understanding how the materials react under various conditions will help engineers design products for efficient manufacture.

Engineers will be designing more inexpensive, commodity-type products, rather than one-of-a-kind products. Experts agree, selling millions of commodity-type components for $1 makes better business sense than selling one product for $1,000,000.

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