Producers of machined components and manufactured goods are continually challenged to reduce cost, improve quality and minimize setup times in order to remain competitive. Frequently the answer is found with new technology solutions. Such is the case with grinding where the traditional operations involve expensive machinery and generally have long manufacturing cycles, costly support equipment, and lengthy setup times. However, the grinding process itself may require several machine tools and several setups to finish all component surfaces. Because grinding can be a slow process with low material-removal rates, there has been a determined search for replacement processes
The newer solution is a hard turning process, which is best performed with appropriately configured turning centers or lathes. Hard turning really started to develop at the beginning of the nineties. The reason for this was the availability of new tool materials and the capability of designing a turning machine that was rigid, stable and accurate enough to successfully finish hard turn. The result of these developments have made finish hard turning a viable alternative to grinding, as an accurate finishing operation.
From an applications standpoint, hard turning is very much a part specific process. It excels at cutting complex geometries that contain intricate arcs, angles, and blended radii. Instead of having to buy a form wheel for the grinder, you can program the lathe's single point much faster and cheaper.
Hard turning can eliminate several types of grinding, as well as lapping and other finishing operations. Not only is removing steps from the process money in the bank, but, for some, it can also mean bringing outsourced work back under their roofs and under their own control.Hard turning is a way to achieve high machining efficiency in an environmentally-acceptable manner and a new technology to machine hardened parts processed by forging or casting. Compared with grinding, hard turning can machine some complex workpieces in one step. The machining cycle time of hard turning can be up to three times faster than grinding. Hard turning also consumes about one-tenth of the energy per unit volume of metal removed than grinding and is more environmental friendly
Hard turning yields very little scrap and minimizes rejected parts. Because it uses the same coolant as soft turning, adding another coolant and its associated waste stream is unnecessary. Better still, hard turning can make cutting dry an option, letting you avoid the expense and waste products of coolant altogether. Hard turning also eliminates annoying grinding slag-and the labor-intensive, cost-laden tasks of recycling and disposing of it.
Hard turning is a developing technology that offers many potential benefits compared to grinding, which remains the standard finishing process for critical hardened steel surfaces. To increase the implementation of this technology, questions about the ability of this process to produce surfaces that meet surface finish and integrity requirements must be answered. Additionally, the economics of the process must be justified, which requires a better understanding of tool wear patterns and tool life predictions.
Hard turning is best accomplished with cutting inserts made from either CBN (Cubic Boron Nitride), or Ceramic. Since hard turning is single point cutting, a significant benefit of this process is the capability to produce contours and to generate complex forms with the inherent motion capability of modern machine tools. High quality hard turning applications do require a properly configured machine tool and the appropriate tooling. For many applications, CBN tooling will be the most dominant choice. However, Ceramic also has a role with this process. CBN is best suited to tolerances under .001" while ceramics can play a roll in tolerances of .001" and above.