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Revolutionary Laser Metal Deposition cuts manufacturing time

Two years of development and six months of demonstration activity, led by the team at TWI’s Technology Centre in South Yorkshire, concluded the validation of CAM-style software tools created as a plugin to TWI’s ToolCLAD software: a software package being developed at TWI specifically for the LMD CAD-to-part-manufacturing process. The plugin maps a five-axis vector toolpath with deposition parameters to guide a three-axis coaxial LMD nozzle across a moving substrate manipulated by a two-axis CNC rotary table, creating a novel method of LMD manufacturing.

With precise synchronisation of the movements of rotation and tilt of the substrate with incremental movements of the coaxial nozzle (predominantly in the +Z direction), a continuous spiralling weld track can be deposited or ‘grown’, layer on layer, out of the substrate. This helical multi-layering technique allows a thin-walled 3D contour to form, which accurately follows the changing directions of the original CAD surface profile (STL file). The process is analogous to a clay pot forming on a potter’s wheel.

Another innovation is the use of an adaptive slicing algorithm which varies the lead distance (distance the nozzle moves away from the substrate in one complete revolution) of the helical tool path according to the tilt angle of the substrate. Without this feature, printed parts would have a sizing error in the Z direction.

By manipulating the substrate, and minimising the movement of the LMD nozzle, features such as overhangs can be generated, with a vastly improved surface quality, without the need for any supporting structure. This leads to some impressive statistics:

  • Component: helicopter combustor casing (Turbomeca)
  • Material: Inconel 718
  • Size: 300mm diameter x 90mm tall.
  • Weld track: 0.9mm wide x 0.2mm deep x 0.5km long.
  • Dimensional variance from CAD: 0.2mm  (average across radius)
  • Surface finish: 15 microns RA (average)
  • Build time: 7.5 hours

Bringing real world benefits, the high integrity of the  final part allows it to be removed, without distortion, from the substrate. However, a final heat treatment step would be required to alleviate residual stresses that build up during manufacture. 

The research leading to these results has received funding from the European Union Seventh Framework Programme [FP7/2011-2014] under grant agreement no 266271.

For more information on LMD technologies please email contactus@twi.co.uk

 

Five-axis manufacture of the helicopter engine combustion casing
Five-axis manufacture of the helicopter engine combustion casing

For more information please email:


contactus@twi.co.uk