Ceramic Fills Gap between Aluminum Oxide and Superabrasives

Grinding shops are faced with a triple threat. The first is the appearance of harder more wear-resistant alloys, which are tough to grind and easy to burn. Next comes automation- CNC grinders need unattended operation and maximum uptime to provide a reasonable payback. Third is steadily rising customer expectations, especially in the areas of delivery and quality.

Such considerations inspired researchers to take a new approach to aluminum oxide. They could see that a niche existed for an abrasive which would exceed the performance of conventional aluminum oxide on ordinary drilling machines, at a price closer to standard abrasives than superabrasives.

Ceramics technology provided the answer. A manufacturing technique based on a sintering process enabled them to control the microstructure of the ceramic grains. The resulting non-fused aluminum oxide abrasive has substantially greater life than fused aluminum oxide products.

In use, the grains fracture along sharp crystal edges rather than flat crystal planes. As the grains fracture, new sharp edges are exposed.

The ceramic aluminum oxide can be used alone or mixed with other abrasives it can be used on ferrous and non-ferrous metals. Metal removal rates can be 50% higher than possible with standard aluminum oxide wheels. While the new type of wheels can take heavier infeeds than regular aluminum oxides, they are no harder on dressing tools than conventional abrasives. They perform best in oil or dry grinding.

Production grinding of end mils was one example of successful use of the wheels. There are 14 steps involved in producing the average end mill, and eight of them involve grinding.

Superabrasives such as diamond or CBN (cubic boron nitride) can produce astonishing productivity improvements, especially in applications involving hardened steels, tool steels and superalloys.

CBN, for example, retains its strength to more than 1000°C and doesn’t chemically react with steel. Finishes are excellent and the product has twice the hardness and four times the abrasion resistance of standard aluminum oxide.

Use of a wheel fabricated with superabrasives will not compensate for a machine in poor condition. The system must be checked for tight spindle bearings. Vibration must be eliminated. This is critical to wheel life, surface finish, and dimensional accuracy. In order to eliminate chatter the operator should closely fit machine slides. Spindle speeds must be steady and high. Vibrations in spindle speeds will reduce wheel life and cutting efficiency. Reliable feed system is necessary for long wheel life, surface finish quality and dimensional accuracy. At last, high volume of coolant should be delivered, either oil-based or dry.