This work used machine learning to forecast product density and optimize the laser powder bed fusion (LPBF) process for parts made of pure zinc (Zn). A relative density of 90-97% (6.42-6.95 g/cm3) was obtained by varying combinations of key process parameters, including laser power, scanning speed, track overlapping, hatch spacing, and layer thickness. Machine learning provided models for density prediction and better comprehension of the impact of input parameters. A SHapley Additive exPlanation (SHAP) analysis quantified the contributions of specific features, enhancing model interpretability. Fifty-one experimental runs were used to test several methods, including Bayesian ridge, CatBoost, elastic net, lasso, linear regression, random forest, ridge regression, and XGBoost. CatBoost performed best, with a test coefficient of determination (R2) of 0.893, a mean absolute error (MAPE) of 0.010 and a root mean square error (RMSE) of 0.015. A feature importance analysis showed that laser power (49%) and scanning speed (42%) had the greatest influence, while hatch spacing (5%) and layer thickness (4%) had minimal impacts on product density. Therefore, selecting the correct optimized set of process parameters determines the resulting density and can support more efficient LPBF process development.

This study examined the melting behavior and flowability of pure magnesium during selective laser melting. The potential to increase product density was also investigated. Various combinations of manufacturing parameters were considered. The laser power was gradually increased in different machine runs, with different scanning speeds for each run to vary the energy density (ED). The laser power ranged from 10 W to 75 W, and the scanning speed ranged from 100 mm/s to 800 mm/s. Lower laser powers resulted in poor melting, while higher laser powers produced better melting, with significant differences even when the ED was the same. High EDs between 3.50 J/mm(2) and 4.30 J/mm(2) led to a lack of melting at low laser power and to an unstable melt pool with significant spattering at high laser power. In contrast, moderate EDs in the range of 1.40 J/mm(2) to 2.90 J/mm(2) resulted in better density at high laser power. Higher scanning speeds helped to avoid the formation of a dense smog cloud and provided sufficient energy in a short time with the aid of higher laser power. Therefore, increasing both laser power and scanning speed improved melting performance and increased product density. The relative product density ranged from 80 % to 96.5 %. Reducing the layer thickness from 50 mu m to 25 mu m at a laser power of 40 W resulted in the formation of a well-formed melt pool in some areas and significant melt spattering in others, which led to a deterioration in density.

BackgroundIncomplete partition type III (IP III) represents a rare malformation of the inner ear, posing challenges during cochlear implantation due to inevitable cerebrospinal fluid (CSF) leaks and the potential misplacement of electrodes within the internal auditory canal (IAC). Despite the absence of a consensus on electrode selection, literature suggests both straight and perimodiolar electrodes as viable options for proper insertion. Limited implantation series contribute to the ambiguity in electrode choice. In this study, we evaluated the insertion performance of three electrode types in a 3D model simulating an IP III patient's inner ear.MethodsA 3D model replicating the inner ear of a patient with IP III undergoing surgery was created, incorporating a canal wall up mastoidectomy and an enlarged round window approach. Insertions were carried out using a straight electrode, a perimodiolar electrode, and a slim perimodiolar electrode, inserted through a sheath in the basal turn of the cochlea. Electrode positions were assessed after each insertion, with each type being tested 20 times.ResultsSuccessful insertion rates were 95% for the slim perimodiolar electrode, 85% for the perimodiolar electrode, and 75% for the slim straight electrode. Notably, the slim perimodiolar electrode required an adapted insertion technique due to the altered cochlear position in IP III cases. Statistical analysis revealed the slim perimodiolar electrode's superiority over the slim straight electrode in achieving successful insertions.ConclusionsThe 3D model of the IP III inner ear proved to be an effective tool for electrode testing and insertion training prior to surgery. Following multiple insertions in the 3D model, the slim perimodiolar electrode demonstrated the highest success rate, emphasizing its potential as the preferred choice for cochlear implantation in IP III cases.

This study investigated how the tensile properties of selectively laser-sintered polyamide 12 (PA12) specimens are affected by aging and refresh ratio. Starting with a new powder, printing cycles of approximately ten hours were performed, during which tensile and density specimens were printed. After each cycle, the powder was tested for melt flow index (MFI). In the first part, the best processing direction was determined. It was found that tensile strength, modulus of elasticity, elongation at break and MFI showed a linear trend, with the independent variable being the number of hours at elevated temperature. This was analyzed by linear regression. MFI increased with the number of hours at elevated aging, while all other properties mentioned decreased.

In this study, several variations of Ti-6Al-4V beta-grains and alpha '-martensites were observed while changing the combinations of laser parameters and keeping the energy density (ED) constant in the laser powder bed fusion (LPBF) process. Several combinations of laser power, scanning speed, and hatch spacing were considered, resulting in high product density between 99.3% and 100.0%. Accordingly, tensile specimens were fabricated to observe the above strategic fabrication and microstructural effects on tensile properties. At the same time, microhardness was also measured to observe the similarities. However, the size and shape of the beta-grains differed significantly, while the scanning speed gradually decreased along with the laser power, with the shape changing from irregular to classically hexagonal and the size increasing sharply. Using the results of differential thermal analysis (DTA), it can be said that most of the tertiary and quaternary alpha '-martensites formed after the following few thermal cycles below 370 degrees C. Similarly, the alpha '-particles decomposed and formed beta-particles due to thermal treatment at 370 degrees C. Therefore, a denser and higher number of tertiary and quaternary alpha '-martensites and a lower number of primary and secondary alpha '-martensites occurred, while the cooling rate decreased and the number of thermal cycles increased due to a lower scanning speed. These phenomena increased the hardness 370-395 HV and deteriorated the yield strength 1250-840 MPa. Changes in track overlap (hatch spacing) of 30-50% affect mechanical and microstructural characteristics more than track overlap of 10-25%. The columnar beta-grains became longer and wider as the lane overlap increased from 30 to 50%. At the same time, some beta-grains also changed to contain finer and fewer alpha '-martensites. These factors reduced both hardness and tensile properties.

Sternal dehiscence is an important complication that increases mortality and morbidity in cardiac surgery. Titanium plates have been used to reconstruct the chest wall for a long time. However, with the rise of 3D printing technology, a more sophisticated method, is making a breakthrough. Custom-made 3D-printed titanium prostheses are increasingly used in chest wall reconstruction because they allow almost perfect fitting to the patient's chest wall and lead to good functional and cosmetic results. This report presents a complex anterior chest wall reconstruction using a custom-made titanium 3D-printed implant in a patient with a sternal dehiscence after coronary artery bypass surgery. At first, reconstruction of the sternum was performed using conventional methods, which failed to give adequate results. Finally, a 3D-printed titanium custom-made prosthesis was used for the first time in our center. On the short- and mid-term follow up, good functional results were achieved. In conclusion, this method is suitable for sternal reconstruction after complications in the healing process of median sternotomy wounds in cardiac surgery, especially where other methods do not provide satisfactory results.

The research focused on the properties of partially fused powder particles and their possible effects on the mechanical and corrosive properties of products produced by Laser Powder Bed Fusion (LPBF). Scanning electron microscopy was used to investigate surfaces and pores, both for adherent particles and for particles completely enclosed in the molten bath. The study focused on Ti-6Al-4V, considering powder particles between 10–45 µm and a layer thickness of 25 µm. Different combinations of laser powers and scanning speeds were chosen to investigate the melting, mixing and solidification behavior. The analysis revealed that certain partially melted powder particles caused microcracks and increased the corrosive surface area, which showed distinct microstructures compared to the core area of the product. The investigation identified fully integrated particles and mostly melted particles by microstructure analysis. The results suggest potential innovative applications in complex product designs where the removal of these particles is a challenge, as well as in bone implantation to improve osseointegration.

Conformal cooling in injection molding of thermoplastics enabled by the additive manufacturing technology is a breakthrough solution to the problem of temperature control at critical locations in the mold. This paper discusses the design and manufacturing of a hybrid mold insert, focusing on evaluating the predictive quality of a simplified simulation model that does not require modeling of the hybrid mold and does not account for the different material properties of the mold components. The hybrid mold was fabricated in a two-step process. The lower part of the insert was fabricated by milling and the upper part of the insert, including the conformal cooling channels, was fabricated using the additive manufacturing technology of selective laser melting. The hybrid mold insert consists of two materials: maraging steel 1.2709 for the upper part of the mold insert and tool steel 1.2343 for all other parts of the mold. To validate the simulation results, experimental measurements were performed after ejection of the product during the injection molding process using a thermal imaging camera. It was confirmed that the simplified simulation model agrees well with the measurement results and that it can be used to simulate the injection molding process when a hybrid mold consists of materials with similar material properties.

When manufacturing complicated products where both material and design play a role, especially thin and curved components, it is difficult to maintain accurate dimensions in Selective Laser Melting. Considering these difficulties, this article presents the dimensional errors in the fabrication of Ti-6Al-4V discs and their thermomechanics during manufacturing. Various combinations of laser processing parameters were used to fabricate the 2.00 mm thick discs with a diameter of 5.70 mm. It was found that the thickness shortened and the round shape changed to an oval shape for most of the discs. The thickness decreased along the build-up direction from the bottom to the top and formed a taper that increased with increasing energy density (ED). The horizontal diameter of the discs changed slightly, while the vertical diameters changed remarkably with increasing ED. On the other hand, reducing the laser power resulted in a reduction of the roundness error, while it caused a reduction of the thickness. The hatch spacing significantly affected the volume of the melt pool and caused a change in the vertical diameter. The central part of the curved surface of the discs became concave and the concavity increased due to the increasing ED.

It has been shown that conformal cooling in injection molding has the potential to replace conventional cooling due to its many advantages. The overall quality of the injection molding process is closely related to heat removal from the product and the mold, which is most uniform and efficient with conformal cooling. The disadvantages of conformal cooling are mainly in the manufacture of the mold, which is more expensive and time-consuming, which also affects the production of spare parts. To examine the current state of conformal cooling, an overview is given, organized according to the life cycle of the injection molding process. The main topics covered are process simulation, mold design and optimization, mold manufacturing, injection molding process control, and final quality evaluation based on product quality and financial benefits. Finally, the most promising solutions and their limitations are presented.

Knowledge of defect formation mechanisms in the manufacturing process helps improve product quality. In this study, defect formation due to re-melting of each layer in selective laser melting of Ti-6Al-4V demonstrated the physical behavior in the manufacture of metallic parts. The re-melting strategy was based on scanning with low energy density (ED) and increased ED with various combinations of laser processing parameters. The increased EDs and their parameters, namely laser power, scanning speed, and hatch distance, were selected based on the previous research experience by the authors. The concept of selecting a low ED followed by a high ED was to reduce the spattering of the powder material during the process. The low ED caused partial sintering of the powder, while the high ED caused the melting of the material, resulting in different metallurgical properties of the manufactured parts. Densities, pore properties, porosity in the initial layers, surface morphologies, and microstructures in the defective areas of the samples were studied to determine the effects of re-melting. Advantages and disadvantages were found with respect to the range of applications of the products.

This study applied a holistic approach to the problem of controlling the temperature of critical areas of tools using conformal cooling. The entire injection molding process is evaluated at the tool design stage using four criteria, one from each stage of the process cycle, to produce a tool with effective cooling that enables short cycle times and ensures good product quality. Tool manufacturing time and cost, as well as tool life, are considered in the optimization by introducing a novel tool-efficiency index. The multi-objective optimization is based on numerical simulations. The simulation results show that conformal cooling effectively cools the critical area of the tool and provides the shortest cycle times and the lowest warpage, but this comes with a trade-off in the tool-efficiency index. By using the tool-efficiency index with non-dominated sorting, the number of relevant simulation cases could be reduced to six, which greatly simplifies the decision regarding the choice of cooling system and process parameters. Based on the study, a tool with conformal cooling channels was made, and a coolant inlet temperature of 20 °C and a flow rate of 5 L/min for conformal and 7.5–9.5 L/min for conventional cooling channels were selected for production. The simulation results were validated by experimental measurements.

This research investigated the geometry, microstructure and tensile properties of Ti-6Al-4 V samples produced by Selective Laser Melting (SLM) and Electron Beam Melting (EBM), which vary due to different heat transfer mechanisms occurring at different locations at the same time. The geometric variations were evaluated by comparing the cranial implants manufactured in this way with their Computer-Aided Designed files using a 3D scanner. The SLM samples were strongly deformed, while the EBM process affected the size but not the shape of the samples. The cooling rate varied from the core to the surface zones, so that the microstructural morphology varied between them. The size and orientation of the precipitated ? phase varied significantly from the core to the surface zones in the EBM. Two new ? colonies were identified; one was nucleated and grew from the prior ?-grain boundary and the other formed parallelograms of equal size consisting of ? lamellae. The tensile samples that were built up in the Z-direction in the EBM had the lowest yield strength and the highest elongation, due to the effect of the slowest cooling rate, which promoted continuous dynamic recrystallization, and ? colonies precipitated from the ? grain boundary. This can provide useful guidance to engineers in developing the functionally graded structure.

The mechanical properties of Co-Cr-W-Mo alloy specimens fabricated concerning different orientations considering the powder coating direction in the Selective Laser Melting process have been investigated. In parallel, the influence of design of the powder coating component on powder particles' alignment and compaction have been examined. The tensile specimens had been located and oriented at three different positions on the build tray. The positions had been chosen considering the start and finish lines of the powder coating process, whereas the samples oriented longitudinally, diagonally and transversely to the powder coating direction. Two different energy densities have been applied for each set of samples to observe the similarities. The position and orientation have a remarkable effect on the density, ultimate tensile strength, yield strength and elongation of the specimens. The metallurgical properties deteriorated gradually along the powder coating direction. The densification of the powder also varied along and across the powder coating direction. Eventually, the stochasticity of metallurgical properties gradually increased toward the distant regions along the powder coating direction. High stochasticity of tensile properties has present in the specimens for a particular fabricating orientation which has been observed for both fabricating energy densities.

Different energy densities in Selective Laser Melting produce different metallurgical properties of the product surface, which include adhered powder particles, waviness, porosity, and microstructure. In this research, the corrosion behavior of these structural properties was investigated and compared with heat-treated samples. The size and arrays of α'-martensitic varied significantly due to the effects of different cooling rates and the number of effective thermal cycles caused by different scanning speeds and energy densities. The surface particles experienced different thermal effects that significantly changed their microstructure with each other and with respect to the main surface, which remarkably affected the corrosion properties. The densities, hardness, and tensile properties of the samples were also presented and interpreted their relations with corrosion. These correlations between the metallurgical and corrosion properties of SLM products support biomedical engineers in the further development of bespoke medical devices, especially implants.

The surface morphology of a product plays a crucial role under mechanical loading and chemical environment. Surfaces of Selective Laser Melting (SLM) products often contain high roughness, which varies in different planes as well. The authors have explored the surface characteristics of the SLM samples that are influenced by different combinations of laser processing parameters. The considered processing parameters were Energy Density (ED) and its technological parameters namely laser power, scanning speed and hatch spacing. Additionally, a comparison study has been executed by rescanning effects considering melting with low ED and, thereafter, rescanning by the best possible laser processing parameters. The results evidently showed that the surface morphologies differ significantly due to different laser processing parameters. Eventually, the thermal and physical behavior of materials, such as the viscosity of the melt pool, thermal and physical stability of the melt pool, solidification time, cooling time, shrinkage, capillary effect, surface tension, balling effect, and the amount of melting of a powder particle, influenced the surface properties of the samples, along with unpredictability. The results showed an interesting correlation between the processing parameters and the occurrence of mi-crocracks on the vertical walls of the specimens caused by the partially melted adhered powder particles.

Učbenik opisuje dodajalno izdelavo in njene lastnosti kot najnovejše področje proizvodnih tehnologij. Razloženo je osnovno načelo delovanja dodajalnih tehnologij in področja njihove uporabe. Pojasnjene so tehnološke posebnosti posameznih vrst dodajalnih tehnologij in značilnosti konstruiranja za dodajalno izdelavo. Skozi oblikovalski vidik konstruiranja za dodajalno izdelavo spoznamo bistvene značilnosti novega tehnološkega postopka in njihov vpliv na industrijski proces. Hitra izdelava orodij je področje, ki je v preteklosti služilo kot vmesna stopnja med izdelavo prototipa z dodajalnimi tehnologijami in pred serijsko izdelavo končnega izdelka. Učbenik pa predstavlja možnosti, ki jih te tehnologije danes nudijo v orodjarstvu. Za uspešno uporabo dodajalne izdelave v industriji je bistvena njena gospodarnost, zato je nadaljevanje učbenika posvečeno ugotavljanju storilnosti in natančnosti dodajalne izdelave. Poglavje o gospodarnosti predstavlja novo in patentirano metodo računanja storilnosti naprav, ki upošteva tako oblikovno zapletenost izdelka kot prostorsko izkoriščenost naprav za dodajalno izdelavo in s tem predstavlja novost na tem znanstvenem področju.

The improvement of the density with functional microstructure is still a challenge in the Selective Laser Melting process considering the laser processing parameters. In this study, the pore formation mechanisms and microstructural changes caused by the effects of laser power and track overlap during the manufacturing process in selective laser melting were examined. Laser power played a crucial role in the geometry and quantity of keyhole pore formation and thus in improving density and quality. In contrast, a slightly higher track overlap led to a significant reduction in porosity, resulting in the production of fully dense samples of a Ti-6Al-4V alloy. The gradual variations in the solid-state phase transformation architecture occurred with variations in laser power and track overlap due to the use of different thermal mechanisms. The associated scanning speeds also significantly affected the microstructural architectures in some states. The melt pool dynamics and thermal properties that influenced the metallurgical properties of the samples are analyzed and interpreted. The analysis of the presented consequences can help the engineers to produce high density products together with functionally graded materials.

Purpose One of the main problems of selective laser sintering (SLS) manufacturing process is the dimensional accuracy of products. Main causes of dimensional deviations are material shrinkage and size of laser heat affected zone (LHAZ). This paper aims to present a new method of adapting SLS manufacturing shrinkage and LHAZ compensation parameters to the geometrical characteristics of processed parts to improve their accuracy. Design/methodology/approach The first part of this work presents a hypothesis asserting that the shrinkage and the LHAZ size depend on geometrical properties of products. A method that defines geometrical properties by numerical influence factors is described in the continuation. A multi-factorial experiment with adaptable test part is set up. Then, test builds are manufactured on an SLS machine and measured with a three-dimensional optical scanner. Afterwards, the results are analysed in relation to the presumed hypothesis. Findings The analysis of variance of multi-factorial experiment proves the hypothesis and the influence of the geometrical properties on the accuracy of the SLS manufacturing process. Afterwards, a part is manufactured with adapted values of compensation parameters and the archived accuracy is discussed. Research limitations/implications Presented research is limited on a single SLS material. Also, some numerical factors are directly linked to the build volume dimensions of the SLS machine that was used in the experiment. However, results can be generalised and some guidelines for shrinkage and LHAZ compensation method are presented. Also, some guidelines for future research are proposed. Practical implications Based on the presented results, it can be determined that using constant shrinkage and LHAZ values on an SLS machine will not yield the same results in terms of accuracy if the geometrical properties of parts change significantly. Social implications By correctly adapting compensation values, the overall achievable accuracy of the SLS process can be achieved, enabling a more reliable production of mass-customised end-user parts such as customised medical accessories and devices for example. Originality/value A similar method of numerically describing geometrical properties of part in regard to SLS and directly adapting shrinkage and LHAZ compensation values to them for every individual build has not yet been proposed.

Using a combination of Computer-Assisted Design (CAD), expert surgical knowledge and Additive-Manufacturing (AM) technologies, it is nowadays possible to offer patients an individualized treatment that is better planned. more predictable and more reliable than traditional surgical procedures. Regardless of the specifics of different medical fields, planning is common to all of them when it comes to an invasive intervention into the human body. Surgical planning is always based on diagnostic data that need to be gathered, presented and evaluated in a way that best suits the final purpose. To understand the general needs of the surgical planning process, several surgical cases have been explored and analyzed in the Additive Manufacturing Laboratory (AML) at the Faculty of Mechanical Engineering, University of Maribor over the past 10 years. The common denominator in all cases is the reconstruction of diagnostic data into a 3D model that is later used for planning and is. after the confirmation of the planned therapeutic parameters, transformed into tangible surgical equipment by means of AM. The 3D planning process has a lot of benefits but requires some skills uncommon among the medical experts. The results of the presented research summarize the particularities of medical 3D planning and provide guidelines for the wider adoption of medical 3D planning and the use of additively manufactured patient-specific instruments.