Fig 2 : 27 cubic metre flexible enclosure used to prevent oxidation of parts during robot controlled WAAM operations .
and various nickel alloys . Since then the focus has shifted to airframes . Although laser and powder methods are useful for certain applications such as rapid prototyping or for small highly complex parts , this technology is limited by its speed and the size of component it can accurately manufacture . In contrast , the processes being developed at Cranfieldare designed for high deposition rates .
To put this difference into context , the centre is currently targeting a deposition rate of 10kg an hour for titanium , compared with a typical 0.1kg using laser + powder methods , which can also potentially carry the risk of the material not being fully consolidated if fusion has not occurred between grains . Additive arc + wire systems are also capable of producing parts several metres in size and simplify the process of producing single piece linear intersections .
One of the main projects at Cranfield ’ s Welding Engineering Research Centre takes the technology one step further . The programme began in 2007 with funding from both the University ’ s Innovative Manufacturing Research Centre and 15 industry partners . The idea is to simplify the process of complete product within a single one-hit additive manufacturing system incorporating a fully integrated robot .
Additive layer manufacturing offers several advantages for certain structural airframe components such as a vast reduction in material wastage , especially when producing many heterogeneous parts , and the ability to produce a great variety of part designs for prototype work quickly .
There is also the key benefit that it allows the consideration of unconventional designs that otherwise would not be practical because of manufacturing or cost constraints due to , for example , complex or unusual geometries , bringing with it many different opportunities and challenges .
Overcoming the problem of oxygen contamination during WAAM
Many alloys may be used during the WAAM process simply by using the welding torch inert gas shroud as protection . However , some materials are much more prone to reaction with residual oxygen and this can lead to fusion zone and surface oxidation . Titanium alloys are particularly sensitive and demand additional inert protection .
With the electron beam process , protection is assured since operations are carried out in a vacuum . Nevertheless this is an expensive alternative to arc welding .
Flexible Enclosure Technology
There have been considerable advances in enclosure development since the concept was introduced over two decades ago . Huntingdon Fusion Techniques Ltd for example has spearheaded a drive to design systems specifically for the welding industry . The company has been at the forefront in developing these enclosures for many years and has exploited the opportunities offered by advanced engineering polymers . These innovative products offered significant attractions over both vacuum and glove box alternatives ;
43 TN MAY 2016