Shop Solutions: Ducati's No-Excuses Approach to Performance
At Ducati Motor (Bologna, Italy) they don’t believe in doing things halfway. For many years, this company’s award-winning motorcycles have been characterized by the highest levels of quality, performance, and innovation. Machining is at the heart of Ducati’s success, and when it came to optimizing a demanding new cam lobe milling application it turned to Walter AG (Tübingen, Germany; Waukesha, WI) for the winning solution.
Nowhere is this commitment to quality more evident than in Ducati’s L-twin engine configuration featuring its desmodromic valve design. Desmodromic valves are closed with a separate, dedicated cam lobe and lifter instead of the conventional valve springs used in most internal combustion engines. This allows the cams to have a more radical profile, thus opening and closing the valves more quickly without the risk of the valve-float that often occurs with a conventional “passive” closing mechanism.
Of course, designs like this are of little use without the machining technology and expertise needed to bring them to life, and here too the Ducati imperative of quality, performance and innovation is in effect. “To continue to increase the performance levels of our engines, it is vital for us to optimize all phases of the various machining processes,” said Pietro Palma, head of the Mechanical Machining Unit. “The two most important steel components, the drive shafts and the camshafts, are machined completely at our plant, because these are key components on which we concentrate our knowledge.”
Palma said that a large part of that continuous improvement process consists of finding and working with companies who share Ducati’s commitment, companies like Walter, long-time suppliers of Ducati’s roughing and finishing tools.
According to Palma, the ongoing challenge is “guaranteeing quality and precision, not forgetting the importance of achieving a sustainable cost on an industrial level.” Walter has worked with Ducati to achieve those goals, becoming “one of our strategic partners and is able to develop technologies that go far beyond those of a simple supplier,” said Palma.
According to David Abate, Ducati’s manager of mechanical machining technologies and process development, “The attention to, and perfection of each machining phase is a daily goal for us. For example, the desmodromic timing system involves twice the number of cams and the timing of the lobes on the shaft must be extremely precise. The cam profiles are complex and therefore, during machining, the milling cutter must follow a profile and not carry out its classic rotary movement around a fixed axis. For this special machining strategy, our initial collaboration with Walter on the development of a special disk tool for this operation was a complete success. But the evolution of this application has not stopped.”
Initial tests on the part, which is made from high-performance steel and requires a large volume of material to be removed, revealed several issues, both in terms of tool life as well as product quality, including high levels of residual stresses on the surfaces of the semimachined part. This led to the creation of a team of product and process specialists from both Ducati and Walter to deal with the problems. They looked at a number of critical aspects, including high specific cutting pressures, a large amount of chips with adhesion, air cutting, and significant sliding between tool and chip. The tool then being used was developing microcracks, and a high coefficient of friction between the tool and chip was causing the cutting area to heat up. There was high thermal stress between the tool and the chip and low resistance of the tool coatings.
To resolve these issues, Abate said Walter designed a new tool with fewer teeth, changing the type of milling cutter to one with radially-mounted tangential inserts and also optimizing the chip discharge area. Another winning solution involved modifying the design of the insert in terms of the microgeometry of the cutting edge, including increasing the top rake angle in order to limit the built-up edge and surface hardening of the machined material. The coating of the insert was also redesigned with Walter Tiger·tec coating which possesses superior toughness and exhibits high resistance to both residual and thermal stresses. The combination of these factors, said Abate, created the ideal conditions for this demanding milling application. ME
For more information from Walter USA LLC, go to www.walter-tools.com/us, or phone 800-945-5554.
This article was first published in the May 2014 edition of Manufacturing Engineering magazine. Click here for PDF.
Published Date : 5/1/2014