Tool Tech: Turbo-Charged Productivity

Currently, lightweighting and downsizing are the dominant issues in the automotive sector. All of the German auto manufacturers, as well as manufacturers from Korea and Japan, are following this trend by developing engines with a considerably reduced cylinder capacity yet achieving the same performance of V6 or straight 6 power units today through the use of turbochargers.

Since the 2014 season even Formula 1 has joined this trend. Engineers developed 1.6-litre V6 engines that provide over 800 horsepower by means of turbochargers and the aid of kinetic energy recovery systems (KERS) units which capture waste energy during braking and transform it into electrical energy.

The target of downsizing is to steadily lower the consumption of the engines while keeping up performance. This results in a constantly growing demand for turbochargers.

Manufacturing and machining of turbocharger components is highly complex and requires high productivity of the manufacturer and particularly process reliability.

The following test case conducted in Germany shows how innovative cutting tools can provide economical and process-safe machining.

For commonly used materials, e.g. heat-resistant cast steels, cutting tool manufacturers customize tool systems. Any specialty metal requires special demands from the cutting tool material and coatings. Due to the continuously unstable cost of nickel (between 2005 and 2013 the fluctuation varied between 5 to 13-Euro per kilo), producers of turbochargers attempted to develop and use materials with low nickel elements. In order to follow this trend and react to the latest developments, three independent Iscar technology centers worked on developing new cutting materials, insert geometries and coatings.

The newly developed S845 SNHU 1305 ANR-MM MS32 with adjustable face milling cutters (fig. 1) for example was found to achieve up to 25 per cent longer tool life compared to alternative tools.

Turbine housings, rotor shafts, turbines, as well as compressor wheels, are of paramount importance in terms of focus components in turbocharger manufacture.

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For the complex V-band machining of turbine housings a plunge operation with tangential inserts was developed. This system is characterized by its high stability as well as its soft cutting geometry (fig. 2). It consists of an insert type fitting into any insert pocket and hence is very user-friendly.

Turning proves to be the most economic machining strategy for the V-band contour as the component allows this way of machining and no collision occurs. For this machining a five-edged Penta insert was used. The star-shaped insert is available in two standard sizes, depending on the depth of the V-band groove. An advantage of the Penta system is the broad product portfolio which provides a large amount of various standard geometries, chipformers, and coatings, as well as solid carbide substrates which were especially developed for this application.

For example see fig. 3, a tool designed for interpolation turning operations. This tool can be adjusted radially and axially so that narrow tolerances of the V-band contour can be realized.

For the bushing bore for the butterfly valve of the turbine housing a modular drilling system with an exchangeable head SUMOCHAM and the modular reaming system BAYO T-REAM were put into action. Like the SUMOCHAM system, the BAYO T-REAM system (fig. 4) provides exchangeable reaming heads. Especially for reaming high heat resistant cast steels, this reaming head was developed and achieves up to 20 per cent longer tool life compared to competitive tools. Possible due to cooling at the cutting zone.

In 2013 ISCAR Germany conducted research focused on machining turbine housings, and successful tests were completed in cooperation with the cooling lubricant manufacturer Blaser Swisslube. A customized benchmark in solid carbide drilling was performed. Using tools designed for each machining operation and the optimal coolant strategy tool life increased up to 1,200 holes at the customer site and 2,000 holes at Blaser’s Tech Center. In face mill roughing, improvements of up to 25 per cent were possible compared to the customer’s previous tool life. Even face mill finishing increased by 45 per cent.

Jens Tempel, business development with ISCAR Germany.