Development of Ni Powder EDM Combined with Electro-rheological Polishing Process
Date Issued
2010
Date
2010
Author(s)
Hung, Ming-Chih
Abstract
In the past half century, EDM（Electrical Discharge Machining）has overcome
the difficulty of shaping hard-cutting materials, which traditional cutting methods could not accomplish. Hence, it plays a vital role in manufacturing. However, owing to electrical and thermal effect, craters and recast layers often appear on surfaces after machining. In this study, we try to combine powder-EDM and electro-rheological fluid, making EDM to become a much more mature machining, and the key points are dielectric selection and gap controlling. First, behaviors of different powders between a fixed gap are observerd by various voltage. Second, the ER effect critical gap and discharging maximum gap are obtained by controlling gap sizes. Furthermore, critical rotation speed is also discussed. Last, many factors are chosed to proceed SKD11 surface polishing, such as viscosity, powder species and mixed ratios, electrode sizes, voltage values, gap depths.
Experiment underwent under 300V. The result shows that ER effect isn’t strong enough when the gap is larger than 300μm, even though the machining time is 1hr, there’s almost no Ra improvement. When the gap is between 100μm and 300μm, it presents an pure ER polishing effect. When the gap is between 50μm and 100μm, ER effect accompanies with discharge, micro discharging points occured on workpiece, but the surface is still lighter and smoother. In all, low viscosity working fluid and mixed ratio 1:1 of starch and Ni are recommanded, the powder EDM could be carried out uniformly when gap is 50μm, and polishing process could be conducted while gap between 120μm and 150μm.
Subjects
Electro-rheological fluid
powder-mixed dielectric discharge
surface improvement rate
Type
thesis
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