Nikolaos M. Vaxevanidis

• Ph.D,
• Professor (Full) at School of Pedagogical and Technological Education

Fused filament fabrication (FFF) is the leading 3D printing material extrusion process renowned for its versatility, affordability and easy production of complex components. Despite its advantages, the bonding quality between layers depends heavily on processing parameters and filament material properties. Using an orthogonal experimental design, t...

Nanocomposites nowadays, have the tendency to replace conventional composite materials in many commercial products. These composites find application in a diverse range of fields, including computer components, data storage systems, various membranes and filters, as well as advanced materials in the automotive and aerospace industries. They are ava...

Thanks to the simplicity and low cost, the open chamber filament material extrusion process, also known as fused filament fabrication (FFF), has spread to customized applications in the fashion and textile industries. This work is an experimental optimization of a 3D printed button changing two primary parameters, the printing speed and temperature...

This work concerns an experimental investigation dealing with the machinability of 60CrMoV18-5 cold-work tool steel under dry CNC hard turning conditions using a CBN cutting insert. A response surface experiment based on the central composite design was set to conduct dry CNC hard-turning experiments with three different levels for cutting conditio...

The present study focuses on an experimental investigation aiming at simultaneously optimizing tensile strength and elastic modulus of 3D-printed polymethyl methacrylate (PMMA) filament material while considering raster angle, printing speed, and layer thickness as the independent process-related control parameters. The Box-Behnken design of experi...

This paper investigates numerically the effect of damage evolution on adiabatic shear banding (ASB) formation and its transition to fracture during high-speed blanking of 304 stainless steel sheets. A structural-thermal-damage-coupled finite element (FE) analysis is developed in LS-DYNA considering the modified Johnson–Cook thermo-viscoplastic mode...

Additive manufacturing (AM) is a modern technology currently adopted by manufacturing industries to benefit from its low-cost applications, versatility and fabrication of complex parts. Fused deposition modeling (FDM) is distinguished among the different AM technologies due to its fast, yet accurate operations. However the properties of fabricated...

Adiabatic shear banding reflects an unstable and dynamic plastic deformation mechanism occurring at high strain and strain rates which is strongly conjugated to fracture. Current work carries out a numerical study on the initiation and development of adiabatic shear bands (ASBs) in blanking process of AISI 4340 steel sheet. A structural-thermal cou...

This paper presents simulation results obtained by a set of modern algorithms adhering to swarm intelligence for minimising wear rate in the case of A356/Al2O3 nanocomposites produced using a compocasting process. Grey wolf optimisation (GWO) algorithm, moth-flame optimisation (MFO) algorithm, dragonfly algorithm (DA) and whale optimisation algorit...

New developments in manufacturing processes impose the need for experimental studies concerning the determination of beneficial process-related parameter settings and optimization of objectives related to quality and efficiency. This work aims to improve cutting geometry, surface texture, and arithmetic surface roughness average in the case of post...

This investigation examines the results of two variable parameters during the fused deposition modeling (FDM) 3D printing process of conventional polylactic acid (PLA) and organic biocompatible compound material with wood (PLA/W; coconut flour), on ultimate tensile strength, UTS (MPa) and modulus of elasticity E (MPa). The parameter optimization is...

This work deals with the experimental investigation and multi-objective optimization of mean kerf angle (A) and mean surface roughness (Ra) in laser cutting (LC) fused filament fabrication (FFF) 3D-printed (3DP), 4 mm-thick polylactic acid (PLA) plates by considering laser feed (F) and power (P) as the independent control parameters. A CO2 laser ap...

This work presents the multi-objective optimization results of three experimental cases involving the laser sintering/melting operation and obtained by a virus evolutionary genetic algorithm. From these three experimental cases, the first one is formulated as a single-objective optimization problem aimed at maximizing the density of Ti6Al4V specime...

During last decades fused deposition modeling (FDM) has emerged as a widely applied additive manufacturing technology for numerous engineering applications. The present work investigates the effects of two independent variables during FDM fabrication of conventional polylactic acid (PLA) and organic biocompatible composite material with coconut flo...

Material extrusion (MEX), frequently known as fused filament fabrication (FFF), is a material extrusion 3D printing process for fabricating cost-effectively functional polymeric parts. Even if the MEX process fabricates fully dense or lightweight specimens with a relatively complex geometry in a reduced time and cost, it presents some drawbacks in...

The current work is a follow-up of previous research published by the authors and investigates the effect of CO2 laser cutting with variable cutting parameters of thin 3D printed wood flour mixed with poly-lactic-acid (PLA/WF) plates on kerf angle (KA) and mean surface roughness (Ra). The full factorial experiments previously conducted, followed a...

Fused filament fabrication (FFF) also referred to as fused deposition modeling (FDM) is the most extensively used among all the additive manufacturing (AM) technologies due to its low cost, ease of use and variety of materials commercially available. An FFF printer generates a 3-dimensional object by extruding a stream of heated and semi-melted the...

As in every manufacturing process, fused deposition modeling (FDM) is strongly related to its operational parameters. 3D-printed components are anisotropic and brittle and this imposes the need to investigate the effect of FDM-related parameters to improve functionality and strength. In this paper the flexural strength of polyethylene terephthalate...

A study of the shape accuracy of pieces created using the Fused Filament Fabrication (FFF) process is presented. Accuracy of the parts coming from 3D Printing (3DP) technologies is an essential criterion, primarily when used in assembly configurations. Two polymers; PLA and ABS, three infill percentages; 20, 50, and 70 (%), three numbers for shells...

Fused filament fabrication (FFF) is an additive manufacturing process, which constructs physical items by fused melt material, selectively deposited layer-by-layer through a heated extrusion mechanism. Parameters’ selection and control in FFF are of utmost importance since they significantly affect the surface quality (SQ) and dimensional accuracy...

Keywords: Slot milling Surface roughness AL 7075 aluminum alloy Full factorial design Fractional factorial design A B S T R A C T This work deals with comparing the fractional and full factorial design of experiments on evaluating surface roughness characteristics during slot milling of Al 7075 alloy. Mean surface roughness (Ra) was selected as the...

This work investigates the effect of 3D-printing parameters on surface roughness in polylactic acid printed material by adopting Taguchi's design of experiments approach. The control parameters under study were: number of shells, printing temperature, infill rate, and printing pattern. As the response, mean surface roughness (Ra) was selected. The...

This study investigates the influence of the stand-off distance (SoD), laser speed (LS) and laser power (LP) on kerf geometry (upper width Wu, down width Wd and kerf angle KA) and mean surface roughness (Ra) during CO2 laser cutting of 3D-Printed Polyethylene-Terephthalate-Glycol (PET-G) thin plates. A full factorial design is implemented, having t...

In this work an enhanced virus-evolutionary genetic algorithm has been developed and applied to optimize a three-objective optimization problem related to an important additive manufacturing/rapid prototyping operation known as selective laser sintering (SLS). Selective laser sintering is a manufacturing process where laser is used as the power sou...

This work investigates the effect of 3D printing parameters on surface roughness in the case of PLA printed material by adopting the Taguchi's design of experiments approach. The control parameters under study were: number of shells, printing temperature, infill rate and printing pattern. As the response, mean surface roughness (Ra) was selected. T...

In this work, two typical surface characteristics, i.e., mean surface roughness and angle of the kerf during laser processing of 3D-printed Polylactic Acid (PLA) plates with 4.00 mm in thickness, are investigated. A carbon dioxide laser was utilized to separate 27 work pieces of rectangular shape. The governing laser parameters, speed of cutting an...

This work deals with the optimization of crucial process parameters related to the abrasive flow machining applications at micro/nano-levels. The optimal combination of abrasive flow machining parameters for nano-finishing has been determined by applying a modified virus-evolutionary genetic algorithm. This algorithm implements two populations: One...

The present work is focused on the direct manufacturing of a hand splint using free-open access software and a low-cost three-dimensional printer (3DP). The hand digital model was created using panoramic photos by a common mobile phone camera. The photos were used as input to the "3DF-Zephyr" free software for creating the hand surface model. Then,...

Fused Deposition modelling (FDM) is one of the most widely used Additive Manufacturing technologies that extrude a melted plastic filament through a heated nozzle in order to build final physical models layer-by-layer. In this research, a virus-evolutionary genetic algorithm (MOVEGA) is developed and implemented to solve a multi-objective optimizat...

This work presents the creation of geometric surface models representing the heart chambers and the aorta for two patient specific cases. The first one concerns an acute ascending aortic aneurysm in the anterior Valsalva sinus and the second one a normal aorta for comparison reasons. The surface modelling was implemented in a medical image reconstr...

A wall mechanics study is performed on two human aortic models, reconstructed from computed tomography (CT) image data using the Materialise Mimics software. The first model represents a rare ascending thoracic aortic aneurysm (aTAA) case with an excessive aortic ballooning that has displaced the cardiac cavities, and the second one a normal case f...

Cr2O3 and TiO2 powders were deposited by atmospheric plasma spray (APS) on steel substrates. Microstructural analysis of the coatings showed typical lamellar structure with good coating quality. Fatigue strength was studied by using cyclic testing (measuring with an inhouse-built apparatus the strength of the coated systems under a wide range of im...

The properties of fused deposition modeling (FDM) products exhibit strong dependence on process parameters which may be improved by setting suitable levels for parameters related to FDM. Anisotropic and brittle nature of 3D-printed components makes it essential to investigate the effect of FDM control parameters to different performance metrics rel...

The evaluation of additively manufactured components is often conducted by means of experiments assessing product quality, build time, dimensional accuracy and tolerances, production cost and tribological properties of parts. As it occurs to any other manufacturing process, the performance of additive manufacturing is strongly affected by its corre...

Fused Deposition Modeling (FDM) is one of the most widely used Additive Manufacturing technologies that extrude a melted plastic filament through a heated nozzle in order to build final physical models layer-by-layer. In this research, a case study is presented in order to optimize process performance of a low cost FDM 3D printer. Taguchi method wa...

This paper studies the effect of cutting conditions (spindle speed - rpm; feed rate - mm/rev and depth of cut - mm) on main cutting force and surface roughness during CNC turning of the commercial tool steel CALMAX® by Uddeholm (Sweden). Experiments have been designed using the Central composite design (CCD) approach. The experimental design involv...

An experimental investigation of the surface quality of the Poly-Jet 3D printing (PJ-3DP) process is presented. PJ-3DP is an additive manufacturing process, which uses jetted photopolymer droplets, which are immediately cured with ultraviolet lamps, to build physical models, layer-by-layer. This method is fast and accurate due to the mechanism it u...

The dimensional accuracy of a simple benchmark specimen fabricated with fused filament fabrication (FFF) route is discussed in the present study. FFF is a low-cost 3D-printing process that builds complicated parts by extruding molten plastic. Experimental method was designed according to Taguchi robust design based on an orthogonal array with nine...

This work suggests the trajectory optimization of three well-known 3-axis surface machining tool-paths available to commercial computer-aided manufacturing systems by means of a genetic algorithm. The toolpaths are Optimized-Z; Raster and 3D-Offset. An original approach involving digitized information derived from solid features of complex sculptur...

This study investigates the machinability performance during dry longitudinal turning of Ti-6Al-4V-ELI titanium alloy using Taguchi Experimental Design (TED) and Full Factorial Design (FFD). Main cutting force (Fc) and mean surface roughness (Ra) are selected as the output machinability parameters. Spindle speed (n), feed rate (s) and depth of cut...

In recent years there is a small but increasing number of articles presenting and/or analyzing the scientific production from discrete geographical regions on a certain scientific topic. These articles applied the so-called bibliometric methods in order to evaluate the contribution of different countries in a scientific research field. In the prese...

Owing to its ability to manufacture complex parts without expensive tooling requirement or human intervention, fused deposition modelling (FDM) is gaining distinct advantage in manufacturing industry. As it occurs to any other engineering process, the properties of FDM-built products exhibit high dependence on process parameters which may be improv...

This investigation concerns the cutting force magnitude during turning of AISI D6 tool steel using both Taguchi Experimental Design (TED) and full factorial design (FFD). Three main cutting parameters namely spindle speed, feed rate and depth of cut were considered as the cutting parameters, each one having three levels, while the cutting force (Fc...

Machinability of engineering materials is crucial for industrial manufacturing processes since it affects all the essential aspects involved, e.g. workload, resources, surface integrity and part quality. Two basic machinability parameters are the surface roughness, closely associated with the functional and tribological performance of components, a...

The present paper discusses the development of a reliable and robust Artificial Neural Network (ANN) capable of predicting the tribological performance of three highly alloyed tool steel grades. Experimental results were obtained by performing plane-contact sliding tests under non-lubrication conditions on a pin-on-disk tribometer. The specimens we...

Nowadays computers have invaded all levels of production, thus improving the quality and quantity of products. Digital manufacturing involves all tools for design, simulate, and programming machine tools in order to manufacture prototypes or tools for production use. This project is a case study of digital manufacturing for prototyping of an intern...

Microcellular materials and specifically metallic foams have attracted the attention of scientific community due to the advanced combination of particular properties that they offer, compared to solid metals. These combined properties make them revolutionary materials for applications requiring more than one function such as high stiffness, fire pr...

One of the tools used within the effort of developing new quantitative scientometric tools, reliable to be used for ranking academic/research unities is the bibliometric analysis of the scientific production from discrete geographical regions on a certain scientific topic. These analyses apply the so-called bibliometric methods. In the present work...

Two critical objectives in sculptured surface tool path optimization are machining accuracy and process efficiency. The former objective is characterized as the combined effect of chord error and scallop height, known as surface machining error, whilst the latter may be reflected by the number of cutting tool locations constituting the tool path. T...

Global optimisation for manufacturing problems is mandatory for obtaining versatile benefits to facilitate modern industry. This paper deals with an original approach of globally optimising tool paths to CNC-machine sculptured surfaces. The approach entails the development of a fully automated manufacturing software interface integrated by a non-co...

This paper investigates the machinability characteristics of a high-leaded Brass alloy (CuZn39Pb3) by considering the effect of rotational speed; feed rate and depth of cut on main cutting force Fc, arithmetic surface roughness Ra and maximum height of profile Rt during its longitudinally turning. An L18 mixed-level Taguchi Orthogonal Array experim...

Book of abstracts/ Oral Presentation --------------------------------------------------------- Abstract— The present paper concerns with the analysis and the optimization of the Surface Roughness (Ra) during turning of Ti-6Al-4V ELI titanium alloy under dry cutting condition by applying both full and fractional experimental design. The main cutting...

In the present study two highly alloyed steel grades, intended for cold working applications, were subjected to plane-contact, non-lubricating sliding friction testing in order to estimate the working regions (applied pressure and sliding velocity) that are governed by mild, moderate and severe wear mechanisms, before and after nitrocarburizing. Fo...

A methodology is presented to optimize the performance of an Artificial Neural Network (ANN) using Design of Experiments (DOE). 8 different feed forward back propagation (FFBP) ANNs were developed and tested according to the L8 full factorial orthogonal array. The 3 parameters tested were: Number of Hidden Neurons, Learning rate, and Momentum; each...

Machinability of engineering materials is crucial for industrial manufacturing processes since it af-fects all the essential aspects involved, including workload, resources, surface integrity and part qual¬ity. Two basic machinability parameters are the surface texture, which is closely associated with the functional and the tribological performanc...

The optimization of process parameters referring to sculptured surface tool path planning increases efficiency and enhances product quality; thus, it is for the major research subject for many noticeable studies. Optimization for process parameters is usually conducted by working with a two-phase scheme; regression modeling based on the results obt...

Stellite 6 powder (CoCrSiW) was deposited using flame spray (FS) and high velocity oxygen fuel (HVOF) techniques on steel substrates. The microstructure of stellite coatings produced with these deposition techniques displayed a rather similar morphology consisting of cobalt-rich dendrites surrounded by hard (Cr3C7) carbide particles. The stellite (...

Material removal processes are fundamental manufacturing operations from which high quality parts are produced and see service in a great variety of industrial applications. In this study, a multi-parameter design of experiments, using Taguchi method, has been conducted to investigate the optimum cutting conditions in turning of 316-L stainless ste...

_______Oral Presentation:______ 3D printing (3DP) refers, in general to processes used to create a three-dimensional object in which material is joined or solidified under computer control to create an item. Whilst there are many different techniques used for 3D printing, all are based on the same principle: a digital 3D model is turned into a soli...

This paper focuses on the development of a multi-axis post-processor engine with a curvature-based feed adaptation module, capable of extracting generic CNC data for high precision machining. The motivation of this work stems from the drawback of standard and commercial post-processors to modify their internal source codes so as to be implemented t...

Sculptured surface machining is a material removal operation essentially adopted to manufacture complex products. Computing optimal tool paths with reference to ideally designed CAD models is indispensable to be able to suggest machining improvements in terms of high quality and productivity. The present paper proposes a new methodology based on a...

The explosive welding method has a wide range of applications, which is still growing. A rapid worldwide growth of interest is evident, since the use of multi-layer materials is becoming increasingly vital for the industry. However, the materials produced by explosive welding rarely possesses their final application characteristics. Therefore, post...

Electro-Discharge machining (EDM) is a thermal process comprising a complex metal removal mechanism. This method works by forming of a plasma channel between the tool and the workpiece electrodes leading to the melting and evaporation of the material to be removed. EDM is considered especially suitable for machining complex contours with high accur...

Electro-Discharge machining (EDM) is a thermal process comprising a complex metal removal mechanism. This method works by forming of a plasma channel between the tool and the workpiece electrodes leading to the melting and evaporation of the material to be removed. EDM is considered especially suitable for machining complex contours with high accur...

The production of extruded polyethylene films rods, tubes and pipes is a typical industrial process that has been extensively investigated over many years. In this study the extrusion of High Density Polyethylene (HDPE) tubes was simulated by using the 3D finite element simulation software StarCCM+®. The simulation was applied in order to examine t...

The present paper concerns with the analysis and the optimization of the main cutting force (Fc) during turning of Ti-6Al-4V ELI titanium alloy under dry cutting condition by applying either full or fractional experimental design. The main cutting variables (spindle speed, feed rate and depth of cut) were treated as inputs in whilst the main cuttin...

This paper investigates the profitability of a dual-curve driven surface finish tool path under the concept of optimizing crucial machining parameters such as toroidal end-mill diameter, lead angle and tilt angle. Surface machining error as well as tool path time are treated as optimization objectives under a multi-criteria sense, whilst a central...

Metal matrix composites (MMCs) represent a new generation of engineering materials in which a strong reinforcement is incorporated into a metal matrix to improve its properties including specific strength, specific stiffness, wear resistance, corrosion resistance and elastic modulus. Aluminum matrix composites (AMCs), a specific type of MMCs, are r...

This paper provides a comprehensive assessment of the tensile and sliding wear behaviour of WC-10Co4Cr agglomerated and sintered powder deposited on aluminum by Hyper Velocity Oxy-Fuel (HVOF) process. Microstructural analysis (SEM) identified grains of tungsten carbide (WC) in the metal matrix of the cobalt-chromium (Co-Cr). A transformation of the...

In today’s modern manufacturing, software automation is crucial element for leveraging novel methodologies and integrate various engineering software environments such Computer aided design (CAD), Computer aided process planning (CAPP), or Computer aided manufacturing (CAM) with programming modules with a common and a comprehensive interface; thus...

This paper suggests the application of genetic algorithms for the intelligent generation of optimum sculptured surface CNC machining tool-paths. Two robust full quadratic mathematical models are developed relating the physical relation among machining surface deviation and resulting cutting time; quality objectives which are treated as conflicting...

One of the key elements of digital manufacturing (including design-planning-production-inspection value chain) is a simulation i.e. virtual modelling of all processes that belong to the manufacturing chain. Simulations are frequently used to optimise some of the processes of digital manufacturing, in order to improve quality of the process itself a...

This paper studies the effect of a cermet HVOF WC-Co-Cr coating on the mechanical behaviour of steel substrate. The HVOF WC-Co-Cr coating was found to reduce the tensile strength of the steel. The failure of the HVOF WC-Co-Cr coated steel specimens initiated by cracking on the coating surface, transverse propagation of the cracks towards the coatin...

International Tolerance (IT) grade approach was applied for tolerance assessment of the PolyJet Direct 3D printing process (PJD-3DP). Linear sizes of parallel opposite surfaces as well as the diameter of cylinders were measured eight (8) times each one, at eight (8) different test parts which were, all of them, printed using the same optimized para...

Low cost 3D printing' is a terminology that referred to the fused filament fabrication (FFF) technique, which constructs physical prototypes, by depositing material layer by layer using a thermal nozzle head. Nowadays, 3D printing is widely used in medical applications such as tissue engineering as well as supporting tool in diagnosis and treatment...

In this study we investigate the dimensional accuracy of 3D printed objects and define the International Tolerance (IT) Grade for the linear sizes of parallel opposite surfaces and the diameter of a cylinder. Eight (8) exact parts were printed by an Objet Eden250 3D printer using the Multi Jet Modelling (MJM) process. The printed objects were measu...