Method of Preparation for Restoration of Worn Nitrided Journals of Crankshafts

The internal combustion engine is the most expensive component of a car, which determines the reliability and efficiency of its use. Studies show that one of the most common reasons for the failure of KAMAZ diesel engines during operation is the underutilization of the crankshaft resource due to wear of parts and couplings that limit its resource. An increase in the resource of crankshafts can be achieved by improving the technological processes of restoration and repair. Full utilization of the resource of KAMAZ nitrided crankshafts is possible by surfacing worn journals only after removing a nitrided layer up to 0.4 mm thick from the journals surface using specialized equipment for electrical discharge machining. Electrical discharge machining is based on the removal of material particles from the surface by an electric discharge pulse between electrodes immersed in a liquid dielectric, in the channel of which a high-temperature plasma is formed.

Development of Multi-Wire Electric Discharge Machining for SiC Wafer Processing

In order to slice the larger size ingot toward 6 inch of silicon carbide (SiC), we are developing Multi-wire Electric Discharge Machining (EDM). To prevent wire break during slicing, we have developed the electric discharge pulse control system. So far, with 10 multi-wires, we have succeeded in slicing of 4 inch SiC balk single crystal without wire break. High quality slicing surface (e.g. small value of around 10 μm of SORI for 3 inchi wafer) was also achieved. By polishing methode, EDM-sliced wafer was estimated to have the uniform thickness of damaged layer over the entire surface. We confirmed that the wafer sliced by EDM can be processed in the later process, by grinding the 3 inch wafer. And it was confirmed that 6 inch ingot can be sliced with 10 multi-wire EDM, by slicing the boule of SiC poly crystal. For the larger diameter ingot than 4 inch, Multi-wire EDM will be practically used by the effective removal of machining chips from the machining clearance between the wire and work.

Influence of Correlation between Electrical Discharge Machining Parameters with the Formation of Surface Defect’s in Products Machined by EDM

This paper shows a study of correlation between EDM´s parameters with the level of superficial defects development, which can lead to premature failure of die cast mold machined by EDM. The correlation of parameters was determined through experimental matrix that uses the DOE methodology (Design of Experiment). In order to evaluate the surfaces of some machined samples a stereo optical microscopy, SEM (the scanning electron microscope) and a micro hardness profile machine were used. The results show that in the worst machining condition, which is caused by association of long electric discharge pulse time-on and graphite machine-electrode, it is possible to minimize the amount of surface defects, without applying a subsequent machining process such as polishing, just using the reduced time-on´s electric discharge pulse, copper electrode and dielectric fluid with base of hydrocarbon.