Micro-EDM manufacturing of different micro-textures for scaffold realization made on Si3N4-TiN has been presented in pursuit of identifying minimum geometrical limits on machinable micro-pins textures. The results show that the minimum machinable pin-size is strictly dependent on the energy level adopted to realize the texture. In fact, a lower energy level implies the possibility of realizing minimum pin-size though, at the same time, a drastic increase in the erosion time should be expected. MRR and TWR have been evaluated for the different machining regimes. Comparing table 2 and table 5 it can be highlighted that: ousing an electrode tool having Del= 0.4mm, a reduction for MRR and TWR has been recorded when cavities with higher AR are machined using high energy levels (E206 and E110); ousing a micro-electrode having Del= 0.1mm, MRR decreases or remains constant (E110 and E15, respectively), TWR increases of the same quantity for both energy levels; ousing a 0.02mm micro-electrode tool diameter, MRR exhibits very small value (almost irrelevant), whereas TWR slightly increases with respect to the one measured for electrode diameter of 0.1mm. Three different textures, using the test results, have been machined as demonstrators: o19 pins, arranged in a square matrix, with a section of 0.05x0.05 mm2 and height equal to 0.2 mm, minimum pin-to-pin distance equal to 0.425 mm, have been machined using energy level E110; o12 pins, arranged in a square matrix, having section of 0.02x0.02 mm2 and height equal to 0.1 mm, minimum pin-to pin distance of 0.12 mm, have been milled using energy level E15. The last texture composed by 12 pins arranged in a square matrix, machined with an electrode diameter of 0.02mm and for a depth of 0.02mm, has not been correctly produced (no pins were found). During all tests and for all considered machining regimes, the process revealed a certain instability, along with the occurrence of sporadic short circuits. Some energy level seems to be less stable than other: E15 and E365 are less stable than E110, instead E206 seems to settle in the middle. These behaviors can be imputed to the presence of a porous surface due to recast of nitrogen particles. This recast layer induced by the ceramic decomposition might cause a process instability.
Ceramic Si3N4-TiN machined via micro-EDM: scaffold fabrication for hard tissue reconstruction
2012
Abstract
Micro-EDM manufacturing of different micro-textures for scaffold realization made on Si3N4-TiN has been presented in pursuit of identifying minimum geometrical limits on machinable micro-pins textures. The results show that the minimum machinable pin-size is strictly dependent on the energy level adopted to realize the texture. In fact, a lower energy level implies the possibility of realizing minimum pin-size though, at the same time, a drastic increase in the erosion time should be expected. MRR and TWR have been evaluated for the different machining regimes. Comparing table 2 and table 5 it can be highlighted that: ousing an electrode tool having Del= 0.4mm, a reduction for MRR and TWR has been recorded when cavities with higher AR are machined using high energy levels (E206 and E110); ousing a micro-electrode having Del= 0.1mm, MRR decreases or remains constant (E110 and E15, respectively), TWR increases of the same quantity for both energy levels; ousing a 0.02mm micro-electrode tool diameter, MRR exhibits very small value (almost irrelevant), whereas TWR slightly increases with respect to the one measured for electrode diameter of 0.1mm. Three different textures, using the test results, have been machined as demonstrators: o19 pins, arranged in a square matrix, with a section of 0.05x0.05 mm2 and height equal to 0.2 mm, minimum pin-to-pin distance equal to 0.425 mm, have been machined using energy level E110; o12 pins, arranged in a square matrix, having section of 0.02x0.02 mm2 and height equal to 0.1 mm, minimum pin-to pin distance of 0.12 mm, have been milled using energy level E15. The last texture composed by 12 pins arranged in a square matrix, machined with an electrode diameter of 0.02mm and for a depth of 0.02mm, has not been correctly produced (no pins were found). During all tests and for all considered machining regimes, the process revealed a certain instability, along with the occurrence of sporadic short circuits. Some energy level seems to be less stable than other: E15 and E365 are less stable than E110, instead E206 seems to settle in the middle. These behaviors can be imputed to the presence of a porous surface due to recast of nitrogen particles. This recast layer induced by the ceramic decomposition might cause a process instability.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
