Figure 1: ISCAR has expanded its line of indexable SiAlON inserts for machining HTSA materials.
Machining for the Aerospace Industry
The aerospace industry is one of the most important driving factors for cutting tool development. Here are the recent tool developments to address the challenges in aerospace parts manufacturing. Article by Andrei Petrilin, ISCAR.
The aerospace industry is not only one of the largest consumers of cutting tools but also one of the most important driving factors for cutting tool development. The aerospace industry features continuous efforts aimed at improving aircraft component manufacturing efficiency, increasing flight safety, and reducing potential environmental damage.
To achieve these goals, the aerospace industry must constantly improve the design of aircraft engines and airframe structural elements, to increase the protection of the aircraft from the damaging action of such dangerous factors as lightening and icing. This, in turn, has resulted in a series of industry demands, including the introduction of engineering materials that require new production technologies, developing appropriate machinery and cutting tools. The aircraft manufacturer has to deal with complex parts, which are produced from various materials with the use of different machining strategies. This is why the aerospace industry is considered as a powerful and leading force for progress in cutting tool development.
Many materials used for manufacturing aircraft components have poor machinability. Titanium with its impressive strength-to-weight ratio, high-temperature superalloys (HTSA) that do not lose their strength under high thermal load, and composites, are difficult-to-cut materials. In order to increase output rate and improve productivity, aerospace component manufacturers must use machine tools capable of implementing advanced machining operations. In such conditions, the role of cutting tools is significantly increased; however, cutting tools can represent the weakest link in the whole manufacturing system due to their low durability as a system element, which can decrease productivity. Customers from the aerospace sector expect higher levels of performance and reliability from cutting tools. Tool manufacturers now are being challenged and inspired, in terms of developing and integrating sometimes unconventional solutions into their products, to meet these expectations.
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Basic Materials
Figure 2: ISCAR’s F3S chipformer was designed specifically for finish turning high-temperature nickel-based alloys and exotic materials.
Most cutting tools continue to be manufactured from cemented carbide. Over recent years, ISCAR has introduced several carbide grades designed specifically for aerospace materials, including
IC 5820. The grade combines the advantages of a new submicron substrate, a progressive hard CVD coating, and a post-coating treatment to substantially increase impact strength and heat resistance. The inserts from this grade are intended mostly for milling titanium. Pinpointed wet cooling and especially high-pressure coolant (HPC) significantly improve grade performance.
Ceramics, another tool material, possess considerably higher hot hardness and chemical inertness than cemented carbides. This means that ceramics ensure much greater cutting speeds and eliminate diffusion wear. One of ISCAR’s recent developments, a family of solid ceramic endmills, is intended for machining HTSA. These endmills are made from SiAlON, a type of silicon-nitride-based ceramic comprising silicon (Si), aluminium (Al), oxygen (O) and nitrogen (N). When compared with solid carbide tools, these endmills enable up to 50 times increase in cutting speed, which can drastically save machining hours.
For turning applications, the company expanded its line of indexable SiAlON inserts for machining HTSA materials. The new products (Figure 1) have already proven their effectiveness in turning aero engine parts from super alloys such as Waspaloy and different Inconel and Rene grades. In contrast to other silicon nitride ceramics, SiAlON possesses higher oxidation resistance but less toughness. Therefore, a key of a SiAlON insert reliability is additional edge preparation. ISCAR’s new TE edge geometry has been developed to increase tool life in heavy load conditions during rough operations and interrupted cuts.
Advanced Geometry
Figure 3: The recently launched modular drills for multi-spindle and Swiss-type machines combine the SUMOCHAM design with a FLEXFIT threaded connection.
Improving a cutting geometry is an important direction in the development of cutting tools. Cutting geometry is a subject of theoretical and experimental researches, and advances in science and technology have brought a new powerful instrument to aid in tool design: 3D computer modelling of chip formation. ISCAR’s R&D team actively uses modelling to find optimal cutting geometries and form the rake face of indexable inserts and exchangeable heads.
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The F3S chipformer for the most popular ISO inserts, such as CNMG, WNMG and SNMG, was designed specifically for finish turning high-temperature nickel-based alloys and exotic materials (Figure 2). It ensures a smooth and easy cut with notable chip breaking results. The remarkable working capability of the designed cutting geometry is a direct result of chip flow modelling.
In hole making, applying modelling to the design process significantly contributed to creating a chip splitting geometry of SUMOCHAM exchangeable carbide heads for drilling holes with depth up to 12-hole diameters in hard-to-cut austenitic and duplex stainless steel.
Flexible Customisation
Figure 4: The need to increase productivity and boost metal removal rates for milling aluminium workpieces, especially large parts of aerospace structural components, has led machine tool builders to develop milling machines with a powerful main drive—up to 150 kW—with high spindle speeds of up to 33,000 rpm.
Aerospace products can vary immensely in material, dimensions, shape , complexity, and more. To make such a diverse range of products, the product manufacturer needs dozens of machine tools and technological processes. Not every standard cutting tool is optimal for performing certain machining operations with maximum productivity and, consequently, the aerospace industry is a leading consumer of customized tools.
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A customer producing titanium parts might be interested in solutions comprising indexable shell mills and arbors from the standard line; while another customer producing similar parts might prefer special milling cutters with an integral body, for direct mounting in a machine spindle.
ISCAR developed the MULTI-MASTER and SUMOCHAM families of rotating tools with exchangeable heads and different body configurations to ensure various tool assembly options that simplify customization and decrease the need for costly tailormade products.
A further example of simplified customisation can be found in ISCAR’s recently-launched modular drills for multi-spindle and Swiss-type machines. The drills combine the SUMOCHAM design with a FLEXFIT threaded connection (Figure 3). Multi-spindle and Swiss-type machines typically have a limited space for tooling, which means that the tools in operation need to be as short as possible to avoid collisions and facilitate easy set up. A wide range of FLEXFIT threaded adaptors and flatted shanks has been designed precisely to fit the drills and maximally shorten an overhang.
Responding to demands from the aerospace sector, the company also expanded the MULTI-MASTER family by introducing a new thread connection to increase the diameter range for the exchangeable endmill heads to 32 mm (1.25″).
Aluminium Machining
Although machining aluminium might appear to be an extremely simple process, effective cutting of aluminium actually represents a whole field of technology with its own laws and challenges.
The need to increase productivity and boost metal removal rates for milling aluminium workpieces, especially large parts of aerospace structural components, has led machine tool builders to develop milling machines with a powerful main drive—up to 150 kW—with high spindle speeds of up to 33,000 rpm. To meet this demand, ISCAR has expanded its family of 90° indexable milling cutters by introducing new tools carrying large-size inserts that enable up to 22 mm (.870″) depth of cut (Figure 4). The tools have been designed to eliminate insert radial displacement, which might occur due to high centrifugal forces during very high rotational speed. This concept facilitates reliable milling in a rotational speed range of up to 31,000 rpm.
In hole making, the company developed new inserts for drilling aluminium with indexable drills from the DR-TWIST drilling tool range. The inserts are peripherally ground and feature sharp cutting edges and polished rake face for light cut, preventing adhesion.
ISCAR’s cutting tool program for the aerospace sector is based on several principles: the complex needs of this industry, taking into consideration trends in metalworking, and the drive to strengthen partnerships with tool consumers. ISCAR believes that such a tri-pronged approach ensures the successful realization of innovative ideas for efficient machining of the difficult-to-cut materials that characterize this challenging and dynamic field.
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