Rapid prototyping

Thursday, February 21, 2013

Tags :  advanced-materials

In the previous article on the advances in rapid prototyping materials and methods, some possible applications were mentioned, especially for exhausts. Laser-sintered exhaust components have been displayed at trade shows for several years now and there are exhaust companies who have used the method to produce real parts for a few years in both high-temperature materials such as Inconel but also titanium.

There are of course other applications for this technology and the increasing range of metallic and non-metallic materials now commercially available. Recently, on the eve of the Autosport Engineering trade show in the UK, I was shown a hollow poppet valve with a very detailed internal structure. Hollow-headed valves are prohibited in many race series such as Formula One. The valve I was shown was produced by metal laser sintering in a high-temperature material. Its internal structure would be impossible to produce by any other production method.

Increasingly, rapid prototyping methods have shown themselves to be a serious production method for niche applications and one-off requirements. Surely the day will come soon when small non-racing automotive producers will look to such methods for producing components in passenger cars, motorcycles or freight vehicles. Much the same happened with titanium valves and con rods, which were once the preserve of racing teams; both are now used in passenger cars and motorcycle engines.

The valve I saw might prove to be very suitable for the new 2014 Formula One rules, or perhaps for the new Le Mans engines also set to début in 2014, but it was actually destined to be tested on a commercial diesel engine. Again, another regulation introduced initially to save cost will only sideline motor racing when it comes to certain areas of component development, putting high-level motorsport one step behind basic automotive research projects.

The prospect of relatively inexpensive hollow-headed valves is something that a lot of engine design and development engineers will find enticing, and I am sure many of them will look towards this manufacturing technique once the materials and methods are proven to produce parts which not only have the desired static mechanical properties but which can also demonstrate adequate fatigue life.

In terms of materials, there are developments going on all the time. Metal matrix composite powders are being investigated with a view to ‘tuning’ the performance of some relatively ordinary powders that are already commonly available.

When it comes to introducing these laser-sintered materials and their eventual success, the limiting factor will be the creativity of the design engineers. Those who are too heavily encumbered with a lifetime of ‘design for manufacture’ will perhaps find it difficult to let go of these constraints and design what they actually want. Often the comment from producers of rapid prototype parts is that the major failing of designers when designing for the new manufacturing technique is that they simply design something very close to what could be produced by conventional methods – for example, a coolant passage in a rapid prototype part designed as a series of straight holes rather than the continuously curved channel, which is better from a flow point of view and which might have been the obvious choice to a complete beginner with no preconceived notions of how a part should be designed.

Written by Wayne Ward

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