Ceramic savvy: Turning Performance

Ceramics are known for their inherent hardness and heat resistance, which makes them suitable for cutting hardened steels and heat-resistant superalloys. They can run at higher cutting speeds than carbide grades, and the success and failure rate of these tools generally comes down to the rigidity and stability of the machine tool. Presented here are five key factors shaping the ceramic tool market.

The ceramic tool market is expanding thanks to machine, ceramic material and programming improvements. Image courtesy Greenleaf.

1. The technology is evolving. Ceramic tools will eventually be the preferred choice for machining both challenging and mundane materials, according to Bill Greenleaf, national sales and marketing manager for Greenleaf Corp., Saegertown, Pa. This will be the result of continued advancements in ceramic materials, application expertise and machine tool technology.

“Today’s machine tools are better equipped to take advantage of the elevated performance of ceramic tools,” he said. “CAM packages are providing more canned programming techniques, and the development of new insert grades are engineered to reach higher feed rates and cutting speeds and extend tool life.”

Neal Buschmohle, marketing and product development manager at NTK Cutting Tools USA, Wixom, Mich., said the industry is developing grades that increase wear resistance, toughness, consistency and repeatability. “Many of these products, such as alumina ceramics, are getting close to the productivity found in CBN tools when hard turning. My guess is we’ll get there within the next 3 years. Some of our ceramic grades have already replaced CBN in certain applications.”

One of the biggest trends in ceramics is the availability of more complex chamfers and edge preps, said Eric Jenkins, senior applications engineer at Kyocera Precision Tools Inc., Hendersonville, N.C. “These are critical to the performance of the tool. Ceramics used for hard turning, for example, normally require a chamfered edge to improve insert strength. This is due to the increase in hard turning cutting forces, which can be 30 to 80 percent greater than the forces seen in traditional soft machining processes.”

2. Ceramic tools require a specific skill set. The application of ceramic tools is unique when compared to carbide cutters. “The principles can be easily learned, but they are profound enough that someone new to ceramic machining should be aware of them prior to attempting their use,” Greenleaf said. “We routinely train our customers in proper ceramic application skills either through dedicated classroom programs or through factory-trained sales and service engineers.”

Jenkins agreed that ceramic tool knowledge is important at the beginning. “Operators should be instructed to handle ceramics with care; don’t throw them in the toolbox, for example,” he said. “They should also take care when indexing the inserts, because overtightening a clamp screw may crack a ceramic insert. Operators should also trust the programming. Higher cutting speeds are normal with these tools, but it may look unusual to an operator running the tools for the first time.”

Many ceramic cutting tools, alumina for example, are getting close to the productivity found in PCBN tools when hard turning. Image courtesy NTK Cutting Tools.

The willingness to learn these skills comes down to the machine operator, who might want to simply stand in front of the machine and go through the motions, according to Buschmohle. “Others might have some programming background and can easily identify the productivity improvements available with ceramic tools. They see the efficiency gains and understand how these tools can help make their job easier and more efficient. These are the kind of operators that become your best salesmen for the technology.”

3. Machine tool stability is key to success. Ceramics do not require anything special from the machine other than rigidity, according to Jenkins. “The majority of machine tools I have encountered in the field are capable of running ceramics, but the difference between success and failure is often related to the stability of the entire process. This includes the placement of the machine tool on the shop floor, how the workpiece is held and the toolholder overhang.”

Carbide tools are brittle and, therefore, also susceptible to rigidity issues, but carbides are generally tougher than ceramics, and, as a result, can be more durable in unstable conditions. The trade-off, however, is the sacrifice in cutting speed compared to ceramics. “A ceramic-savvy shop can machine an aerospace component in a fraction of the time that it will take for a carbide-only shop to do the same job,” Jenkins said.

Many companies run old, low-power machine tools into the ground instead of upgrading to new equipment, which can be a disadvantage for ceramic tools. “The lack of horsepower makes a difference,” Buschmohle said. “Our customers that own the latest machine tool technology have a significant advantage with more tooling options.”

4. Social media shows tricks of the trade. In the past, ceramic tools were considered a niche technology. This perception is changing thanks partly to the online manufacturing community.

“The use of social media and the Internet has provided more opportunities for machinists and programmers to share the application techniques required to successfully use advanced ceramic tools,” Greenleaf said.

The majority of machines are capable of running ceramic tools, but the difference between success and failure is often related to stability. Image courtesy Kyocera Precision Tools.