Philipp Wüst

Material extrusion of thermoplastics (fused filament fabrication, FFF) commonly deposits solid strands. Foams combine low density with functions such as damping and thermal insulation, making cellular strands a desirable extension of FFF. We demonstrate dissolution-assisted physical foaming inside the nozzle of an FFF system: an external gas booster supplies supercritical CO ₂ through a lateral port into the melt, and a static mixing element upstream of the 0.60 mm nozzle promotes dissolution before foaming occurs at the nozzle exit. This transfers inline gas dosing and melt homogenization, established in foam extrusion, into an FFF printhead. We printed foamed strands and ring-shaped specimens from PETG and characterized them by microscopy and micro-computed tomography (µCT). Full-volume µCT analysis yielded an overall porosity of 75.3% (70.0–79.8% across segmentation thresholds), with a denser skin surrounding a more porous core. Using only gas, the polymer remains free of foaming additives, and we initiated pore formation locally on demand through the gas supply alone.

The aim of this work is to generate two extreme wetting states on metallic surfaces by means of laser structuring/treatment and to examine the physical and chemical processes behind it. For this purpose, four different metallic samples were laser-structured and then stored in atmospheric air and examined at certain time intervals using contact angle measurement. Immediately after laser structuring, the samples have shown a superhydrophilic wetting behavior, which then changes to the opposite after 10 days at the latest and exhibit superhydrophobic wetting behavior. The samples were then subjected to a second laser treatment to produce extreme wetting behavior, similar to those of a conventional printing plate. Additionally, the topology of the samples as well as an XPS analysis was carried out. It could be shown that wetting properties for possible use in offset printing can be achieved by laser structuring and that a multiple modification of the wetting properties is possible.

The substitutability of conventional coating systems with (“green”) coating systems based on renewable raw materials is being investigated with regard to the properties of graphic printing. In addition to color and rheological properties, the main focus is on technical printing properties such as abrasion resistance, static and dynamic friction, and wet block resistance. The four “green” coating systems tested show differing performance on three different substrates. Only the matte coating system proved to be fully acceptable as a substitute, while the glossy coatings tested showed only limited performance.

Screen printing is a well-established printing technique that typically uses petrochemical inks, which can be problematic both for the environment and recycling. This study investigates the development and characterization of bio-based screen-printing inks as a sustainable alternative. Various bio-based inks using materials such as starch, chitosan and cellulose were formulated, and their viscosity was analyzed using a rotational rheometer. The print quality was examined by screen printing tests on various substrates and subsequent visual and color density assessment. Rubbing fastness and light fastness were determined using a crockmeter resp. xenon light. The results show that the print quality is only slightly dependent on the viscosity, although there is an optimum viscosity range. A higher polymer concentration in the ink led to a slightly improved resistance to rubbing, while the light fastness was exclusively influenced by the pigment used. Several bio-based formulations showed equivalent or better print quality than the petrochemical reference ink, especially in terms of edge sharpness. These findings highlight the potential of bio-based screen-printing inks for a more environmentally friendly printing industry. The study shows that sustainable formulations with renewable raw materials are a promising alternative to conventional inks.

Fused filament fabrication (FFF) is a widely used additive manufacturing method in which the process forces within the hotend play an important role in terms of print quality and speed, particularly in high-throughput applications. This work reports on the influence of filament diameter, melting zone length, and nozzle set temperature on the process forces and the maximum achievable volumetric flow rate. Experimental measurements were carried out using a test rig that integrates a load cell to capture the resulting forces, complemented by non-isothermal numerical simulations. The results show that increasing the melting zone length reduces process forces and increases the attainable volumetric flow rate at high feed rates, as the filament has more time to melt. However, the effect depends strongly on filament diameter. For a diameter of 2.85 mm, extending the melting zone leads to a monotonic increase in the maximum achievable flow rate across the entire investigated range. For a diameter of 1.75 mm, an optimum is observed at an intermediate melting zone length, beyond which additional flow resistance outweighs the benefit of improved melting and thus reduces the attainable flow rate. When normalizing for the maximum transferable extruder force, the smaller filament diameter consistently yields superior throughput performance. The simulations reproduce the experimentally observed trends well and support the interpretation that throughput is limited by the competition between heat-transfer-controlled melting and viscous pressure losses.

This article examines additive manufacturing and robotic fabrication methods for hollow, lightweight structures in the field of architecture, engineering, and construction (AEC) industries. This article examines hollow, lightweight mineral building elements and their manufacturing methods. More specifically, this article explains the novel additive manufacturing method Blow Extrusion (BX) in detail. Blow Extrusion is an extrusion-based method for large-scale 3D printing of hollow strand structures. Blow Extrusion (BX) enables the production of lightweight, air-filled, strand-based structures significantly reducing material use while maintaining structural integrity. Hollow structural elements have historically played a critical role in reducing material consumption, optimizing weight, and improving construction material efficiency in construction. For instance, RotoForm, a sequential robotic casting process for mineral-based materials, is a robotic additive manufacturing method, resulting in hollow building elements. Beside the technical insights, this paper outlines the potentials of additive manufacturing in enhancing reduction material consumption through design and manufacturing procedures for cavities. The paper discusses the mechanical challenges, computational frameworks, prototyping challenges, and future applications of these methods in structural design, prefabrication, and lightweight construction.