Continuous Extrusion Research Articles

Continuous Extrusion Forming Technology of Magnesium Alloy Thin-Walled Tubules.

This paper proposes a new technology of superimposed billet extrusion-forming for thin-walled magnesium alloy tubes. This process represents an improvement over the current technology, which suffers from low production efficiency, poor forming accuracy, and low material utilization. We developed a detailed forming process and mold structure, in which the excess material of the front billet is extruded out of the mold as the rear billet pushes on the front one. Through continuous extrusion, online direct water cooling, and cutting, the automated continuous production of thin-walled tubules is achieved. The optimization of the mandrel structure and its hovering action is also included, with the aim of improving the lifespan of the mandrel and the accuracy of tube size. The numerical simulation method evaluates the effect of the die angle (α) on the tube, formed using FORGE NXT 1.1. The results show that for an angle of less than 70°, the defect length of the tube decreases as the die angle decreases, forming an ordered flow of superimposed billets. If the angle is less than 50°, the two adjacently formed tubes separate automatically, with no need for the subsequent cutting process. The best choice of die angle is about 50°, which takes into account the effect of the change in extrusion force.

Improvement in Mechanical Properties of Al2024 Alloy Using Mechanical Working and Heat Treatment.

Extrusion speed has a significant influence on the extrusion temperature, microstructure and mechanical properties of the material in the repetitive continuous extrusion forming (RCEF) process. In this work, the mechanical properties of Al2024 were improved by adjusting the speed (with a general range of 2-10 rpm) of repetitive continuous extrusion and applying subsequent heat treatment. During the RCEF process, an increase in the extrusion speed from 4 to 8 rpm was found to increase the extrusion temperature and then enhance the solid solution function. The grain size was affected by the combined effect of deformation speed and its induced temperature. A high-strength Al2024 (ultimate tensile strength of 497.6 MPa) with good elongation (12.93%) was obtained by increasing the extrusion speed and conducting solid solution and artificial aging treatments. The main strengthening mechanisms could be attributed to finer grain size and a larger amount of S (Al2CuMg) precipitates.

Numerical simulation of five different screw configurations used during the preparation of hot-melt extruded Kollidon® and Soluplus® based amorphous solid dispersions containing indomethacin

This work developed immediate-release hot melt extruded pellets containing the poorly aqueous soluble drug Indomethacin with five different screw configurations for oral application. Moreover, numerical simulation concerning residence time was performed for each configuration to give valuable tools for better process understanding and ease of scale-up. The pellets were prepared using immediate-release matrix-forming polymers such as Kollidon® and Soluplus® by coupling hot melt extrusion (HME) with a die-surface cutting pelletizer. The HME extruded filaments were pelletized with a die-surface cutting pelletizer into 1.5 mm pellets. The extruded pellets were characterized by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), in vitro release testing, drug content, and stability studies. DSC data revealed the formation of the amorphous solid dispersions of Indomethacin in both polymeric blends. FTIR spectra did not reveal any incompatibilities between the drug and the polymers. SEM micrographs revealed a smooth surface without any cracks. In vitro release studies demonstrated that the Indomethacin dissolution rate was significantly improved from both polymeric matrices for all the tested screw configurations compared to the bulk drug. However, the numerical simulation studies showed no significant difference between predicted and experimental extrusion residence time for only four screw configurations. In conclusion, the current investigation revealed the potential use of the continuous hot-melt extrusion technology for large-scale production of Indomethacin pellets with good prediction tools for the experimental extrusion residence time with standard, conveying, distributive, one mixing screw configurations for both polymers.

Properties of PLA-co-PBSu Copolymers Rapidly Synthesized by Reactive Processing

This work describes the synthesis of poly(lactic acid) by the ring-opening polymerization of L-lactide in the presence of oligo(butylene succinate) with two different molecular weights (Mn = 6100 and 16300 g/mol) as a macroinitiator during reactive processing. The macroinitiators were added in concentrations 1 wt%, 2.5 wt%, 5 wt%, 10 wt% and 15 wt% in respect to the L-lactide mass in the premix. The properties of the received copolymers were extensively studied with spectroscopic techniques, GPC, DSC, XRD, TGA as well as nanoindentation. Blocky copolymers were received with number average molecular weights ranging from 30 to 100 kg/mol, which decreased with increasing the PBSu content in the feed. The introduction of the flexible PBSu chains decreased the single glass transition detected, while DSC and XRD gave indications that both components crystallized in the copolymers with PBSu premix content > 5 wt%. Thermal stability was maintained and depended on the composition and molecular weight. Nanoindentation showed that despite the decreasing trend of hardness and elastic modulus with increasing PBSu content, the PLA-PBSu 2.5% copolymers had simultaneously higher elasticity modulus and strength compared to the other compositions, possibly because of a complementary effect of their high molecular weight and crystallinity. These copolymers were promising for production with continuous reactive extrusion, a novel, fast and economically viable method to commercially produce PLA-based polymers.

Electronic-Control Friction Behavior of Porous Metal-Organic Framework@Ag Nanocrystals as Self-Repairing Lubricant Additive.

The low conductivity and poor antifriction performance of lubricants are the main causes of wear failure in mechanical equipment under electronic-control friction. Metal-organic framework (MOF) nanocomposites can be used to fabricate a new kind of lubricant additive. Herein, porous Cu-BTC@Ag MOF nanocrystals were successfully synthesized via an in situ generation method. Transmission electron microscopy results showed that the nano-Ag element was evenly dispersed throughout the Cu-BTC matrix. Cu-BTC@Ag nanocrystals can significantly improve the electrical conductivity of the EMI-BF4 ionic liquid, which increased by 38.8%. The average coefficients of friction (COF) and wear volume of EMI-BF4 ionic liquid with 0.5 wt % Cu-BTC@Ag decreased by 8.3 and 16% without applied voltage, respectively. This finding was due to the continuous extrusion of the EMI-BF4 stored in the Cu-BTC@Ag pores under external load. It entered the contact zone, thereby maintaining the continuous supply of lubricant. At 20 V applied voltage in the friction process, the COF of the EMI-BF4/2.0wt %Cu-BTC@Ag lubricant decreased by 18.8%, and its wear volume decreased by 32.7%. The Cu-BTC@ Ag nanocrystals adsorbed onto the metal surface to form a friction reaction film by the action of electric fields, which can repair the wear defects on the friction interface. Therefore, Cu-BTC@Ag nanocrystals acting as an additive in lubricant have remarkable prospects in the area of electronic-control friction.

Solid Stir Extrusion: Innovating friction stir technology for continuous extrusion process

Solid Stir Extrusion: Innovating friction stir technology for continuous extrusion process

Influence of nozzle structure and process parameters for 3D printing HTPB-based propellant

This paper studies the influence of nozzle structure and process parameters on the solid propellant 3D printing process, so as to better guide nozzle structure optimization and process improvement, and realize continuous extrusion and molding of solid propellant. Four characteristic parameters such as nozzle diameter, nozzle shrinkage angle, process temperature, and wall slip coefficient are selected, and the influence of these four parameters on the extrusion speed and pressure of solid propellant slurry in the nozzle is discussed by using the orthogonal test principle and ANSYS/POLYFLOW. The results show that the most significant factor affecting the outlet velocity uniformity index and outlet pressure is the wall slip coefficient, followed by the nozzle diameter, and the influence of temperature and contraction angle is small.

A Novel One-Step Reactive Extrusion Process for High-Performance Rigid Crosslinked PVC Composite Fabrication Using Triazine Crosslinking Agent@Melamine-Formaldehyde Microcapsules.

In this work, we propose, for the first time, a simple, fast, and efficient strategy to fabricate high-performance rigid crosslinked PVC composites by continuous extrusion. This strategy improves the poor processing fluidity of composites and solves the impossibility of conducting extrusion in one step via using microcapsule-type crosslinking agents prepared by in situ polymerization to co-extrude with PVC blends. The results demonstrate that the PVC/microcapsule composites were successfully prepared. Within the studied parameters, the properties of crosslinked PVC gradually increased with the addition of microcapsules, and its Vicat softening temperature increased from 79.3 °C to 86.2 °C compared with pure PVC. This study shows the possibility for the industrial scale-up of the extrusion process for rigid crosslinked PVC.

Deformation mechanisms and mechanical properties of the high-strength and ductile Al-Zn-Mg-Cu alloys processed by repetitive continuous extrusion forming process with different heat treatments

Continuous severe plastic deformation (SPD) processes, which overcome the limitations of economic efficiency and sample size for classical SPD approaches, are promising industry technologies for manufacturing aluminum alloy products with refined microstructures and enhanced properties. In the present work, the repetitive continuous extrusion forming (R-Conform) process combined with auxiliary thermal treatments was implemented in Al-Zn-Mg-Cu alloys, which had poor workability. By combining microstructural observation, mechanical testing and finite element simulation, the influence of auxiliary heat treatments on the mechanisms of grain refinement and strengthening for Al-Zn-Mg-Cu alloys processed by R-Conform were systematically investigated. The results indicated that the grains of Al-Zn-Mg-Cu alloys were significantly refined by a continuous dynamic recrystallization (CDRX) during the R-Conform process with special thermomechanical conditions. The increased supersaturated solid solution concentration and constituent precipitate fraction caused by prehomogenization were found to accelerate CDRX for grain refinement through the pinning effect on dislocation motion. Due to the simultaneous effect of shear deformation and online solution, the R-Conformed alloys contained massive lattice distortions and high concentrations of solute atoms. As a result, the processed Al-Zn-Mg-Cu alloys combined with prehomogenization and direct aging treatments possibly possess a good combination of strength and ductility due to the integrated functions of fine grains, massive lattice distortion, and evenly distributed nanosized precipitates.

A strategy for extending the processing temperature for polypropylene in foam extrusion and its theoretical validation

The quite narrow PP foaming temperature window is the main challenge for continuous extrusion foaming of polypropylene (PP) using supercritical CO2. In this study, high impact polystyrene (HIPS) is added to PP to widen the polypropylene foaming temperature range by reducing the temperature sensitivity of the melt strength of the blend. The behavior of crystalline, dynamic rheology, and extensional rheological of PP/HIPS blends are analyzed. The results show that the crystallinity and crystallization temperature of PP/HIPS blends decreased significantly, the temperature dependence of the blends’ extensional viscosity and melt strength became weaker, and the activation energy of extensional viscosity and melt strength activation energy decreased, while the elastic modulus and viscosity and the system relaxation time increased. It means that the addition of HIPS reduces the crystallinity of PP, improves the cell morphology and to a certain extent overcomes the problem of a sharp decrease in PP melt strength with increasing temperature. The addition of HIPS extends the foaming temperature range of the PP material from 4 K to a maximum of 12 K. Furthermore, we simply estimated the temperature window for extruded foams using the Arrhenius equation. The estimated values have the same trend as the experimental results and are analyzed.

Enhancing the strength and ductility in an Al–5Mg alloy via accumulative continuous extrusion forming at room and cryogenic temperatures

In this work, the microstructural evolution of Al–5Mg (wt%) alloy fabricated by accumulative continuous extrusion forming (ACEF) at room temperature (RT) and cryogenic temperature (CT) was investigated. The grain refinement mechanism during ACEF was revealed. The strengthen and ductility enhancements of the alloy were discussed. The results showed that good grain refinement effect was achieved in the alloy after multi-pass RT-ACEF, and was further enhanced in the alloy fabricated by 1 pass CT-ACEF. High-density dislocations, as the driven force of continuous dynamic recrystallization, were achieved in the 1 pass CT-ACEFed alloy, and the growth of recrystallized grains was limited at CT. As a result, superior grain refinement effect was obtained in the alloy after CT-ACEF. Simultaneous strength and ductility improvements were found in the ACEFed alloy. The ultimate tensile strength and elongation were enhanced to 294.3 MPa and 55.1 % of the alloy after 1 pass CT-ACEF. Grain boundary strengthening and dislocation strengthening dominated the strength enhancement of the ACEFed alloy. The high work hardening exponent and wide strain interval were responsible for the increase in ductility of the CT-ACEFed alloy. The purpose of this study is to provide a high-efficiency strategy to achieve Al–Mg alloys with superior mechanical performance and overcome the strength-ductility trade-off.

Formulation and processing of solid self-emulsifying drug delivery systems (HME S-SEDDS): A single-step manufacturing process via hot-melt extrusion technology through response surface methodology

The objective of the current study is the formulation development and manufacturing of solid self-emulsifying drug delivery systems (HME S-SEDDS) via a single-step continuous hot-melt extrusion (HME) process. For this study, poorly soluble fenofibrate was selected as a model drug. From the results of pre-formulation studies, Compritol® HD5 ATO, Gelucire® 48/16, and Capmul® GMO-50 were selected as oil, surfactant and co-surfactant respectively for manufacturing of HME S-SEDDS. Neusilin® US2 was selected as a solid carrier. The design of experiments (response surface methodology) was employed to prepare formulations via a continuous HME process. The formulations were evaluated for emulsifying properties, crystallinity, stability, flow properties and drug release characteristics. The prepared HME S-SEDDS showed excellent flow properties, and the resultant emulsions were stable. The globule size of the optimized formulation was 269.6 nm. The DSC and XRD studies revealed the amorphous nature of the formulation and FTIR studies showed no significant interaction between fenofibrate and excipients. The drug release studies showed significant (p < 0.05) improvement in solubility compared to the pure drug (DE15 = 45.04 for the optimized formulation), as >90% of drug release was observed within 15 min. The stability studies for the optimized formulation were conducted for 3 months at 40 °C/75% RH.

Microcellular extrusion foaming of long-chain branched polyamide 6 composites

In this study, by introducing the long-chain branched (LCB) structure into the polyamide 6 (PA6) matrix, low-density microcellular PA6 composite foams with favorable cell morphology were prepared using supercritical CO2 extrusion foaming. PA6/talc composites with varying degrees of LCB were prepared using a twin-screw extruder. Rheological tests showed that the LCB-4.0 T sample with an ultra-high LCB degree had more apparent strain-hardening behavior and higher instantaneous elongational viscosity of 4.40 × 108 Pa·s. Isothermal crystallization tests revealed that LCB-4.0 T had lower crystallization rate. The effect of the degree of LCB on the gas solubility of CO2 in the PA6 composites was also examined. The foamability of the PA6/talc composites was verified via continuous extrusion foaming. High-performance PA6 composite foams with an average cell size as low as 66.7 µm, cell density as high as 2.53 × 107 cells/cm3, expansion ratio as high as 11.8, and foaming temperature window as wide as 16 °C were successfully obtained.

Influence of Pre-Heat Treatment on the Deformation Behaviors, Microstructural Characteristics, and Mechanical Properties of a Continuously Cast Al-Cu-Mg Alloy during Continuous Extrusion Process.

The presence of a second phase in Al-Cu-MG alloys, with various sizes and supersaturation-solid-solubility, which can be changed by pre-heat-treatment, could have remarkable influence on hot workability and mechanical performance. In the present work, a continuously cast 2024 Al alloy was homogenized and then subjected to hot compression and continuous extrusion (Conform) along with the initial as-cast alloy. The results showed that the 2024 Al alloy specimen with pre-heat treatment had a higher resistance to deformation and dynamic recovery (DRV) during hot compression process compared with the as-cast sample. Meanwhile, dynamic recrystallization (DRX) was advanced in the pre-heat-treated sample. After the Conform Process, the pre-heat-treated sample also attained better mechanical properties without additional solid solution treatment. The higher supersaturation solid solubility and dispersoids generated during pre-heat treatment was proved to play a key role in restricting boundary migration, tangling dislocation motion and promoting the precipitation of S phase, which raised resistance to DRV and plastic deformation and enhanced the mechanical properties.

Control System of the Continuous Extrusion Line Using PLC and Conventional Regulators

This paper presents the functional characteristics of the line parameters based on the developed control software for speed, tension, regulation of traverse device for proper arrangement of the material on drum and temperature regulation. Speed and tension regulation is performed using the PLC controller S7 1500 series and conventional converters and inverters of the Sinamics DCM and G120 series. A control method was used where one device is the leader and all the others follow its speed with a given ratio and tensile control. Setting the parameters of conventional converters and inverters for controlling multi-motor drives was realized using the StartDrive tool. The temperature control of the extruder zones was done taking into account the mutual influence of the zones. Control and monitoring are implemented with software written in TIA Portal V15.1. software package.

Prediction of CTCF loop anchor based on machine learning.

Introduction: Various activities in biological cells are affected by three-dimensional genome structure. The insulators play an important role in the organization of higher-order structure. CTCF is a representative of mammalian insulators, which can produce barriers to prevent the continuous extrusion of chromatin loop. As a multifunctional protein, CTCF has tens of thousands of binding sites in the genome, but only a portion of them can be used as anchors of chromatin loops. It is still unclear how cells select the anchor in the process of chromatin looping. Methods: In this paper, a comparative analysis is performed to investigate the sequence preference and binding strength of anchor and non-anchor CTCF binding sites. Furthermore, a machine learning model based on the CTCF binding intensity and DNA sequence is proposed to predict which CTCF sites can form chromatin loop anchors. Results: The accuracy of the machine learning model that we constructed for predicting the anchor of the chromatin loop mediated by CTCF reached 0.8646. And we find that the formation of loop anchor is mainly influenced by the CTCF binding strength and binding pattern (which can be interpreted as the binding of different zinc fingers). Discussion: In conclusion, our results suggest that The CTCF core motif and it's flanking sequence may be responsible for the binding specificity. This work contributes to understanding the mechanism of loop anchor selection and provides a reference for the prediction of CTCF-mediated chromatin loops.

Design and development of a new machine tool for continuous friction stir extrusion

Design and development of a new machine tool for continuous friction stir extrusion

Fast layer fiber orientation optimization method for continuous fiber-reinforced material extrusion process

Material extrusion (MEX) is an additive manufacturing process that uses thermoplastic layer-by-layer building. The use of continuous fiber-reinforced filament enhances mechanical properties, making MEX suitable for use in aerospace, automotive, and robotics industries. This study proposes a laminate optimization method to improve the stiffness of printed parts with low computing time. The 2D stress-flow-based method optimizes fiber’s orientation for each layer in the stacking direction, giving results for a 3D part optimization in a few minutes. Developed with Ansys Parametric Design Language, the computation tool was tested on printed wrenches, resulting in an 18% increase in stiffness. The proposed method is applicable to any printable shape.

Two-Phase Flow Coordination Characteristics of H62 Brass Alloy Prepared by Up-Drawing Continuous Casting

In this study, the two-phase flow coordination characteristics between α and β phases of H62 brass made by up-drawing continuous casting are investigated based on the upsetting process. An in situ and new research method for two-phase flow is put forward, and the two-phase flow and grain refinement characteristics are observed under different deformation conditions. The results show that α phase flows fast under 400 °C, β phase is pulled and overridden by α phase under this temperature. When the temperature increases to 500 °C, which is higher than β phase transition temperature, the flow velocity of β phase increases, and the deformation of β phase is found to bulge. The flow of β phase is more sensitive to low deformation rates than α phase. The deformation amount has a more significant impact on β phase than α phase, and the deformation of β phase promotes the grain fragmentation and refinement of α phase accompanied by huge β phase bulging obviously. Under the conditions of high temperature, low deformation rate, and large deformation amount, both phase α and β of up-drawing continuous casting brass alloy are broken and the grains are refined. Based on the two-phase flow characteristic, numerical simulation is used to obtain the optimal continuous extrusion parameters of the H-shaped wire of up-drawing continuous casting H62 brass. Then, the optimized complex cross-section wire is prepared by continuous extrusion experiment. This research aims to provide guidance for the complex processing of two-phase alloys.

Initial Commissioning Test Results of the Wendelstein 7-X Continuous Pellet Fueling System

A continuous pellet fueling system (CPFS) for use on the Wendelstein 7-X (W7-X) stellarator has been fabricated and assembled with commissioning tests completed at the Oak Ridge National Laboratory (ORNL). Continuous fueling is accomplished by cutting pellets from the cross section of a continuous solid extrusion produced by a twin-screw extruder and accelerated by a gas gun cutter mechanism. The pellets travel through a series of straight guide tubes before entering the stellarator through a curved guide tube. The CPFS has an array of diagnostics that include the extruder torque, rotation rate, and thrust. A shock and pressure sensor provide verification of proper pellet cutting and acceleration. Two ORNL-developed microwave cavity diagnostics within the injection line guide tubes provide pellet speed and relative mass measurements. For commissioning, a high-speed camera has been positioned at the base of the extruder to verify extrusion speed and quality as well as the pellet cutting process, and a third microwave cavity has been mounted after the curved guide tube to verify pellet quality and size. Maximum injection rate, pellet speed, barrel and guide tube induced erosion, and pellet survivability data have been recorded. This paper presents the laboratory experimental setup and results of these commissioning tests.