Influence Of Screw Speed Research Articles

Experimental Research on Optimization Extruder Process Parameters for Pineapple Pomace-Based Fish Feed

A single screw water-cooled jacketed extruder has been proposed to produce the fruit waste extrusion process of fish feed because of its superficial characteristics. This research mainly examined the effects of various extrusion conditions: feeding rate, screw speed, feed moisture, barrel temperature, cutting speed, and die open surface area. While maintaining the feed specifications (38% proteins and 5% lipids), four formulations with different pomace inclusions were obtained. The processing methodologies (with mash moisture and varied extruder parameters) were then based on three fundamental aspects (machine torque, apparent viscosity, and efficiency). They were studied using Response Surface Methodology (RSM). The influence of screw speed, moisture, and pomace inclusion was most significant. Optimum extrusion conditions were found at a feed rate of 1.47 kg.min-1, screw speed of 356.44 rpm, humidity of 16.04%, temperature of 60 °C, cutting speed of 1300 rpm, pomace inclusion rate of 10.59%, and an open surface die obtained 88.63%. The maximum desirable value of 0.61 resulted in 444.16 Nm-1 torque, 1008.98 Pa-s apparent speed, and 75.21% efficiency. The extruder evaluation demonstrated remarkable performance in producing pineapple pomace extrudates without impeding machine operating principles, redefining the robustness of extrusion process factors and their interactions in the process state.

Influence of extrusion screw speed on the properties of halloysite nanotube impregnated polylactic acid nanocomposites

Abstract Poly (lactic acid)/halloysite nanotube (PLA/HNT) nanocomposites have been studied extensively over the past few years owing to the interesting properties of the polymer, PLA, and the nanoclay, HNT, individually and as composites. In this paper, the influence of the screw speed during extrusion was investigated and was found to have a significant impact on the mechanical and thermal performance of the extruded PLA/HNT nanocomposites. To determine the effect of screw speed on PLA/HNT nanocomposites, 5 and 10 wt% of HNTs were blended into the PLA matrix through compounding at screw speeds of 40, 80, and 140 rpm. Virgin PLA was compounded for comparison. The resultant polymer melt was quench cooled onto a calendar system to produce composite films which were assessed for mechanical, thermal, chemical, and surface properties. Results illustrate that in comparison to 40 and 80 rpm, the virgin PLA when compounded at 140 rpm, indicated a significant increase in the mechanical properties. The PLA/HNT 5 wt% nanocomposite compounded at 140 rpm showed significant improvement in the dispersion of HNTs in the PLA matrix which in turn enhanced the mechanical and thermal properties. This can be attributed to the increased melt shear at higher screw speeds.

Analysis on Dynamic Contact Characteristics and Dynamic Stiffness Estimating Method of Single Nut Ball Screw Pair Based on the Whole Rolling Elements Model

The purpose of this paper is investigating the characteristics of dynamic contact and dynamic stiffness of the single nut ball screw pair (SNBSP). Then a new sensorless method is proposed to extract the SNBSP dynamic contact stiffness of a mass production CNC machine tool feed system. First of all, the transformation relationship between each coordinate system of SNBSP is established. Secondly, the dynamic model of all ball–raceway contact pairs is established. Based on this, a dynamic contact stiffness model is established. The dynamic contact parameters are obtained by the numerical method. It is found that the influence of screw speed on screw and nut raceway normal force distribution are opposite. This will affect the variations of dynamic contact stiffness. It is also clear that the effect of axial load on dynamic stiffness is significant. Then, an effective method is proposed to estimate the dynamic contact stiffness of a mass production CNC machine tool feed system without any external sensors. The axial force of feed system is estimated by using torque current of servo motor. Current signals can be obtained through FANUC Open CNC API Specifications (FOCAS) library functions, and then dynamic contact stiffness can be calculated through the stiffness model without external sensors. Finally, a feed system dynamic model is built, and the contact model and sensorless stiffness estimating method are verified by experiments in this dynamic system.

Impact of fill-level in twin-screw granulation on critical quality attributes of granules and tablets

In a previous study a change of the fill-level in the barrel exerted a huge influence on the twin-screw granulation (TSG) process of a high drug loaded, simplified formulation. The present work investigated this influence systematically. The specific feed load (SFL) indicating the mass per revolution as surrogate parameter for the fill-level was applied and the correlation to the real volumetric fill level of an extruder could be demonstrated by a newly developed method. A design of experiments was conducted to examine the combined influence of SFL and screw speed on the process and on critical quality attributes of granules and tablets. The same formulation was granulated at constant liquid level with the same screw configuration and led to distinctively different results by only changing the fill-level and the screw speed. The power consumption of the extruder increased at higher SFLs with hardly any influence of screw speed. At low SFL the median residence time was mainly fill-level dependent and at higher SFL mainly screw speed dependent. Optimal values for the product characteristics were found at medium values for the SFL. Granule size distributions shifted from mono-modal and narrow shape to broader and even bimodal distributions of larger median granule sizes, when exceeding or falling below a certain fill-level. Deviating from the optimum fill-level, tensile strength of tablets decreased by about 25% and disintegration times of tablets increased for more than one third. At low fill-levels, material accumulation in front of the kneading zone was detected by pressure measurements and was assumed to be responsible for the unfavored product performance. At high fill-levels, granule consolidation due to higher propensity of contact with the result of higher material temperature was accounted for inferior product performance. The fill-level was found to be an important factor in assessment and development of twin-screw granulation processes as it impacted process and product attributes enormously.

Influence of Screw Speed on Texture, Colour and Microstructure of String Cheese

Influence of Screw Speed on Texture, Colour and Microstructure of String Cheese

Effect of natural fibres on the mechanical properties of thermoplastic starch

Abstract This paper presents the results covering the mechanical properties of thermoplastic potato starch granules with flax, cellulose fibre, and pine bark addition. A modified single screw extrusion-cooker TS-45 with L/D = 18 and an additional cooling section of the barrel was used as the processing unit. The establishment influence of the fibre addition, as well as the extrusion-cooker screw speed, on the mechanical properties of the thermoplastic starch granules was the main objective of the investigation. The maximum force during compression to 50% of the sample diameter, elastic modulus, and compression strength were evaluated. Significant differences were noted depending on the amount of fibre used, while only an insignificant influence of screw speed on the mechanical properties of the granulate was reported. An increased amount of fibres lowered the maximum force as well as the elastic modulus and compression strength of the thermoplastic starch granulates.

Rheological Characterization and CFD Simulation of Soy White Flakes Based Dough in a Single Screw Extruder

AbstractUnderstanding the rheological properties such as shear profile, viscosity of a dough inside the extruder is very important for product development, process control, final product quality and scaling up operations. This study aims to characterize the rheological properties of high‐protein dough and perform isothermal flow simulation in a complex geometry for generalized Newtonian fluids. The flow of soy white flakes based dough in a single screw extruder was simulated by using computational fluid dynamics. Process conditions considered were screw speeds (40, 80, 120, 160 and 200 rpm), barrel temperature (100, 120 and 140C) and soy white flakes contents (30, 40 and 50% db). A mesh superposition technique was used to reduce the geometrical complexity. Simulation results were validated quantitatively by experimental data. The results showed good agreement between experimental and computational results. Moreover, the flow profile in the extruder was analyzed by using the influence of screw speed and level of soy white flakes content. Qualitative behavior of local shear rate and viscosity along the screw are analyzed and comparisons of different process conditions are presented. The results of these simulations can be used to optimize processing conditions and also to improve the product quality of extrudates.Practical ApplicationsThe flow of material within the extruder is complicated due to its helical screw configuration and the different zones of solids‐conveying, melting and melts conveying. Shear profile and viscosity of dough within the extruder directly influences the product quality. In the present study, rheological characterization of dough inside the extruder was done by using online capillary die rheometer. The flow of dough during extrusion processing was simulated using computational fluid dynamics. The results of the simulation can be used to optimize the extrusion process influenced by complex flows of relatively high concentration of soy white flakes based dough in an extruder and also to improve the product quality.

Application of a New Twin-Screw Extruder to the Waste Tire Regeneration

This paper uses a new twin-screw extruder for regeneration of waste tire crumb rubber, discusses the influence of screw speed and reaction temperature on the physical and mechanical properties of reclaimed rubber. Experimental results show that different screw speed and reaction temperature has a great impact on the physical and mechanical properties of the reclaimed rubber. When controls screw speed in the 60 ~ 90 r / min, reaction temperature at 170 to 210°C,the regeneration effect is the best. At this time, the physical and mechanical properties of reclaimed rubber, such as tensile strength, tear strength and elongation at break rate, is the best.

Analysis of the dispersive mixing efficiency in a twin-screw extrusion processing of starch based matrix

The flow of plasticized maize starch in a co-rotating twin screw extruder was simulated by using computational fluid dynamics (CFD). Sensitivity of the simulation to the selected viscosity model was analyzed. The results suggest that about 16 times increase in zero shear viscosity has no influence on the flow, whereas a slight change in viscosity at the shear thinning region leads to significant increase in pressure drop along the mixing zone of extruder. Simulation results were validated quantitatively by experimental data. Furthermore, the flow type and profile in the extruder were discussed by using the influence of screw speed and screw configuration as exemplary process parameters. To evaluate the dispersive mixing efficiency, material specific critical capillary number was implemented into particle tracking simulations. Maximum shear stress generated at the tip of the screws was used to calculate the maximum capillary ratio, and therefore to determine the dispersive mixing efficiency. The results show that increase in screw speed led to better dispersive mixing, although the generated shear stresses decreased. To investigate the influence of screw geometry, two different screw configurations were simulated. The results show that the dispersive mixing efficiency can be improved by using reverse kneading blocks at which more particles are exposed to high shear stresses.

Influence of Screw Speed on Electrical and Rheological Percolation of Melt‐Mixed High‐Impact Polystyrene/MWCNT Nanocomposites

AbstractThe influence of screw speed on the electrical and rheological percolation of HIPS/MWCNT composites prepared via melt mixing was investigated. Microscopic examination of these composites using POM, FESEM and HRTEM revealed optimum MWCNT dispersion was achieved at intermediate screw speeds. On addition of MWCNTs to HIPS, the electrical conductivity of HIPS increased by up to 12 orders of magnitude. At screw speeds up to 100 rpm an electrical percolation of 1–3 wt.‐% was achieved. This increased to 3–5 wt.‐% when the screw speed was increased to 150 rpm. The onset of a rheological percolation was detected for an MWCNT loading of 5 wt.‐%, irrespective of screw speed employed. An up‐shift in the Raman G‐band of 24 cm−1 was observed, implying strong interfacial interaction between HIPS and MWCNTs. magnified image

A study of residence time distribution in co‐rotating twin‐screw extruders. Part I: Theoretical modeling

AbstractA theoretical model to determine the residence time distribution (RTD) in a co‐rotating twin‐screw extruder is proposed. The method consists of coupling a continuum mechanics approach with a chemical engineering one and allows us to obtain the RTD without any adjustable parameter. The process parameters are obtained using Ludovic® twin‐screw modeling software, and ideal reactors are chosen to depict the screw profile. The influence of screw speed, feed rate and viscosity on RTD are described on a fictive screw profile. The predictions of the model are in qualitative agreement with literature data. The key point of this procedure is obviously the correct association between an ideal reactor and a screw element.

Compatibiliser activity and morphology stability during twin-screw extrusion and injection moulding of compatibilised blends

The influence of screw speed, agitator configuration, and compatibiliser, namely maleated polypropylene (mPP), during twin-screw extrusion upon the morphology, dispersion stability, and properties of polyamide-6/polypropylene (PA6/iPP) blends has been investigated. For mPP contents of 2.4 vol% and greater, the number average domain diameters measured in the extruded compound, D n(ex), were found to decrease to a limiting value at the specific mechanical energy input, S e, around 0.07 kW h kg −1, when S e was controlled by the screw configuration and screw speed. For mixing energies greater than 0.07 kW h kg −1, the domain size was principally determined by the ratio of specific interfacial area, S ext, between the PA and iPP phases to the estimated volume fraction of in situ formed copolymer, φ c; S ext /φ c ≈45 μm −1. The difference, Δ D n, between D n(ex) and the average domain diameter measured in the cores of the samples after injection moulding, D n(m), was calculated: Δ D n=| D n(ext)− D n(m)|. It was found that Δ D n∝ D n(ext); i.e. larger droplets in the extrudate underwent the greatest changes in dimension in the subsequent moulding process.

Mixing analysis of reactive polymer flow in a single-screw extruder channel

In this study, the finite element method was used to investigate the influence of screw speed, entering peroxide distribution, pressure-to-drag flow ratio, and channel geometry on the mixing characteristics of steady non-isothermal reactive flows. The reaction considered was the peroxide-initiated degradation of a polypropylene resin in the metering zone of a single-screw extruder. The predicted average degree-of-freedom profiles from the simulations largely conformed to expectations. The average flow efficiencies for all runs were found to vary little along the channel length, remaining at values close to that for two-dimensional flow. No significant effect of either screw speed or peroxide distribution was found on the flow efficiencies. However, both the pressure-to-drag flow ratio and the channel aspect ratio were found to have significant influences.

Formation of Resistant Starch by a Twin‐Screw Extruder

ABSTRACTThe objective of this study was to evaluate the potential to increase the level of resistant starch (RS) in extruded products by optimizing extruder conditions. Three experiments were conducted as randomized complete block designs with two replicates. In the first experiment, corn starch, wheat starch, and potato starch were added at a level of 30% (w/w) to degerminated yellow corn meal to investigate the influence of starch type. In the second experiment, citric acid (CA) monohydrate was added to corn meal at levels of 0, 2.5, 5, and 7.5% (w/w). The third experiment was a full‐factorial arrangement to evaluate the effect of high‐amylose corn starch (HACS) level (0, 15, 30%, w/w) and CA level (0, 5, 7.5%, w/w) at two screw speeds (200 and 300 rpm). In the first experiment, the means for RS plus dietary fiber for the different starch formulations ranged from 1.27 to 2.28%. In experiment 2, adding CA increased RS plus dietary fiber content to a maximum of 5.23% at 7.5% CA. In the third experiment, the means for RS plus dietary fiber ranged from a low of 1.75% for 100% corn meal at 300 rpm to 14.38% for 7.5% CA and 30% HACS at 200 rpm. The results indicated a highly significant positive relationship between CA and RS formation and the same for amylose content. The RS formation had a negative relationship with screw speed, but the influence of screw speed was small when compared with that of CA and HACS.

Use of a Power‐Consumption‐Controlled Extruder in the Development of Pellet Formulations

Shape is an important characteristic of pellets that is highly influenced by the water content of the extrudate during spheronization. The power‐consumption‐controlled extruder (pcc‐extruder) is an appropriate tool to adjust the required water content to yield round pellets. For this purpose, it is necessary to run the extruder at a specific level of power consumption. In the first part of the study, this approach was employed to screen different drugs as well as excipients to prove the concept of the pcc‐extruder. Usually round pellets were obtained but a few formulations did not produce round pellets. In the second part of the study, the influence of screw speed and powder feed rate on the required level of power consumption was investigated. A correlation between the water content and the shape of pellets was evident. To account for screw speed, it was necessary to adjust net power consumption instead of total power consumption. The influence of the screw speed on water content of extrudate and consequently on the shape of pellets was not significant in the studied range. Variations of the powder feed rate affected both the water content and the shape of pellets. However, the water content was not only dependent on the level of net power consumption. The specific power is the ratio of net power consumption to extrusion rate, and it correlates well with water content and pellet shape. Using the specific power, it is possible to adjust the net power consumption in response to changes in powder feed rate.

Development and control of a blend morphology by In situ cross‐linking of the dispersed phase

AbstractThe development of the morphology of a reactive blend along a twin‐screw extruder has been experimentally studied. A transesterification reaction activated by a catalyst allowed a cross‐linking of the dispersed phase during the flow in the extruder. In comparison with the nonreactive system (without catalysts), the resulting morphologies were characterized by larger dimensions. Influence of screw speed and feed rate were similar for both systems, whereas the changes along the screws were more pronounced for the reactive blend. It appeared that the local morphology was strongly dependent on the extent of the reaction. At low extent, the equilibrium between breakup and coalescence was shifted toward coalescence, whereas at high extent, the classical mechanisms were largely modified and replaced by a “coagulation” mechanism. It was shown that, for the fully cross‐linked dispersed phase, the final morphology remained remarkably stable during successive extrusion steps. For such products, the observation of a low‐frequency plateau of the elastic modulus suggested the formation of a copolymer at the interface with the matrix. © 1994 John Wiley & Sons, Inc.