Research Projects

Cranioplasty a surgical procedure is required to repair the skull defect affecting due to the road side accidents and brain tumor injuries. Ti-6Al-4V alloy is the most preferred material due to its biocompatibility, osseointegration, and corrosion resistance properties. Though, laser and electron beam melting processes are currently being used to manufacturing complex anatomical models and implant with good fitting and geometrical accuracy, however, high initial set-up cost along with longer processing time and higher cost of operation limit their widespread usage for medical implant application. Also, patients have to pay hefty amount to procure these implants for surgical purpose. There is an urgent need to develop a cost-effective cranial implant manufacturing method with better dimensional and fitting accuracy for the patients. Single-point incremental forming (SPIF) proves suitable to manufacture highly customized components like implants. It is a technique in which the localized plastic deformation of metallic sheet is realized using a ball nose or hemispherical tool moving along a pre-defined path to form desired shape on sheet material without any dedicated die or mold making. The SPIF fixture can be fixed on a regular vertical CNC machining center, thereby offering significant cost and setup time reduction over the conventional metal forming techniques which would require a high tonnage press and special die for deformation of hard-to-form titanium alloys for implant manufacturing. The die-less forming process has also shown benefits in terms of low material wastage and high flexibility for rapid prototyping. In SPIF, the formability of part depends on the material properties, shape complexity, toolpath planning, and forming parameters. The forming parameters like spindle speed, feed rate, step depth, and working temperature along with tool tip design and its diameter effects the material formability and surface finish of the final product. It is necessary to optimize the input parameters along with different tooltip design and lubricants to improve the part accuracy as well as the quality of the formed implant surface. This group has successfully optimized the forming parameters of Ti grade 5 material and performed cranial implant forming using SPIF process at room temperature under previous CRG project (CRG/2021/00348). However, SPIF of Ti grade 5 at room temperature shows the formability issue along with high spring back and warpage on release of product from the forming fixture. As a follow on project, it is proposed to develop heat-assisted SPIF along with effective lubrication, to improve material formability by providing localized heat to the sheet while manufacturing complex implant shape using Ti-6Al-4V alloy sheet. Further, post-forming heat treatment will be carried out to relieve the internal stresses induced while forming different wall angle feature shapes like cranial implant. The proposed work aims to develop patient-specific cranial implant with better geometrical accuracy and high mechanical strength along with improved surface finish to provide their efficacy for real-time clinical application.