The main limiting factors of throughput and reduced idle times are cutting speeds, work piece loading methodology and ease of machine setup. In high volume production these are decisive economical factors. The K 160 Gear Hobbing Machine from Koepfer presently holds the world record in chip-to-chip times for the machining of shafts and pinions with the least number of teeth. However, the company in Villingen-Schwenningen, Germany, is at this moment building a machine that will once again smash that record.
KOEPFER: K 160 The perfect shaft in record time
07/11/2008 - Oliver Hagenlocher
Dry or wet machining? This decision has to be made by the customer and is requirement-based. The same applies to the choice of automation and auxiliary equipment. The new generation of Koepfer K 160 gear hobbing machines for the high-speed machining of gears up to module 2.5 does not make that choice any easier. However, where machining times are concerned, the main objective is always the same: as fast as possible.
The basic prerequisites for fast chip-to-chip times are high spindle speeds for the cutter and work axes. These features will allow the machine to take advantage of high cutting speeds. But to make the manufacturing process truly efficient you also have to reduce the times for loading, unloading, setting and programming to their absolute minimum. Over the last few years users of the K 160 appear to have these factors well under control. Considering the fact that only 8 or 10 years ago the machining of armature shafts took 20 to 25 seconds, the K 160 has been achieving a world best of 8 to 10 seconds for some years now. The dry, high-speed hobbing of planetary gears or the high-speed gear cutting on armature shafts using the “fly-hobbing” process, are as much a part of the reason for the success as is the possibility to use the tangential hobbing process to generate the gear teeth on worm wheels. The greatest time saving, however, could be the optional work piece loading concept, where the parts are loaded through the spindle. This concept has now evolved to the next level with further developed and fine-tuning by Koepfer. Armin Wacker, VP-Sales and Marketing at Koepfer Verzahnungsmaschinen GmbH & Co. KG, sees this development as a real quantum leap and a measurable time saving: „Our K 160 already gives us the fastest manufacturing time for shafts in the world. The new concept, in which the work pieces are literally ‘shot’ through the spindle, almost completely eliminates idle / changeover times. It allows us to reduce the machining time for a shaft by yet another two seconds. In other words, we have made the leap from eight to six seconds.” The new concept also includes a brand new shifting hob head with a maximum hob shift of 160 mm and new software with dialogue programming facility. Programming has been greatly simplified – even for operators that lack special qualification – by the BWO control with conversational dialogue, full colour touch panel, and 1 MB of memory. The combination of new software and drive technology allows the customer to achieve a level of precision that has previously only been possible with grinding. Such quality makes the K 160 also a viable proposition for the machining of components with special safety requirements, including those for the aerospace industry. As mentioned earlier, chip-to-chip times are mainly dependent on spindle speeds and cutting speeds. In its standard version, the K 160 has a work spindle speed of 1,000 rpm and a maximum cutting spindle speed of 5,000 rpm. The latter can, without problem, be increased to 12,000 rpm, where the application requires.
This provides a power reserve that, according to Armin Wacker, serves a valuable purpose: „On the one hand, we are not maxing out any of our machines, as we not only want to but must ensure they always suit the prevailing customer requirements. On the other hand, tooling manufacturers have – over the last few years – made enormous strides with, for example, coating processes. The much greater wear resistance of today’s tool alloys allows us to increase spindle speeds and cutting speeds. 5,000 rpm is already pretty fast, but we have to be able to increase that, when necessary. “
The standard version that sets a new benchmark
With the standard work spindle speed the user can produce armature shafts with 4 teeth, using a 24 mm hob at a cutting speed of 300 m/min. The standard machine is rated at a maximum work piece length of 300mm and a maximum hobbing length of 200 mm. A long-bed version of the K 160 with a maximum hobbing length of 480 mm and a maximum work piece length of 600 mm is also available. The standard machine can be equipped with a variety of different Koepfer automation systems. First, there is the integrated gantry loader with flexible work piece magazines, chain loader and conveyor belt storage section. A rotating twin-gripper offers shortest loading and unloading times. Optionally, a high capacity re-circulating storage system allows the machine to be run a number of hours and is quick and easy to reset - accommodating both gears and shaft- or pinion-type components. Using a special metering hopper with multiple feeder rails, the work pieces can be loaded diagonally, which considerably increases the autonomy of the machine. Also available as an option is an auxiliary tool that can be used for deburring operations (via deburring disc or rotating tool), as a vibration dampener, as a holder for the sensor that allows the automatic timing of work pieces with hardened gear teeth, or for special purpose applications such as live deburring tools. The flexibility of the K 160 continues to show when the machine is integrated into a production cell that includes gear hobbing, washing, measuring, etc.
All in all, the K 160 Gear Hobbing Machine sets the new standard for the future. It is easy to calculate the amount of savings that will accrue as a consequence of a two second time saving per armature shaft, of which a million are produced every year.
The advantages of the K 160 at a glance
- High degree of efficiency, achieved by shortest possible cutting times and minimal chip-to-chip and idle times
- Time savings thanks to the simplicity of the Koepfer dialogue-based programming software whose menu navigation keys make programming easy - even for inexperienced operators.
- Wide range of applications through highest precision. The K 160 is also suitable for the machining of safety-relevant components for the aerospace industry.
- Many customer-specific automation solutions can be implemented due to the flexibility of the machine.
- There is no problem in integrating the machine into a manufacturing cell that includes gear cutting, washing, measuring and damage-free storage.