Nicolae Balc

This paper will discuss the solutions and the main parameters used to print a mold that will be used in a manufacturing process for a personalized implant in orbital fracture situations. The main purpose of this article is to rebuild the damaged orbit. The new orbit should have dimensions and accuracy similar to one of the original elements. Based on the computed tomography (CT) of the patient, the images are extracted and processed. With that information, a customized implant is manufactured. In this article, a case study of a patient suffering from an orbital fracture is presented. Based on the CT images, a mold was printed on additive manufacturing equipment (AM). The manufacturing parameters being highly correlated with the requirements that are needed for this case such as hardness, accuracy, surface roughness and support removal were chosen based on a series of tests and results from other studies. Another aspect that was analysed was related to the material from which was man...

The paper aims to offer the readers knowledge and information, to support new implementation and use of the SLM technology for practical applications and to obtain good metal parts for end users. The SLM parameters and conditions were evaluated to set up a scale and estimate how reliable the SLM-AM process is, on a particular type of machine. The experimental research was carried out in the last years by the authors, using the Realizer 250 machine. Many times, there is a lack of repeatability and reliability of the SLM process. The paper is presenting a new method to evaluate the repeatability and the surface roughness, when processing four types of powder materials, mainly for medical applications. Specimens were manufactured from four materials considered as being bio-metals: pure Titanium, Ti6Al7Nb, CoCr, and CoCrWMo. All these important features of the SLM parts were for seen by the authors in close relation with the mechanical characteristics of the parts. In this way, a good i...

Recent advances in laser technologies offer significant flexibility in the additive manufacturing domain. Extensive work was focused on material processing using laser-directed energy deposition for repairing parts. This pilot study investigated the use of selective laser melting (SLM) for depositing a superior material such as CoCr on an existing stainless steel base. The interface between these dissimilar materials was analyzed. During fabrication, both metals were gradually mixed in the liquid state as the first CoCr powder layer was melded on the steel base without obvious defects. According to SEM and EDAX, the heat-affected zone has a limited depth (<20 µm). XRD patterns recorded across the CoCr–304 interface show a homogenous mixture of γ(Fe) and α(Co) solid solutions. The microporosity calculated by CT was under 0.5%. Microhardness was measured at and near the interface region, showing that the intermixing zone has high hardness (470–480 HV1), which may be related to the ...

Recent advances in laser technologies offer significant flexibility in the additive manufacturing domain. Extensive work was focused on material processing using laser-directed energy deposition for repairing parts. This pilot study investigated the use of selective laser melting (SLM) for depositing a superior material such as CoCr on an existing stainless steel base. The interface between these dissimilar materials was analyzed. During fabrication, both metals were gradually mixed in the liquid state as the first CoCr powder layer was melded on the steel base without obvious defects. According to SEM and EDAX, the heat-affected zone has a limited depth (<20 µm). XRD patterns recorded across the CoCr–304 interface show a homogenous mixture of γ(Fe) and α(Co) solid solutions. The microporosity calculated by CT was under 0.5%. Microhardness was measured at and near the interface region, showing that the intermixing zone has high hardness (470–480 HV1), which may be related to the ...

STATEMENT OF PROBLEM The selective laser melting (SLM) process has become popular for the fabrication of frameworks for metal-ceramic restorations, although their surface roughness is greater than with cast or milled frameworks. Limited information is available regarding the surface mechanical characteristics of cobalt-chromium (Co-Cr) SLM-manufactured restorations. PURPOSE The purpose of this in vitro study was to adapt the laser parameters for a remelting strategy, scanning the outer boundary of Co-Cr specimens, to reduce surface roughness and solidification defects, to determine microhardness, to investigate surface morphology and microstructure, and to establish surface mechanical characteristics. MATERIAL AND METHODS Co-Cr specimens were SLM manufactured by using a typical melting (TM) strategy and an adaptive remelting (AR) strategy. The AR strategy involves rescanning 50% of the contour, varying the laser parameters. The roughness parameters considered were Ra and Rz. Vickers hardness was measured by microindentation with a 9.81-N force (ASTM E384-17). The surface morphology was investigated by scanning electron microscopy, the chemical composition by energy-dispersive X-ray spectroscopy, and the phase identification by using X-ray diffraction. The mechanical surface properties measured were the nanohardness, elastic modulus, and dissipation energy. One-way ANOVA with the Tukey procedure was used to compare the groups (α=.05). RESULTS The innovative AR strategy reduced the surface roughness by 45% compared with TM, comparable with their cast counterpart. The smoothest AR surface was obtained by using 75 W and 350 mm/s for the first scanning of the contour, followed by a second remelting with 80 W and 700 mm/s. The microstructure of AR specimens had limited solidification defects, a chemical composition similar to that of raw powder, and a surface microhardness over 600 HV1. A fine grain structure in a single matrix phase was detected both on TM and AR specimens. The mechanical characteristics of the smoothest Co-Cr surface were 218 GPa elastic modulus, 746 HVIT Vickers nanohardness, 21 243 pJ plastic energy, and 26% nanoindentation work ratio. Significant differences were observed between the melting strategies (P<.05) both for surface roughness and microhardness. CONCLUSIONS The laser scanning strategy affects both the surface roughness and the hardness of SLM-manufactured specimens. The results show that using the AR strategy and proper laser parameters can reduce the roughness and increase the surface hardness of Co-Cr specimens made of conventional powder feedstock.

The purpose of this article is to present researches for optimizing the vacuum casting process, by dimensioning the feeding system. To manufacture metallic complex parts through investment casting process using wax patterns, with a good quality surface and a high dimensional accuracy it is necessary to optimize the feeding system. In this study, starting from the classic metal casting process a method to calculate the optimal dimensions of the gating system has been proposed, using mathematical relations for the gate, sprue and feeders. Thus we can say that by applying the feeding system dimensioning algorithm and by correcting the master model dimensions with the shrinkage value, we can manufacture complex metal parts through investment casting with a high precision and a good surface accuracy.

The paper presents some possible solutions for creating elements of the human machine interface of complex virtual equipments. This ongoing research is a part of a complex project of designing virtual machine tools, which could be very useful in training the students and/or CNC operators. .After analyzing some possible software solutions, the paper shows two Java-related solutions: usage of the old Java2D class collection and a more modern one based on the recent GUI class collection known as Java FX 2.0. For every solution the paper presents the code of two classes necessary for creating two common controls, a push button and a rotating wheel. As the virtual equipment is created mainly for teaching purposes, the designing solution helps the trainees also by suggesting the possible controls that should be used in their training stage.

The tripod used for emergencies has been analyzed in different positioning cases of  its legs to its symmetry axis (the symmetry axis being the support of the buckling force), simulating different accidentally scenarios within the rescue interventions. Each case has been three times analyzed, to each analyze being related one type of material(Al2014, Al6082 and carbon fiber); the analysis have been performed by the help of finite element analysis, using ANSYS software. Key words: Buckling, FEM, ANSYS, tripod

3 University Craiova, 13 A. I. Cuza, 200585, Craiova, Romania The specific objectives of this study are to synthesize and characterize nano-scale hydroxyapatite particles in laboratory for use in immobilizing heavy metals. Nano hydroxyapatite (HAP) was synthesized by reacting CaCl 2 and Na 2 HPO 4 as raw materials, a precipitation reaction occuring at the room temperature. Crystal phases were determined by X-ray diffraction (XRD). Scanning electron microscope (SEM) was applied to investigate the morphology. The microstructure of the HAP products was further observed by transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) with energy- dispersive X-ray spectroscopy (EDX). The purity and chemical composition of the as-synthesized powder was analyzed by FTIR. Soil contamination by heavy elements represents therefore a worldwide environmental concern mainly because these elements can be transferred to the hydrosphere and biosphere, thereby p...

Within this paper is presented the optimizing activity of a clamping jaw used for gripping and fixing revolution or/and prismatic work-pieces, by the help of CREO design software, using Creo Parametric and Creo Simulate modules. The article approaches a case study, within two loading situations of the gripper jaw, mounted on an industrial arm robot, are presented. Also, CAD and finite element method (FEM) advantages have been presented.

The paper deals an experimental study on cutting composite materials (CFRP) using abrasive water jet cutting (AWJC) process. The influence of the feed rate on surface roughness is studied using acoustic emission (AE) monitoring. For monitoring the process two acoustic emission sensors was mounted, on the CFRP workpiece and on the cutting head. This monitoring technique has proved that, between process parameter (feed rate and amplitude of AE signal) is a clear connection. The surface roughness can be predicted using online monitoring with acoustic emission (AE).

This study was concerned with the adhesion of resin cement to metal surfaces obtained by selective laser melting process (SLM), and how it could be improved the bond strength at the biocomposite-metal junction. The SLM substrates were manufactured out of pure titanium (Ti), Ti6Al7Nb, and CoCr alloys. The metallic surfaces were covered with 5 types of biocomposites: 2 commercially resin-modified glass-ionomer cements (GC Fuji Plus and KETAC CEM) and 3 types of in-house developed materials. These biocomposites were mechanical characterized under compression and bending trials. The biocomposites-metal adhesion was settled both on as built metallic surfaces and after they were sandblasted with alumina. All the sandblasted SLM surfaces presented higher adhesion strength in comparison with the untreated specimens. The CoCr specimens show the highest bonding value. Additionally, the morphological aspects of joining interfaces were investigated using a scanning electron microscope (SEM). Th...

This paper presents a new method of piercing the carbon fibre reinforced polymer (CFRP) with abrasive water jet (AWJ), which can avoid delamination. The method consists of adding the abrasive particles in the water jet at the very beginning of jet formation, thus obtaining a mixed abrasive water jet during the first impact with the composite work piece. A new cutting system was designed and set up based on the proposed piercing method and was compared with a conventional AWJ cutting system. The main added values brought by this paper are: it validates our original concept; provides synthetic analyses, the effects of the AWJ homogeneity, and the abrasive inlet angle on the CFRP delamination, and it brings a complete set of recommendations on how to overcome the industrial difficulties caused by the delamination of the composite materials, during the piercing with AWJ.

Purpose This paper aims to decrease the cost of repairing operations, of the damaged mechanical components, by enabling the strong automation of the process and the reduction of manual labor. The main purpose of the hybrid repair process is to restore the original shape of the mechanical parts, by adding and removing material according to the mismatch between the damaged object and the virtual model, to restore its geometrical properties. Design/methodology/approach The DUOADD software tool translates the information collected from a 3D scanner into a digital computer aided design solid model, which can be manipulated through Siemens NX computer aided manufacturing (CAM), to obtain the tool paths, for the Direct Laser Deposition (DLD) technology. DUOADD uses octrees to effectively analyze the damaged region of the mechanical part and then to discretize the volume to be added to export CAM-compatible information as a 3D model, for additive operations. Findings DUOADD is the missing l...

Additive Manufacturing (AM) has become indispensable in the context of digitalization and Industry 4.0 and is said to be a mega trend of the 21st century. The technology offers immense opportunities to revolutionize the production of parts and components in all industries. Despite of the outstanding technical possibilities, the industry-wide adaptation rate is low. The current approach of looking at AM from a mostly technological view is a major reason for this. The challenge is to efficiently integrate 3D printing and other additive processes into existing manufacturing processes and systems. AM must be perceived as a multidimensional topic and viewed from different perspectives, two of which are the AM technology and the planning and management of production systems. These two perspectives have to be addressed simultaneously and cross-linked. In order to use AM to tackle some of the most challenging problems in modern manufacturing systems like increasing variant diversity, shorte...

Lead by the results of our previous work, in which we designed the sweat glands prototype according to AM (Advanced Manufacturing) requirements, in this study we aimed to integrate the previously manufactured channels into a stereolithography (SLA)-manufactured module, in order to avoid support structures inside the channels and the model cavities. That was achieved by distributing the channels in the manner which approximates the sweat glands distribution on an equivalent real body part and to be able toadjust the sweat quantity, to the estimated sweat rates found in the literature. The manufactured module has integrated humidity and temperature sensors, which will allow an accurate quantitative assessmentof the thermoregulation of the individual modules and the sweat glands prototype as a whole.

This paper presents the machining process of the complex copper electrodes. Machining of the complex shapes in copper is difficult because this material is soft and sticky. This research presents the main steps for processing those copper electrodes at a high dimensional accuracy and a good surface quality. Special tooling solutions are required for this machining process and optimal process parameters have been found for the accurate CNC equipment, using smart CAD/CAM software.

The aim of this systematic review was to identify new methods of surface treatments applied on titanium grafts and their clinical and histological outcomes, including different routes for surface treatments, respectively the results of in vitro or in vivo tests. These surface modifications analysed meet three main requirements: to prevent nonspecific absorption of denatured protein on the surface, to attract native tissue cells or progenitor cells capable of differentiation in an appropriate manner or to facilitate biochemical signals to induce biochemical healing mechanisms. Therefore, cells will recognize these surface modifications and will be influenced in their adhesion behavior, profiling and differentiation. This review summarizes some of the recent developments in coatings for medical field.

Purpose – The purpose of this paper was to present how customized implants could be made with specific properties, by setting different values of the laser power, within the selective laser melting (SLM) process. A detailed case study was undertaken and a new multi-structured femoral prosthesis was designed and analyzed, to simulate its behavior for a specific case study. Design/methodology/approach – The materials and manufacturing methods are presented, with details regarding the SLM process, using the Realizer 250 machine. The laser power was varied between 50 and 200 W, thus obtaining samples with different physical and mechanical characteristics. All those sample parts were characterized and their properties were measured. Findings – A practical methodology was found to produce multi-structured implants by SLM. Significant changes of the porosity and properties were found, when modifying the laser power at the SLM machine. The studies have indicated an open porosity varying bet...

This study evaluates the manufacturability and performances of periodic cellular lattice structures designed by repeating a cubic unit cell and produced by SLM using titanium powder. The effects of unit cell size on the manufacturability, density, compression and bending properties of the manufactured cellular lattice structures were investigated. Lattice structures manufactured with various unit cell sizes ranging from 0.5 to 1.2 mm could be produced free of defects by the SLM process, with a novel type of supports. By the increasing of the cell size, a decrease of the applied load together with an enhancement of the flexure extension were observed. Specimens with a cell size higher than 1 mm manifested an excellent flexibility by flexure tests.

VIORICA SAPLONTAI1*, MONICA SAPLONTAI1, IOAN ROMAN3, DAN LEORDEAN1, ROXANA TRUSCA3, TAMAS ROBERT TOTH1, ILEANA COJOCARU4, NICOLAE BALC1, MARIOARA MOLDOVAN2 1Technical University of Cluj-Napoca, Cluj Napoca, 103-105 Muncii Str., 400641, Cluj-Napoca, Romania 2”Babes Bolyai” University – “Raluca Ripan” Chemistry Research Institute, 30 Fantanele Str., 400294, Cluj-Napoca, Romania 3 S.C.Metav-Research Development S.A., 31 C.A. Rosetti Str., 020011, Bucharest, Romania 4University of Craiova, 13 A. I. Cuza Str., 200585, Craiova, Romania

This paper presents a production approach for modern manufacturing on Trumph Trumatic presses in computer environment. For model creation using advanced forming functions SolidWorks software was used. finite element method (FEM) analysis by means of Abaqus 6.4-1. software in order to evaluate strain energy of forming processes was used. ToPs 300 software is used for creating of CNC programs for Trumph Trumatic presses in order to produce sheet metal products.

To manufacture custom medical parts or scaffolds with reduced defects and high mechanical characteristics, new research on optimizing the selective laser melting (SLM) parameters are needed. In this work, a biocompatible powder, 316L stainless steel, is characterized to understand the particle size, distribution, shape and flowability. Examination revealed that the 316L particles are smooth, nearly spherical, their mean diameter is 39.09 μm and just 10% of them hold a diameter less than 21.18 μm. SLM parameters under consideration include laser power up to 200 W, 250–1500 mm/s scanning speed, 80 μm hatch spacing, 35 μm layer thickness and a preheated platform. The effect of these on processability is evaluated. More than 100 samples are SLM-manufactured with different process parameters. The tensile results show that is possible to raise the ultimate tensile strength up to 840 MPa, adapting the SLM parameters for a stable processability, avoiding the technological defects caused by ...

The demand of lattice structures for medical applications is increasing due to their ability to accelerate the osseointegration process, to reduce the implant weight and the stiffness. Selective laser melting (SLM) process offers the possibility to manufacture directly complex lattice applications, but there are a few studies that have focused on biocompatible Ti6Al7Nb alloy. The purpose of this work was to investigate the physical–mechanical properties and the microstructure of three dissimilar lattice structures that were SLM-manufactured by using Ti6Al7Nb powder. In particular, the strut morphology, the fracture characterization, the metallographic structure, and the X-ray phase identification were analyzed. Additionally, the Gibson-Ashby prediction model was adapted for each lattice topology, indicating the theoretical compressive strength and Young modulus. The resulted porosity of these lattice structures was approximately 56%, and the pore size ranged from 0.40 to 0.91 mm. Un...

This is a conference paper. From CAD and Virtual Prototyping, there are already available many Rapid Prototyping (RP) techniques to produce physical, hand hold able parts. A brief overview is presented of some important aspects regarding how to get a good 3D solid model, how to transfer it to RP machines and how to produce quickly a physical prototype. The RP models could be used for different downstream applications. The paper gives some alternative tooling routes, depending on some criteria, such as: volume production, material and complexity of the parts. The RP models could be used as master models for vacuum casting, metal spraying, investment casting and other innovative manufacturing techniques.

This is a conference paper. Design for assembly (DFA) is a well-establish technique that has proved beneficial in many companies in different manufacturing sectors. It aims to simplify the assembly of a product by reducing the number of components and by making sure that they fit together easily. Often, a DFA analysis will show a theoretical improvement in the assemblability of a product, but the re-design is not implemented because there is no way of verifying the findings of the analysis. Rapid prototyping (RP) enables physical models to be made directly from CAD data in a relatively short period of time. Using RP, it is possible to build the re-designed product and test the accuracy of the DFA analysis. This paper describes the procedure that can be followed to achieve this and demonstrates its practicality through use of a case study. Key words: Design for assembly, rapid prototyping, design verification.

A theoretical model of the Selective Laser Sintering (SLS) contractions has been developed. The finite element analysis results are presented, for the spatial deformations of the complex metal parts made from Laserform ST-100 material. The experimental researches were undertaken at the Technical University of Cluj-Napoca (TUCN) and the accuracy is compared with the theoretical estimations and simulations.

Selective laser melting (SLM) is one of the most important technologies used when complex metallic parts need to be rapidly manufactured. There are some requirements related to the quality of the manufactured part or the accuracy of the process control, in order to turn SLM process into a production technique. This paper presents a case study undertaken at the Technical University of Cluj-Napoca (TUCN) in cooperation with an industrial company from Romania, focusing on the accuracy issues. Finite element analysis (FEA) and Design Expert software were jointly used in order to determine the optimum process parameters required to improve the accuracy of the SLM metallic parts. Experimental results are also presented in the paper.

ABSTRACT In this paper the authors shows hydroforming of tubular parts. Also it presents the technology of the hydroforming of the tubular parts. It is presented some experimental research compared with the prediction of the numerical simulation of this process. There are presented also the mechanical parameters of the material which are used in the field of the deforming process.