Design of a pulse power supply unit for micro-ECM

Electrochemical micro-machining (μECM) requires a particular pulse power supply unit (PSU) to be developed in order to achieve desired machining performance. This paper summarises the development of a pulse PSU meeting the requirements of μECM. The pulse power supply provides tens of nanosecond pulse duration, positive and negative bias voltages and a polarity switching functionality. It fulfils the needs for tool preparation with reversed pulsed ECM on the machine. Moreover, the PSU is equipped with an ultrafast overcurrent protection which prevents the tool electrode from being damaged in case of short circuits. The developed pulse PSU was used to fabricate micro-tools out of 170 μm WC-Co alloy shafts via micro-electrochemical turning and drill deep holes via μECM in a disk made of 18NiCr6. The electrolyte used for both processes was a mixture of sulphuric acid and NaNO3 aqueous solutions.The research reported in this paper is supported by the European Commission within the project “Minimizing Defects in Micro-Manufacturing Applications (MIDEMMA)” (FP7-2011-NMP-ICT-FoF-285614

Design of an electrochemical micromachining machine

Electrochemical micromachining (μECM) is a non-conventional machining process based on the phenomenon of electrolysis. μECM became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro applications including microfluidics systems, stress-free drilled holes in automotive and aerospace manufacturing with complex shapes, etc. This work presents the design of a next generation μECM machine for the automotive, aerospace, medical and metrology sectors. It has three axes of motion (X, Y, Z) and a spindle allowing the tool-electrode to rotate during machining. The linear slides for each axis use air bearings with linear DC brushless motors and 2-nm resolution encoders for ultra precise motion. The control system is based on the Power PMAC motion controller from Delta Tau. The electrolyte tank is located at the rear of the machine and allows the electrolyte to be changed quickly. This machine features two process control algorithms: fuzzy logic control and adaptive feed rate. A self-developed pulse generator has been mounted and interfaced with the machine and a wire ECM grinding device has been added. The pulse generator has the possibility to reverse the pulse polarity for on-line tool fabrication.The research reported in this paper is supported by the European Commission within the project “Minimizing Defects in Micro-Manufacturing Applications (MIDEMMA)” (FP7-2011-NMPICT- FoF-285614)

Maternal factor V Leiden mutation is associated with HELLP syndrome in Caucasian women

Objective. There is growing evidence that hypertensive pregnancy complications and other adverse pregnancy outcomes are associated with the presence of inherited or acquired thrombophilias. As hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome is one of the most severe forms of pre-eclampsia we aimed to assess the prevalence of the factor V Leiden, the prothrombin 20210G >A mutation and the methylenetetrahydrofolate reductase (MTHFR) 677C >T polymorphism in women with HELLP syndrome and in their fetuses from the same index pregnancy. Design. The study was performed retrospectively in a case-control design. Sample. Seventy-one mother-child pairs with HELLP syndrome and 79 control mother-child pairs with uncomplicated pregnancies were included in the study. Methods. Genotyping of the three thrombophilic mutations was performed using the LightCycler technology. The chi-squared test was used for statistical analysis. Main outcome measures were maternal and fetal genotypes and their correlation with clinical parameters. Results. Maternal heterozygosity for factor V Leiden was significantly more prevalent in the HELLP group than in controls (OR 4.45, 95% CI 1.31-15.31). No significant association was observed for maternal prothrombin mutation or MTHFR polymorphism (p=0.894, p=0.189, respectively). The fetal genotype was not associated with HELLP syndrome for any of the three mutations investigated. Analysis of gene-gene interactions and genotype-phenotype correlation with respect to clinical parameters and perinatal outcome revealed no further differences. Conclusions. Our study confirms that women heterozygous for factor V Leiden have an increased risk of developing HELLP syndrome, while the most frequent mutations of the prothrombin and MTHFR gene do not play a major role in the pathogenesis of HELLP syndrome