Papers by Keyword: Extrusion

Abstract: 3D printing of ceramics grabbed its attention recently because of its ease of shaping. The extrusion-based 3D printing technique is widely used for ceramics as it involves paste formulation. However, the slurry is often formulated and mixed initially by hand kneading and later by a high-speed mixer. This phenomenon leads to the evaporation of water quickly while combining or out of its insufficient time allowed for extrudable slurry or paste formulation. The slurry's printable time is also reduced due to this phenomenon. This study prepares a hybrid ceramic mixture comprising silica gel, and printable time is calculated. Triaxial porcelain is used as a model ceramic.

Abstract: The lubricant thickness in cold forging was estimated by machine learning of the in situ captured images of the die–workpiece contact interface. The images were in situ captured by a high-speed camera from the backside of the transparent glass die during forging of commercially pure aluminum workpiece. On the other hand, the images of the lubricated workpiece were individually captured as training images for random forest with classification. The classification accuracy of the lubricant thickness was confirmed to be approximately 75% (classification ability: 5–10 μm in lubricant thickness) in the training images with 22,500 px (50 px/mm). The in situ captured images of the die–workpiece contact interface during forging were classified by random forest using the training images. The estimated lubricant thickness of the in situ captured image almost agreed with the lubricant thickness estimated from the mean brightness value of the in situ captured image.

Abstract: In this paper, a numerical simulation methodology has been applied to optimize the design of extruded aluminium products. The methodology, PRO^{3 TM} , incorporates product properties, production-and material costs as well as CO₂ footprint in an optimisation procedure. This allows for multi-objective optimisation and avoids sub-optimisation of for instance properties on the expense of production costs or CO₂ emissions. The outcome that follows from this multi-objective optimisation procedure, is that the resulting profile cross section will be different when the optimisation is based solely on property considerations, than when costs and CO₂ emissions are introduced in the optimisation procedure. The present methodology requires that the main processes and operations along the aluminium process chain are represented by physics based, predictive models of various types, including material-and mechanical models, in addition to cost-, and sustainability models. A standard multi-objective optimization algorithm is used to combine the models and for automatic running through-process simulations in iterations. In this article, the PRO^{3 TM} methodology has been applied for optimisation of the profile cross section in case-studies with various user requirements. It has been demonstrated that the resulting cross section geometry depends on the specified relative importance of conflicting requirements like the desire for high productivity on the one hand, and the desire for low material costs and low CO₂ emissions on the other.

Abstract: The paper presents the experience of development and implementation of an integrated approach of extrusion simulation with the automated design of the dies as a new way to speed up the technology development and its optimisation based on the QForm UK Extrusion simulation program and QForm Extrusion Die Designer (QExDD) design system. Bearing and prechamber optimisation types are considered for the porthole design. Welding quality and possible streaking lines in the profile are analysed for the tool construction with optimised prechamber contour.

Abstract: The velocity fields of axisymmetric direct extrusion of metals was analysed by the upper-bound method and compared with the results from the finite-volume method, FVM. The upper-bound technique proposed by Avitzur and by Zhao et al. together with the streamline functions were employed to calculate the analytical velocity fields, which consider the friction at die wall. Moreover, the components of strain-rate are also presented. Additionally, the axisymmetric extrusion process was modelled by the FVM method to calculate the velocity fields and compared with the Avitzur’s and by Zhao’s solutions. The FVM velocity fields were calculated by using the Eulerian approach of fixed grid, the governing equations of metal plastic flow and conservation laws discretized by the FVM and the Explicit MacCormack method in structured and collocated mesh were also employed. Friction at die wall was modelled by the friction factor model, using the tangential shear stress boundary conditions. The examined material experimental parameters were obtained from the Al 6351 aluminium alloy in the direct extrusion process at 450^o C. Velocity fields of the longitudinal and radial velocity distributions by the upper-bound and FVM methods are presented and compared. Good agreement is shown between the radial velocity component V_r from the Avitzur´s and FVM results, but poor for the longitudinal velocity V_z. From the analysis of velocity fields, the most severe condition of wear on the inner wall of the die and material surface damage occurs in the area near the exit corner of the die. However, the predicted location of the severe wear region in the die wall by the FVM method is located prior to the point predicted by the Avitzur model.

Abstract: The microstructure evolution during the extrusion process of AA6XXX aluminum alloys is getting a significant interest from extruders and researchers because of the effect of the grain structure on the extruded component properties. Several process and material parameters such as chemical composition, homogenization, temperature evolution, extrusion speed, geometries and quenching have a direct impact on the final grain size of extruded profiles. Because there are so many affecting elements, it is extremely challenging to forecast the microstructure evolution and, as a result, research activities are still required to understand and control the aluminum alloy recrystallization behaviour. In this work, a methodology for the microstructural characterization of AA6XXX aluminum alloys is proposed. The methodology involves the experimental investigation of the profile grain evolution during the extrusion process, the development of a AA6XXX recrystallization model optimized to describe the AA6063 recrystallization behaviour and the simulation by means of finite element method of the final microstructure of the extruded profile.

Abstract: Fused filament fabrication (FFF) has nowadays become a popular 3-dimensional (3D) printing technique for the fabrication of polymeric components with customized and complex-shape design, including biomedical implants. However, the use of this technique is often constrained by the limited number of polymeric materials that can be printed to form the final product. Despite excellent wear resistance and widely used as the acetabular component of a joint prosthesis, ultra-high molecular weight polyethylene (UHMWPE) is among such the rarely-found filament material in the market. In this research, preliminary work to fabricate UHMWPE filament for the FFF processing is carried out by using extrusion. The influences of extrusion temperature, addition of polyethylene glycol (PEG), and rotational speed of the extruder’s screw on the physical, chemical, and mechanical properties of the extruded UHMWPE filament were determined. The result demonstrated no change in the chemical compositions of the filament due to the processing parameters applied, as noted from the FTIR spectra. The result of the tensile test showed that the highest tensile strength of UHMWPE filaments could reach 23.5 MPa.

Abstract: A novel Zn biodegradable composite was produced by direct extrusion of Zn powders at room temperature. The powders were efficiently consolidated to a high relative density, and the composite reached a UTS higher than 120 MPa and elongation of almost 70%. Microstructural observations showed ultra-fine Zn grains decorated by well-dispersed ZnO clusters at the grain boundaries. The degradation behavior of the composite and an as-cast Zn reference accessed by immersion tests in HBSS for both materials were similar and gave an equivalent corrosion rate. Additional static immersion tests in DMEM + 5% FSB showed a similar corrosion rate (0.015 mm/y), but SEM analysis of the corroded surface suggested that the degradation process of each as-cast or DE consolidated composite differs. MTT assays with extracts of both as-cast and extruded composites showed similar cytotoxicity, which was dependent on the dilution of the extracts. It was concluded that the proposed methodology brings the potential for an interesting solution to produce a sound Zn-ZnO composite with good biocompatibility, satisfactory corrosion rate, and high yield strength.

Abstract: The development of a low cost 3D printer is presented for high performance polymers by example of a PEI type material. The development steps and technical alternatives opted for during the design process are outlined in two cycles targeting first printing of non-demanding thermoplastics, such as ABS, PLA etc., followed by an upgrade to printing PEI and similar high performance polymers. Subsystems discussed pertain to the frame, CNC axes including feed motors and motion control, the extruder, hot end and nozzle. Of particular interest are modifications concerning the temperature setting and regulation subsystems of the printer work volume and the printing table. Calibration procedures with pitfalls and solutions is discussed and a documented series of finally successful tests for Ultem1010^TM is presented.

Abstract: The microstructure, texture, and tensile properties of hot extruded Mg-6Zn-1Y-1Ce alloy obtained at a temperature range of 300 °C to 400 °C were studied. Electron back-scatter diffraction (EBSD) results revealed that strong basal plane texture was found along extrusion direction in the sample extruded below 340 °C due to discontinuous dynamic recrystallization (DRX) mechanism. In the sample extruded at 340 °C the average value of Schmid factor (SF) of {0001}〈11-20〉 slip system was 0.09. However, the sample extruded above 370 °C had weak basal texture under the control of continuous DRX mechanism, and the SF was well-distributed with an average value of about 0.32. The strengths of as-extruded samples decreased with increase of extrusion temperatures. In addition to fine grain strengthening, texture strengthening had a significant contribution to the high strength for the sample extruded at low temperature.