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Process Improvement Passau is the production and development location of ZF


Friedrichshafen where axles, transmissions, and drive com- ponents are manufactured for construction and agricultural machinery, buses and cars, including a 700-mm-long central drive and transmission output shaſts for cars and commercial vehicles. Between 14,000 and 16,000 are produced annually. Also manufactured in Passau are so-called special shaſts for tractor and automatic transmissions. Te typical material of these shaſts are 16MnCr5 (1.7131) and 42CrMo4 (1.7225) steels. Te number of deep holes required in each shaſt range between one and five.


The Parameters For hole diameters


up to 7.5 mm the maxi- mum depth is 600 mm, of which the first 410 mm is currently machined with Mitsubishi’s solid-carbide drills. Single-flute gun- drill-type tools are used for the remaining depth. Standards for tolerance and surface quality are +0.2/-0.1 mm for diam- eter, 1-mm positional tolerance, 2 mm for depth tolerance and Rz


100 max. surface roughness. Te tool life of the drill ranges


between 40 and 100 m depending on the work material. “Rather than switching operations to specialized equip-


ment or investing in a new deep-hole drilling machine, we perform this operation on an existing standard machining center,” said Production Manager Franz Schwarzmüller. A sav- ing on this investment may not have been possible with other drills. Additionally, Mitsubishi’s drills, with a suitable holder, were stored in the tool magazine and changed at the spindle in the same way as any standard tool. “Tis saves a considerable amount of time and money. Because the deep-hole drill- ing process is now so reliable, it also saves the costs of drill breakage, the workpiece itself, and the machine downtime if a breakage should occur. Te savings can soon reach the four- figure mark,” said Schwarzmüller. “Seeing and hearing the ease with which the drill cuts


testifies to its quality,” said Manfred Bartl, one of the 25 machining center operators that oversee deep-hole drilling on various machining centers, during a three-shiſt system at ZF in Passau. “Te drills also work with a 50 bar coolant pressure, twice that of a normal tool,” said Bartl.


78 Motorized Vehicle Manufacturing


Mitsubishi MHS drills are used for drilling small-diameter holes to 60 × D depths in case-hardened and heat-treated steel on standard machining centers, instead of special machines.


Another cost-saving feature is that the drills can be re-


ground and coated, with about 30 pieces undergoing this pro- cess every week. Problems with fluctuations in performance and quality of the re-ground drills are unknown. It remains to be seen whether the end of improvement cycle has been reached or if the process can still be further improved as new technology is developed.


Deep-Hole Drilling Evolution Wilfried Dyduch and


Albert Häring, application engineering and technical consultants from Mitsubishi, have followed the deep-hole drilling project from the outset. “In 2005, 30 × D was the standard and it was far from certain who would become established leader in the area of deep-hole drilling, especially as rivals for this consisted of most of the leading tool manufactur- ers,” said Dyduch. “Constant development, presence at customers and quick feed- back finally paid off. Every second week throughout this whole process we had a


progress meeting with ZF Passau,” said Dyduch. “Te functionality of the drill is perfect and coordination


and engineering support are always extremely competent. We work here with many well-known tool manufacturers, but where deep-hole drilling is concerned, Mitsubishi is the leader,” said Lang. Petra Reinhold, technical department manager at Mit-


subishi, summarizes the trend in the area of deep-hole drill- ing tools: “Every 10 years they become 100-mm longer and a total length of 490 mm is now the maximum. Te internal coolant pressure has also risen, from 30 to 50 bar and in the future 60 or 70 bar is expected. Te coating is also expected to make similar progress as time goes by. Importantly for re- liability, we also recognize that the specifications of compo- nent materials fluctuate, but our drills are capable of coping with those fluctuations and produce almost identical results time aſter time.” Te supplier of ZF Passau’s deep-hole drills is MMC Hartmetall GmbH, a group company of Mitsubishi Materials.


Edited by Senior Editor Jim Lorincz from information provided by Mitsubishi Materials.


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