Emila Brancewicz-Steinmetz

This study investigates the effect of 3D printing speed on the mechanical strength of parts produced with high-speed PLA. Samples were tested according to the ISO 527-1 standard, focusing on tensile strength. The results reveal that increasing the print speed from 30 mm/s to 500 mm/s reduces the mechanical strength of the samples, although the difference is minimal and does not affect the surface quality when the material is appropriately selected. Additionally, the orientation of the samples on the build plate had a significant impact on their strength, with samples printed along the Y-axis exhibiting better tensile performance. Ironing, which smooths the surface at the end of the print, improved the fracture surface consistency and tensile strength, regardless of the print speed. The improvement in tensile strength observed in ironed specimens can be attributed to improved bonding of the layers, reduced porosity, and a reduction in stress concentration points, which ultimately contributed to more uniform stress distribution and less risk of premature failure. Thermal camera images indicated no significant deviations in heat distribution, excluding this factor as a cause for inconsistent fracture points. This study concludes that higher printing speeds offer time and energy savings with minimal impact on mechanical properties, making them suitable for prototyping and decorative elements, although the effects of print speed and orientation should be considered for applications requiring higher strength.

This article provides a comparative analysis of the dimensional accuracy and post-surface characteristics of gears produced by the 3D printing technique Direct Metal Laser Sintering (DMLS) from 1.2709 steel immediately after printing and after grinding and grinding treatment. The following tests were performed on the fabricated samples: metallography, hardness measurement, self-stress, surface roughness, and the gears’ shape were dimensioned and measured. The results show that post-processing influences the distribution of residual stress and the printed model’s hardness. The results show that heat treatment results in clear directionality marks and micropores, increasing the material’s hardness to 54.3 HRC ± 0.6 HRC, indicating effective strengthening. Grinding significantly improved the holes’ accuracy, changed the compressive intrinsic stresses to a tensile state, and reduced radial runout, improving gear geometries. In addition, it was noted that different results were obtained for roughness parameters depending on the gear tooth tested.

Fused Filament Fabrication (FFF) printing is one of the most all-purpose manufacturing techniques, allowing many complicated parts to be obtained at lower cost. This is especially important in prosthetics, where more complex prostheses, especially of a hand, can cause enormous expense. However, providing the full functionality of a prosthesis often requires combining materials with different properties, such as rigidity and flexibility. The use of such a combination in multi-material printing involves a problem of delamination at the interface between two materials. The research described in this article focused on modifying the structure of the interface to improve adhesion between rigid and flexible materials. Polylactide (PLA), thermoplastic polyurethane (TPU), and acrylonitrile butadiene styrene (ABS) were used. PLA-TPU85, PLA-TPU98, ABS-TPU85, and ABS-TPU98 joints were tested in a three-point bending test. Among the above-mentioned joints, the one called PLA-TPU85 presented the best properties, that is, the ability to transfer forces. Therefore, this joint was selected for further modifications. To improve the adhesion in PLA-TPU85 joint, a sandwich-type structure was designed, and its effectiveness was tested in a shear test. The samples lacking this structure became delaminated during the test, whereas those with the sandwich structure maintained the integrity. Thus, the effectiveness of such a solution was confirmed and applied to the connection of rigid and flexible materials in the final printing of the prosthesis.

This study aims to investigate the adhesion of combining two materials with different properties (PLA-TPU and TPU-PLA) printed in FFF (fused filament fabrication) with post-processing treatments.The scope of the study includes making variants of samples and subjecting them to three different post-printing treatments. After processes, shear tests were conducted to determine the adhesion.The post-printing treatment results in a stronger inter-material bond and increased adhesion strength; the best average shear strength results were achieved for annealing without acetone and for PLA/TPU samples for treatment in cold acetone vapour.In the study, adhesion was considered in the circular pattern of surface development.Reinforcement of the biopolymer broadens the possibilities of using polylactide. Examples of applications include personalised printing items, where the elastomer will strengthen the polylactide.These studies aim to promote the use and expand the possibilities of using PLA biopolymer. The strength properties of printouts from different materials are often insufficient, hence the proposal to use post-printing processing.

3D printing is a revolutionary additive manufacturing method that enables rapid prototyping and design flexibility. A variety of thermoplastic polymers can be used in printing. As it is necessary to reduce the consumption of petrochemical resources, alternative solutions are being researched, and the interest in using bioplastics and biocomposites is constantly growing. Often, however, the properties of biopolymers are insufficient and need to be improved to compete with petroleum-based plastics. The paper aims to analyze the available information on elements produced from more than one material, with additive manufacturing resulting from 3D printing using biopolymer Polylactic Acid (PLA). The study notes the possibility of modifying and improving the properties of PLA using layered printing or by modifying PLA filaments. Several modifications improving and changing the properties of PLA were also noted, including printing parameters when combined with other materials: process temperatures, filling, and surface development for various sample geometries.

A 3D printer in FDM technology allows printing with two nozzles, which creates an opportunity to produce multi-material elements. Printing from two materials requires special consideration of the interface zone generated between their geometrical boundaries. This article aims to present the possibility of printing with PLA and TPU using commercially available filaments and software to obtain the best possible bond strength between two different polymers with respect to printing parameters, surface pattern (due to the material contact surface’s roughness), and the order of layer application. The interaction at the interface of two surfaces of two different filaments (PLA-TPU and TPU-PLA) and six combinations of patterns were tested by printing seven replicas for each. A total of 12 combinations were obtained. By analyzing pairs of samples (the same patterns, different order of materials), the results for the TPU/PLA samples were better or very close to the results for PLA/TPU. The best variants of pattern combinations were distinguished. Well-chosen printing parameters can prevent a drop in parts efficiency compared to component materials (depending on the materials combination).