[Editor's Note] Parts are often machined under surface hardening conditions, whether they are hardened or not, to achieve higher accuracy in a more efficient way. As this process becomes increasingly common, hard part turning has become a key area for tool development. In the automotive industry, numerous components require hard machining, such as transmission gears, fuel injection pump nozzles, bearing races, steering gears, brake discs, axles, camshafts, valve seats, pistons, and cylinder liners. Hard machining places higher demands on cutting tools, making it an essential challenge in modern manufacturing. Recently, two manufacturers have significantly boosted their production efficiency for hardened parts by 116% and 322%, respectively. The improvement was achieved without replacing equipment or introducing new methods—just by changing the type of indexable inserts used in the turning process. The new insert design allows for a threefold increase in feed rate, reducing machining time and lowering overall costs. This breakthrough has proven highly effective in enhancing productivity during hard turning operations. The insert responsible for this major efficiency gain is the Sandvik Coromant Xcel insert. It enables a higher feed rate while maintaining low surface roughness, marking a significant advancement in hard part turning technology. Its innovative design has had a profound impact on the industry. Requirements for Hard Part Turning Hard part turning presents unique challenges in terms of cutting force. Under normal conditions, the tool experiences greater pressure compared to other materials. Additionally, the abrasive nature of hardened workpieces accelerates tool wear and increases heat generation. Cubic boron nitride (CBN) tools, second only to diamond in hardness, are ideal for this application. Today, a range of high-performance CBN-based inserts is available for hard part turning, offering improved performance and reliability. The Xcel blade concept represents a significant leap forward in hard part turning performance. For finishing processes, its advantages are fully realized when surface roughness requirements are met. In roughing operations, it also demonstrates excellent feeding capabilities. When stability is ensured, the Xcel blade can achieve a feed rate of up to 0.5 mm/r with sufficient clearance along the shoulder. Pairing it with a Wiper blade that operates at twice the speed of a standard tool ensures stable processing and predictable results. For hard part turning, the best approach is to use Xcel inserts for roughing and Wiper inserts with WG grooves for finishing, especially when using a CNC lathe. Key Features of the Xcel Blade The Xcel insert is designed for optimal performance, with an ideal feed rate ranging from 0.3 to 0.5 mm/r. The recommended maximum depth of cut is 0.25 mm. When using a CNGX insert for shoulder machining, special attention must be given to the insert’s shape: at least 2.7 mm should be avoided unless there is an undercut. Cutting speeds can reach up to 300 m/min, but the recommended range is usually between 150 and 200 m/min. To maximize efficiency, start by determining the feed rate and then adjust the cutting speed accordingly. Xcel inserts are particularly well-suited for large diameter shafts, sleeves, and gears that require longitudinal and face turning with good stability. Typical materials include hardened steel or case-hardened steel, such as 16MnCr5 (hardness > 60 HRC) or 17CrNiMo6. In gear machining, a hard-soft cutting scenario may occur, where the outer diameter reaches 62 HRC while the center remains at 30 HRC. CBN is not recommended for materials below 45 HRC, but it can be combined with carbide tools for certain applications. Cutting can be continuous or intermittent, such as when machining gear teeth or shaft features. Selecting the right insert material helps optimize the process. Surface roughness values can typically reach Rz = 1 μm or Ra = 0.25 μm, with dimensional tolerances maintained within 0.01 mm. High feed rates result in excellent surface quality: Ra = 0.3 μm at 0.3 mm/r, Ra = 0.5 μm at 0.4 mm/r, and Ra = 0.8 μm at 0.5 mm/r. In semi-finishing operations, Xcel inserts demonstrate exceptional efficiency. Hard part turning is a viable alternative to grinding, and the two methods complement each other. Modern CBN materials have led to more durable cutting tools, and current blade technologies offer increased productivity and finishing capabilities. When using the maximum chip thickness as a basis for feed rate, Xcel inserts outperform standard rounded tip blades. With a small lead angle, the thin chips produced by the straight edge enhance productivity and provide more space for operation. Mechanically locked CBN insert fillets provide the strength and safety needed for multi-edge inserts, making them cost-effective and reliable. The Safe–Lok multi-fillet technology ensures a securely welded CBN fillet that stays away from the hot cutting zone during hard part turning (see image). Stability of the Xcel Blade Stability is crucial for all CBN blade applications. To ensure optimal Xcel blade performance, the workpiece aspect ratio should remain within 4:1. Standard round head inserts generate the lowest cutting forces, but feed rates are limited by the relationship between the tool nose radius and surface roughness. Wiper inserts with WH grooves achieve good surface quality at lower feed rates and with less stability, while at very high feed rates, better surface quality is achieved but requires more stability. Xcel inserts deliver high-quality surfaces even at high feed rates, though they demand greater stability. Even at lower feed rates, they still produce excellent results. When using a very small lead angle (10°), the depth of cut is always limited during hard part turning. Conventional round head inserts cause varying chip thickness along the cutting edge, but Xcel inserts maintain thin and uniform chip thickness, enabling high feed processing capability. Tool Life Standard round head inserts suffer from high wear due to the grooves on the cutting edge, which limits their lifespan. In contrast, Xcel inserts distribute wear evenly across the cutting edge, improving tool life. The extended life is partly due to reduced contact time and lower temperatures, which minimize diffusion along longer straight edges. Even with a significant increase in feed rate, Xcel inserts can process more parts efficiently. Xcel inserts are available in two types based on cubic boron nitride (CBN). This material offers high thermal hardness and resistance to plastic deformation, allowing for higher combinations of feed and cutting speed when machining hardened materials. Current CBN materials also exhibit good toughness, strength, thermal shock resistance, and abrasion resistance. They contain 40% to 65% CBN and ceramic binders for enhanced chemical resistance at elevated temperatures. Some versions feature higher CBN content with metal binders for improved toughness. Cooling Tower Fan Blades,Fan Impeller,Cooling Column Fan Blades,Condenser Axial Fan Wings Changzhou Keyleader Fan Technology Co. Ltd. , https://www.keyleaderfan.com
Safe–Lok multi-rounded blade