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Since the inception of modern metal cutting, tools have traditionally been crafted from integral steel through grinding. However, starting in the 1950s, indexable carbide inserts brought about a revolutionary change. Yet, in the realm of Gear cutting—specifically hobbing—the solid high-speed steel (HSS) hob remains dominant today.
Despite technological maturity, the inherent inefficiencies of HSS hobs have constrained their advancement. These tools require regular resharpening and recoating, which involves extensive logistical efforts. A production manager looking to purchase an HSS hob must consider acquiring multiple units simultaneously to keep machines running continuously. Typically, this involves having five to ten hobs in rotation: one for cutting, another for sharpening, one for recoating, and additional ones for measurement and standby. The management of these tools adds complexity to operations.
In stark contrast, indexable insert tools eliminate much of this maintenance hassle, requiring just two cutters for continuous operation—one in use and the other in standby or replacement. Additionally, the absence of coolant presents another significant advantage. While HSS tools often rely on cutting oil to avoid overheating, carbide tools excel at high temperatures. By eliminating the need for coolant, manufacturers save on procurement, storage, and disposal costs, while fostering a cleaner, safer, and more environmentally friendly workplace.
The inherent characteristics of solid carbide enable higher cutting parameters and extended tool life, directly boosting productivity. This enhanced performance provides flexibility in adjusting production levels or reducing operational costs when fewer machines are required. This capability has a direct impact on the investment decisions for new tooling equipment, potentially lowering capital expenditures.
Sandvik Coromant's recent advancements in indexable insert hobbing technology bring substantial benefits to this niche field. The new CoroMill 176 concept, featuring carbide inserts optimized for steel processing, leverages today’s robust and high-powered hobbing machinery.
While it is widely acknowledged that solid tools are more precise than indexable insert tools, new high-quality HSS hobs can meet these expectations. However, worn tools require regrinding and recoating to maintain accuracy. Indexable inserts, on the other hand, merely need replacement or indexing, provided the blade-clamping system meets requirements, thus minimizing any impact on precision.
A key feature of this new concept is its iLock blade interface. This clamping system, consisting of blades, wedges, and bolts (one per seat), enables quick and easy use. After rigorous testing, one customer reported reducing blade replacement time to just seven seconds per blade. For tools with up to 100 inserts, this efficiency becomes evident. A guide rail on the support surface ensures blade stability, preventing lateral movement and ensuring accuracy and repeatability.
At a broader level, this new hobbing concept reflects a larger technical shift from traditional solid tools toward more efficient and economical indexable insert solutions. The rugged new machinery is particularly well-suited for indexable carbide hobs.
**Case Study:**
Parts: Spline shaft
Gear parameters:
Module: 5 mm, Teeth: 30
Tip diameter: 159 mm, Tooth width: 22 mm
Material: Low-alloy steel, ST52
HSS vs. CoroMill 176:
Roughing: 180 minutes → 60 minutes
Finishing: 90 minutes → 30 minutes
Total: 270 minutes → 90 minutes
Savings: 180 minutes per workpiece
In summary, a new indexable carbide hob concept offers a cost-effective alternative to HSS hobs. Replacing solid tools with indexable tools drastically reduces associated maintenance tasks. This innovative hob is user-friendly, features high cutting parameters, and leads to a significant increase in productivity.
[Attached Image: Comparison of traditional and new hobbing methods]