cc
Preface
In the machining of aerospace parts, the main challenges are related to the part material. The difficulty of machining titanium alloys, high-temperature superalloys (HTSA) and creep-resistant steel is a processing bottleneck for the entire aircraft supply chain. These materials have poor machinability, resulting in low cutting speeds, greatly reducing productivity and shortening tool life. And these factors are directly related to the tool. In fact, when working with typically difficult-to-machine aerospace materials, tool functionality determines the level of productivity available. The actual situation is that the development of cutting tools lags behind that of machine tools, and this gap limits the performance of high-end machine tools in manufacturing aerospace components.
In modern aircraft, especially unmanned aerial vehicles (UAVs), the proportion of composite materials used has increased significantly. The efficient machining of composite materials requires special tools and is the focus of technological leaps forward in the aerospace industry.
Aerospace-grade aluminum remains a widely used material for airframe components. Machining aluminum may seem simple, but choosing the right tool is the key to successfully and efficiently machining aluminum.
Complex part shapes are a hallmark of turbine engine technology. Most geometrically complex aero-engine components operate in extremely corrosive environments and are made from materials that are difficult to machine, such as titanium alloys and high-temperature superalloys (HTSA), to ensure the required life cycle. Complex shapes, poor machinability and the need for high precision combine to form major difficulties in producing these parts. Advanced multi-axis machining centers enable various stock removal strategies to more efficiently machine complex contours. However, the tool is in direct contact with the part and has a great impact on the success or failure of the processing. Excessive tool wear can affect part surface accuracy, while unpredictable tool breakage can cause the entire part to be scrapped.
Advanced multi-tasking machines, Swiss-type lathes and lathes with powered tool holders have profoundly changed the manufacturing of small parts, such as various hydraulic and pneumatic systems, actuators and accessories in aircraft. Therefore, the aerospace industry requires more and more special tools designed for these advanced machine tools to maximize processing efficiency.
Cutting tools—the smallest elements in a manufacturing system—become a critical support for significantly improved performance. Therefore, aerospace parts manufacturers and machine tool manufacturers urgently need technologically innovative solutions from tool manufacturers to bring chip removal rates to a new level. The goal of the solution is clear: increase productivity and extend tool life. Machining special aerospace parts and large airframe components with complex shapes requires a predictable tool life cycle for reliable process planning and timely replacement of failed tools or replaceable cutting components (such as blades).
Tool manufacturers have limited options when it comes to finding the ideal solution, perhaps in terms of tool material, edge shape and a reliable and robust design. Despite limited choices, tool manufacturers are going all out to provide a new generation of cutting tools to meet the growing needs of the aerospace industry. Although the new coronavirus has severely hindered the development of the industry, it does not mean that industrial demand has decreased. The latest tool designs are a testament to tool manufacturers’ response to the needs of aerospace component production.
cooling jet
High-pressure cooling (HPC) is an effective tool to improve performance and processing efficiency when machining titanium alloys and high-temperature superalloys (HTSA) and creep-resistant steels. The precise and direct high-pressure cooling jet (HPC) can significantly reduce the temperature of the cutting area and ensure the formation of small flake chips. This helps achieve higher cutting parameters and longer tool life compared to traditional cooling methods. Accurate and direct high-pressure cooling HPC is increasingly used in the processing of difficult-to-cut materials, which is a clear trend in aerospace parts manufacturing. Therefore, tool manufacturers consider high-pressure cooling HPC tools to be an important research and development direction.
ISCAR, one of the leading companies in the field of tool manufacturing, has a rich and diverse range of high-pressure cooling tools. In 2020, ISCAR expanded its product range with the introduction of new double-edge milling cutters with the “classic” HELI2000 and HELIMILL indexable inserts (Fig. 1). This step is another milestone in Iskar’s development of this product range.
In the 1990s, the HELIMILL series of indexable milling cutters first introduced by ISCAR clamped spiral edge milling inserts. The new design keeps the rake angle and clearance angle of the blade formed after the blade is clamped on the cutter body, making cutting light and smooth, and significantly reducing the power consumption of the machine tool. The design concept of HELIMILL milling cutters has become a widely known and recognized concept in the design of 90° leading angle indexable milling cutters.
Through the gradual revision and improvement of HELIMILL milling cutters, ISCAR has added additional milling product series and inserts with more cutting edges under the same concept. Excellent performance and rich tool peripheral products make it widely used in the machining industry. Therefore, adding a modern high-pressure cooling HPC tool design to the proven HELIMILL range is a direct response to customer demand and is the next step in the development of the tool range.
In turning, ISCAR has significantly expanded its range of assembled modular tools to include toolholders with indexable inserts and interchangeable heads. By using a serrated contact surface connection, these tools can be adapted to a variety of tool heads with different insert shapes, including thread turning and standard ISO turning inserts, providing greater flexibility for different applications.
ISCAR offers tool holders in both traditional and vibration-resistant designs, differentiated according to the application: cylindrical shank or polygonal tapered shank. A common feature of cylindrical nose milling cutters is the direct delivery of an internal cooling jet to the desired insert cutting edge (Figure 2). Depending on the diameter of the cylindrical shank tool, the maximum pressure of the cooling jet varies from 30 bars to 70 bars. Tools with polygonal taper shanks can achieve ultra-high pressure cooling of 300 bars. The adequate supply of cooling jets increases tool life by lowering temperatures in the cutting zone and improving chip control and evacuation. Applications of this product range should be significantly increased in the aerospace industry.
Drilling solutions
Composite material processing is full of pitfalls and pitfalls. The high wear resistance of composite materials accelerates tool wear, which shortens tool life and affects tool performance. Drilling is the most common cutting operation in composite machining, so even small improvements in the functionality of drilling tools are critical.
ISCAR has developed a new series of drill bits specifically for composite material processing. In order to improve wear resistance, the cutting edge portion of these drills is usually made of super-hard polycrystalline diamond (PCD) or diamond coating. Depending on the diameter of the drill, the drill tip can use either a solid PCD tip or a PCD welding blade, and in both cases can be regrinded up to 5 times. Another unique design point of CVD diamond-coated solid carbide drill bits is that the main cutting edge is in a zigzag shape. When processing composite materials, processing vibration is more likely to occur. The zigzag design of the cutting edge greatly reduces delamination and burrs, especially when processing carbon fiber reinforced plastic (CFRP) and carbon fiber laminates.
In addition to composite materials, diamond-coated drill bits are also suitable for processing other wear-resistant engineering materials. If necessary, an option with internal cooling through-holes is also available.
Drilling small-diameter deep holes is a common operation in manufacturing aerospace parts. ISCAR's new solid carbide drill bits, available in diameters ranging from 3-10 mm (0.125"-0.391") (Figure 3), are designed specifically for this type of work. This drill series combines a drill tip shape, dual guide bar design, polished chip flutes, composite coating and internal cooling through holes to achieve high performance in machining difficult-to-machine austenitic stainless steels, creep-resistant steels and iron-based alloys. Achieving a 50xD drilling depth ratio in one feed.
No fear of any complex processing applications
Due to the definition of aerodynamics, aircraft engine turbines, compressors, impellers and integral blade rotors (IBR) need to have complex shapes. New developments aimed at improving the efficiency of aircraft engines have added to this complexity. Advances in technology have brought about new methods of producing molded parts, especially 3D printing, which greatly reduces the margin of workpiece material. However, machining remains the most common method of final forming for manufacturing aerospace parts with complex shapes. Advances in five-axis machining and CAD/CAM systems have enriched manufacturers’ solutions to overcome difficulties in part production.
Drum milling cutters have good application prospects in five-axis machining of aerospace parts with complex-shaped surfaces. ISCAR has developed a series of drum milling cutters in the diameter range 8 – 16mm (.312" - .500"), available in two designs: solid carbide end mills and convertible with Transformer threaded interfaces. Replaceable head tool. The use of these tools in machining can effectively optimize the production of blades.
Reliable multitasking
When machining on compact multi-tasking machines and Swiss-type lathes, effective chip evacuation largely depends on the correct tool selection. To increase productivity, it is necessary to maximize tool stiffness and minimize tool overhang for machining operations in confined spaces.
Recently, ISCAR has launched NEOCOLLET circlip chuck, a new tool holder series that provides an alternative to ER circlips for clamping tools. One of the typical tool holders adapted for this series is a tapered shank, which is built directly into the collet chuck tool holder (Figure 4), ensuring a rigid and reliable connection to improve tool performance. New series of clamps for ISCAR carbide T-shaped interchangeable grooved face milling cutter heads. As mentioned earlier, the use of high-pressure cooling can greatly improve machining results, especially when machining titanium, high-temperature superalloys (HTSA) and difficult-to-machine stainless steels, which are the main materials for aircraft hydraulic and pneumatic systems and small accessories. The new turning tool series features square shanks and screw-clamped 55° diamond inserts using HPC technology to facilitate longitudinal turning, face turning and copy turning on small diameter parts (Figure 5).
All cases illustrate how tool manufacturers are trying to find more efficient solutions to meet the new requirements of the aerospace industry. Industrial growth has slowed and aircraft production has declined due to the impact of the coronavirus, but toolmakers' focus on the needs of their partners has not diminished. Instead, ISCAR has developed new advanced cutting tools and is working to successfully upgrade them for use in the upcoming resumption of aircraft production.
