Machine and material under the microscope: A research project is investigating the additive manufacturing of filled rubber mixtures to be crosslinked based on liquid rubber polymers.Hexagonal lattice structure additively manufactured from LIR-390 with a web width of 0.8 mm and a thickness of 0.4 mm.(Image: DIK)An annual growth of 25% has been determined since 2014 with a current total market volume of USD 12.1 billion.Further development is forecast with an average growth of 24% up to the year 2024 [4].The range of new materials for established AM processes has increased enormously over the past few years and, in addition to standard plastics, offers a variety of modified materials for high-performance applications and special requirements.In comparison to thermoplastic elastomers, elastic photopolymers and reactive resin systems, the class of materials filled with silica or soot and rubbers to be vulcanized has so far been largely untapped.In a first publication, Wittek et al.the technology transfer from the original Fused Filament Fabrication process (FFF) to the new "AME process (Additive Manufacturing of Elastomers)" is described [5].In this case, the material is conveyed and metered using a 9 mm twin screw extruder, which can move numerically in three spatial directions in the installation space of the test facility.An additional thermoplastic extruder enables the production of shell structures to stabilize the structure of the highly viscous rubber mixture that is still flowable until vulcanization in the autoclave.Construction and commissioning of the machine setup described is carried out by Sundermann et al.carried out and the potentials validated on the basis of different rubber compound recipes [6].A similar structure was found by Drossel et al.can be reproduced with a small single-screw granulate extruder [7, 8].With this approach, simple geometries made of carbon black-filled, sulfur-crosslinked NBR mixtures could be manufactured additively.It's almost gigantic.The world's largest 3D printers not only manufacture cars additively, but entire houses.The expert blog '3Dmake' has compiled the 3D printers with the largest installation space.The printing technique is different.Did you know?In addition to the necessary vulcanization process for final geometry stabilization, the high viscosity of such mixtures during the additive manufacturing process in particular represents a challenge for the process.In a new research approach, liquid rubbers are used as part of the material base.These have a significantly lower molecular weight and lower viscosity than conventional ball rubbers, resulting in new process options for 3D printing rubber compounds.The development and processing of mixtures based on liquid rubbers with a dispenser system was carried out by Thiel et al.has already been described in detail and is summarized in this report [1–3].For the geometrically stable and robust production of components, the amount of material discharged by the dispenser unit must be reproducible, controllable and ideally process-integrated.The viscosity and the pseudoplastic behavior of the material pose a further challenge to the technology used.While a wide variety of pneumatic or piezoelectric discharge mechanisms are possible for low-viscosity media (<5 pa * s) [9], the viscosity of filled mixtures based on liquid rubber (approx. 10–100 kpa limits this selection.after market research, a dispenser unit type vipro-head 5 from viscotec pumpen- u. dosiertechnik, töging am inn, is selected for developed 3d printer.the material metering in endless piston principle, which individual, separated portions are conveyed and metered by an eccentrically running screw.with temperature control up to 70 ° c pre-pressure that can be applied supply, cavities screw even with highly viscous pasty media reproducible dosing possible.the designed manufacturer use additive manufacturing systems comparatively light at around 750 g.with pt100 thermal sensors, 24 v heating power supply stepper motor drive, easily integrated into process (for example marlin firmware).a converted x400 system innovatiq (formerly german reprap), feldkirchen, latest electronics used as test system.the supplemented high-temperature extruder (450 c) dual-drive filament order cover all possible combinations if required.the chemical structure monomer units rubbers equivalent ball very similar, but vary greatly terms molecular weight chain lengths, significantly lower rubbers.as result, polymers already state room temperature, which, depending type, comparable honey (a few hot glue hundred s).a particularly challenging aspect compound production enable sufficient dissipative shear energy input disperse fillers other constituents distribute them homogeneously.in addition, crosslinking density polymer matrix must achieved via reaction (vulcanization), means sulfur accelerator desired “performance” molded part only when it networked.since there published reports experiences such mixing recipes, both recipe were verified advance.the results shown using mixture lir-390 (kuraray, hattersheim) blend less regular ir (natsyn 2200).lir-390 copolymer isoprene butadiene low weight.a without goods serves reference.the dosage adapted optimal rubber-based formulation regard raw concentrations.additive future technology becoming more important branches industry.to develop technology, university bayreuth, together innovation project group fraunhofer ipa, stuttgart, founded research center campus additive.innovations (ca.i) april 2020.scientists five faculties than 26 chairs four non-university institutions work innovative solutions.at same time, they will cooperate across industries companies regional environment, who find contact point questions about ca.i.you out establishment herethe classic compounds internal mixers rolling mills unsuitable pasty, low-viscosity formulations.due viscosity, not enough introduced during processes, why new two-stage was preparation mixture.in first step, masterbatch produced mixer, solid components being added reduced content.the remaining portion dissolved stoichiometrically granulated parts planetary mixer [10].in high take place homogenize constituents.the degassed under vacuum cartridges compatible delivery characteristics suitable parameter ranges determined static preliminary tests.since mixture-specific pseudoplastic behavior vary, screening carried before each test.the g-code creation analogous fff process.however, since does have melted case thermoplastics, storage container zone controlled these parameters.the nozzle diameters correspond common sizes flm varied between 0.4 1.0 mm, layer thickness printed corresponds 50% diameter.at current view development, speed limited 10 mm>