Search results

This study aims to investigate and model interrelationships between process parameters, geometrical profile characteristics and mechanical properties of industrially extruded aluminum alloys.

Statistical design of experiments (DOE) was applied to investigate and model the effects of eight factors including extrusion ratio, stem speed, billet-preheat temperature, number of die cavities, quenching media (water/air), time and temperature of artificial aging treatment and profile nominal thickness on four mechanical properties (yield strength, ultimate tensile strength, percent elongation and hardness). Experiments were carried out at an actual extrusion plant using 8-in. diameter billets on an extrusion press with 2,200 ton capacity.

Main factors and factor interactions controlling mechanical properties were identified and discussed qualitatively. Quantitative models with high prediction accuracy (in excess of 95%) were also obtained and discussed.

The obtained results are believed to be of great importance to researchers and industrial practitioners in the aluminum extrusion industry.

All practical and relevant parameters have been used to model all important mechanical properties in a collective manner in one study and within actual industrial setup. This is in contrast to all previous studies where either a partial set of parameters and/or mechanical properties are discussed and mostly under limited laboratory setup.

This study aims to focus on the effect of interlayer bonding and thermal decomposition on the mechanical properties of fused filament fabrication-printed polylactic acid specimens at high extrusion temperatures.

A printing process, that is simultaneous manufacturing of contour and specimen, is used to improve the printing accuracy at high extrusion temperatures. The effects of the extrusion temperature on the mechanical properties of the interlayer and intra-layer are evaluated via tensile experiments. In addition, the microstructure evolution affected by the extrusion temperature is observed using scanning electron microscopy.

The results show that the extrusion temperature can effectively improve the interlayer bonding property; however, the mechanical properties of the specimen for extrusion temperatures higher than 270°C may worsen owing to the thermal decomposition of the polylactic acid (PLA) material. The optimum extrusion temperature of PLA material in the three-dimensional (3D) printing process is recommended to be 250–270°C.

A temperature-compensated constitutive model for 3D printed PLA material under different extrusion temperatures is proposed. The present work facilitates the prediction of the mechanical properties of specimens at an extrusion temperature for different printing temperatures and different layers.

The purpose of this paper is to verify the effects of extrusion temperature on orthotropic behaviour of the mechanical properties of parts obtained by fused filament fabrication (FFF) under quasi-static tensile loads.

Tensile tests were performed on single layer specimens fabricated in polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) to evaluate the mechanical properties at different extrusion temperatures and raster orientations (0°, 45° and 90°). Furthermore, a detailed study of morphological characteristics of the single layer samples cross-section and of the bonding quality among adjacent deposited filaments was performed by scanning electron microscopy to correlate the morphology of materials with mechanical behaviour.

The results show that the orthotropic behaviour of FFF-printed parts tends to reduce, while the mechanical properties improved with increase in extrusion temperature. Furthermore, the increase in extrusion temperature led to an improvement in inter-raster bonding quality and in the compactness and homogeneity of the parts.

The relation between the extrusion temperature, orthotropic behaviour and morphological surface characteristics of the single layer specimen obtained by FFF has not been previously reported.

This paper aims to understand the effect of extrusion conditions on the degree of foaming of polylactic acid (PLA) during three-dimensional (3D) printing. It was also targeted to optimize the slicing parameters for 3D printing and to study how the properties of printed parts are influenced by the extrusion conditions.

This study used a commercially available PLA filament that undergoes chemical foaming. An extrusion 3D printer was used to produce individual extrudates and print samples that were characterized using an optical microscope, scanning electron microscope and custom in-house apparatuses.

The degree of foaming of the extrudates was found to strongly depend on the extrusion temperature and the material feed speed. Higher temperatures significantly increased the number of nucleation sites for the blowing agent as well as the growth rate of micropores. Also, as the material feed speed increased, the micropores were allowed to grow bigger which resulted in higher degrees of foaming. It was also found that, as the degree of foaming increased, the porous parts printed with optimized slicing parameters were lightweight and thermally less conductive.

This study fills the gap in literature where it examines the foaming behavior of individual extrudates as they are extruded. By doing so, this work distinguishes the effect of extrusion conditions from the effect of slicing parameters on the foaming behavior which enhances the understanding of extrusion of chemically foamed PLA.

Extrusion-based additive manufacturing (AM) has been considered as a promising technique to fabricate scaffolds for tissue engineering due to affordability, versatility and ability to print porous structures. The reliability and controllability of the printing process are necessary to produce 3D-printed scaffolds with desired properties and depend on the geometric characteristics such as porosity and pore diameter. The purpose of this study is to develop an analytical model and explore its effectiveness in the prediction of geometric characteristics of 3D-printed scaffolds.

An analytical model was developed to simulate the geometric characteristics of scaffolds produced by extrusion-based AM using fluid mechanics. Polycaprolactone (PCL) was chosen as a scaffold material and was assumed to be a non-Newtonian fluid for the model. The effectiveness of the model was verified through comparison with the experimental results.

A comparison study between simulation and experimental results shows that strut diameter, pore size and porosity of scaffolds can be predicted by using extrusion pressure, temperature, nozzle diameter, nozzle length and printing speed. Simulation results demonstrate that geometric characteristics have a strong relationship with processing parameters, and the model developed in this study can be used for predicting the scaffold properties for the extrusion-based 3D bioprinting process.

The present study provides a prediction model that can simulate the printing process by a simple input of processing parameters. The geometric characteristics can be predicted prior to the experimental verification, and such prediction will reduce the process time and effort when a new material or method is applied.

This paper aims to discuss the physical and thermal properties of the three-dimensional (3D) printing natural composite filament, as well as the tensile behaviour of the printed composites to get an insight of its possibility to be used as an ankle–foot orthosis (AFO) material.

Physical test that was conducted includes scanning electron microscopy analysis, thermogravimetric/differential scanning calorimetry analysis as well as the effect of fibre load after extrusion on the filament morphology. Tensile test was conducted with different amounts of fibre loads (0, 3, 5 and 7 Wt.%) on the printed specimens.

There is an increment of strength as the fibre load is increased to 3 Wt.%; however, it decreases significantly as it is increased to 5 and 7 Wt.% because of the presence of voids. It also shows that the extrusion temperature severely affects the structure of the filaments, which will then affect the strength of the printed composites. Based on the results, it is possible to use kenaf/polylactic acid (PLA) filament to print out AFO as long as the filament production and printing process are being controlled properly.

The unique aspect of this paper is the investigation of kenaf/PLA filament as a material for 3D printing, as well as its material consideration for AFO manufacturing. This paper also studies the effect of extrusion temperature on the morphological structure of the filament and its effect on the tensile properties of the printed kenaf/PLA specimen.

This study aims to investigate the impact of layer thickness, extrusion temperature, extrusion speed and build plate temperature on the tensile strength, crystallinity achieved during fabrication (herein, in-process crystallinity) and mesostructure of Poly(lactic acid) specimens. Both tensile strength and in-process crystallinity were optimized and verified as the function of processing parameters, and their relationship was thoroughly examined.

The four key technological parameters were systematically varied as factors on three levels, using the statistically designed experiment. Surface response methodology was used to optimize tensile strength and crystallinity for the given ranges of input factors. Optimized factor settings were used in a set of confirmation runs, where the result of optimization was experimentally confirmed. Material characterization was performed using differential scanning calorimetry and X-ray diffraction analysis, while the effect of processing parameters on mesostructure was examined by scanning electron microscopy.

Layer thickness and its quadratic effect are dominant contributors to tensile strength. Significant interaction between layer thickness and extrusion speed implies that these parameters should always be varied simultaneously within designed experiment to obtain adequate process model. As regards, the in-process crystallinity, extrusion speed is part of two significant interactions with plate temperature and layer thickness, respectively. Quality of mesostructure is vital contributor to tensile strength during FDM process, while the in-process crystallinity exhibited no impact, remaining below the 20 per cent margin regardless of process parameter settings.

According to available literature, there have been no previously published investigations which studied the effect of process parameters on tensile strength, mesostructure and in-process crystallinity through systematic variation of four critical processing parameters.

The performance of parts produced by fused filament fabrication is directly related to the printing conditions and to the rheological phenomena inherent to the process, specifically the bonding between adjacent extruded paths/raster. This paper aims to study the influence of a set of printing conditions and parameters, namely, envelope temperature, extrusion temperature, forced cooling and extrusion rate, on the parts performance.

The influence of these parameters is evaluated by printing a set of test specimens that are morphologically characterized and mechanically tested. At the morphological level, the external dimensions and the voids content of the printed specimens are evaluated. The bonding quality between adjacent extruded paths is assessed through the mechanical performance of test specimens, subjected to tensile loads. These specimens are printed with all raster oriented at 90º relative to the tensile axis.

The best performance, resulting from a compromise between surface quality, dimensional accuracy and mechanical performance, is achieved with a heated printing environment and with no use of forced cooling. In addition, for all the conditions tested, the highest dimensional accuracy is achieved in dimensions defined in the printing plane.

This work provides a relevant result as the majority of the current printers comes without enclosure or misses the heating and envelope temperature control systems, which proved to be one of the most influential process parameter.

The purpose of this paper is to propose a mathematical model to estimate required energy and temperature distribution during cold extrusion process.

An admissible velocity field is generated based on stream function technique. Then, the required energy and the temperature distributions in the metal and the extrusion die are determined by a coupled upper bound‐finite element analysis.

To examine the proposed model, cold extrusion of AA6061‐10%SiC_p is considered and the predicted extrusion force‐displacement diagrams in different reductions are compared with the experimental ones and reasonable agreement is observed. Furthermore, it is found that there is a linear relationship between maximum temperature and logarithm of ram velocity for the examined composite.

This approach requires shorter run‐time as compared with fully finite element analyses while the model is particularly appropriate for high speed extrusion processes where the adiabatic heating is of importance.

The purpose of this study was to formulate a complete protein food from lentil flour (LF) and egg powder (EP) through microwave-assisted extrusion technology.

In the first part of the hybrid technology, the feed proportion and extrusion conditions were optimized through design expert using central composite rotatable design. In the second part of hybrid technology, the optimized protein pellets (PP) obtained were subjected to microwave heating (MH) for 50,100, 150, 200 and 250 s.

The optimum predicted conditions for development of pellets using extrusion cooking were feed proportion (85% LF and 15% EP), barrel temperature (140°C), screw speed (340 rpm) and feed moisture content (12%). When these pellets were subjected to MH, 150 s of heating time was considered as prudential to induce desirable quality changes in PP. The increase in sectional expansion index, crispness and overall acceptability from 0.637 to 0.659, 4.51 to 6.1 and 3.27 to 3.59 with corresponding decrease in bulk density and breaking strength from 73.33 to 69.75 kg/cm³ and 6.24 to 5.13 N during 150 s of MH indicated that quality characteristics of extruded PPs were improved after MH.

Nowadays, consumers have become more health conscious than ever, and the demand for nutritious snacks has increased many folds. However, the high protein content restricts expansion of snacks, which was overcome by subjecting extruded pellets to MH to produce third generation pellets. Furthermore, the PP has a protein content of 31.62%, which indicates that if an average person consumes 100 g of these snacks, it will suffice 60% of total recommended dietary intake (0.75 g/kg body weight/day). Lentil-based pellets expanded by use of such hybrid technology (microwave-assisted extrusion cooking) can help to provide a feasible, low cost and protein-rich diet for malnourished population besides being a value addition to lentils.

LF in combination with EP was tested for the first time for development of nutrient dense pellets. Moreover, use of microwave-assisted extrusion cooking offers a workable and innovative technique of developing protein-rich pellets with improved physico-chemical and sensory attributes.