Fused deposition modelling (FDM) 3D printers have the highest annual growth of 21.15% in the field of 3D printing. FDM desktop 3D printers account for 23.69% of FDM printers. The major drawback of FDM desktop printers is product accuracy, which is particularly pronounced when dimensionally inaccurate and multi-part printed products need to be fit together into a functional assembly. The research presented in this paper aims to determine the accuracy limits of FDM 3D printers when producing elements for assembly using a 3D printer in a tolerance-fit system. A novel method of computer-aided design (CAD) based on ISO 286 and the systematic calibration procedure of 3D printers were presented to achieve the dimensional accuracy of 3D printed parts. For this purpose, a set of nominal dimensions within the clearance fit was selected, and various CAD models were created according to the ISO 286 system of limits and fits. The CAD Slicer software–3D printer interaction was systematically examined for the best hardware and software features. It was found that the Horizontal Expansion parameter should be 0.0 mm and the Hole Horizontal Expansion parameter should be 0.13 mm. The Linear Advance factor was found to be 25. The measurement results showed that the desired tolerance ranges, system, and type of clearance fit could be achieved with a desktop 3D printer. The roundness tolerance for all clearance fits and shaft tolerance ranges in the hole base system was determined to join the parts into a clearance fit.

The aim of this paper is to establish yield load solutions when the materials inhomogeneity within the weld is present, which is usually the case in repair welding. The effect of yield strength mismatch of welded joints performed with different geometry on the yield load value has been investigated in the context of single edge notched fracture toughness specimen subjected to bending SE(B) using the finite element method. The crack was located in the center of the weld and the two most important geometrical parameters were identified as: crack length ratio a / W as well as slenderness of the welded joint, which were systematically varied. One practical and four additional combinations of filler materials, with the same portion of overmatched part and undermatched part of the weld, were analyzed, and plane strain FE solutions for the case when the crack is located in the overmatched half of the heterogeneous weld were obtained.

Boronizing is a thermochemical treatment performed to produce hard and wear-resistant surface layers. In order to control the process and obtain boride layers with the desired properties, it is very important to know how the boronizing parameters and the chemical composition of the treated steel affect the boronizing. The aim of the present study is to investigate the influence of carbon content in carbon steels, boronizing temperature, and boronizing duration on the growth kinetics of boride layers. For this purpose, three carbon steels (C1y5, C45, and C70W2) were boronized in solid medium. The experimental results show that there is a linear relationship between the carbon content and the activation energy values, and between the carbon content and the frequency factors. In addition, a statistical analysis was performed to determine the contribution of each factor. The ANOVA showed that boronizing temperature has the highest effect on the boride layer thickness, followed by the boronizing duration, while the carbon content of the steel has the least effect on the boride layer thickness. Based on a regression model, an empirical equation was derived to estimate the thickness of the boride layer on carbon steels as a function of carbon content, boronizing temperature, and duration.

The objective of this work was to investigate the fracture behavior of a heterogeneous I-shaped welded joint in the context of yield load solutions. The weld was divided into two equal parts, using the metal with the higher yield strength and the metal with the lower yield strength compared to base metal. For both configurations of the I-shaped weld, one with a crack in strength in the over-matched part of the weld and one for a crack in the under-matched part of the weld, a systematic study of fracture toughness SE(B) specimen was carried out in which the crack length, the width of the weld and the strength mismatch factor for both weld metals were varied, and the yield loads were determined. As a result of the study, two mathematical models for determination of yield loads are proposed. Both models were experimentally tested with one strength mismatch configuration, and the results showed good agreement and sufficiently conservative results compared to the experimental results.

Since welded constructions are widely used in engineering, a certain flaws in welded joints may occur either in process of welding or in exploitation period. Easiest way to prolong working life of such welded construction is to repair welded joint to eliminate possibility of construction failure. Process of repair welding usually gives heterogeneous welded joints because during process of repair additional material is introduced into welded joint, resulting in heterogeneity from the presence of materials in welded joint point of view. Such difference in materials usually results in yield strength difference between materials, represented with mismatch ratio, and it is commonly present in welds where high strength low-alloyed (HSLA) steels were welded. Since I butt welded joints are very common in welding, a systematic investigation of such welds is performed and presented in this paper. Therefore in this investigation the influence of present material in heterogeneous weld and geometry of weld is investigated in context of fracture resistance of welded joint represented as yield load solutions in the first place. A flaw in form of crack was implemented in such heterogeneous weld and using finite element method yield load solutions for different combinations of weld geometry and material strength are obtained and presented in form of diagrams.

This article focused on the experimental and statistical analysis of the mechanical properties of dog-bone samples manufactured by fused deposition modelling (FDM). Two identical materials were examined, i.e., Onyx with carbon fiber but from differen...