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14-edge face mill with positive cutting action
Source：International Metalworking News for Asia - December 2016
Date Published：3/23/2017 05:03:23 PM
There are many trends arising in large batch machining that present production engineers in sectors such as automotive with numerous opportunities to make competitive gains, including greater demand for near-net-shape forged components and flexible machines replacing dedicated transfer lines. To help maximise the yield from these shifts in approach, as well as satisfy the need to reduce component costs, new milling cutter innovations are pivotal. With this in mind, Sandvik Coromant introduced its first double-sided, multi-edged face mill to offer cutter a positive cutting action.
With a total of 14 true cutting edges, CoroMill® 745 is set to offer a good solution in applications where productive face milling, low cutting forces and low cost per component are prerequisites. Among the many advanced features of this innovative cutter is its unconventional insert inclination angle, which is designed to provide a large positive angle on the main cutting edge, leading to excellent chip formation, a smooth, soft sound and low cutting forces.
Of course, double-sided inserts have been around for a while, but their concept often produces higher cutting forces than single-sided alternatives. As a result, Sandvik Coromant has set about developing a double-sided, multi-edge cutter that is able to offer both light cutting forces and favourable chip formation.
Advantages are also obtained when used on flexible transfer lines or when maximum tool utilisation is important. Here, this productive and versatile face milling cutter is likely to be heavily utilised thanks to its ability to offer increased tool life at a lower cost per component. What’s more, it is set to boost the options for engineers requiring lower cutting forces in the machining process, perhaps when using low-powered machines, for example, or where the set-up is not particularly robust.
Better cost per component
CoroMill 745 has been developed for roughing to semi-finishing operations on steel and cast iron workpieces (ISO P and ISO K materials). The upshot of deploying this double-sided, multi-edge cutter is that production economy and cost-per-component can be improved considerably. In essence, the positive cutting action mirrors that of a single-sided concept face mill, but with the new cutter there are cutting edges on both sides of the insert. With 14 cutting edges available, face milling operations up to 5.2 mm (0.205”) maximum depth of cut are expected to benefit.
Although the general engineering segment will benefit from the high productivity, reliable performance and low cost per component introduced by the innovative cutting action and strong inserts, manufacturers in industries where automated production is more prevalent can also anticipate significant advantages. For example, those relying on unmanned production will be able to leverage the cutter’s high security and predictable performance.
CoroMill 745 is able offer process and cost improvements on familiar automotive parts that include engine blocks, connection rods, universal joints, gearboxes and rear axles, for both on- and off-highway vehicles. This is because reliability was a central issue at the heart of the cutter’s development. Secure insert positioning, for example, is a prerequisite for many machine shops that demand trouble-free, dependable machining. Furthermore, CoroMill 745 inserts are purposely thick and secure with strong, sharp edges for high precision and a robust cutting process, while the precision-ground geometries are designed to avoid workpiece frittering in cast iron, which can often occur at the cutter exit side of the component.
The insert position and heptagonal (seven-cornered) insert shape make for easy replacement and indexing in line with modern timesaving and ‘green light’ machining demands. Indexing, in fact, can be performed without operators having to remove their gloves. When replacing inserts, operators are able to keep them in the pocket when mounting due to the insert design and its position in the tip seat. In effect, the insert position can be secured before tightening the large M7 screw (deployed for extra process reliability). As a further benefit, due to the large screw hole, less powder is used in the insert manufacturing process at Sandvik Coromant, thus benefiting the environment.
Another useful feature for production engineers is the availability of a unique differential pitch (MD pitch) up to 160 mm (6”) diameter for roughing operations where reduced vibration is essential. This medium pitch MD design was developed using advanced genetic algorithms to reduce vibration when machining components that are sensitive to resonance or reverberation. Here, the insert position is compensated radially for an even chip load. Sandvik Coromant specifically designed MD as a problem solver to the issue of vibration, thus providing a good alternative to pitches such as M for general applications and the close H pitch for higher productivity.
In terms of insert geometries, Sandvik Coromant is initially introducing the E-M30 and E-M50 types for CoroMill 745, where E-M30 is first choice for steel and cast iron workpieces, as well as in vibration-sensitive operations and when less power consumption is required. Conversely, E-M50 is a tougher geometry for more demanding operations or when higher productivity is needed. E-M50 should also be selected for grey cast iron (GCI) workpieces found commonly in numerous automotive applications, as well as in nodular cast iron (NCI) machining. Ultimately, these precision geometries in combination with the tool’s inherent light cutting action can help lower power consumption and reduce noise for the operator, thus promoting a better working environment.
Available as a standard, stocked cutter, CoroMill 745 is set to transform the landscape of face milling for the benefit of the entire company. Arbor, Coromant Capto® and CIS arbor coupling variants can be selected, with through-coolant in cutters up to 160 mm (6”) diameter. All CoroMill 745 milling cutter bodies offer an entering angle of 42°, although among future planned additions to the range is a high-feed variant featuring a 25° lead angle, which will offer feed rates of up to 0.7 mm/tooth (0.028”/tooth).