Five best bets

March 1, 1998
Five research projects are shaping the future of machine-tool technology.

Five research projects are shaping the future of machine-tool technology.

This poster illustrates the 1996 advances made with cluster spindles. The research was done through the Strategic Machine Tool Technologies:Spindles project.

The M-1000V high-pressure, high-volume coolant system blasts fluid to the chip-tool interface for faster cutting.

Sandia researcher makes an 11-in. mini skyscraper using the Laser Engineered Net Shaping (LENS) technique.

The Viking grinder from Cincinnati Milacron is the end result of an advanced centerless grinding reaserch project that involved several companies including the National Center for Manufacturing Sciences.

When manu-introduce a new product—be it a cutting system, grinder, spindle or something else—they are often showcasing the products of thousands of hours of research and development.

Historically, R&D projects have led to innovative new products that raise industry standards and expectations by breaking records in time, accuracy, and cost. Witness advances in high-speed cutting or dry machining for example. What tomorrow's breakthroughs will be is anyone's guess, but here are five research projects that have already, or soon will, improve shop production.

Strategic Machine Tool Technologies: Spindles
For competitive manufacturing of high-quality parts, the spindle is the most critical component of a machine tool. During the last decade, the push toward higher cutting speeds, faster spindles, and greater power has also created a host of new problems: limited bearing life from higher bearing temperatures and greater loads; difficulties in maintaining part accuracy from increased shaft thermal expansion; loss of bearing preload; and greater sensitivity to imbalance.

However, a project called The Strategic Machine Tool Technologies: Spindles is working to address spindle weaknesses. Spearheaded by the National Center for Manufacturing Sciences and companies including Giddings and Lewis, the project is working on advancing cutter technology.

The project aims to develop motorized, ultra-lightweight spindles with 35 to 150 hp and clustered spindles in the center-tocenter range of 40 to 120 mm. It began in June of 1994 and has already had great success.

In 1996, the NCMS spindles team built and tested three prototype spindles that raised machining performance benchmarks.

In addition, tests of new spindle-drive technology have shown torque levels and speed ranges that allow efficient cutting of both steel and aluminum, making it possible to use one versatile spindle in place of two specialized spindles. Also in multispindle applications, tests have shown that new self-compensated bearings, lubricated with cutting fluid, have exceptional stiffness and dampning characteristics.

The technical objectives for the cluster spindle have been met. Stiffness at the cutting tool has increased so that the current process for the gear carrier test part could be performed in one operation rather than three. Quality also increased as measured by statistical parameters for hole diameter, squareness, and true position.

More recently, tests of a 75-hp rolling element spindle indicate that project goals for spindle size, weight, and torque-speed will soon be reached. This will result in a compact spindle with unmatched torque over a speed range from 500 to 12,000 rpm.

The rolling element, 75-hp spindles are supported on modified tapered roller bearings lubricated by a jet system. The motor is a permanent magnet brushless DC design with a special winding configuration. On a milling cut taken on a cast iron engine block, the cut drew 220 amp peak to peak while roughing surfaces. The 35-hp spindle is designed to run to 20,000 rpm. Dynamometer tests have been completed and cutting tests are scheduled in March.

Giddings and Lewis executive project manager Bruce C. Cuppan says the company got involved in hopes of using new spindle technology on its equipment. "The Giddings & Lewis goals were to further develop our knowledge and expertise in the areas of this project and to eventually acquire additional small size, high-power, high-speed spindles to enhance our product offerings."

Giddings & Lewis contributed to the project, according to Cuppan, in two ways. First G&L brought real-world experience and knowledge of applying spindles to machine tools. Secondly, he says, "We provided a machine tool to serve as a platform for the testing and the practical knowledge."

Nanomaterials for better inserts
Material research is being done in regard to nanomaterials at AB Sandvik Coromant headquarters in Sandvikin, Sweden. The company is working on a project together with the German Institut für Neue Materialen in Saarbücken. The objective of the re-search is to study property changes in current metal-cutting materials when nano-particles are involved and also to increase knowledge about the actual development of nanostructural materials.

According to research director Goran Berter, the timeframe for the project is currently unknown and depends on what other re-search is being conducted. "There are different activities going on globally and the interest in nanomaterials will determine the development of all related projects." The company feels that the re-search can be used in metal-cutting applications.

Nano signifies 10 9 m (nm). A nano-material is built up from elements and can be constructed of a range of a few to 100 nm particles. Normal material used today such as aluminum, silicon nitride, or carbide is made from elements 10 6 m (µm).

Using smaller particles increases hardness and in ceramics, for example, can make them plastically deformable. However, working with nanomaterials poses some problems because of the small size of the raw material powder and its chemically reactive nature. The smaller particles also have a tendency to agglomerate instead of taking on an even distribution pattern.

"Right now we are attempting to stabilize materials so we will be able to more easily handle them," says Berter. The task at hand in the research is to use colloidal and surface chemistry to modify the surface of nano-scale particles so that they can be handled under normal conditions and eventually processed to create the microstructural materials. The technique for modifying the particles involves the use of short-chained organic molecules to stabilize the surface through electrostatic or electrosteric means.

The project is working on combining different nanoparticles into micron-sized aluminum and silicon as a reinforcing agent. "We use these particles to improve the strength of the material. We could then improve the productivity when machining heat-resistant materials, hard components, and cast-iron," explains Berter. The influence of these particles on mechanical properties will then be evaluated.

Cutting with high-force coolant
ChipBlaster Inc., in association with Castrol and the Fraunhofer Resource Center in Massachusetts, is investigating the effects of high-pressure and high-volume coolant in metal removal. The project goal is to remove barriers that slow metal-cutting speed and affect reliability. Researchers are testing the hypothesis that properly applied high-pressure/high-volume coolant can have a significant positive effect in removing heat, reducing tool breakage, and limiting lubricity problems.

Castrol estimates that during machining coolant doesn't hit the part or the tool roughly 40% of the time. Even when coolant is prop-erly directed, there is often so much heat that the coolant boils away before it can reach the chip tool interface where metal is cut.

Tests are now being conducted on a new coolant system that causes a localized pressure increase. A large amount of liquid is forced into a cutting zone to remove heat-with no vapor formation because of the pressurization. This mass of liquid provides lubrication and flushes chips away from the cut.

Testing is tightly controlled to determine the exact effectiveness of high-pressure coolant in differing situations. The intent of this study is to regulate as many elements of the process as possible. The high-pressure and high-volume coolant phase uses turning tools, milling cutters, and inserts (composition and geometry) specially designed for low-temperature, high-speed metal cutting. The coolant type and concentration, coolant temperature, pressure, volume, direction, and coherence are all controlled.

A representative series of tests were conducted on a Haas HL-2 turning center. The objective was to compare performance of the cutting process with and without this coolant system. Aluminium, 4140 steel, and Inconel 718 were chosen as cutting materials due to their inherent qualities and well-documented machining history.

The turning tool was set up with a solid-carbide insert, spec. C2 CB 737 CNMG - 432. 4140. On steel, at a feedrate of 0.25 ipm, depth of cut 1 mm, and a cutting speed of 1,000 sfm, a tool life of 443 feet was achieved. This test did not use any cooling fluid. Spiral chip formation, with an average length of 5 in., was observed.

Using the same machine parameters, but introducing the coolant at 880 psi, researchers marked a 13-fold increase in tool life, and over 5,880 ft was achieved. Very small, slightly curled chips were formed, averaging 0.125 inches in length.

Results from all tests have proven successful so far, and the new turning tools allow faster metal cutting with the coolant focused at the chip-tool interface. The coolant system is commercialized and is available through ChipBlaster Inc.

Creating a complex metal part in a day
Commercialization of a possibly pivotal manufacturing technology is the goal of ten companies teamed in a $3 million, two-year agreement with Sandia National Laboratories. LENS—Laser Engineered Net Shaping—uses computer-controlled lasers that, in hours, weld air-blown streams of metallic powders into custom parts and manufacturing molds. The technique produces shapes close enough to the final product to eliminate the need for rough machining.

While the technology has worked in Sandia's laboratories, the purpose of the Cooperative Research and Development Agreement (CRADA) is to produce an industrial tool that works automatically, robustly, and without constant supervision.

When perfected, LENS should provide CRADA companies a lead of several weeks in bringing to market new products, as well as the capability to quickly vary the shapes and materials of products as market conditions shift.

The purpose of LENS is to make small lots of high-density parts or molds, a difficult operation because high temperatures make it hard to form accurate, smooth objects from molten metals.

Nozzles each direct a stream of metal powder at a central point beneath them. Simultaneously, that point is heated by a high-power laser beam. The laser and jets remain stationary while the model and its substrate are moved to provide continually new targets on which to deposit metal.

According to Duane Dimos, manager of Sandia's Direct Fabrication Department, "The process produces materials with outstanding mechanical properties — very high strength and high ductility." Another plus, he says, is the process's ability to mix powder streams of different materials.

"Our goals are to make intricate material combinations in complex geometries out of hard-to-ma-chine materials," says Jon Mun-ford, manager of the Mechanical Engineering Department.

Problems to be worked out include dimensional accuracy and better finish on the metal. The finished product now has a slightly corrugated surface.

Advanced centerless grinding
Back in 1994, the National Center for Manufacturing Sciences, along with several companies including Cincinnati Milacron, Cincinnati, set out to design and build centerless grinders with advanced performance features and validate improvements on prototype machines in a production environment. This project recently left the research labs and made it onto the production floor.

Because of the increasing industry demand for precisely ground cylindrical parts, the project aimed to lower the purchase price of grinding machines as well as increase machining accuracy, reduce required floorspace, boost cutting power, and expand the capability to implement superabrasive technology efficiently. All objectives for required stiffness, superabrasive capability, and low cost have been met.

The benefits of the research include the design of a centerless grinder that costs $200,000 rather than $500,000. Accuracy specifics on this grinder are characterized by the ability to hold a 10 min. tolerance on diameter in high production runs. This is a factor of two-fold improvement over machines built around the start of the project. By using cubic boron nitride or diamond grinding wheels, machines are stiffer and deliver twice the cutting power of comparable systems.

The commercial derivative of the machine called "Viking," built and marketed by Milacron, occupies almost half the floorspace of comparable machines.

Kevin Bevan, project manager, says Milacron plans to individually continue grinder development. "We are working on doing open-architecture and electrical developments on our own with another company."

Bevan feels that the project has been beneficial, helping his company come out with a unique product. "The program met our goals. It was the collaboration between NCMS, the other companies involved, and the customer input that made this machine better than anything we could have designed on our own. This program helped us develop a state-of-the-art grinder that puts us a step ahead of everyone in the business."

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