This research paper reviews the test results involving viscoelastic properties of cellular structure models made with the PolyJet Matrix—PJM additive technology. The designed test specimens were of complex cellular structure and made of three various photo-curable polymer resin types. Materials were selected taking into account the so-called “soft” and “tough” material groups. Compressive stress relaxation tests were conducted in accordance with the recommendations of standard ISO 3384, and the impact of the geometric structure shape and material selection on viscoelastic properties, as well as the most favorable geometric variants of the tested cellular structure models were determined. Mathematica and Origin software was used to conduct a statistical analysis of the test results and determine five-parameter functions approximating relaxation curves. The most favorable rheological was adopted and its mean parameters determined, which enables to match both printed model materials and their geometry in the future, to make a component with a specific rheological response. Furthermore, the test results indicated that there was a possibility of modelling cellular structures within the PJM technology, using support material as well. Full article

The paper presents the results of mechanical tests of models manufactured with two 3D printing technologies, FDM and CFF. Both technologies use PLA or PA-based materials reinforced with carbon fibers. The work includes both uniaxial tensile tests of the tested materials and metrological measurements of surfaces produced with two 3D printing technologies. The test results showed a significant influence of the type of technology on the strength of the models built and on the quality of the technological surface layer. After the analysis of the parameters of the primary profile, roughness and waviness, it can be clearly stated that the quality of the technological surface layer is much better for the models made with the CFF technology compared to the FDM technology. Furthermore, the tensile strength of the models manufactured of carbon fiber-enriched material is much higher for samples made with CFF technology compared to FDM. Full article

The main objective of the study was to design a pneumatic directional control valve for controlling pneumatic drives and produce it using a rapid prototyping technique. As the basic design assumption was to achieve high performance through a high flow rate and a low pressure drop, it was necessary to determine two flow parameters: the sonic conductance and the critical pressure ratio. The flow rate of compressed air and the diameters of the pneumatic conduits and fittings are important as they affect the rate of travel of the pneumatic cylinder piston. The 3D solid model of the directional control valve, developed in a CAD program, was used to simulate and optimize the flow rate. The analysis was performed by means of ANSYS CFX, a computational flow dynamics program. The main elements of the valve, i.e., the spool and the body, were produced using the PolyJet Matrix technology. The prototype was tested experimentally to determine the nominal flow-rate, calculate the flow parameters in accordance with the ISO 6358-1989 standard and compare them with the CFD simulation data. The simulation results showed very good agreement with the measurement data. The CFD analysis of the 3D solid model enabled us to optimize the flow of compressed air through the valve. The rapid prototyping method was found to be suitable to produce a fully functional directional control valve, which was confirmed through measurements at a test stand. The attempt to combine rapid prototyping used to fabricate pneumatic directional control valves with CFD used to simulate their operation was successful. The study shows that it is possible to design and construct a fully functional directional control valve characterized by high efficiency, high performance and a small pressure loss in a very short time and at a very low cost, which makes rapid prototyping superior to conventional methods of prototype making. Full article

The paper describes the mechanical properties, determined on the basis of a tensile strength test of a composite material based on glass-fiber reinforced polyamide and obtained by Selective Laser Sintering—SLS. The material used is PA 3200 GF. Thin walled samples with non-standard nominal thicknesses of 1, 1.4 and 1.8 mm, manufactured in three printing directions X, Y and Z, were used. The description included the impact of printing direction on the geometry of the obtained samples and tensile strength as well as the dependency of tensile strength on the sample thickness. The results can be useful for design engineers and process engineers designing thin-walled components produced with SLS. Thin samples were obtained with a considerable deviation spread of the actual dimension from the nominal one. It was found that the tensile strength of thin samples is much lower than those of standard cross-sections, which should be taken into account in the design of thin-walled elements. Full article

The article presents the design of the upper limb joints of an anthropometric dummy intended for rear crash tests for low impact speeds. These joints represent the connection of the hand to the forearm, the forearm to the arm, and the arm to the shoulder. The designed joint is adapted to the construction of a dummy representing the 50th percentile male. The joints currently used on Hybrid III dummies require calibration after each crash test. The construction of the new joint ensures the appropriate strength of individual joint elements and the repeatable value of the joint characteristics without the need for frequent calibrations. The designed joints have the ability to set a variable stiffness characteristic, thanks to which it is possible to use this joint universally in dummies representing populations of other percentile sizes. The range of movement of the joints has been selected to reflect the range of mobility of the upper limb of an adult. The characteristics of the joints were compared with those used in the joints of the Hybrid III 50 percentile male dummy. Moreover, it should be noted that the constructed joints of the upper limb are made by hand; therefore, their comparison with the Hybrid III dummy shows some deviations in the moments of resistance. Making the joints with a 3D printer, taking into account the appropriate material, will ensure greater accuracy and will also result in joining the individual elements of the joint into a whole. The obtained results show slight differences between the moment of resistance in the joints of the constructed anthropometric dummy compared to the hybrid III dummy. Full article