An artificial neural network for dimensions and cost modelling of internal micro-channels fabricated in PMMA using Nd:YVO4 laser

For micro-channel fabrication using laser micro-machining processing, estimation techniques are normally utilised to develop an approach for the system behaviour evaluation. Design of Experiments (DOE) and the Artificial Neural Networks (ANN) are two methodologies that can be used as estimation techniques. These techniques help in finding a set of laser processing parameters that provides the required micro-channel dimensions and in finding the optimal solutions in terms reducing the product development time, power consumption and of least cost. In this work, an integrated methodology is presented in which the ANN training experiments were obtained by the statistical software DoE to improve the developed models in ANN. A 33 factorial design of experiments (DoE) was used to get the experimental set. Laser power, P; pulse repetition frequency, PRF; and sample translation speed, U were the ANN inputs. The channel width and the produced micro-channel operating cost per metre were the measured responses. Four Artificial Neural Networks (ANNs) models were developed to be applied to internal micro-channels machined in PMMA using a Nd:YVO4 laser. These models were varied in terms of the selection and the quantity of training data set and constructed using a multi-layered, feed-forward structure with a the back-propagation algorithm. The responses were adequately estimated by the ANN models within the set micro-machining parameters limits. Moreover the effect of changing the selection and the quantity of training data on the approximation capability of the developed ANN model was discussed

Evaluation of the effect of ND:YVO4 laser parameters on internal micro-channel fabrication in polycarbonate

This paper presents the development of Artificial Neural Network (ANN) models for the prediction of laser machined internal micro-channels’ dimensions and production costs. In this work, a pulsed Nd:YVO4 laser was used for machining micro-channels in polycarbonate material. Six ANN multi-layered, feed-forward, back-propagation models are presented which were developed on three different training data sets. The analysed data was obtained from a 33 factorial design of experiments (DoE). The controlled parameters were laser power, P; pulse repetition frequency, PRF; and sample translation speed; U. Measured responses were the micro-channel width and the micro-machining operating cost per metre of produced microchannel. The responses were sufficiently predicted within the set micro-machining parameters limits. Three carefully selected statistical criteria were used for comparing the performance of the ANN predictive models. The comparison showed that model which had the largest amount of training data provided the highest degree of predictability. However, in cases where only a limited amount of ANN training data was available, then training data taken from a Face Centred Cubic (FCC) model design provided the highest level of predictability compared with the other examined training data set

Analysis of the Effects of 3DP Parameters on Part Feature Dimensional Accuracy

3D printing (3DP) is a widely investigated scaffold manufacturing process for Tissue Engineering (TE). Useful scaffold geometries should have high porosity (60-80%) with small (100-500 μm) interconnected pores. Therefore dimensional accuracy on the micron level is one of the crucial parameters of the bone scaffolds. Previously it was shown that the behavior of scaffold geometries can be well simulated with Finite Element Modeling (FEM) however the prediction of actual strength and stiffness values are dependent on dimensional accuracy. This accuracy is in turn dependent on several parameters including particle size and shape, powderbinder interaction, and machine setup. In this work different scaffold strut sizes (0.3 - 0.5 mm) have been fabricated using two different plaster powders (zp102 and zp130) with variations in shell saturation levels, part print position, and part print orientation. The parameters for each powder were analyzed using a full 35 factorial experimental design. It was found that the part size and orientation had a significant effect on the dimensional accuracy while the influence of the shell saturation and position was relatively small. The results allow for better dimensional specification for scaffold geometry fabrication by defining the process parameters in 3DP that may be used further in scaffold accuracy optimization.Mechanical Engineerin

Designing pulse laser surface modification of H13 steel using response surface method

This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software was used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 8m and 150 8m. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 8m. The maximum hardness achieved was between 728 and 905 HV0.1.These findings are significant to modern development of hard coatings for wear resistant applications

Laser surface modification of Ti-6Al-4V for biomedical applications

Introduction. Ti-6Al-4V is used in biomedical engineering due to its excellent properties: high strength to weight ratio, low density, high corrosion resistance and good biocompatibility. However, the use of the alloy under severe friction conditions is restricted due to poor tribological properties such as high coefficient of friction and low hardness [1, 2]. Laser surface modification is known for its improved mechanical and tribological properties for biomedical titanium alloys. The treatment produces minimal contamination and increases osseointegration [3-5]. The present study evaluated the effects of high speed, laser processing parameters on surface roughness, hardness, chemical composition and biocompatibility. Materials and Methods A 1.5KW CO2 laser in continuous mode was irradiated on flat Ti-6Al-4V samples at three levels of irradiance 15.72, 20.43 and 26.72 KW/cm2 and three levels of residence time 1.08, 1.44 and 2.16 ms. Evaluation of the surface was carried out by scanning electron microscope (SEM) examination and mechanical profilometry in accordance to ISO 4287/4288. SEM analysis of the surface topography resulting from the various laser treatments was carried out. Energy Dispersive Spectroscopy (EDS) analysis was used to determine the chemical composition of the treated areas. The effect of surface topography on cellular attachment was investigated in vitro using MC3T3-E1 pre-osteoblast cells. Cell attachment was determined using the Hoechst DNA assay and cell morphology was examined using SEM analysis. Results and Discussion An increase in residence time resulted in improved depth of processing. An increase in irradiance did not always produce an increase in depth of processing; however higher irradiance levels were found to provide for a more uniform depth of processing which reached a maximum of 80 µm. Irradiation with the scanning beam produced a single phase microstructure, see Figure 1. This single phase occurred when various constituents in the alloy have dissolved with rapid solidification thwarting segregation of the various alloying elements into high and low concentration [6]. Improved homogenous chemical composition of the laser modified region was verified by the EDS analysis. Microhardness examination revealed an increase in hardness of up to 67% after laser treatment. A relationship between irradiance and roughness was observed, roughness decreasing with increase in irradiance

Employer and student perspectives on skills for engineers in the twenty first century and beyond

This research focused on skills identified among final year engineering students. It provided evidence of different levels of skills by students and identifies their greatest learning influences in these areas. The skills were self-assessed by students and covered seven areas designated by Engineers Ireland. Competency levels such as science, software, creativity, engineering practice, social and business, ethics, discipline specific were assessed. It also investigated the important role that work placements play in skills developed by students. Key skills sought by leading Engineering firms from graduates now and in the next five years were also researched in this paper. Employers were surveyed to determine and investigate skills needed from graduate engineers and how best to meet these challenges. The emphasis on work placements and its impact on skills’ development in engineering students such as business acumen and working effectively and efficiently in industry were highlighted

Investigation of factors affecting the learning of final year advanced materials and manufacturing students

An investigation was recently conducted into the delivery of an Advanced Materials and Manufacturing Processes module which was presented to a sub-group of the final year engineering students at Dublin City University (DCU). Results from the class which has just completed their final year studies were examined in relation to the method of delivery. This cohort consisted of 25 students, 13 which studied for the Computer Aided Mechanical and Manufacturing Engineering (CAM) degree and 12 which studied for the Business and Manufacturing Engineering (BME) degree. This paper presents an examination of some of the factors affecting the overall results of these students. Factors evaluated include attendance of the student, as well as individual performance in continuous assessment and examination. Overall attendance at the lecture, the organised seminar series, and practical work were recorded. Results indicate a direct link between attendance and marks awarded. Students with higher attendance achieved better grades. Good continuous assessment performance did not automatically indicate good exam performance. Contrary evidence to this is discussed in relation to student learning styles where students may show better ability in exams with poorer ability in continuous assessment and vice versa

The dynamic viscoelastic characterisation of the impact behaviour of the GAA sliotar

In recent years variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, became evident in championship matches. The current standard has not provided adequate repeatability of ball performance. A new method for assessing the dynamic impact behaviour of approved sliotar cores has been characterised. This test system was developed to measure the performance characteristics, such as coefficient of restitution, deformation and contact time, and the viscoelastic properties of dynamic stiffness and hysteresis energy dissipation. In this paper, the relationship between the viscoelastic properties and the coefficient of restitution is presented

Affects of student attendance on performance in undergraduate materials and manufacturing modules

This paper investigates the class attendance of second year, third year and fourth year students and their overall performance at the school of Mechanical and Manufacturing Engineering in Dublin City University (DCU). An investigation was recently conducted into the delivery of different module which was presented to a group of second year, third year and fourth year engineering students at DCU. Attendance in the class was recorded and the continuous assessment results and the final overall performances were investigated with their attendance. Student performance on Strength of materials – part 1 (SM1), Strength of materials part - 2 (SM2), Mechanics of Materials and Machine (MMM) and Advanced Materials and Manufacturing Processes (AMMP) modules are presented in this paper. This paper presents an examination of some of the factors affecting the overall results of these students. Factors evaluated include attendance of the student, as well as individual performance in continuous assessment and examination. Overall attendance at the lecture, the organised seminar series, and practical work were recorded. Results indicate a direct link between attendance and marks awarded. Students with higher attendance achieved better grades