Characterization and processing of composite PP/UHMWPE filament for fused deposition modelling application

In this thesis Polypropylene/Ultra-high Molecular Weight Polyethylene (PP/UHMWPE) biomaterial composite was employed to manufacture implant to reconstruct large skull bone defect using Fused Deposition Modelling (FDM). This effort aimed to reduce the cost and processing time of manufacturing of a product like this and make it available to all. The effects of addition UHMWPE on the mechanical, thermal, rheology and toxicity of PP were investigated. All the blends composition were compounded using melt blending in an internal mixer and then extruded into single filaments characterized according to FDM filament specification. Subsequently, the prepared filament was underfed to FDM to manufacture tensile, flexural, and impact samples. This was done under the default setting of process parameters in order to investigate the mechanical behaviour of the composite. Structural morphology of the fracture surfaces of impact samples were investigated to explore microstructure changes related to UHMWPE content. Furthermore, thermal and rheological characterizations were conducted to explore the degradation temperature and process ability of the composites in order to accomplish successful processing in both filament extrusion and FDM processes. MTT assay was also conducted to investigate the composite toxicity. Full and Fractal Factorial Design were employed to investigate the effect of process parameters on the process response for filament extrusion and FDM processes respectively. The study results proved that the addition of 10% of UHMWPE resulted in 57% improvement in impact strength, 9.6% improvement in thermal stability, and 17.9 % in biocompatibility compared to pure PP. In addition, the impact strength improved once again at an estimation of 40.6% increment due to optimization of FDM setting parameters. As a case study, a skull implant was manufactured for a patent in USMUniversity Hospital with 88.13%-dimensional accuracy. Keywords: Biomaterials melt blending, Polymer extrusion, Fused Deposition Modelling (FDM), Bone reconstruction

Diameter prediction and optimization of hot extrusion-synthesized polypropylene filament using statistical and soft computing techniques

In this study, statistical and soft computing techniques were developed to investigate effect of process parameters on diameter of extruded filament made of polypropylene in hot extrusion. A multi-factors experiment was designed with process parameters of screw speed, roller speed and die temperature. According to the design matrix, twenty four experiments were conducted. The diameter of the extruded plastic filament was measured in each experiment. Subsequently, statistical analysis was used to identify significant factors on diameter of extruded filament. Predictive models of response surface methodology (RSM) and radial basis function neural network(RBFNN)were applied to predict the diameter of extruded filament. The optimal process parameters to maintain the diameter of the filament closest to the target value were identified using the cuckoo search algorithm (CSA), and particle swarm optimization (PSO). Performance analysis demonstrated the superior predictive ability of both models, in which the prediction errors of 0.0245 and 0.0029 (in terms of mean squared error) were obtained byRSM and RBFNN, respectively. Considering the optimization methods, the optimization approaches of using CSA and PSO were promising, in which average relative error of 1.28% was obtained in confirmation tests

Elements and materials improve the FDM products: a review

This work aims to provide a review of available published literature that explores the opportunities to improve the quality of fused deposit modelling (FDM) products, particularly in medical applications. The paper presents details concerning the basis of the technology, process parameter settings and their responses, and reviews the properties of common FDM engineering/bio-materials and the available methods applied for improving their performance. Based on the researches which have been reviewed, FDM technology development is based on three elements namely; raw material, process parameters settings, and slicing software. The present paper deals with the first two elements owing to their importance. FDM works within a complex environment from process parameters. Thus it can achieve good results only with the proper settings for these parameters according to the properties of the material used. Improving the polymers is essentially based on the correct selection of additive materials, which can particularly enhance the key property/properties in the matrix material. This review provides a brief insight into FDM technology, a clear idea for the process parameter settings, available/suggested materials and ways of modifying their properties to consequently improve the quality of FDM products