Analysis Of Manufacturing Error And Its Orientation Effect On The Bone Scaffolds Fabricated By Additive Manufacture

Recent decades have witnessed an increasing number of patients with bone defects among the gradually aging population,so it is of great importance to find reliable treatments for the disease.Among many therapies,bone tissue engineering scaffolds have the characteristics of wide sources and will not cause secondary trauma.They are one of the important therapies for the treatment of bone defects.The triply periodic minimal surfaces(TPMS),which has the characteristics of high specific surface area and zero average curvature similar to natural human bone,is an ideal structure for constructing scaffolds.Because additive manufacturing technology can better control the internal characteristics of the structure,it is widely used in scaffold manufacturing.Due to the strict medical performance criteria for the scaffolds and high requirements for the repeatability and quality of manufacturing technology,additive manufacturing as an emerging technology still faces many difficulties in the field of scaffold manufacturing.Therefore,investigating the manufacturing error and the orientation effects of TPMS scaffolds manufactured by additive manufacturing technology has important reference value for the performance evaluation of scaffolds and the improvement of additive manufacturing technology.In this dissertation,two groups of scaffolds based on Gyroid structure were fabricated along orthogonal building directions using selective laser melting.In order to study the geometric manufacturing errors of scaffolds,the actual geometry of the scaffolds was obtained by scanning the scaffolds using micro-CT,and then was compared to the design model to work out the geometric differences.Mechanical error of the scaffold was studied by numerical and experimental analysisThe results showed that,in terms of the geometric error,compared with the design value,the size of the scaffold is smaller in the manufacturing direction and larger in the other directions,and the porosity of all scaffolds is about 10% larger.The surface deviation error mostly occurs in the opposite direction to the building direction.When the structure lacks support,the surface deviation is large.When the building direction is different,the distribution of the surface deviation error has a significant difference.The equivalent compression modulus of the manufactured scaffold is lower than the designed value.In terms of the mechanical properties,the equivalent compression modulus of the manufactured scaffold is lower than the design value.Compared with the compression in the building direction,the yield strength of the scaffold is greater when the compression is perpendicular to the printing direction but less energy is absorbed per volume.The strain energy density is more discretely distributed in the manufactured scaffold than that in the designed model,and the distribution in the height direction is affected by the cross-sectional area.Based on the results,the TPMS scaffolds made by selective laser melting have errors in geometric and mechanical properties.In this paper,a new method for evaluating the manufacturing errors of TPMS scaffolds was proposed,which provides important reference for evaluating the effects of manufacturing errors on the performance of scaffolds and reducing the manufacturing errors of additive manufacturing.