In the world of metalworking, there is this constant tussle between raw materials and processing tools. Take machining exotic materials as an example, in one corner, we have the obstinate Titanium, the unyielding Inconel and a whole host of other exotic materials that can be a real tough nut to crack. 

In the other corner, apart from steely resolve, we have high-pressure coolant, special cutting tools and modern machine tools. While special cutting tools and high-pressure coolant strategies could well be formulated specifically to tackle difficult materials, there is no machine tool in the market today that is built specially to machine one type of material.

Machine tools are usually defined by its operating range and capability rather than the materials it is able to machine. While there are obvious business reasons for doing so, it does not mean modern machine tools have fallen behind their cutting tool counterparts in the quest to process exotic materials. It is just that they have left it to the users to make the right decisions in terms of machine selection and processing strategies.

Difficult-To-Machine Materials

Mr Nakashima feels using reliable five-axis and multitasking machines can help machinists deal with exotic materials better.

Machining exotic materials is usually a significant endeavour for a job shop. Most of the time, operators are faced with tough materials that go through expensive cutting tools far too quickly for anyone’s liking. To compound the problem, the parts probably come with complex shapes and tight tolerances as they are often deployed in the aerospace, oil & gas and medical industry where accuracy and surface quality are top considerations.

“Exotic materials, we call special hard materials, are used in the aircraft, medical and oil & energy industries,” said Akihiko Nakashima, assistant GM in charge of the sales engineering department at Yamazaki Mazak HQ in Japan.

According to Mr Nakashima, he said materials like Titanium, Inconel, Udimet Waspaloy and Ceramic Matrix Composites (CMCs) are materials used in the aerospace sector to make airframe bodies whereas Inconel and Cobalt-based materials are used in the oil & gas and medical industries respectively.

Although the usage of these materials represents a breakthrough in technology in the industries, their introduction into machining has been a hot topic of discussion, even for machine tool builders.  

Multitasking Machines For Exotic Materials

Like a smartphone that has a built-in music player, voice recorder and camera, multitasking machines allow users to combine several cutting processes, including turning, milling, drilling, tapping and deep-hole boring or even non-traditional processes such as grinding and polishing on one machine as opposed to having those same processes handled by multiple machines. 

For Mr Nakashima, he believes that using five-axis and multitasking machines can help machinists deal with exotic materials better. The key reason he feels, is the rigidity of the machine, as well as its ability to produce finish parts in one process.  

“High rigidity machine means you can minimise vibration. Vibration is the biggest enemy of the cutting tool. Therefore, it is important that we select or build machines that are rigid enough for those kind of exotic materials as their low heat conductivity and high hardness typically generate vibrations during cutting,” he said.

“Process integration is also very important. We call that ‘Done in One’. In the case of special hard materials, you need process integration because special material parts have high prices as well as high demands in accuracy.”

He also pointed out that in process integration, machine tool builders have moved away from the traditional milling and turning combination. They have gone on to include processes like gear milling, buffing, grinding, ceramic buffing and other processes to make process integration more complete. 

It’s About Making The Right Choice

Unlike cutting tools, he conceded that five-axis and multitasking machines are not specially manufactured for exotic materials. They are developed for every material. It is therefore important to work with machine tool builders in order to pick out a machine that is suitable. Giving an example, he said: “For Aluminium cutting, we will recommend the high-speed type of machine.” 

Machining of a titanium hip implant by five-axis multitasking mill turn. 

Away from the capability of the machine tool, he said cutter path or tool path is another crucial factor. He also paid tribute to CAD/CAM developers on designing five-axis trochoidal machining strategies as they enable cutting special hard material types from a solid material to a complete part by adopting a circular reciprocating motion to maintain chip load and cutting forces.  

In summary, according to him, so long as the three crucial points (cutting tools, tool path and process integration) are taken into consideration, exotic or not, machinists should not be overly troubled by the materials they are given as multitasking machines are designed with the required capability to go through materials in an efficient manner.