The process of grinding was at one time the preferred method of producing workpieces with very high tolerances before the development of high-precision hard turning machines. Thanks to both new technologies and careful designs, these precise turning centers are able to produce results that are comparable to grinding.
It can be argued that these high-precision turning centers are a more economical and practical purchase than a specialized grinder, purchasable at a lower cost and offering a more flexible, broader range of processes.
These machines repeatedly achieve accurate results, having been precisely designed to turn hardened materials with the use of off-the-shelf ceramic and CBN cutting tools.
Just one machine and its operator are needed in the hard turning process, resulting in the production of high-precision parts at a faster throughput rate. This simple, practical process results in a lower cost per part.
The result of these merits is that hard turning has become more commonplace around the world and replaced many traditional grinding processes.
Though for many, grinding is still the preferred method for certain applications or organizations – as in the creation of medical parts, long and thin items, or components requiring tolerances less than ±0.0002 inch – its myriad benefits indicate that hard turning should not be dismissed as a frontrunner in the field.
The process of hard turning usually refers to the use of a lathe or turning center, using single-point turning tools to process materials that have hardness values over 45 HRc. These values are usually in the 58-68 HRc range.
This process can produce grooves and contours, even high precision threading, in a single chucking, by virtue of using single-point cutting and turning.
Indeed, when used as a replacement for grinding operations or as a pre-grinding process, hard turning can be used with success on complex materials like case-hardened steel, steel alloys and sintered tungsten carbide.
Benefits of Hard Turning
- Cost Savings – Generally speaking, when contrasted with specialized grinding machines, CNC turning centers are cheaper and can perform more of a range of functions. Selecting hard turning eliminates both coolant costs and the need for coolant disposal, as it is a highly flexible process that can often be used dry. Additional savings are present in the form of tooling inventory, which is reduced.
- Machining Flexibility – Multiple operations are also possible with a single set-up, with a turning center or lathe, which are also more easily configured for automated operations.
- Faster Set-Up and Cycle Times – Hard turning can speed up production cycles at the same time as minimizing machine downtime, thanks to its qualities of having a faster machine set-up and metal removal rates typically 3-6 times faster than grinding. Hard turning production cycles are also shortened by shorter part loading and unloading times.
- Simplified Operation – When it comes to a hard turning center, standard PCBN inserts can be used, the benefits of which are that they can be quickly switched out and used to produce complex shapes. This is in contrast to a customized dressed wheel, which is often required for grinding applications. And some operations which may require multiple grinders can be completed on a single turning center.
- More Environmentally Friendly – Turning centers can also offer its users some real environmental benefits, thanks to the fact that they consume less electricity than grinding machines. This both reduces monthly electric bills as well as saving the planet. In addition, leftover metal chips from hard turning processes can be recycled (which the swarf generated by grinding cannot – needing instead to be disposed of as industrial waste).
Methods for Hard Turning Success
It must be acknowledged that not all turning centers and lathes are going to be appropriate for hard turning applications. It’s important for the machine to have high precision positioning in order to create parts with the correct surface finish and tolerance successfully.
It is essential for the machine to have maximum machine rigidity to suppress vibration, and though while not crucial, it’s a benefit to have a machine base with high static/dynamic stiffness.
It is also key for the CNC machine to have a set-up that can meet the cutting conditions and speed requirements of the cutting tools, as well as being able to efficiently dissipate the heat buildup. The combination of machine and thermal stability, ameliorated by rigid tool- and workholding support, helps to guarantee that the finished results are high-quality.
Hardinge – A Market Leader in Hard Turning & Metal Cutting Solutions
Hardinge has been a market leader for decades when it comes to delivering hard turning and advanced metal-cutting solutions. The Hardinge® SUPER-PRECISION® T-Series turning center has long been recognized for its accuracy and efficiency, offering accurate results for even complex applications.
The T-Series machines have the functionality of managing two-axis high-precision machining as well as the capacity to multi-task applications; and have been designed to produce complex and precise parts in the tool industry. Its capacities include the manufacturing of delicate items as well as parts needing completion in a single set-up.
This information has been sourced, reviewed and adapted from materials provided by Hardinge Inc.
For more information on this source, please visit Hardinge Inc.