For highest productivity, the goal is to increase the number of parts between dress cycles, or to reduce the dress depth (compensation), resulting in more parts per wheel and fewer wheel changes. A common approach to do this has been to try the latest and greatest conventional grinding wheel specifications in an effort to reduce wheel usage.
Increased demand from machine tool builders, as well as from automotive component manufacturers, for higher production is driving abrasives manufacturers to develop new vitrified cBN products. The new developments lower the cost per unit by making longer lasting, faster grinding abrasives with higher material removal rates.
Advancements in vitrified bond technology coupled with the correct choice of superabrasive grain provide better form holding while grinding at the same or lower power. This is a key benefit because new advanced materials such as High-Velocity Oxygen Fuel (HVOF) coatings are being introduced for today’s gas engine components. It is also important that the risk of introducing heat into the part be eliminated to meet the changing needs in grinding.
The need for reduced stress or even stress-free grinding is pushing abrasives manufacturers to develop new, sharper, freer cutting superabrasives. New cBN grains that resist dulling and stay sharper longer, provide higher material removal rates (Q’) and also grind more efficiently. These grains require a much lower energy-to-grind ratio and self-sharpen, making them freer cutting, resulting in lower residual part stress after grinding.
Coupling these new grains with newly developed bond technologies help the grains achieve maximum performance. The new bond system has far better grain retention, allowing the wheel to hold form longer, allowing the cBN grain to work as intended by maximizing its potential and performance.
The ever-expanding usage of wear-resistant materials and the need to finish them requires abrasives that are more durable.
For example, the finishing of ceramic coatings that are applied to provide wear resistance, make superabrasives a good choice to grind these materials economically.
Although vitrified cBN is still the most common technology, we are seeing more plated and MSL (Metal Single Layer) options and opportunities for operations with complex forms and geometries, where higher stock removal and reduced cycle times are required.
Superabrasive product selection is process driven. Part geometry, stock removal, and finish requirements, as well as the material being ground, all help determine the grain size and type, the grade, concentration, and bond.
Some of the main factors used to help manufacturers specify the proper grinding wheel are:
Proper coolant type should also be considered. Coolant removes the chips and heat from the grinding zone, while protecting against chemical reactions caused by the grinding process. Oil-based fluids are best when working with vitrified cBN to maximize wheel life. Low vaporization temperatures limit the lubricity of water-based fluids and the high-temperature steam promotes oxidation of the cBN crystal.
To help understand why there is a shift to superabrasives, it is useful to compare conventional and superabrasives to highlight the differences that make superabrasives more productive.
Companies such as Norton | Saint-Gobain offer process solutions that capitalize on the benefits provided by superabrasives.
These benefits include:
All of which deliver the performance and cost-saving advantages that justify the move from conventional abrasives.
The hardness and durability of the superabrasive also make it an excellent choice to grind hard and difficult-to-grind materials. In some applications, they also allow replacing machining operations. With the right product, finished parts can be produced from blank or solid stock by eliminating the machining operations in a process Norton refers to as “machining-to-grinding.”
It can be demonstrated time and again that selecting and properly utilizing the correct superabrasive can optimize the grinding process in most automotive related grinding operations. Converting to superabrasives can make the process more productive and offer greater cost-saving options than most conventional abrasives, including some of today’s premium conventional abrasive products.