https://cdn.mtdcnc.global/cnc/wp-content/uploads/2021/01/30212957/Fig.1-640x360.jpg
    Tooling

    Machining exotica

    • By Iscar
    • January 30, 2021
    • 6 minute read

    What are exotic metals, why are they so rare, and how are they machined? To understand this, let’s start by defining it…. There are exotic types of materials that were developed to answer specific demands. These exotic materials suit a dedicated application – they are rare, not commonly used and are generally more expensive and challenging to fabricate and machine.


    A
    strict agreed definition of an exotic material does not exist. Many experts refer to them as metals like Beryllium, Zirconium and their alloys, ceramics, composites and superalloys. When considering the use of structural materials, superalloys and composites should be distinguished.

    The metalworking industry mainly deals with these types of materials for several reasons, one of which is that machining exotic materials is problematic. Superalloys, or more specifically, high-temperature superalloys (HTSA), are intended for operating under heavy mechanical load in combination with high temperatures. They are largely used in gas turbines and in various valves and petrochemical equipment. The ‘exoticism’ of superalloys is their metallurgical design, which provides high creep resistance to keep strength at high temperatures. According to the main components, HTSA can be divided into three groups: Nickel (Ni), Cobalt (Co), and Iron (Fe) based superalloys. Superalloy chemistry, especially in the case of Ni and Co based HTSA, results in poor machinability.

    Composites are multi-component materials. When compared with a traditional engineering material, such as steel or aluminium, composite workpieces are nearer-to-net shape and do not require significant material removal. Nevertheless, composite components have different properties and when combined, they produce a heterogeneous structure that makes machining problematic. The process of machining composites differs from machining metals and it often looks more like shattering than cutting. High composite abrasiveness can lead to intensive tool dulling and various performance problems such as a degradation of accuracy or non-repairable machining defects.

    The metalworking industry has made significant progress in machining exotic materials. Advanced tools and effective machining strategies have already lifted the performance of machining operations to a totally new plane. An impressive leap forward in 3D printing, which may significantly diminish machining operations, looks very promising. But there is one ‘exception’, which still limits manufacturers from taking full advantage of the considerable increase of machine tool capabilities. This ‘exception’ is the cutting tool. Despite the distinct progress, cutting tools remain the bottleneck for machining efficiency. Hence, the plans of a breakthrough in the productive machining of exotic materials have much to do with the cutting tool.

    Cutting tool manufacturers keep up their efforts to find productive and reliable solutions for machining exotic materials. Sometimes, it may seem that traditional sources for a major advance are almost non-existent and that a great step forward is only connected to a real novelty. Regardless, cutting tool manufacturers still manage to provide interesting products that combine available means and resources with new ideas. Recent ISCAR developments give a good example of such products and ISCAR’s attempt to resolve the existing bottleneck and find new ways to move forward.

    Exotic for Exotic: advantageous ceramics

    Cemented carbide is still the main cutting material for machining. Introducing carbide tools revolutionised the metalworking industry, ensuring a significant growth of productivity due to sharply increased cutting speeds. However, despite this, even today, cutting speeds for difficult-to-machine Ni and Co based high-temperature superalloys (HTSA) are low: typically within the range of 25 to 50m/min. How do we expand the speed boundaries?

    Exotic ceramic materials have already found themselves as cutting materials. Using exotic ceramic material ensures a different level of cutting speeds. For example, machining superalloys with ceramic tools, a cutting speed of 1000m/min is completely feasible. Therefore, ceramic tools become more and more common in the machining of HTSA.

    Recently, ISCAR developed a family of indexable shell mills carrying double-sided inserts made from ceramics (Fig. 1). The mills are intended mostly for rough and semi-finish machining of planes and 3D surfaces at extremely high cutting speeds. The economical double-sided insert design provides high ceramic utilisation. The inserts are made from several ceramic grades such as ‘black’ ceramics, whisker reinforced ceramics and SiAlON (a type of silicon-nitride-based ceramic). Applying the new mills is directed at maximising metal removal rate (MRR) and a dramatic reduction in cycle time.

    One more example of successful usage of cutting ceramics is another of ISCAR’s latest products: a family of solid end mills from SiAlON. The end mills were designed specifically for productive rough machining of Ni-based superalloys such as various grades of inconel, incoloy and others in the aerospace industry. In comparison with typical solid carbide end mills, SiAlON end mills allow an increase in cutting speed by up to 50 times!

    It should be noted that ceramic tools behave differently from carbide tools. Generally, the end of tool life is determined by the acceptable level of surface finish or generated burrs and not by tool wear.

    Cutting Diamond

    When manufacturing parts from composites, drilling is widely regarded as a major cutting operation. Improving the capabilities of drilling tools has had a direct impact on the effectiveness of machining composites and composite stacks.

    Most recently, ISCAR introduced a series of new solid drills, in the diameter range of 3.3 to 12mm, which are specially designed for composites (Fig. 2). The common feature of these tools is the use of polycrystalline diamond (PCD) or diamond coating to ensure high abrasion wear resistance. There are several types of these new drills; one of them is based on using a PCD nib as a central point of a drill, another type has a diamond wafer. Both drill types offer a large area for multiple regrinds.

    Coolant Solver

    When machining exotic superalloys, effective coolant supply is a cornerstone of success. Pinpointed high-pressure cooling (HPC) can be a significant tool to improve cutting performance. It is a real source for greater tool life, better chip control and higher productivity.

    One of the latest ISCAR developments is a family of turning tools with ISO-type indexable inserts (Fig. 3). The tool design utilises an upper clamp for reliable securing of the inserts even during heavy and interrupted cuts. The previous turning tools with the HPC option had a lever clamping mechanism as an upper clamp that would obstruct a jet of coolant from reaching the cutting edge. The newly developed tools integrate a hollow upper clamp that solves two problems. It provides strong and rigid insert clamping and it eliminates any obstacle for the coolant jet on its way to the cutting edge. Hence, the clamp, which serves in the new tools as a coolant nozzle, received an additional important functional feature.

    In parting and grooving, especially in deep grooving, efficient chip forming has crucial significance. Pinpointed high-pressure cooling of a cutting edge significantly diminishes chip jamming and reduces built-up edges. Within the past year, ISCAR expanded the range of its HPC products by introducing new face grooving tools with a HPC option (Fig. 4). These tools are suitable for coolant pressure of up to 140 bar.

    https://cdn.mtdcnc.global/cnc/wp-content/uploads/2021/01/30212957/Fig.1-640x360.jpg

    Machining exotica

    What are exotic metals, why are they so rare, and how are they machined? To understand this, let’s start by defining it…. There are exotic types of materials that were developed to answer specific demands. These exotic materials suit a dedicated application – they are rare, not commonly used and are generally more expensive and challenging to fabricate and machine.


    A
    strict agreed definition of an exotic material does not exist. Many experts refer to them as metals like Beryllium, Zirconium and their alloys, ceramics, composites and superalloys. When considering the use of structural materials, superalloys and composites should be distinguished.

    The metalworking industry mainly deals with these types of materials for several reasons, one of which is that machining exotic materials is problematic. Superalloys, or more specifically, high-temperature superalloys (HTSA), are intended for operating under heavy mechanical load in combination with high temperatures. They are largely used in gas turbines and in various valves and petrochemical equipment. The ‘exoticism’ of superalloys is their metallurgical design, which provides high creep resistance to keep strength at high temperatures. According to the main components, HTSA can be divided into three groups: Nickel (Ni), Cobalt (Co), and Iron (Fe) based superalloys. Superalloy chemistry, especially in the case of Ni and Co based HTSA, results in poor machinability.

    Composites are multi-component materials. When compared with a traditional engineering material, such as steel or aluminium, composite workpieces are nearer-to-net shape and do not require significant material removal. Nevertheless, composite components have different properties and when combined, they produce a heterogeneous structure that makes machining problematic. The process of machining composites differs from machining metals and it often looks more like shattering than cutting. High composite abrasiveness can lead to intensive tool dulling and various performance problems such as a degradation of accuracy or non-repairable machining defects.

    The metalworking industry has made significant progress in machining exotic materials. Advanced tools and effective machining strategies have already lifted the performance of machining operations to a totally new plane. An impressive leap forward in 3D printing, which may significantly diminish machining operations, looks very promising. But there is one ‘exception’, which still limits manufacturers from taking full advantage of the considerable increase of machine tool capabilities. This ‘exception’ is the cutting tool. Despite the distinct progress, cutting tools remain the bottleneck for machining efficiency. Hence, the plans of a breakthrough in the productive machining of exotic materials have much to do with the cutting tool.

    Cutting tool manufacturers keep up their efforts to find productive and reliable solutions for machining exotic materials. Sometimes, it may seem that traditional sources for a major advance are almost non-existent and that a great step forward is only connected to a real novelty. Regardless, cutting tool manufacturers still manage to provide interesting products that combine available means and resources with new ideas. Recent ISCAR developments give a good example of such products and ISCAR’s attempt to resolve the existing bottleneck and find new ways to move forward.

    Exotic for Exotic: advantageous ceramics

    Cemented carbide is still the main cutting material for machining. Introducing carbide tools revolutionised the metalworking industry, ensuring a significant growth of productivity due to sharply increased cutting speeds. However, despite this, even today, cutting speeds for difficult-to-machine Ni and Co based high-temperature superalloys (HTSA) are low: typically within the range of 25 to 50m/min. How do we expand the speed boundaries?

    Exotic ceramic materials have already found themselves as cutting materials. Using exotic ceramic material ensures a different level of cutting speeds. For example, machining superalloys with ceramic tools, a cutting speed of 1000m/min is completely feasible. Therefore, ceramic tools become more and more common in the machining of HTSA.

    Recently, ISCAR developed a family of indexable shell mills carrying double-sided inserts made from ceramics (Fig. 1). The mills are intended mostly for rough and semi-finish machining of planes and 3D surfaces at extremely high cutting speeds. The economical double-sided insert design provides high ceramic utilisation. The inserts are made from several ceramic grades such as ‘black’ ceramics, whisker reinforced ceramics and SiAlON (a type of silicon-nitride-based ceramic). Applying the new mills is directed at maximising metal removal rate (MRR) and a dramatic reduction in cycle time.

    One more example of successful usage of cutting ceramics is another of ISCAR’s latest products: a family of solid end mills from SiAlON. The end mills were designed specifically for productive rough machining of Ni-based superalloys such as various grades of inconel, incoloy and others in the aerospace industry. In comparison with typical solid carbide end mills, SiAlON end mills allow an increase in cutting speed by up to 50 times!

    It should be noted that ceramic tools behave differently from carbide tools. Generally, the end of tool life is determined by the acceptable level of surface finish or generated burrs and not by tool wear.

    Cutting Diamond

    When manufacturing parts from composites, drilling is widely regarded as a major cutting operation. Improving the capabilities of drilling tools has had a direct impact on the effectiveness of machining composites and composite stacks.

    Most recently, ISCAR introduced a series of new solid drills, in the diameter range of 3.3 to 12mm, which are specially designed for composites (Fig. 2). The common feature of these tools is the use of polycrystalline diamond (PCD) or diamond coating to ensure high abrasion wear resistance. There are several types of these new drills; one of them is based on using a PCD nib as a central point of a drill, another type has a diamond wafer. Both drill types offer a large area for multiple regrinds.

    Coolant Solver

    When machining exotic superalloys, effective coolant supply is a cornerstone of success. Pinpointed high-pressure cooling (HPC) can be a significant tool to improve cutting performance. It is a real source for greater tool life, better chip control and higher productivity.

    One of the latest ISCAR developments is a family of turning tools with ISO-type indexable inserts (Fig. 3). The tool design utilises an upper clamp for reliable securing of the inserts even during heavy and interrupted cuts. The previous turning tools with the HPC option had a lever clamping mechanism as an upper clamp that would obstruct a jet of coolant from reaching the cutting edge. The newly developed tools integrate a hollow upper clamp that solves two problems. It provides strong and rigid insert clamping and it eliminates any obstacle for the coolant jet on its way to the cutting edge. Hence, the clamp, which serves in the new tools as a coolant nozzle, received an additional important functional feature.

    In parting and grooving, especially in deep grooving, efficient chip forming has crucial significance. Pinpointed high-pressure cooling of a cutting edge significantly diminishes chip jamming and reduces built-up edges. Within the past year, ISCAR expanded the range of its HPC products by introducing new face grooving tools with a HPC option (Fig. 4). These tools are suitable for coolant pressure of up to 140 bar.