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Extrusion is the operation of forming and shaping a molten or dough-like material by forcing it through a restriction, or die. It is applied and used in many batch and continuous processes. However, extrusion processing technology relies more on continuous process operations which use screw extruders to handle many process functions such as the transport and compression of particulate components, melting of polymers, mixing of viscous media, heat processing of polymeric and biopolymeric materials, product texturization and shaping, defibering and chemical impregnation of fibrous materials, reactive extrusion, and fractionation of solid-liquid systems. Extrusion processing technology is highly complex, and in-depth descriptions and discussions are required in order to provide a complete understanding and analysis of this area: this book aims to provide readers with these analyses and discussions. Extrusion Processing Technology: Food and Non-Food Biomaterials provides an overview of extrusion processing technology and its established and emerging industrial applications. Potency of process intensification and sustainable processing is also discussed and illustrated. The book aims to span the gap between the principles of extrusion science and the practical knowledge of operational engineers and technicians. The authors bring their research and industrial experience in extrusion processing technology to provide a comprehensive, technical yet readable volume that will appeal to readers from both academic and practical backgrounds. This book is primarily aimed at scientists and engineers engaged in industry, research, and teaching activities related to the extrusion processing of foods (especially cereals, snacks, textured and fibrated proteins, functional ingredients, and instant powders), feeds (especially aquafeeds and petfoods), bioplastics and plastics, biosourced chemicals, paper pulp, and biofuels. It will also be of interest to students of food science, food engineering, and chemical engineering. Also available Formulation Engineering of Foods Edited by J.E. Norton, P.J. Fryer and I.T. Norton ISBN 978-0-470-67290-7 Food and Industrial Bioproducts and Bioprocessing Edited by N.T. Dunford ISBN 978-0-8138-2105-4 Handbook of Food Process Design Edited by J. Ahmed and M.S. Rahman ISBN 978-1-4443-3011-3

In this study, textured vegetable protein (TVP) based on soy protein isolate, wheat gluten, and corn starch was prepared at a 5:3:2 (w/w) ratio using a low-moisture extrusion process. To evaluate the effects of extrusion parameters, die temperature and screw rotation speed, on the properties of TVP, these two parameters were manipulated at a constant barrel temperature and moisture content. The results indicated that increasing the die temperature increased the expansion ratio while decreasing the density of the extrudates. Simultaneously, increasing the screw rotation speed clearly increased the specific mechanical energy of the TVP. Furthermore, mathematical modelling suggested that the expansion ratio increases exponentially to the die temperature. However, extreme process conditions bring about a decrease in water absorption capacity and expansion ratio, as well as undesirable texture and microstructure. The results suggested that the properties of SPI-based TVP are directly influenced by the extrusion process parameters, screw speed and die temperature.

Wide stiffened aluminium panels are extensively used in aerospace, marine, and civil industries due to their light-weight structure and high stiffness. In this paper, a wide stiffened aluminium panel was manufactured using the principle of the multi-container extrusion, and a comparative study was conducted using two different die designs at the same extrusion condition, in which metal flow behaviour, extrusion force, welding quality, and billet material utilisation have been investigated numerically. Additionally, the effect of extrusion speed on the extrusion process was evaluated with the modified design. It was shown that, compared with the initial design, better metal flow behaviour can be obtained in the modified design. Multi-container extrusion greatly reduces the extrusion force, and the modified design results in a more uniform extrusion force for each extrusion container. The total extrusion force for the modified design is slightly higher compared with the initial die design, due to the increased friction in the upper die channels and the second-step welding chamber. Besides, the modified design of the multi-container extrusion can obtain better welding quality evaluated by different welding criteria, and the extrusion speed has a minor effect on the welding quality. The most notable feature is that the modified design greatly improves the material utilisation, which could save 39.5% material compared to the initial design.

The fused deposition modeling (FDM) process, an extrusion-based 3D printing technology, enables the manufacture of complex geometrical elements. This technology employs diverse materials, including thermoplastic polymers and composites as well as recycled resins to encourage sustainable growth. FDM is used in a variety of industrial fields, including automotive, biomedical, and textiles, as a rapid prototyping method to reduce costs and shorten production time, or to develop items with detailed designs and high precision. The main phases of this technology include the feeding of solid filament into a molten chamber, capillary flow of a non-Newtonian fluid through a nozzle, layer deposition on the support base, and layer-to-layer adhesion. The viscoelastic properties of processed materials are essential in each of the FDM steps: (i) predicting the printability of the melted material during FDM extrusion and ensuring a continuous flow across the nozzle; (ii) controlling the deposition process of the molten filament on the print bed and avoiding fast material leakage and loss of precision in the molded part; and (iii) ensuring layer adhesion in the subsequent consolidation phase. Regarding this framework, this work aimed to collect knowledge on FDM extrusion and on different types of rheological properties in order to forecast the performance of thermoplastics.

Polylactic acid (PLA) has been widely used in the field of medical devices. However, few studies have been conducted on the extrusion molding of PLA micro tubes for the preparation of biodegradable vascular stents. In this paper, the extrusion die for PLA single-cavity micro tubes was designed and manufactured by micro-extrusion theory. Taking the outer diameter, wall thickness, wall thickness uniformity and ovality of micro tubes as the evaluation index, the influence of the main extrusion process parameters on the evaluation index was studied. The experimental results show that the outer diameter and wall thickness are significantly affected by screw speed, pulling speed and gas flow rate; extrusion process parameters have little influence on wall thickness uniformity and ovality within a certain range, which mainly depends on the processing accuracy and assembly accuracy of the extrusion die. However, excessively high screw speed and low gas flow rate have significant effects on ovality. Finally, according to the influence of extrusion process parameters on the evaluation index, a series of micro tubes that meet the design requirements are extruded and carved into vascular stent structures.

The objective of this work is to evaluate the reprocessing of PLA 3D printing waste from different origins, into filaments and films, and without the addition of any additive. Two types of waste were considered: a blend of different printing wastes (masks, visors, other components) of personal protective equipment coming from an association of Spanish coronamakers, and PLA waste from a single known commercial source. Both types of materials were subjected to repeated extrusion cycles and processed into films by compression molding. Samples were characterized after each cycle and their mechanical and viscosity properties evaluated. Diffusion-ordered NMR spectroscopy (DOSY) experiments were also carried out to estimate molecular weights. The results show a better performance for the PLA waste from the known origin, capable of withstanding up to three re-extrusion cycles per two for the waste blending, without significant degradation. Additionally, a model to address collection and mechanical recycling cycles under two different scenarios (full traceability and not full traceability) was proposed.

The present review paper would celebrate the 25 years anniversary of the ESAFORM association by summarizing the studies performed by the delegates of the ESAFORM conference series within mini-symposium “Extrusion and Drawing” and of the papers published in the International Journal of Material Forming in the same fields. The 160 analyzed papers have been divided in four main categories corresponding to the paper main chapters (Hot Metal Extrusion, Cold Metal Extrusion, Polymer Extrusion and Drawing) then further divided in sub-chapters in order to group them in more specific research subjects. The aim of this review paper is then to provide to the reader a complete overview of the investigated topics and of the research trends over the years within the ESAFORM associate researchers.

The application of additive manufacturing (AM) for tooling in the mould and die industry brings a disruptive potential in process performance, design flexibility and product enhancements. Maturing of existing AM technologies and emerging technologies such as metal-fused filament fabrication (metal FFF) can further support the applicability of AM tooling in polymer profile extrusion. This study provides a complete characterization of metal FFF 17–4 PH stainless-steel die inserts and evaluates their applicability in a polymer extrusion process chain. The presented experimental assessment pivots on the metrological characterization of the produced inserts and the impact of the insert characteristics on the final extrudates’ product. Considering a conventionally manufactured benchmark insert, produced via subtractive methods (CNC machining and electrical discharge machining), comparable results for AM tools in terms of extrudates’ quality and process repeatability are presented. It was found that despite significant higher average surface parameters for AM insert tools ( Sa  = 2–9 µm vs. Sa  = 0.3–0.9 µm for dies manufactured by machining), a much smaller difference was observed in the resulting quality of polymer extrudates’ product. The roughness generation effect of polymer profile extrusion based on the different dies’ internal surface roughness topography and the effect on extrudates product was evaluated. Three-dimensional average roughness Sa on acrylonitrile butadiene styrene extrudate surfaces obtained from conventionally machined dies was in the range of 0.3 µm. For extrudates obtained from additively manufactured dies, their Sa was in the rage of 0.5 µm (despite the much higher surface roughness of FFF dies compared to machined dies). The results confirm that with suitable extrudates’ product requirement, it is feasible to apply metal FFF as the selected manufacturing method for tooling in polymer profile extrusion.

This paper presents a systematic review on extrusion additive manufacturing (EAM), with focus on the technological development of screw-assisted systems that can be fed directly with granulated materials. Screw-assisted EAM has gained importance as an enabling technology to expand the range of 3D printing materials, reduce costs associated with feedstock fabrication, and increase the material deposition rate compared to traditional fused filament fabrication (FFF). Many experimental printheads and commercial systems that use some screw-processing mechanism can be found in the literature, but the design diversity and lack of standard terminology make it difficult to determine the most suitable solutions for a given material or application field. Besides, the few previous reviews have offered only a glimpse into the topic, without an in-depth analysis about the design of the extruders and associated capabilities. A systematic procedure was devised to identify the screw-assisted EAM systems that can print directly from granulated materials, resulting in 61 articles describing different pieces of equipment that were categorized as experimental printheads and commercial systems, for small- and large-scale applications. After describing their main characteristics, the most significant extruder modifications were discussed with reference to the materials processed and performance requirements. In the end, a general workflow for the development of 3D printers based on screw extrusion was proposed. This review intends to provide information about the state-of-the-art screw-assisted EAM and help the academy to identify further research opportunities in the field.

This work aims to better understand the type of thermoplastic binders required to produce highly loaded copper filaments that can be successfully printed via low-cost filament-based material extrusion (MEX). Compounding feedstock material with 55 vol.% of copper and three multi-component binder systems has been performed. The MEX behavior of these feedstocks was evaluated by depositing material at different speeds and appropriately selecting the extrusion temperature depending on the binder composition. The rest of the MEX parameters remained constant to evaluate the printing quality for the different feedstocks. Printable filaments were produced with low ovality and good surface quality. The filaments showed good dispersion of the powder and polymeric binder system in SEM analysis. The feedstock mechanical properties, i.e., the tensile strength of the filament, were sufficient to ensure proper feeding in the MEX machine. The viscosity of the feedstock systems at the adjusted printing temperatures lies in the range of 102–103 Pa·s at the shear rate of 100–1000 s−1, which appears to be sufficient to guarantee the correct flowability and continuous extrusion. The tensile properties vary greatly (e.g., ultimate tensile strength 3–9.8 MPa, elongation at break 1.5–40.5%), and the most fragile filament could not be reliably printed at higher speeds. Micrographs of the cross-section of printed parts revealed that as the printing speed increased, the porosity was minimized because the volumetric flow of the feedstock material increased, which can help to fill pores. This study offers new insights into the feedstock requirements needed to produce low-cost intricate copper components of high quality in a reliable and efficient manner. Such components can find many applications in the electronics, biomedical, and many other industries.