Daniel Ghiculescu

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.

Kinematic Design of Parallel Delta System in Matlab

The paper presents the problem of modelling the parallel kinematic delta system using specialized software Simmechanics constituting the extension of the Matlab environment. Parameterized model of the parallel delta robot was developed and kinematic analysis was performed. The results of the model was used to correction of design and real construction. Designed robot is intended to direct a tool according to the program recorded by machine commands (G-code).

The Concept of Robotic Station for Measurement of the Friction Force between Fibre-Optic Cable and Duct

The interaction of an optotelecommunication cable and casing depends on numerous factors e.g. the type of cable, its structure, dimensions, as well as applied lubricants and sliding layers [8]. In addition, the course of the cable, velocity of installation and its maximum force also play a role in the interaction of the tribological pair. The paper outlines the idea and operation of a robotized testing station for evaluation of sliding friction. The station enables cables’ friction to be determined in relation to the length of contact between the cable and the casing.

A Model Regarding Material Removal Using FEM at Ultrasonic Aided EDM of Metal Matrix Composites

The paper deals with phenomena occurring at the ultrasonic aided electrical discharge machining (EDM-US) of electro-conductive metal matrix composites materials (EC-MMCs-Al/Al2O3p). Starting from the analysis of the cavitational phenomena due to the forced ultrasonic longitudinal vibrations of the electrode and the phenomena caused by the thermal shock, a physical-mathematical model of the material removal process was developed consisting mainly by boiling, vaporization and spalling. Based on the Finite Element Method (FEM), the thermal shock phenomenon, as well as its influence on the material removal process, is described.

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.

On Correlation of Pulses and Tool Elongations at Micro-Electrical Discharge Machining Aided by Ultrasonics

The paper deals with Finite Element Method (FEM) of thermal and mechanical-hydraulic components of material removal mechanism at micro-electrical discharge machining aided by ultrasonics (μEDM+US), due to EDM and US contribution. The dimensions of craters produced by single discharges under μEDM+US conditions are determined with different pulse durations in order to establish a machining strategy with correlation of pulses and tool elongations.

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.