The figure aside shows a ring with a spark eroded(EDM) virtual pivot proper to accommodate two leaflet in ceramic material having the function of cardiac valve with low hemolysis and high biocompatibility. EDM technology was proved perfectly suitable to the removal of small quantities of titanium with great precision and reproducibility of results. Each ring previously worked on conventional machine for chip removal is mounted in the frames that allow movement along the production layout. The first step of this path consists in the removal of 90% of the material of the virtual pivot using a roughing electrode in graphite and appropriate electrical parameters designed to streamline operations. After a similar operation carried out on the same ring, but on the opposite side to obtain a second pivot, it passes to the finishing step always with EDM, but with different parameters suitable to produce the maximum dimensional accuracy of the two impressions-hinge by providing at the same time finishing an excellent surface for the continuation of the further steps of polishing provided from the layout. At the end are fitted with two wings that rotate on the hinges practically without friction .
Bileaflet valve – virtual pivots
