Ready to use additive manufacturing

Posted on 10 Dec 2009 by The Manufacturer

Ready-to-use Additive Manufacturing (RUAM) is a new technology developed by Cranfield University, which aims to improve industry’s ability to manufacture high precision ready-to-use functional parts for a range of applications from small turbine blades to large aerospace structures. Cranfield’s Dr Jörn Mehnen explains.

Imagine a single machine that can help you repair turbine blades quickly, build large aeroplane wing structures in short timescales, re-produce worn metal parts, or generate light weight metal structures from CAD or scanned data. Imagine a machine that is also economically friendly, easy to handle and maintain.

Energy, metal and good ideas are the ‘fuel’ of this machine; ready-to-use parts are the immediate results.

The idea may sound futuristic, but Cranfield University is currently working on such a machine.

RUAM combines multi-axes grinding and additive manufacturing. Currently, additive manufacturing generates robust three dimensional metal objects and multi-axes grinding generates high precision free form surfaces. Their integration allows for manufacturing of high precision three dimensional geometries which cannot be produced using conventional techniques.

The RUAM process does not follow the typical rapid prototyping concept. The project aims to manufacture ready-to-use parts made of steel, aluminium or titanium structures with dimensions from several inches up to 30 metres. Surface integrity and precision is achieved — where necessary — via well-aimed machining. The integrated concept of the machine reduces issues such as re-clamping and the awkward handling of workpieces. A high performance grinding machine provides the grinding facilities and housing for the integrated RUAM machine.

Innovative additive layer welding techniques such as Cold Metal Transfer (CMT) helps deposit metal with relatively high speed. High flexibility in the shape of the parts is achieved via a welding robot. A quick and user-friendly interface developed at Cranfield University reads CAD data and helps avoid the often long periods associated with robot training. The optical scanner supplies the system that provides important information about the quality of the workpieces at any time of the process.

The successive layer-by-layer technology allows for flexible welding strategies. The successive process also allows for the mixing of strategies and materials as well as for amending already existing metal workpieces. Engineers do not need to think in terms of ‘cast objects’ any more. The RUAM process is much more flexible, capable of producing geometries that fit various demands.

Team effort
The complex research is still ongoing. The Cranfield team is currently exploring various questions such as the distortions due to the intense thermal influence. This is dealt with by extensive finite element method (FEM) analyses leading to optimised welding and cutting strategies.

The use of FEM analyses will lead to a whole library of rigid, light weight and fit-for-purpose geometries.

Thorough experiments and statistical analysis are being conducted, with the aim of identifying optimal welding parameters. Current RUAM research considers optimal welding strategies for titanium or aluminium parts. Here the introduction of a new local gas shielding technique is of special interest. Material properties are also being analysed by the University of Manchester. In addition, research regarding economic and environmental aspects will highlight areas where the RUAM process will give industry special advantages and where it can leverage new routes to innovative production processes.

Supported by EPSRC through the Cranfield Innovative Manufacturing Research Centre (IMRC) and supported by a range of industrial collaborators, the £2 million RUAM project has attracted considerable industrial and scientific interest since it began in late 2007. The RUAM project is currently supported by 18 industry partners with leading contributors such as Airbus, Doncasters and Bombardier. RUAM also collaborates with two UK universities.

Current state-of-the-art ALM technologies are a long way from addressing this challenge, which is why we are highly active in this field of research.

Scaling up will drive new integrated research on materials, process and control. RUAM represents an integrated approach to research, and not just with the industrial partners but also the academic integration across institutes and PhD studentships.” Keith Birmingham of aerospace-grade welding filler supplier VBC says: “The RUAM project is visionary and its rapid progress has delivered excellent examples of what can be produced when industry interacts with a top class welding engineering university such as Cranfield and its dedicated academics.” Martin Stevens of A1 Technologies also considered the smaller applications of the technology.

“Working together with Cranfield, we at A1 Technologies intend to bring the RUAM technology to market for less demanding 3D metal applications.”