Niculae Marinescu

On Overlapping the Pulses on Cumulative Microjets Stage at Ultrasonically Aided Electrical Discharge Machining

The paper deals with a solution to increase the machining rate at electrical discharge machining aided by ultrasonics (EDM+US), i.e. the overlapping the voltage pulses provided by EDM generator on the cumulative microjets stage (CMS), which occurs at every final of an ultrasonic period by collective implosion of the gas bubbles from the working gap. This overlapping moves the limit of the removed material by a discharge from the boiling isothermal (at classic EDM) to melting isothermal (at EDM+US) as it is emphasized by the results of finite element analysis. The preliminary experimental data analyzed in the paper are obtained in case of random overlapping at ultrasonic frequency of 20 kHz. They demonstrate an increase of machining rate with more than 300% at EDM+US in comparison with classic EDM in the same working conditions.

Some Issues Regarding Finite Element Modelling of Micro-Electrical Discharge Machining Aided by Ultrasonics

The paper deals with finite element modelling (FEM) of the process of micro-electrical discharge machining of micro-holes aided by ultrasonic longitudinal oscillations of workpiece (μEDM+US). FEM of the process comprises two components: the thermal one due to μEDM removal mechanism, and the ultrasonic one caused by cavitation effect generated inside the lateral working gap. The FEM results obtained are validated by experimental data in terms of craters dimensions produced by single discharges, leading to optimization strategy of process parameters.

Customer Matrix with Different Time Horizons Applied to Electrodischarge Machines

A very effective method to evaluate the products is the Customer Matrix (CM) that uses two coordinates: Perceived Used Value (PUV) and Perceived Price. Our researches extend this basic concept by adding the time variable, creating CM with different time horizons that assures a better understanding of competitive environment. In the first stage, the Customer Matrix is associated with a forecast method. The relevance tree method was used to predict the most probable evolution paths of electrodischarge machines. In the second stage, the CM with different time horizons is constructed, considering products evaluation for short, medium and long time. Finally, a strategy is conceived for an organization that attempts to ameliorate and consolidate its long term position against the main competitors, aiming at obtaining sustainable competitive advantage.

SMEs creativity and smart regional development

The paper presents new methods of smart regional development, starting from a question and one answer: How do we go about building our local smart ecosystem? Make one step at a time. This step is achieved through a number of seven elements: the SMEs network, the relations between universities and the labour market, the efficient using of transport infrastructure, the interactions specific to the various forms of capital with accent on intangible assets, smart relocation, online and offline interactions in smart communities, the used of young staff as a source of creativity and innovation, oriented to smart specialization, leading to sustainable competitive advantage.

Finite Element Modeling of an Ultrasonic Horn Integrating the Tool for Micro-Electrical Discharge Machining

The paper deals with a strategy to obtain a complex conical ultrasonic horn, which integrates the tool for micro-drilling through ̵̵̼̳̹̳̱̼̈́͂˰̴̸̷̵̹̳̱̓͂˰̸̷̱̳̹̹̽̾̾˰˸ڌ̝̔̕˻̥̣˹˰̵̴̲̱̓˰̿̾˰̖̹̾ite Element Method (FEM) modeling. This approach comprises more than 20 stages, starting with preliminary determination of a basic profile stepped horn through mathematical relations. The next stages are based on Comsol Multiphysics FEM modeling, changing gradually different horn constructive elements and integrating the tool and their clamping parts. The entry data for horn geometry determination were the dimensions and own frequency of transducer subassembly, joining ultrasonic horn. Finally, the CAD file of horn was transferred to CAM file and CNC machined. Horn real own frequency obtained was very close to the result provided by FEM modeling.

Experimental Study on Unsynchronized Ultrasonic Assistance of Electro Discharge Machining Process

The paper deals with experimental study on unsynchronised (out of phase) ultrasonic assistance (US) of electrical discharge machining (EDM) process, considering finishing and semi-finishing operations. The main output technological parameters at classic EDM are not as good as they are expected due to instability of material removal process and long duration of gas bubble formed around plasma channel. The US longitudinal oscillations of electrode-tool produce cavitation within frontal working gap leading to collective implosion of gas bubbles. This hydraulic phenomenon can remove the workpiece material in solid or plastic state or even in liquid state. The goal of our study is to emphasize and quantify the influence of US assistance into EDM process and also to determine a correlation between EDM and US parameters, considering an unsynchronised condition. Nevertheless some optimization conditions of working parameters are needed to attain notable expected performances. From experimental data analysis, it can be noticed that significant growth in process productivity is achieved when EDM process frequency is equal with the ultrasonic assistance frequency.

On Romanian SMEs Development Using Concentrated Energies Technologies Based on Updated Greiner's Model

The paper deals with an updated Greiners model, defining its final stage, Development through Alliance, in the frame of actual knowledge based economy, and with introduction and characterization of its final crisis, Incompatibility crisis. The research method is based on analysis of SMEs characteristics that use concentrated energies technologies, correlated with characteristics of actual economy. This led to some elements of the final stage of Greiners model, which were developed together with managerial methods of organizational development as well as solutions to avoid or ameliorate the final crisis of Incompatibility, applied to SMEs, using the approached technologies. It was also identified a trend concerning small and medium enterprises (SMEs) evolution from Romania, which use concentrated energies technologies. Some generic development solutions for the mentioned organizations in actual economy are provided.

Aspects of Finite Element Analysis of Microdrilling by Ultrasonically Aided EDM and Related Knowledge Management

Ultrasonic vibrations of electrode-tool and workpiece were applied successfully in specific cases to increase some parameters at micro-EDM, this working mode being characterized through machining instability due to vary narrow working gap. Our researches proved that all main technological parameters of micro-EDM can be improved by ultrasonic aiding (μEDM+US) in terms of machining rate, volumetric relative wear and surface roughness if some optimization conditions of working parameters are fulfilled. A multiphysics Finite Element Analysis (FEA) of material removal mechanism was achieved using two time dependent modules of Comsol 4.2 in order to attain the working parameters optimization. The FEA results compared to experimental data aiming at model validation led to some useful measures to optimize the working parameters. The knowledge management process was approached in order to suggest how human resource from an organization that uses μEDM+US can apply and improve the research results. Our EDM+US strategy is based on relative long pulse time with very low current overlapped on collective bubbles implosion occurring at the final of a liquid ultrasonic stretching semiperiod, and relative low consumed power on ultrasonic chain, contributing to increase the main output technological parameters mentioned above.

Specific Aspects on Modelling and Simulation of the Synchronized Ultrasonic Assistance of the Electro-Discharge Machining Process

The context of our research is based on the conclusion that simulation is used to describe and analyse the behavior of an existing or conceptual system. Electro discharge machining aided by ultrasonics EDM+US (as well as micro) is a complicated process that requires a powerfull tool to simulate. In this study we considered COMSOL multiphysics FEA software, using our own developed parametric model based on literature survey knowledge and our own previuos researches on subject. Some preliminary simulations results and conclusions are also presented.