Abstract

Abstract

Optimum implant positioning and technique used for its alignment are vital parameters to improve clinical results. Visual cues and jigs are utilized in the recent surgical techniques, which lead to some errors in the flexion-extension axis identification. Surgeons have used computer-assisted surgery for the alignment of the hip, knee, and shoulder. However, there is a restricted application of this technology to the elbow. In this study, a technique was used to model a drill guide template to precisely place an implant in the bone. The computed tomography dataset was used to construct four different elbow bones, and an elbow implant was modeled. The surgical drill guides were designed based on the computed tomography data. The drill guide templates and constructed bones were fabricated, using a 3D printer. The accuracy of the surgical guides was validated experimentally. The results showed that the mean deviations between the achieved and planned positions of the hole at the bone apex and base of bones were less than those reported in previous studies in both medial/lateral and posterior/anterior positions. The low positioning errors observed in this study proposed that the implant’s location can be precisely aligned to its target using the introduced technique.

Abstract

The objective of this paper is to optimise the internal structure of 3D printed parts produced by Fused Deposition Modelling (FDM) process. In 3D printing, the term infill refers to the internal structure of the part. The infill design is generally uniform throughout the part. In this paper, we propose a methodology based on an iterative process using remeshing techniques coupled to Finite Element simulation (FE simulation) to control the internal structure of the part without changing the contour. The aim of this methodology is to reinforce the part in the area where the mechanical strength must be improved in order to strengthen the structure, but also to minimize the amount of material in order to minimize the printing time. The proposed method is integrated in a computational environment using the ABAQUS (6.14) and the BL2D adaptive mesher. To validate this methodology, it has been applied on a structure subjected to four point bending. The material used for this structure is PLA (Poly lactic acid).

Abstract

The photopolymerization-based additive manufacturing process, including 3D printing techniques such as stereolithography and digital light processing, has undergone considerable development over the last few decades. These techniques provide flexibility in the physical and chemical properties of 3D printed materials. The photopolymerization process is based on ultraviolet (UV) curing of liquid-state monomers/oligomers in the presence of photopolymerizable photoinitiators, which is known as the UV irradiation curing process. The UV light intensity has a significant effect on the reactivity and solidification process, modeling which has many challenges. In this work, we present a novel model that determines the required UV light intensity in the photopolymerization process. To make meaningful predictions of the UV light intensity influence on the curing process, it is essential to appropriately model the UV light waves. Maxwell’s equations are considered for this purpose. The photopolymerization process itself is described by the reaction-diffusion equation, which is coupled to Maxwell’s equations in a unit square of the resin. Isogeometric analysis is used to discretize the produced coupled system of equations. We present numerical results that demonstrate the light intensity influence on the UV curing process.

Abstract

Three dimensional (3D) printing or Rapid Prototyping (RP) provides an innovative additive manufacturing method for prototypes and functional components. Fused deposition modeling (FDM) is a fast growing rapid prototyping technology for fabricating thermoplastic parts due to its ability to build functional parts having complex geometrical shapes in reasonable time periods with the advantages of low cost, minimal wastage, and no tooling or touch labour. The quality of a built part (surface finish, dimensional accuracy or mechanical properties) depends on several process variables. Assessing the influence of these process parameters on mechanical properties is vital for understanding the performance of 3D printed materials, and to determine the needs for further research.

The aim of this study is to characterize and assess of different process parameters on the mechanical performance of PLA and ABS samples manufactured with low cost 3D printing. Tensile and three-point bending tests series were carried out to determine the mechanical response of the printed specimens with different process parameters. Finally, the practicality of the results was assessed by testing an evaluation structure as a case example.

Abstract

In the present work the feasability of 3D printintg, more specifically the FDM (Fused Deposition Modeling) technology, to manufacture moulds of RTM in the phase of prototyping has been demonstrated. The upper part of the mould for a side-intrusion bar of a front door of a car has been manufactured, since the bottom mould is the original metallic. Printing of the mould took 104 hours and 3.8 kg of plastic were used. For the employed PLA, it has been established that up to 5 mm thick the translucency is sufficient to observe the resin flow pattern during injection. In order to increase the rigidity of the mold, different geometries of vertical reinforcements have been analyzed by means of finite element simulations. Finally, the honeycomb-like structure has been selected. At the stage previous to the injection, when the vacuum is made, the presence of the glass fiber preform reduces the displacements measured at different points on the mould. Additionally, the tightness has been good even without applying any kind of surface treatment. However, when the resin is injected the intrinsic stiffness of the mould has not been sufficient to limit displacements and to make a good piece. This has been solved by using a 30 mm thick methacrylate plate to stiffen the mould, which in turn allows the visualization of the flow through the mould.

Abstract

3D printing is a promising additive manufacturing technology capable of producing functional parts of continuous fibre reinforced thermoplastic composites (CFRTPCs). Thus recyclable parts having complex geometries are obtained in a simple manner [1]. In addition, the use of thermoplastic polymers significantly reduces the manufacturing costs because, unlike thermoset polymers, autoclave is not required for curing purposes. This is one of the greatest opportunities for 3D printing as an alternative to conventional manufacturing processes [2, 3]. Pieces obtained from both, conventional manufacturing methods and 3D printing technology, consists on a sequence of stacked sheets. Although greater automation and the possibility to optimize the design of each sheet are advantages of 3D printing, the adhesion between the matrix and the reinforcement fibres is insufficient and consequently, parts with inferior mechanical properties are obtained. Some studies have been interested in the effect of different process parameters on the mechanical performance of the printed parts, however, further research is required. A fundamental challenge is to get good consolidation between the fibres and the polymer matrix, with control of the fibre orientation and low cost [4, 5]. The aim of this work was to evaluate the mechanical properties of multidirectional 3D printed continuous carbon, glass and Kevlar fibre reinforced nylon composites, manufactured by FDM technique. Special attention was paid to the impact damage resistance and tolerance. [1] L. Nickels, Strengthening the 3D printing composites field, Reinforced Plastics, 62 (2018) 298-301 [2] L.G. Blok, M. L. Longana, H. Yu and B. K. S. Woods, An investigation into 3D printing of fibre reinforced Thermoplastic composites, Additive Manufacturing, 22 (2018) 176-186 [3] T. Liu, X. Tian, M. Zhang, D. Abliz, D. Li and G. Ziegmann, Interfacial performance and fracture patterns of 3D printed continuous carbon fibre with sizing reinforced PA6 composites, Composites Part A: Applied Science and Manufacturing, 114 (2018) 368-376 [4] R. Velu, F. Raspall and S. Singamneni, 3D printing technologies and composite materials for structural applications, Green Composites for Automotive Applications, chapter 8 (2019) 171-196 [5] Q. Hu, Y. Duan, H. Zhang, D. Liu, B. Yan and F. Peng, Manufacturing and 3D printing of continuous carbon fiber prepreg filament, 53 (2018) 1887-1989

Abstract

Additive manufacturing, and more specifically FFF (Fused Filament Fabrication), makes it possible to manufacture complex designs that are difficult to manufacture using conventional processes that improve the mechanical behaviour of the component. In the present work, the axial impact behaviour of cylindrical tubes with a reentrant auxetic structure has been characterized. The material used is a polyamide 6 reinforced with short carbon fibre. As a reference, a solid thickness tube with the same outer diameter and mass as the tube with the auxentic structure has been designed. The main result is that the auxetic structure not only improves the specific absorption capacity, but also allows a progressive collapse thanks to the design and location of fault initiators. For this reason, 3D printing technologies have very attractive properties for the design of impact absorbers in the transport sector.

Abstract