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Nowadays, the liquid nitrogen cooling in aluminium extrusion is a widely adopted industrial practice to increase the process productivity as well as to improve the extruded profile surface quality by reducing the profile exit temperatures. The cooling channels are commonly designed on the basis of die maker experience only, usually obtaining modest performances in terms of cooling efficiency. Trial-and-error approach is time and cost consuming, thus providing a relevant industrial interest in the development of reliable numerical simulations able to foresee and optimize the nitrogen cooling effect during the die design stage. In this work, an extensive experimental campaign was performed during the extrusion process of an AA6060 industrial hollow profile, in different conditions of nitrogen flow rate and ram speed. The monitored data (die and profile temperatures and extrusion load) were compared with the outputs of a fast and efficient numerical model proposed by the authors, and developed in the COMSOL Multiphysics code, able to compute not only the effect of nitrogen liquid flow but also the gaseous condition. The results of the simulations showed a good agreement with experimental data, and evidenced how far the experimental cooling channel design from an optimized condition was.

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.

Texturing can be used to functionalize the surface of plastic parts and, in particular, to modify the interaction with fluids. Wetting functionalization can be used for microfluidics, medical devices, scaffolds, and more. In this research, hierarchical textures were generated on steel mold inserts using femtosecond laser ablation to transfer on plastic parts surface via injection molding. Different textures were designed to study the effects of various hierarchical geometries on the wetting behavior. The textures are designed to create wetting functionalization while avoiding high aspect ratio features, which are complex to replicate and difficult to manufacture at scale. Nano-scale ripples were generated over the micro-scale texture by creating laser-induced periodic surface structures. The textured molds were then replicated by micro-injection molding using polypropylene and poly(methyl methacrylate). The static wetting behavior was investigated on steel inserts and molded parts and compared to the theoretical values obtained from the Cassie–Baxter and Wenzel models. The experimental results showed correlations between texture design, injection molding replication, and wetting properties. The wetting behavior on the polypropylene parts followed the Cassie–Baxter model, while for PMMA, a composite wetting state of Cassie–Baxter and Wenzel was observed.

In the context of aluminum alloy extrusion, the presence of the skin contamination defect imposes the scrap of the contaminated profile length due to its lower mechanical properties. For understanding the evolution of the defect, comprehensive analyses, either experimental investigations or reliance on predictive techniques, are mandatory. Recently, numerical methods have gained interest in predicting the development of skin contamination, although their level of accuracy remains uncertain. This research focuses on a detailed experimental and numerical analysis of three different AA6XXX industrial extruded profiles. The aim is to compare the evolution of the skin contamination experimentally observed with the outcomes of the simulation using the commercial finite element code Qform Extrusion UK. The main findings of the analysis confirmed the potentiality and the accuracy of the numerical tools, also evidencing the current limitations of the empirical and analytical industrial practices.

During the hot extrusion process of metals, billets are continuously loaded into the press and joined together under high hydrostatic pressure, forming a single extruded profile. Contamination at the billet-to-billet interface, such as oxides and dust residues, produces a welded zone (i.e. charge welds) with compromised mechanical properties, leading to the scrap of the resulting profile portion. To optimize the discharging process, the exact starting point and the extent of the billet-to-billet interaction must be precisely identified. This study aims to develop an innovative model based on phase field method to capture the interaction between immiscible fluids at high viscosity, capable of predicting the charge welds evolution within the COMSOL Multiphysics FEM code. To validate the model, two industrial case studies were experimentally investigated, involving the extrusion of AA6060 and AA6082 profiles with different process parameters and cooling conditions. The collected data were compared with simulation outcomes, revealing a good agreement with errors always below the 8% both in terms of charge welds onset and extent. This validation proved the reliability of the proposed model in accurately predicting extrusion defects.

The microstructure of 6xxx aluminum alloys deeply affects mechanical, crash, corrosion and aesthetic properties of extruded profiles. Companies, especially in the transportation sector, require control over the grain structure in order to ensure the quality and the performance of the products. A main challenge for the extrusion companies is to accurately predict the profile microstructure at the design stage, trying to limit the formation of coarse grains and, consequently, the reduction of the mechanical properties of the component. In this work, the modeling of the stored energy, driving force for the recrystallization, was carried out and implemented within the Qform Extrusion FEM code. A novel approach for the evaluation of fibrous and recrystallized microstructures in 6XXX aluminum alloy profiles was proposed and tested in a campaign of experiments involving the extrusion of AA6082 round bars under several die designs and processing conditions. The outcomes proved the good accuracy of the recrystallization predictions during the extrusion of AA6082 aluminum alloy.

Polymers are versatile materials widely used in various industries, with significant applications in biomedicine where biofouling on polymer surfaces presents major health and economic challenges. Biofouling, initiated by bacterial adhesion, can be mitigated by modifying surface properties through laser micro- and nano-texturing, an approach that offers advantages over chemical treatments. This study introduces an economical mass production process for textured polymeric components using injection molding to replicate hierarchical textures. Testing revealed that all textured samples significantly reduced bacterial adhesion compared to untextured surfaces across different designs and bacteria types after 24 h of culture. The study examined factors like wettability, nanoscale roughness, and pattern dimensions to explain these outcomes, comparing them with existing studies. Despite all textured samples showing decreased wettability and roughness, these factors alone did not ensure reduced bacterial adhesion. The most effective anti-adhesive performance was observed in surfaces with parallel ridge patterns, which segmented the surface into isolated areas that limited bacterial interaction and hindered micro-colony formation, highlighting the importance of specific surface patterning in combating biofouling.

Biomedical implants interact with human tissues introducing significant perturbation into the body. Implant surfaces can be then functionalized enabling better biocompatibility. At the same time, the additional use of a coating provides further functions such as corrosion protection, osteointegration, and drug delivery. In this context, a composite made of chitosan and bioactive glass nanoparticles has been used for coating Ti6Al4V alloy samples processed beforehand using different processes, i.e., polishing, milling, grit blasting, and electrical discharge machining. Experiments have been carried out to correlate substrate surface conditions and coating effectiveness in terms of scratch resistance with the final aim to obtain suitable guidelines to improve substrate-coating performances.

The distribution of fibers in injection-molded thermoplastic-reinforced parts is known to significantly affect both the final mechanical properties and the appearance of defects related to undesired shrinkages and warpages. Even if the numerical modelling of the process is in the state of the art, the selection criteria of the model for the fiber orientation predictability and the influence of the models’ parameters are not yet clearly understood. The complexity of the matter increases further considering that, inside the same injection-molded part, the fiber orientation distribution could differ from one region to another depending on the local melt shear flow type. In this context, the aim of this study is to investigate the orientation of fibers in regions of non-simple shear flow in an injection-molded short glass fiber-reinforced part. X-ray microcomputed tomography is used to experimentally investigate fiber distribution and orientation. Furthermore, a number of numerical simulations of the injection molding process are performed in Moldflow® by varying the mesh type (2D/3D), the selected predictive model, and the models’ coefficients. The main findings indicate that, in regions with non-simple shear flow, a 2D mesh fails to capture accurate fiber orientation. A 3D mesh is essential for reliable predictions. MRD-specific parameters from the literature reduce prediction error by 37.5% compared to Moldflow’s default MRD parameters. Regarding the RSC model, both Wang’s optimal retarding rate parameter and AMI’s default retarding rate parameter result in similar 5% prediction errors. However, employing a literature-suggested interaction coefficient raises the prediction error to 26%.

The die cooling by means of liquid nitrogen is a widely adopted industrial practice used to increase the production rate in the hot extrusion process of light alloys. The development of a reliable numerical model able to simulate the cooling channel efficiency has become of primary interest for the extrusion sector in order to avoid ineffective die cooling and time-consuming trials and errors. In this work, H13 die inserts with a helicoidally conformal channel were designed and printed by means of the SLM additive technology. Billets of AA6063 aluminum and ZM21 magnesium alloys were extruded at different process speeds under monitored conditions to verify the insert resistance and the cooling effectiveness. A 3D finite element model of the extrusion process coupled with a 1D model of the cooling channel was generated within the COMSOL simulation environment. The experimental outputs were also used to validate the numerical predictions of the developed simulations. The FEM results showed a good matching with the loads and temperatures obtained in the experimental trials. Moreover, the endurance of the AM tool validated the prediction of the stress field, thus proving the reliability of the numerical model for the application in the extrusion of light alloys sector.