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.