Stergios Maropoulos

Process build‐time estimator algorithm for laminated object manufacturing

A method for estimating the build‐time required by the laminated object manufacturing (LOM) process is presented in this paper. The proposed algorithm – taking into account the real process parameters and the information included in the parts STL‐file – performs a minimum manipulation of the file, and calculates total volume, total surface area and flat areas involved in fine cross‐hatching. A number of experiments performed verify the applicability of the algorithm in process build‐time estimation. The time prediction estimates are within 7.6 per cent of the real build‐times for the LOM process. It is believed that, through specific minor adjustments, the algorithm could well be employed in process build‐time estimation for similar rapid prototyping processes.

A parameter design of CNC plasma-arc cutting of carbon steel plates using robust design

An optimisation of the cutting parameters during CNC plasma-arc cutting of St37 mild steel plates is attempted using robust design. The process parameters tested were plate thickness, cutting speed, arc ampere, arc voltage, air pressure, pierce height, and torch standoff distance. An orthogonal matrix experiment [L18 (21 × 37) ] was conducted and the right bevel angle was measured and optimised according to the process parameters using an analysis of means and an analysis of variances. The results show that the arc ampere has an effect mainly on the bevel angle (50.89%), while the plate thickness and torch standoff distance also have an influence of 6.22 and 15.9% respectively. The other parameters have an F factor smaller than one, and thus their variations do not significantly affect the bevel angle in the experimental region. Finally, an additive model was applied on the experimental results to predict the optimum combination and was compared with actual values.

An investigation of surface texture parameters during turning of a reinforced polymer composite using design of experiments and analysis

The influence of cutting speed and feed rate during turning on the arithmetic mean roughness (Ra), the maximum peak to valley (Rt), and the fractal dimension (D) of a glass fibre polymer composite (Ertalon 66 GF-30) was experimentally investigated. Test specimens in the form of bars and a P20 cemented carbide cutting tool were used with the cutting depth kept constant during the experiment. Robust design using an orthogonal matrix experiment was conducted and the experimental results were analysed using an ANOM and an ANOVA analysis approach. Based on the statistical analysis of the experimental results it was found that the arithmetic mean roughness, the maximum peak to valley and the fractal dimension depend mainly on the feed rate parameter. Also, based on the interaction charts and evaluation experiments it was found that regression modelling applies only for the arithmetic mean roughness.

An ANN Approach on the Optimization of the Cutting Parameters During CNC Plasma-Arc Cutting

The objective of the present study is to develop an Artificial Neural Network (ANN) in order to predict the bevel angle (response variable) during CNC plasma-arc cutting of St37 mild steel plates. The four (4) input parameters (plate thickness, cutting speed, arc ampere, and torch standoff distance) of the ANN was selected following the results (relative importance) of the Analysis Of Variance (ANOVA) performed based on seven (7) factors (plate thickness, cutting speed, arc ampere, arc voltage, air pressure, pierce height, and torch standoff distance) in a previous study. A multi-parameter optimization was carried out using the robust design. An L18 (21 × 37 ) Taguchi orthogonal array experiment was conducted and the right bevel angle was measured, aiming at the investigation of the influence of plasma-arc cut process parameters on right side bevel angle of St37 mild steel cut surface. The selection of quality characteristics, material, plate thickness and other process parameter levels and experimental limits was based on the experience and current needs of the Greek machining industry. A feed-forward backpropagation (FFBP) neural network was fitted on the experimental data. The results show that accurate predictions of the bevel angle can be achieved inside the experimental region, through the trained FFBP-ANN. The developed ANN model could be further used for the optimization of the cutting parameters during CNC plasma-arc cutting.Copyright

Medical Rapid Prototyping and Manufacturing: Status and Outlook

Rapid Prototyping (RP) has been considered, over the last decades, as a highly promising technology for reducing product development time and cost, as well as for addressing the need for customization and faster response to the market needs. Nowadays this technology is also used widely in medical applications (Medical Rapid Prototyping – MRP), supporting diagnosis and treatment in Neurosurgery, Orthopedic and Dental-Cranio-Maxillo-Facial surgery as well as in Tissue Engineering. The scan data that are usually obtained by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) are used to build a 3D CAD model of the patient’s pathological region. The 3D model is used to construct the real size prototype using one of the existing RP processes. This assists surgeons in gaining a detailed insight of the problem, making the diagnosis and treatment easier and more reliable. This study presents the current benefits and barriers of Rapid Prototyping and Manufacturing methods and applications in the field of medicine. Most of the recent state-of-art developments and case studies of MRP are presented. Their limitations are discussed along with the challenges to be addressed in the future.Copyright

The Impact of FEM Modeling Parameters on the Computed Thermo-Mechanical Behavior of SLA Copper Shelled Electrodes

In this study, the authors use the finite element method to model and analyse a cylindrical copper shelled SLA electrode for EDM operations, which is investigated experimentally in literature. A uniform silver paint thickness and copper shell thickness is assumed around the SLA epoxy core. In the experiment, 2-D analysis was used due to the axissymmetric shape, and steady state and transient die sink EDMing simulations were followed. Modelling parameters are varied and their impact on the resulting temperature and stress fields is evaluated. The intermittent nature of the electrode thermal loading is also simulated with FEM transient analysis. It is shown that, using the finite element method, the influence of the copper shelled SLA electrode manufacturing and EDM-process parameters can be studied.