Search

People who suffer an amputation at the transtibial level choose to wear an ankle prosthesis to make their walk like a person without disabilities. In the present investigation, an ankle prosthesis design and simulation are made, which involves a restricted patella mechanism and a linear actuator capable of granting two degrees of freedom. A ball joint is designed where twelve springs that support the weight of a person are located, six springs comply with the eversion movement and the rest comply with the inversion movement, likewise, the actuator performs the dorsiflexion and plantar-flexion movements. The simulations were made in Inventor software. The results obtained on the ‘Y’ axis indicate a patella displacement in the inversion and eversion movement of 13.65 mm and 11.89 mm, respectively. These values are obtained when a tension of 1876.1 N is applied to the twelve springs. With these data obtained, stability and support for a person weighing 70 kg can be guaranteed, in addition, the established movement angles are com-plied. The prosthesis was built using additive and subtractive manufacturing.

Purpose This paper aims to describe the influence of maleinized linseed oil (MLO), when used as a lubricant, on the thermal and rheological properties of PLA/MWCNTs (polylactic acid/multi-walled carbon nanotubes) and PLA/HNT (halloysite nanotubes) nanocomposites, as a reference for application in 3D printing processes. Design/methodology/approach Nanocomposites were obtained by melting in a twin-screw extruder, mixing PLA with MWCNTs and HNTs in different percentages of 0.5, 0.75 and 1 Wt.% for subsequent mixing by the same process with 5 phr MLO, for application in additive manufacturing, as analyzed by means of differential scanning calorimetry (DSC), capillary rheometry, melt flow rate (MFL) and field emission scanning electron microscopy (FESEM). Findings The results obtained for thermal characterization by using DSC indicate the non-variation of glass transition temperature Tg = 62 ± 2°C and a melting temperature (Tm) around 170°C. Crystallization temperature dropped by approximately 12°C, which should be kept in mind during the transformation processes. The values obtained by capillary rheometry indicate that the material’s viscosity is reduced by the influence of the MLO plasticizer’s lubricant effect on the PLA’s molecular structure. The melt flow index values confirm a rise of approximately 46% in the flow index and back up the capillary rheometry results. The values obtained were as follows: PLA/0.5 Wt.% MWCNT/MLO 5 phr 54.07, PLA/0.75 Wt.% MWCNT/MLO 5 phr 53.46, PLA/1 Wt.% MWCNT/MLO 5 phr 51.84y PLA/0.5 Wt.% HNT/MLO 5 phr 61.8, PLA/0.75 Wt.% HNT/MLO 5 phr 68.3 and PLA/1 Wt.% HNT/MLO 5 phr 71.2 g/10 min. Apart from the nanocharge distribution, the information obtained from the FESEM shows the existence of a cluster, which could have been avoided by more energetic stirring during the nanocompound manufacturing process. Social implications This paper presents an analysis of the insertion of plasticizer in nanocomposites for the application in additive manufacturing processes in fusion deposition modelling (FDM) system. Originality/value This is a novel original research work.

In the present investigation, the design and simulation of a polycentric knee mechanism with four-bar of voluntary control is performed, posing its mathematical model using the vector loop equation, so that its instantaneous center of rotation (CIR) meets the stability criteria established by Hosmer-Dorrance. The design of a four-bar system and the clamping for a hydraulic actuator were performed, followed by the simulation using finite elements in SolidWorks. The results obtained indicate that the maximum Von Mises tension in the four-bar mechanism is 5.161x107N/m2 and 3.834x107N/m2 in the actuator clamp, with a safety factor of the entire system greater than 1, guaranteeing to support a maximum weight of 102Kg. A prototype was built by additive and subtractive manufacturing, verifying the correct operation of the system, complying with angular displacements.

Purpose This paper aims to propose using polylactic acid (PLA) as an alternative to nanocomposites in additive manufacturing processes in fusion deposition modelling (FDM) systems and describe its thermal and rheological conditions with multi-wall carbon nanotube (PLA/MWCNT) and halloysite nanotube (PLA/HNT) composites for possible applications in additive manufacturing processes. Design/methodology/approach PLA/MWCNTs and PLA/HNTs were obtained through fusion in a co-rotating twin-screw extruder. PLA was mixed with different percentages of MWCNTs and HNTs at concentrations of 0.5 Wt.%, 0.75 Wt.% and 1 Wt.%. Differential scanning calorimetry (DSC) and capillary rheometry were used to characterise these products, together with an analysis of the melt flow index (MFI). Findings The DSC data revealed that the nanocomposites had a glass transition temperature Tg = 65 ± 2°C and a melting temperature Tm = 169 ± 1°C. The crystallisation temperature of PLA/MWCNTs and PLA/HNTs was between 107 ± 2°C and 129°C, respectively. The viscosity data of PLA/MWCNTs and PLA/HNTs obtained by capillary rheometry indicated that the viscosity of the materials is the same as that of neat PLA. These results were confirmed by the higher fluidity index in the MFI analysis. Originality/value This paper presents an alternative for the applications of nanocomposites in additive manufacturing processes in FDM systems.

This research paper presents the characterization of a nanocomposite of polylactic acid (PLA) and carbon nanotubes (MWCNTs) with different percentages of mixture in weight. This thermal characterization determines the influence carbon nanotubes have when those are added into PLA. This last one been used for additive manufacturing (FFF technology).. Once finished the tests, it was observed that the nanocomposite PLA/MWCNTs have a positive application during 3D printing. The extrusion temperatures used in tests were between 177 and 185oC. The parameters given for the SLISER software, obtained a promising result for the application of a PLA / MWCNT nanocomposite into 3D printing.