Research on the process of multi-point forming for the customized titanium alloy cranial prosthesis

Titanium alloy cranial prosthesis can be formed with multi-point forming (MPF) technology. The 3D curved surface of prosthesis is realized by following processes, 3D reconstruction according to the sufferer's primary cranium CT data, transformation of model data, adjustment of the matrices of punches to curved surface, and forming of titanium alloy retiary sheet. Three forming modes, i.e., (i) titanium alloy retiary sheet is contacted with the element groups directly, (ii) titanium alloy retiary sheet is sandwiched by elastic cushions and contacted with the element groups indirectly, and (iii) titanium alloy retiary sheet is sandwiched by steel paddings and contacted with elastic cushions and the element groups indirectly with blank-holder device, were simulated by an explicit finite element software. Numerical simulation results show that dimples and wrinkles occur at the surface of titanium alloy cranial prosthesis in the first two forming modes, but are suppressed when the last forming mode is adopted. Meanwhile, the 3D curved surface of prosthesis with good quality can be acquired. Finally, the forming tests were performed and the results coincide with the simulation results quite reasonably.