Joint “attack” on the camshaft

05/03/2012 - Oliver Hagenlocher

The international automobile market is still in the middle of a period of dynamic growth. The number of automobiles sold on a global basis rose by three percent in 2011 compared to the figure for 2010 according to the American market research institution, Polk. The production situation at many automobile manufacturers as well as their suppliers is characterized by a great deal of enthusiasm. The “just in time” quantities of a component that are required are also increasing rapidly. Quality is also being tested right now. The fact that new mechanical engineering technologies can meet these challenges with ease is demonstrated by a particularly demanding application that has a major influence on the quality of the entire engine, the grinding of crankshafts and camshafts. The synchronous support grinding technology developed by EMAG allows productivity in the production of the components to be improved by up to 70 percent – a quantum leap.


The international automobile market is still in the middle of a period of dynamic growth. The number of automobiles sold on a global basis rose by three percent in 2011 compared to the figure for 2010 according to the American market research institution, Polk. The production situation at many automobile manufacturers as well as their suppliers is characterized by a great deal of enthusiasm. The “just in time” quantities of a component that are required are also increasing rapidly. Quality is also being tested right now. The fact that new mechanical engineering technologies can meet these challenges with ease is demonstrated by a particularly demanding application that has a major influence on the quality of the entire engine, the grinding of crankshafts and camshafts. The synchronous support grinding technology developed by EMAG allows productivity in the production of the components to be improved by up to 70 percent – a quantum leap.

For example in China – even if the automobile market in the country is currently growing more moderately, the “Middle Kingdom” is still the driving force on the global market. Around 11 million automobiles were produced in China in 2009 and the figure rose to around 14 million in 2010. In 2011, production growth slowed to about 15 million vehicles (source: PwC, Statista). Imports of automobile components, complete engines and gear boxes are also increasing rapidly. On a global scale, according to the foreign trade experts from Germany Trade and Invest, China is already the third largest importer. How can these rates of increase be managed using economical and high quality processes, both at established production locations outside China and also when planning new production plants?

Crankshaft and camshaft machining – a prime example

The production of crankshafts and camshafts are a prime example because both components are at the heart of engine production and their extraordinary geometry demands complex production processes. Grinding has a special role to play in the overall process because it must ensure that the components are true to size. At the same time, the process is often time-consuming and demanding – in particular, shafts which are very slim are not very strong in the machining direction which often means that sophisticated stabilization methods must be used with multiple trailing steady rests. Consequently, only comparatively low feed rates can be used – particularly to eliminate true running inaccuracies. This naturally results in long cycle times and low output. “We decided to tackle this problem head on in our development of a new grinding technology based on the vertical clamping of the component. Our idea was to reduce the forces which act on the component during the grinding process. Ultimately that will allow higher feed speeds,” explains Dr Guido Hegener, CEO of EMAG Salach Maschinenfabrik GmbH.

Low forces acting on the component
The development of synchronous support grinding, which is used on the VTC 315 DS vertical grinding machines, supplied by EMAG marks a breakthrough by developers in this sensitive application. The principle is based on the use of two grinding wheels which act on the crankshaft or camshaft from two sides moving in different directions. The normal forces which occur in the feed direction are compensated by the fact that the grinding wheels are mounted opposite each other and machine the component simultaneously. At the same time, a simple NC-controlled support is used to press against the workpiece from one side. This means that the workpiece cannot move in any direction and also eliminates tangential forces. “This design therefore has multiple positive effects,” says Guido Hegener. “On the one hand, extremely high feed speeds for grinding delicate workpieces such as a crankshaft or camshaft are possible due to the rigid clamping operation. On the other, two grinding wheels are used simultaneously. This drastically reduces the machining time compared to the conventional grinding processes in use today.”

Vertical design positive
The design principle of the EMAG grinding machine is another major factor in ensuring that the components can be ground at low cost. The shaft is clamped vertically inside the VTC 315 DS. The workpiece spindle is at the top, the tailstock is at the bottom. The entire grinding process on the shaft takes place in this position. The vertical position of the component also assists in producing good chip flow. This means that the removed material can be removed particularly easily and efficiently together with the cutting fluid. In addition, the cutting fluid does not flow over the structure of the machine and its temperature is not subject to fluctuation at any time during the process. “This is a point which ultimately has a direct bearing on machining quality because the whole subject of heat management in the system is insignificant,” says Guido Hegener. At the same time, the vertical design makes the system simpler to operate and ensures that the production process can be completed efficiently. Furthermore, there is generally no need for separate catching on the VTC 315 DS. This, in turn, simplifies the setting process.

4-cylinder camshafts with high true to size precision

What have been the experiences of users of the synchronous support grinding principle? “The response that we have had has been extremely positive,” says Guido Hegener. “The principle can also be used for transmission shafts, propeller shafts, pump shafts and compensating shafts with a maximum length of up to 600 millimeters. In every case, there has been a massive leap in productivity. In some cases, the machining time has been cut by up to 70 percent compared to traditional grinding.” On the other hand, the machining quality is improved. One example of this is the experience by a user in the production of a cast 4-cylinder camshaft for a car. The machining of the main bearing takes place in several sequences each with a grinding time of five seconds. Despite the short grinding time, true running inaccuracy levels of less than 10 mm have been recorded. This is much lower than the maximum tolerance limit and marks a clear improvement compared to the grinding process used in the past – in other words, a leap forward in quality.

Joint attack on the camshaft
Synchronous support grinding is not just appropriate for circular grinding but also produces positive effects for non-circular applications. Pairs of cams on 4-cylinder camshafts can be machined simultaneously which means that four grinding wheels can grind a single camshaft at the same time. This process on the one hand results in drastic reductions in machining times while on the other increasing the quality of the cam shape. This produces double benefits for the user.
This machining process means that EMAG can now complete the entire process chain for a camshaft comprising end machining, turning, deep hole drilling, milling, circular grinding and non-circular grinding with vertical clamping.   

Major market opportunities
The fact that the management team at EMAG believes that this process has major opportunities on the market will certainly not come as a surprise. But there are a whole host of other arguments in favor of synchronous support grinding including the fact that the much shorter machining times also mean considerably lower energy costs. “The energy per piece cost is much lower. This also means lower costs for the user,” confirms Guido Hegener. Furthermore, there is the fact that the vertical systems require less space than machines with a horizontal design. “Economical processes, simple handling, high quality – the many benefits of synchronous support grinding compared to traditional grinding process will quickly become established on the market,” says Guido Hegener with a great deal of confidence.

Contact

Oliver Hagenlocher

Press and publishers

Phone:+49 7162 17-267
Fax:+49 7162 17-199
E-Mail:communications@emag.com

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