Surface roughness analysis of medical grade titanium sheets formed by single point incremental forming

Abstract

Single point incremental forming (SPIF) process has proven benefits in terms of formability, flexibility, and low cost as compared to conventional sheet forming, although it has some issues such as dimensional accuracy and low quality of surface finish for some materials. The SPIF is considered as a potential method of producing customised medical parts such as craniofacial implants using a titanium sheet. This investigation aims to analyse the overall surface roughness of grade 1 pure titanium along the wall of the hyperbolic truncated cone formed by the SPIF process with different forming parameters (i.e., forming tool diameter, step size, and feed rate). Focus variation microscopy was used to measure the surface roughness experimentally along the wall of the truncated cone. Abaqus/Explicit was used to predict the equivalent stress and equivalent plastic strain along the wall of the truncated cone part from the top to the fractured region to evaluate the relationship between the stress, strain, and roughness distribution. It was found that the surface roughness changes with the deformed part height and rough surface could be produced in the region of high equivalent stress and low equivalent plastic strain. Such a surface roughness and equivalent stress and plastic strain correlation has a clear implication to the design and the surface quality of sheet parts made by SPIF.

Research on progressive forming quality control technology for sheet metal parts

“…The surface corrugability Wt of the forming parts is theoretically equal to the residual wave peak height hs between layers. The mathematical analytical model of residual wave peak height hs is established according to the characteristics and geometric characteristics of the parts in the machining process [6] . As shown in Fig.…”

“…The larger the diameter of the tool head is, the better the surface quality of the forming part is. This is because as the forming trajectory increases with the diameter of the tool head, the larger the contact area between the tool head and the metal sheet to be formed, the larger the repeated machining area between the trajectory of the previous layer and the trajectory of the next layer, so the better the surface quality of the formed part is [7] . The larger the diameter of the tool head is, the better the surface quality of the forming part is.…”

"A Review for the Formability of Single-Point Incremental Forming (SPIF) Process "

“…Murugesan and Jung [44] inspected the formability of an AA3003-H18 sheet during SPIF process utilizing response surface methodology and Design of Experiments to identify the optimal parameters of forming. Gatea and Ou [45] carried out investigational experiments on various values of surface roughness in incrementally formed sheets of grade 1 pure titanium taking into consideration the process parameters such as feed rate, step size, and tool diameter. It was noticed that surface roughness differed with the deformation depth of the incrementally formed part, and a rough surface could be realized in zones with low equivalent plastic strain and high equivalent stress.…”

Emerging Trends in Single Point Incremental Sheet Forming of Lightweight Metals

“…Murugesan and Jung [164] investigated the formability of an AA3003-H18 sheet in SPIF using Design of Experiments and response surface methodology to determine the optimal forming parameters. Gatea and Ou [165] performed investigations on variations of surface roughness values in incrementally formed grade 1 pure titanium sheets considering the process parameters such as tool diameter, step size, and feed rate. It was observed that surface roughness varied with the depth of deformation of the incrementally formed part, and a rough surface could be generated in zones with high equivalent stress and low equivalent plastic strain.…”