Abrasive machining to win bigger metalworking role.

Manufacturing engineers and production managers must achieve increasingly tight tolerances--geometry, surface finish, surface quality, and consistency--and they must do so with harder, difficult-to-grind materials at ever-higher productivity rates. The combination of harder materials, containing higher-temperature alloying materials, and tighter tolerances will lead to a greater reliance on abrasive finishing processes.

The functional quality of the workpiece--especially wear parts--is highly dependent on the microstructure of the material at the surface and on the tolerances of the geometry and other surface features. This dual requirement for closer control over surface quality, as well as the surface features themselves, will become even more important as demands increase for better component performance.

When gears are produced with closer tolerances, they roll on each other more easily, with less noise and less frictional loss. That means the gears themselves can be lighter weight. But, for lighter weight gears to last longer, surface quality must be better than ever. The same applies for camshafts, crank shafts, and cutting tools--all are now being made from higher-strength, wear-resistant alloys and, hence, are more difficult to machine.

Manufacturers are also required to achieve greater productivity. This translates into a minimum of interruptions for setups, wheel changes, and wheel dressing.

Abrasive products

Abrasive selection is key to achieving tighter tolerances and consistency. Abrasive selection revolves around evaluation of the four components of abrasives--the abrasive material itself, the bond (matrix for holding the abrasives for their optimal use), porosity (enhances the interactions in the grinding zone), and design (to achieve the desired form and function). Advances are being made in each of these areas, leading to new products and applications. One result of these advances in abrasive products is the highly permeable TG2 grinding wheel developed by Norton Co. Designed to minimize frictional losses in the grinding zone, it is made from a filament-shaped, advanced ceramic grain and incorporates new developments in grain, bond, filler and design technologies.

Porosity content, for example, is related to permeability for entry and penetration of coolant into the grinding zone, through the grinding wheel. Higher permeability translates into better cutting efficiency and less metallurgical damage to components. Milling operations, which are difficult to set up and run efficiently can now be performed with these highly porous and efficient grinding wheels. They are particularly efficient in profile grinding.

Significant improvements are also being made in coated abrasives and superabrasives. Surfaces being prepared for electroplating, for example, require more consistent surface quality and texture than ever before. A new coated abrasive product, engineered with a unique, three-dimensional structure (called NORaX by Norton Co), achieves this surface finish.

As manufacturers push for greater productivity, they will increasingly look to high productivity abrasive finishing tools, such as cubic boron nitride (CBN), especially for large-volume production operations. The combination of CBN and CNG controlled machines is proving to be effective in many production grinding applications. While there will be notable application of hard turning for small lots or simple geometry parts, there will be increasing reliance on high productivity grinding processes for high volume and closer tolerance parts.

Ultra precision finishing

There also are developments in abrasive finishing processes themselves. For example, in traditional processing, grinding is followed by loose abrasive lapping or polishing. Now, these two processes are being combined into a one-step grinding operation. Developments in finishing electronic components (e.g. , read-write heads and microchips) are leading to enhancements in finishing metallic components. Surface finishes measured in nanometers in electronic ceramic components will be achievable with metallic components. Now, such finishes can be achieved only through lapping and polishing. Soon, they will be achievable by grinding alone.

With increased emphasis on the environment, manufacturers are looking to eliminate use of multiple coolants within a plant. Serious efforts will be made to reduce the wasteful application of coolants. Elimination of mineral oils as coolants will continue to be the goal.

Grinding systems

Information technology also is becoming more of a factor in the improvement to grinding systems themselves. Grinders will be equipped with more powerful controllers, sensors, and data acquisition systems. As a result, complex grinding cycles, including complex contours and multi-axis grinding operations, will be monitored with real-time process control and database management systems. The result will be fewer machine setups and minimal downtime.

There also will be a much more integrated approach to managing the grinding process itself, with abrasives manufacturers, machine tool builders, tooling and coolant suppliers, and end customers all playing a role.

There will be a focus on surface generation solutions where abrasives and other consumables will be integrally linked to the grinding process itself, with day-to-day management of the process based on real-time information. Abrasive suppliers, for example, are already taking their process data to machine tool builders with recommendations for process innovations.

The "black box" approach to grinding processes is already a thing of the past. In the grinding system, input of every kind--machine tool, work material, abrasive product, and operational factors--will be measured, monitored, and analyzed for causal relationships and adjusted through scientific principles to achieve both improved technical and economic output. In the process of deploying such technology, the separation between vendor/supplier and end user will dissolve.