Martin Kotus

This study focuses on evaluating the effect of annealing time on the mechanical properties and structural changes in polyamide-based materials manufactured using fused filament fabrication (FFF) technology. Three materials were experimentally analysed: neat polyamide PA6, polyamide reinforced with 30% glass fibers (PA6 GF30), and the composite material Onyx. After fabrication, the test specimens were annealed at a temperature of 180 °C for 30, 60, and 100 min. Mechanical properties were evaluated by tensile testing in accordance with ISO 527, and the obtained data were further processed using machine learning methods (Linear SVM, Quadratic SVM, and K-NN) to classify individual levels of thermal exposure. The results showed that annealing significantly improved the tensile strength of Onyx from 50.78 ± 1.46 MPa (0 min) to 60.09 ± 1.30 MPa after 30 min, corresponding to an increase of approximately 18%, while further annealing (60 and 100 min) resulted in values between 59.23 and 62.12 MPa without statistically significant additional improvement. In contrast, PA6 GF30 exhibited a progressive decrease in tensile strength from 76.85 ± 0.87 MPa (0 min) to 51.91 ± 8.03 MPa after 100 min, representing an overall reduction of approximately 32%, indicating degradation of the polymer–fiber interface. For neat PA6, tensile strength decreased from 55.31 ± 3.83 MPa to 40.03 ± 9.36 MPa, but these differences were not statistically significant (p > 0.05). Machine learning classification confirmed predominantly linear material behavior, with Linear SVM achieving accuracies of 85% for Onyx and PA6, and 95% for PA6 GF30, outperforming Quadratic SVM and K-NN models. These findings provide valuable insights for optimizing post-processing conditions of FFF-manufactured polyamide materials and composites.

This study focuses on the prediction and analysis of temperature distribution during end milling of AISI 4340 steel. The influence of cutting parameters—cutting speed, feed per tooth, and depth of cut—on temperature generation in the cutting zone was investigated using a CCD experimental plan. Temperature was measured with a thermal imaging camera, while the milling process was simulated using Third Wave AdvantEdge 7.1 FEM software. The obtained temperatures ranged from 74 °C to 200 °C, depending on the cutting conditions. A second-order regression model with three factors was developed and showed an average prediction error of 8.62%, while the alternative fitted model had an average error of 10.91%. FEM simulations using AdvantEdge 7.1 demonstrated a somewhat higher deviation, with an average error of 14.75% relative to experiments. The highest deviations for all approaches occurred at extreme cutting parameters (very low or very high depth of cut). The study demonstrates that FEM simulations are an effective tool for predicting thermal behavior in milling and optimizing cutting parameters. Accurate prediction of cutting zone temperatures can improve tool life, enhance process efficiency, and support the selection of optimal machining conditions, which is very important from an industry point of view.

The article examines how relative humidity affects the wear resistance and mechanical properties of PA6, PA6 GF30, and Onyx, processed by 3D printing. Findings show that mass loss rises with humidity across all materials, with Onyx exhibiting the lowest average mass loss despite larger percentage increases. At pressure value of 0.32 N·mm-2, mass loss increased due to their properties compared to metallic materials by 2.4% from 33% to 65% humidity, then by 10.5% from 65% to 97%. Notably, at high humidity, there were significant differences in wear loss between parallel and vertical orientations, with Onyx showing a 36% difference at 97% humidity. Tensile tests revealed a strong correlation between humidity and tensile strength in PA6 of 0.9331 correlation coefficient value, while PA6 GF30 showed inconsistent properties. For Onyx, higher humidity led to substantial drops in tensile strength (0.911 correlation coefficient value) and increases in elongation (0.603 correlation coefficient value). The contribution of this study lies in its ability to guide the selection of composite materials, for wet and abrasive conditions, optimizing wear resistance and extending component lifespan while reducing maintenance needs.

The wear and degradation of tools applied in the high-pressure die casting of Al alloys induce significant financial losses. The formation of failures on the surface of mold parts caused by erosion, thermal fatigue, corrosion, and soldering negatively affects the surface quality of castings. In this study, the lifetime of inserts protected by physical-vapor-deposited coatings (TiN, TiAlN, and CrAlSiN) is examined under real manufacturing conditions while considering requirements for the castings’ surface quality (maximum average roughness Ra) defined by the customer. The goal was to identify the most suitable solution for HPDC in the foundry organization. After the deposition of PVD coatings on the inserts, the hardness (HRC) values increased from two to five depending on the coating used, and also the surface roughness was higher in the case of all inserts (Ra values increased from 0.24 to 0.36 µm). The lifetime of all PVD-coated inserts was higher compared to the uncoated insert. The highest lifetime was achieved by the application of a TiN coating, when 15,000 shots were achieved until the inserts’ wear negatively affected (increased) the surface roughness of castings, considering the customer requirements for the maximum Ra value. SEM analysis was used to identify examples of wear and degradation on the surface of the TiN coated insert.

This scientific article deals with cyclic corrosion testing of bimetallic joints in order to describe the influence of different surface treatment as a protection against galvanic corrosion on bimetallic materials. Multi-material body parts joined with advanced manufacturing technologies are used to achieve the required car properties. Metallic materials have different values of electronegativity and joining increases the risk of corrosion. Different types of coatings are used to prevent galvanic corrosion, but each increases investments and costs. Galvanic corrosion affects the lifecycle of the car. Cyclic corrosion testing provides replicable results to estimate the range of corrosion in a real environment. Test specimens from different materials were riveted and treated with various surface treatments. The method and design of samples preparation is unique and reflects the reality more than current methods. It has not yet been published in any literature. The corrosion test was performed for 6 weeks. Samples were subjected to a salt mist with temperatures of 25 °C and 50 °C, wetting and drying phases. The samples were evaluated according to the standard EN ISO 4628-1:2016. Microscopic and energy-dispersive analysis were performed. Tests have shown considerable galvanic corrosion on uncoated samples. On the samples with ecoated surface galvanic corrosion was not recorded.

When using various types of services, the customer may experience positive or negative situations, incidents. These incidents may affect the customer's satisfaction or dissatisfaction. Therefore, these incidents can be a source of very valuable information for the enterprise about the quality of the services it offers. The problem, however, is their analysis, because such incidents can affect different aspects of the service, but also, as mentioned earlier, can have a positive or negative impact on customer satisfaction. The Critical Incident Technique (CIT), often mentioned in the literature, can be used for such an analysis. With this method, it is possible to isolate situations that are typical of the negative and positive feelings of the customers, as well as to determine the frequency of their occurrence. The purpose of the papers was to analyze the quality of services offered by the chosen catering enterprise with use of CIT. The research took form of a direct interview with customers after delivery of the chosen service. Data obtained on this basis was analyzed: all incidents were first divided into groups and categories as well as positive and negative incidents, and then statistics for individual categories were presented. This research allowed to indicate the strengths and weaknesses of the research service, but at the same time to indicate the areas of potential improvement.

The paper deals with the issue of occupational health and safety in a metalworking manufacturing organization. Hazard and threat have been defined when cutting metal materials with a band saw. We assessed the risk by an extended point method, where we determined the risk rate values. In most cases of sawmill work, we found a “moderate” or “negligible” risk. The highest, ‘serious’ risk we found in a possible electric shock. In this case, we have also taken the necessary actions. As a precaution, we have also proposed safety measures for other threats.

The quality of refractory materials plays an important role especially in high temperature processes. In case of violation of qualitative properties of refractory materials, the safety of the use of the technological equipment in which these materials are used is compromised. The requirements on the quality of refractories and their properties are now high, as their operating life should be as long as possible. The aim of the article is to point out the quality of refractory material in contact with corrosive media, to analyze the technological factors that affect the quality and safety of technological equipment. An analysis of the refractory material, as well as the analysis of the melt was performed. Subsequently, an experiment was realized, which was evaluated by macroscopic analysis and chemical analysis. After the experiments, we found that the melt had penetrated the masonry and consequently created corrosion layers in the masonry. These layers have affected the life of the material and reduced the safety of the technological equipment in which they were used.

Technological progress has brought a large amount of complex machinery into the work processes, which represents a potential source of serious injuries, accidents, or breakdowns. The aim of this paper is to follow new trends in the FMEA and their use in our study. We have chosen the Turning Machine Doosan V-Puma Doosan PUMA V550R Machining Centre with manufacturing diameters and mechanical machining operations. We have created the FMEA team, which participated in the entire evaluation and analysis. We identified possible failures and causes of failures in the given operations. We applied the conventional PFMEA and identified the RPN risk number. We also used DEMATEL model. Using DEMATEL matrices, we identified a binding between the individual failures and the causes of the failures. Some failures will become the main cause of other failures and the causes of the failures; some arise as a result of other failures or causes of failures. Finally, we evaluated the applicability of individual methods and models. By the DEMATEL model we clarified the significance and bindings between individual failures.