Under the term “additive manufacturing”, commonly known as 3D printing, we distinguish various methods of manufacturing technologies. Common to all these processes is manufacturing a modellayer by layer from a digital form. The aim of this paper is to experimentally determine which material provides dimensionally more accurate prototypes on a Fused Deposition Modelling (FDM) additive machine. Acrylonitrile Butadiene Styrene (ABS) and PolyLactic Acid (PLA) materials were used. The di- mensional accuracy was checked by comparing the Computer-Aided Design (CAD) model with each of ten models obtained by the method of 3D scanning. The results show that prototypes manufactured from PLA are dimensionally more accurate those made from ABS.

The paper presents the development of a correlation model for initial tensile elastic modulus for flexible polymers as a function of Shore hardness in OO and A scale based on measurement. Measured polymers are in groups of silicone rubber, nitrile butadiene rubber (NBR), thermoplastic polyurethane (TPU) and silicone. The model is composed of piecewise exponential functions with fixed coefficients chosen to minimize the S₂ error norm and absolute value of relative error at the measured data points. Every chosen section of the hardness scale has one exponential function correlating the hardness to tensile elastic modulus with the argument in the form of a polynomial up to the fourth degree. The coefficients for the polynomial arguments were determined by enforcing interpolation conditions in a chosen set of points in the logarithmic scale for the elastic modulus. The correlation model possesses C0 continuity. For each material, five specimens were used for hardness measurements and five for the elastic modulus testing. The correlation model gives a positive value for elastic modulus of 0 for hardness, and a “finite”, “reasonable” value of 100 for hardness and is monotonic. Tensile properties were evaluated using true stress and logarithmic (Hencky) strain, with iterative correction of the changing cross-sectional area to account for large strain. The maximum relative error achieved in the correlation model for the OO scale is 13.4%, while for the A scale it is 7%. The developed model provides a practical and rapid method for estimating the initial tensile elastic modulus from non-destructive hardness measurements and is particularly useful in industrial applications and in the development of material models for dental surgery simulations.

Flexible thermoplastic polyurethane (TPU) materials fabricated using fused deposition modeling (FDM) are increasingly used in engineering and biomedical applications where exposure to moisture is unavoidable. However, the relationship between material hardness, water absorption, diffusion behaviour, and dimensional stability remains insufficiently understood and investigated. In this study, the hygroscopic behaviour of eight commercially available TPU filaments (60A–98A Shore hardness) was systematically investigated. Specimens were produced using an FDM 3D printer under controlled processing conditions and immersed in physiological solution (0.9% NaCl) for up to 96 h. Water absorption, dimensional changes, and diffusion characteristics were analyzed. Diffusion coefficients were determined using the Fickian diffusion model based on the initial stage of water uptake. The results suggest a transition in behaviour between lower- and higher-hardness materials. Softer TPU materials (60A–85A) exhibited higher water absorption (up to ~1.80%) and an apparent linear trend between hardness and absorption within the investigated material group (R² = 0.999). In contrast, higher-hardness materials (89A–98A) showed lower absorption (~1.18–1.42%) and a weaker apparent relationship with hardness (R² = 0.4214). Diffusion coefficients ranged from 1.40 × 10⁻¹³ to 3.40 × 10⁻¹² m² s⁻¹, with no monotonic dependence on hardness. Additionally, no clear correlation between diffusion kinetics and equilibrium absorption or volumetric expansion was observed. These findings indicate that hygroscopic behaviour of FDM-printed TPU materials cannot be reliably predicted based solely on hardness, and that diffusion, absorption, and swelling may be influenced by different mechanisms. The identified transition from hardness-dependent to behaviour potentially influenced by material structure provides new insight for the design and selection of flexible polymer components in moisture-exposed environments, particularly in biomedical applications.

Modern production is characterized by great variability, with the possibility of making complex parts. However, as modern technology helps increase the efficiency of factors of production, it can also replace labour to reduce costs. For example, Artificial Intelligence and robotic systems are used in manufacturing, to achieve greater productivity and reduce costly human errors. That is why human resources are being replaced gradually by automated robotic systems. In this paper a novel approach was used to sand and polish freestanding bathtubs, using an industrial manipulator and a standardised procedure of sanding, with automatic detection of force when in contact with a part. This process resulted in over 30% of savings in consumable materials (sand paper, etc.) and an almost 50% increase in productivity. To conclude, using two robotic cells in the process of manufacturing of freestanding bathtubs produced four times greater labor saving in comparison to manual sanding.

Numerous studies have demonstrated that tooth-supported dental guides improve the accuracy of implant placement. However, current manufacturing procedures and available materials are not yet optimal and may still lead to deviations from the planned implant position. The influence of the surgeon’s manual force on the deformation of dental guides during implant placement has not yet been sufficiently investigated. Therefore, this study evaluates the mechanical behavior of dental guides using finite element analysis (FEA) in order to assess the influence of the surgeon’s hand force during clinical application. Finite element simulations of deformation and stress were performed for four types of tooth-supported dental guides, including cantilever dental guides with free ends and beam-type guides with a large span between the supporting teeth. The manual force applied by the surgeon was arbitrarily set to 30 N. Simulations were conducted for five commonly used biocompatible polymer materials: Stratasys MED610, VeroGlaze MED620, EOS PA2200, Formlabs FLSGAM01, and Stratasys ULTEM 1010. The numerical results quantified the deformation of dental guides caused by the applied manual force during surgical manipulation. For all analyzed guide designs, the deflection was primarily influenced by the arm length, i.e., the distance between the support and the point of force application. Based on the obtained results, design diagrams were developed to provide guidelines for the design of beam-type (A and A1) and cantilever-type (B and B1) tooth-supported dental guides.

Flexible thermoplastic polyurethane (TPU) materials fabricated using fused deposition modeling (FDM) are increasingly used in engineering and biomedical applications where exposure to moisture is unavoidable. However, the relationship between mate-rial hardness, water absorption, diffusion behaviour, and dimensional stability re-mains insufficiently understood and investigated. In this study, the hygroscopic behaviour of eight commercially available TPU filaments (60A–98A Shore hardness) was systematically investigated. Specimens were produced using FDM 3d printer under controlled processing conditions and immersed in physi-ological solution (0,9% NaCl) for up to 96 h. Water absorption, dimensional changes, and diffusion characteristics were analysed. Diffusion coefficients were determined using the Fickian diffusion model based on the initial stage of water uptake. The results revealed a clear transition in behaviour between lower- and high-er-hardness materials. Softer TPU materials (60A–85A) exhibited higher water absorp-tion (up to ~1.80%) and a strong linear relationship between hardness and absorption (R² = 0.999). In contrast, higher-hardness materials (89A–98A) showed lower absorp-tion (~1.18–1.42%) and no clear correlation with hardness (R² = 0.4214). Diffusion coef-ficients ranged from 1.06 × 10⁻¹² to 3.40 × 10⁻¹² m²s-1, with no monotonic dependence on hardness. Additionally, no clear correlation between diffusion kinetics and equilibrium absorption or volumetric expansion was observed. These findings demonstrate that hygroscopic behaviour of FDM-printed TPU materials cannot be reliably predicted based solely on hardness, and that diffusion, absorption, and swelling are governed by different mechanisms. The identified transition from hardness-dependent to structure-controlled behaviour provides new insight for the design and selection of flexible polymer components in moisture-exposed environ-ments, particularly in biomedical applications.