Nicolae Bâlc

Basic Research on Lattice Structures Focused on the Tensile Strength

This scientific survey is about the mechanical properties of lattice structures which are made by Selective Laser Melting. It’s a process based on Additive Manufacturing technologies. This technology allows the manufacturing of complex lattice structures, and further the integration of lattice structures into different applications. Focusing on the integration of these structures, it is necessary to know what kind of effect they have on applications and what positive properties they might support. More and more the industry searches for new supporting technologies and the trend is towards lightweight and material saving possibilities. [1, 2] A survey on this topic is indispensable. The main aim is to analyze different parameters that affect the mechanical properties. First of all the definition of the experimental set-up and the definition of the, to be tested, parameters are necessary. Furthermore the aim is to find several different parameters that have a positive effect on the mechanical properties. Above all the focus is on experimental set-ups that use mechanical tests, beginning with the test on tensile strength in accordance with DIN 50125. Depending on the results an application area could be chosen and assigned.

Research on Improving the Outer Surface Quality of the Parts Made by SLM

The paper presents an application of the ANOVA method within the Selective Laser Melting (SLM) process. A new mathematical model was developed, to calculate the surface roughness of the SLM parts made from titanium powder, as function of the important SLM parameters: point distance, exposure time and laser power. Preliminary experiments were undertaken according to the Design Experts work plan and the new mathematical formula was tested by further experimental research, to validate the optimized SLM parameters.

Surface Roughness Prediction During Dry Turning of Austenitic Stainless Steel AISI 304

The objective of this paper is to predict and analyze the surface roughness during dry turning of austenitic stainless steel AISI 304. In this study a new carbide insert developed by Mitsubishi was used for the cutting of this material. By using the ANOVA method, the influence of the main processing parameters on the surface quality was analyzed. By using a mathematical regression method a mathematical model was developed. It can calculate the surface roughness taking into account the cutting speed, the feed rate and the depth of cutting.

The Accuracy of the Plastic Parts Milling Process Executed by a Six Axes Robot

The objective of this paper is to analyze the precision of plastic parts made by using robot milling. Currently, the robots have good precision, rigidity, flexibility and they are able to machine parts. By using a six axis Kuka robot and an electric spindle, a plastic part was milled. The paper presents the advantages and disadvantages of this new technology, analyzing the dimensional accuracy, surface quality and costs.

Finite Element Analysis to Predict the Mechanical Behavior of Lattice Structures Made by Selective Laser Melting Technology

Within this article, there are presented a series of researches that are related to the field of customized medical implants made by Additive Manufacturing techniques, such as Selective Laser Melting (SLM) technology. Lattice structures are required in this case for a better osteointegration of the medical implant in the contact area of the bone. But the consequence of using such structures is important also by the mechanical resistance point of view. The shape and size of the cells that are connected within the lattice structure to be manufactured by SLM is critical in this case. There are also few limitations related to the possibilities and performances of the SLM equipment, as well. This is the reason why, several types of lattice structures were designed as having different geometric features, with the aim of analyzing by using finite element method, how the admissible stress and strain will be varied in these cases and what would be the optimum size and shape of the cells that confers the optimum mechanical behavior of lattice structures used within the SLM process of the customized medical implant manufactured from titanium-alloyed materials.

Research Concerning the Springback Prediction in the Bending Operations

Nowadays firms are required to obtain high quality products in order to increase their competitiveness. The time required to obtain a new product is also essential to fight the concurrence. For manufacturers of bent parts, accurate prediction of the springback is very important. Therefore, this paper investigates the applicability of artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) to predict the springback in the free cylindrical bending process of metallic sheets. The finite element method (FEM) was used to simulate the springback in the free cylindrical bending process and the results were used as training data for ANN and ANFIS. The finite element results were validated by comparison with experimental data. Statistic criteria were used to evaluate the performance of the developed ANN and ANFIS models. It was found that the predictions are in good agreement with the FEM data.

Estimating the Life-Cycle of the Medical Implants Made by SLM Titanium-Alloyed Materials Using the Finite Element Method

Within this article, there are presented a series of researches that were developed for the first time in Romania, in the field of customized medical implants made by using the Selective Laser Melting (SLM) technology. Finite Element Method (FEM) has been successfully used in order to analyze the fatigue and to determine the durability of a customized medical implant that has been selected for the made analysis. The material characteristics taken into consideration within the Finite Element Analysis (FEA) that has been performed were the ones of two types of dedicated metallic powders which are commercially available (TiAl6Nb7 and TiAl6V4 material) and suitable for the SLM 250 HL equipment from the SLM Solutions GmbH Company from Lubeck, Germany. The Finite Element Analysis made in the case of these two types of SLM titanium alloyed materials, proved that the modified characteristics, such as the yield strength and hardness of the material are significantly influencing the durability of the medical implants made by SLM technology.

Research on Producing Complex Metal Parts with Lattice Structure by Selective Laser Melting

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.

Design and Analyses to Determine the Minimum Acting Force of a Gripper for Handling the Parts with Robots

This paper presents a model of gripper designed for KUKA robot, together with a series of static and dynamic analyses for different loadings of it. Both the 3D design and static and dynamic analyses have been conducted using the design of Creo package with Parametric and Simulate the modules. The Gripper designed has in its composition a mechanism type rack-pinion type and a quadrilateral mechanism, for carrying out a parallel movement of jaw. It was determined the minimum force of actuation of the pinion-rack mechanism of gripper for maintaining the piece caught in gripper jaws, at the maximum speeds of rotation of the robot.

How the Crystallization Process in Metal Casting is Influenced by the Mold Filling and Cooling Methods

The paper presents a case study on a aluminium part obtained by three different casting methods: die casting, investment casting and sand casting. The article analyzes the mold filling method, solidification time and crystal structure type obtained for each casting process. The purpose was to obtaine more homogenous crystalline structure of the cast parts, with better mechanical properties. The mold filling method with molten metal and heat transfer method influences the mechanical properties of the cast parts.