Experiments with an instrumented twin-screw extruder using a single-step granulation/extrusion process (original) (raw)
Related papers
The operating characteristics of twin screw extruders
Polymer Engineering and Science, 1978
The operation of a twin screw extruder processing a powder or granular solid is reviewed. The operating variables of screw speed and barrel temperature profile interact with a number of design parameters-screw design, die geometry, feed zone geometry and with the material properties, in determining machine performance. The factors that determine output and pressure development are specified in a sequence of block diagrams. The dynamic response of an operating machine to disturbances in the steady state conditions is explained in the light of the established relationships and interpreted in conventional control theory terms. Attention is drawn to the importance of mixing in the chambers formed by the screw channels and of the residence time distribution in determining the quality of the final product.
Comparison of two twin-screw extruders for continuous granulation
European Journal of Pharmaceutics and Biopharmaceutics, 2009
A comparison was made between two twin-screw extruders (APV Baker and Leistritz Micro) used for continuous wet granulation. Both extruders had similar screw configurations, based on the length-to-diameter ratio of the screws, existing out of a conveying zone of 20 D, i.e. 20 times the screw diameter and a granulation zone of 4 D. The kneading blocks in the granulation zone were 2.2 and 2.5 D for the Leistritz and APV extruders, respectively. An experimental design was used to investigate the influence of process parameters (total input rate and screw speed) and extruder type on granule and tablet quality. Dicalcium phosphate and a-lactose monohydrate were used as water-insoluble and water-soluble excipients, respectively. For dicalcium phosphate, the amount of fines (<125 lm), median granule size and granule friability were significantly influenced by extruder type and total input rate. For lactose, the amount of oversized agglomerates and median granule size were significantly affected by extruder type and total input rate. The granule formulations were properly agglomerated on both the extruders, although the extruder type had an important influence on the granule properties, which was more pronounced for dicalcium phosphate. This study shows that a given formulation cannot simply be interchanged between the two extruders without further work on the geometrics of the extruders.
Aaps Pharmscitech, 2021
In order to be at pace with the market requirements of solid dosage forms and regulatory standards, a transformation towards systematic processing using continuous manufacturing (CM) and automated model-based control is being thought through for its fundamental advantages over conventional batch manufacturing. CM eliminates the key gaps through the integration of various processes while preserving quality attributes via the use of process analytical technology (PAT). The twin screw extruder (TSE) is one such equipment adopted by the pharmaceutical industry as a substitute for the traditional batch granulation process. Various types of granulation techniques using twin screw extrusion technology have been explored in the article. Furthermore, individual components of a TSE and their conjugation with PAT tools and the advancements and applications in the field of nutraceuticals and nanotechnology have also been discussed. Thus, the future of granulation lies on the shoulders of continuous TSE, where it can be coupled with computational mathematical studies to mitigate its complications.
A Basic Model for a Twin-Screw Extruder
Journal of Food Science, 1989
A model based on solving thermal balance and Stokes equation in a corotating twin-screw extruder with deep screw channels was developed. The present stage of the model described the evolution of temperature in the conveying section and the isothermal evolution of pressure in the melt pumping and reverse screw elements, with a Newtonian viscosity adapted to each part of the screw; residence time distribution in the whole extruder was also computed. Experimental validation was carried out on a pilot scale Win-screw extrudcr CLEXTRAL BC 45 fed with maize starch. Good agreement was found between the theoretical and actual temperature and pressure profiles, as well as with residence time distribution. In standard operating conditions (30 kg/hr, 200 rpm), the pressure generation in one C-shaped chamber was computed to be about 2.2 MPa, while pressure drops were about 0.3 MPa (intermeshing zone) and 0.5 MPa (reverse screw element) while the major part of the residence time per unit of screw length was spent in the reverse screw element.
Research Square (Research Square), 2024
The study of die swell phenomenon in Material Extrusion Additive Manufacturing (MEX-AM) technologies holds great importance in order to maintain the control over the extruded beads diameter to ensure surface quality, dimensional precision, adhesion between adjacent beads (intra and inter), as well mechanical properties on manufactured parts. This paper addresses an experimental procedure to analyze the in uence of extrusion parameters on the die swell phenomenon on extruded beads printed from a 3D customized equipment containing a customized co-rotating vertical twin-screw extrusion unit (Co-TSE AM). In this context, an analytical estimation of shear rate in the screws and die was performed; a design of experiments (DOE) was conducted to evaluate the in uence of factors as of screw rotational speed (40 rpm and 80 rpm), output rate (20 g/h and 40 g/h), and nozzle diameter (0.4 mm and 0.6 mm) on the die swell ratio (DSR); and scanning electron microscopy (SEM) was employed to assess the morphology in the cross-sectional area of the beads, as well as qualitative aspects of surface texture. Additionally, print line experiments were conducted to examine the in uence of platform speed and standoff distance on bead width and bead height. It was observed that the DSR average varied between 1.28 and 1.67. Output rate and nozzle diameter are the parameters that most strongly in uence DSR. Screw rotational speed has not signi cant in uence on the thermomechanical environment that in uences material swelling. The bead width and bead height are differently in uenced by the standoff distance and print platform speed. Highlights Analysis of the die swell phenomenon in the processing of a thermoplastic material (polypropylene) in a customized equipment with a vertical co-rotating twin-screw Co-TSE AM extrusion system; Analysis and evaluation of rheological characteristics associated with the extrusion process applied to miniaturized and innovation equipment for additive manufacturing by single step extrusion process using feedstock in polymer-based powders where the study was led by design of experiments; Evaluation of the beads pro les and printed basic geometry dimensions; The results obtained on the die swell in the customized equipment presented values close to literature report using FDM 3D printers; The CO-TSE equipment presents potential application in the single step additive extrusion processes based on powder feedstock in order to generate distributive and dispersive mixtures in the laboratory-scale to the blends formulations, a new approach to produce new laments which will can use in desktop FDM 3D printers; The results presented by CO-TSE additive equipment indicate the potential use on manufacturing of small parts and test specimens for research purposes.
Engineering Analysis and Design of Twin-Screw Extruders for Reactive Extrusion
= Process developments in reactive extrusion or reactive compounding are largely carried out in closely intermeshing corotating twin-screw extruders. The aim of this article is to present an analytical process model for this reactor type in order to facilitate the design of screw geometry and the settings of process parameters. Taking simultaneously into account aspects of flow behavior, heat transfer, thermodynamics, physics, and chemistry, a powerful mathematical model has been developed which was compared with practical results (e.g., residence time, pressure buildup, drive energy, bulk temperature, and conversion) on lab and production scale machines. The experiments were mostly carried out for the anionic bulk polymerizations of nylon 6 and polystyrene. Furthermore the reactive blending of nylon 6 and polyethyleneterephthalate was examined. Based on these chemical systems the practical use of computer-aided process design will be discussed.
Scientific Proceedings Faculty of Mechanical Engineering STU in Bratislava, 2013
This paper is concerned with experimental tests of the process of extrusion with hot granulating of polymer, conducted to determine the influence of a change in the value of the cutting edge angle of a granulator knife on the basic parameters of the obtained pellets and on the process of extrusion with granulation. The available literature does not raise this issue. In the present study, the process of extrusion with hot granulation was studied with the use of low-density polyethylene.
International Polymer Processing, 2018
The task of the solid conveying section is to collect the entering material and transfer it to the melt dominated sections. Therefore, its upstream interface is the hopper and its downstream interface is the section in which the first melting occurs. Beneath the hopper opening, the screw rotation collects and conveys the material forward. It is hereby assumed that the friction forces among the particles are higher than the transferring forces on the screw and barrel. For that reason commonly known models for describing the solid conveying in single screw extruders assume that the screw channel is always completely filled so that a plug flow occurs. At high screw speeds, however, these assumptions are no longer valid. To analyze and mathematically describe the solid conveying behavior at screw speeds up to 2000 rpm, simulations based on the Discrete Element Method have been executed in previous investigations. Based on this, a model for describing the solid conveying behavior was dev...
Flow patterns in twin-screw extruders
Journal of Materials Processing Technology, 1999
Flow visualisation studies in an intermeshing co-rotating twin-screw extruder operated under starve-fed conditions are presented. Different numbers of kneading discs and relative staggering angles were used in the de®nition of the mixing blocks. Conveying and lefthanded elements were also utilised. The images recorded provided information on¯ow patterns, on the degree of ®lling of the screw channels and on the number of ®lled turns. Local¯ow times were estimated. Partial residence time distribution (RTD) functions were determined by inserting especially designed collecting devices along the barrel, and measuring the evolution with time of the concentration of a tracer.
Flow/pressure characteristics and modeling of deformation processes of single-screw extruders
Polymer Engineering & Science, 2010
One of the most widespread practical methods of polymer processing is the extrusion method that is based on pressing a polymeric melt through channels of the molding tool which have different geometrical cross sections. The principal technical characteristic of extruders, named flow/pressure balance, and also modeling of deformation processes permit to evaluate their practical output in processing various polymers as a function of the hydraulic resistance which depends on the flow of an extruded polymeric material through the channels of the forming tool. The validity of obtained and presented results permits to recommend them reasonably not only for estimation of extruder output but also for making calculations necessary in extruder equipment design: checking calculation of strength and stability of a screw, calculation of driving power of the equipment being designed, strength calculation of a plasticizing cylinder, etc.