“Reducing mass is an effective way to reduce vehicle emissions,” according to the International Council of Clean Transportation (ICCT)’s Fact Sheet Europe Report. The onus is on automotive manufacturers to produce more weight-efficient components. Yet heavy cast iron and forged steel remain popular and manufacturers must design and engineer these ‘heavy’ metals into being weight-efficient. Here, Sangram Dash, Product Application Manager for Indexable Milling at Sandvik Coromant, explains why lighter and closer-cutting shoulder milling and face milling tools are the answer.
Further to the ICCT’s findings, McKinsey & Company’s ‘Lightweight, heavy impact’ report offers in-depth calculations as to how lighter vehicles emit fewer CO2 emissions: “Lightweighting measures can help reduce CO2 emissions to a certain extent (approximately 0.08g CO2 reduction per kilogram saved). If an OEM manages to reduce the vehicle weight by 100kg, it saves approximately 8.5g CO2 per 100km.”
In response to findings like these, automotive manufacturers are turning to ‘lightweighting’ to facilitate better fuel efficiency and handling. Lighter metals like aluminium and magnesium can help in this regard, but lightweight is about more than simply choosing whichever material weighs less – especially when heavier materials are still widely used in vehicle manufacturing.
Manufacturers must design and engineer these metals into being a weight-efficient and strong alternative to lighter metals. This means producing more complex, near-net-shaped parts based on more complex designs, which is tough when producing ISO-K materials that are more difficult to machine. What’s more, all cast irons contain silicon carbide (SiC), which is very abrasive to the cutting edge. When there is a need to produce a variety of components – shoulder milling is the best approach. The basic-yet-versatile milling application ensures a lighter cutting action that minimises impact on the tool and ensures the component stays in shape. With shoulder milling, the tool creates a plane and shoulder surface, simultaneously.
A ‘light touch’
Generally, 90-degree milling angle inserts have eight edges – four on the front and four on the back to produce the shoulder and plain simultaneously. Sandvik Coromant felt there was room for a new shoulder milling concept; one that would bring greater productivity, tool-life advantages and economic benefits for OEMs.
In response to the above challenges, Sandvik Coromant developed its CoroMill® MF80 inserts. Designed for automotive milling applications in ISO-K and ISO-P materials, the inserts have eight cutting edges, chip protection and an optimised micro geometry. The tools are designed to be ideal for thin-walled components and machine setups with limited stability. The cutting edge is inclined for smooth cutting action and to promote low cutting forces. This gives better security and chip evacuation, as well as a wiper edge for a superior surface finish.
CoroMill® MF80 isn’t entirely new, but based on a technology platform similar to Sandvik Coromant’s existing Coro-Mill® 345. This new milling concept offers a 40% lighter cutter body with shim protection and a high number of inserts for secure and stable machining, even in vibration-prone overhang applications.
Performance tests
In one case, CoroMill® MF80 was run against a competitor’s mill in a rough shoulder milling application to produce pump and valve components from an ISO-P carbon steel part. The mills were run with identical cutting data with one exception, the competing mill was run at 375mm/min and CoroMill® MF80 was run at 600mm/min. The CoroMill® MF80 gave a productivity increase of 60%. The competing mill produced nine components while CoroMill® MF80 produced 15. As for tool life, the CoroMill® MF80 gave a tool life increase of 67%. The key advantage for the customer was that the mill’s shim protection and the high number of insert edges can lower the cost-per-part in roughing or shoulder milling.
