The turbocharger, essentially a gas-driven turbine rotating at more than 300,000 r/min, makes a vehicle’s engine run cleaner and more efficiently by compressing a large volume of ambient air for combustion.
An ordinary motorist associates the turbo mainly with improved fuel efficiency with no need to compromise on the fun of driving. For diesel vehicle owners, the key benefit is compliance with CO2 and NOx emission limits while maintaining vehicle performance: A turbo diesel is up to 40 percent more fuel-efficient than a comparable free-breathing vehicle. Furthermore, modern vehicles may have up to three turbochargers instead of a single one.
In the larger view, turbocharging is a key enabler for increased vehicle power density – in other words, getting more output from smaller engines. A major manufacturer expects the average engine displacement to decrease during the next 10 years from 3.6 litres to 3.0 litres in the United States and from 1.7 litres to 1.5 litres in Europe. With increasing demand for smaller, more efficient engines, around 85 percent of all new light vehicles in Europe are likely to be turbocharged by 2020.
Sandvik Coromant M612 is a dedicated face milling cutter designed to tackle the challenging roughing operations on turbo exhaust housings. A short, robust tool suitable for the vibration-prone operation, M612 features round, negative inserts with positive geometry for smooth cutting action at high metal removal rates. A low cost per part is achieved by the inserts with 12 cutting edges, six on each side, and a maximum three-millimetre depth of cut.
The faces of the M612 indexable inserts mate with the similarly shaped insert pockets to secure robust coupling with excellent accuracy and repeatability.
The versatile CoroDrill® 460 high-performance drill and CoroTap™ 300 spiral flute taps complement the package with an efficient hole-making and tapping solution.
High-precision coolant delivery through fixed nozzles of the CoroTurn® HP tools dramatically improves chip breaking, process security and productivity. When turning austenitic stainless steel with a 100-bar coolant pressure, up to seven times longer tool life can be achieved compared with conventional tools.
The exhaust side housing in a turbocharger must operate in temperatures ranging from 850 to more than 1,300 degrees Celsius (1,562 to 2,372 degrees Fahrenheit). The extreme heat requires advanced and highly abrasive stainless steel or advanced cast iron materials.
The heat-resistant materials and other technologies, such as aerodynamics, rotor dynamics and testing procedures, are not unlike those used in the aerospace industry.
A particular machining challenge is vulnerability to vibration due to the complex, thin walled design of the component, which calls for careful clamping and robust tool setups.