Experimental investigation for fine finishing of the tapered mould cavity using a newly developed GWMRF process

Moulds are being used for the manufacturing of plastic parts in most of the industries. Some of these plastic parts need fine-finished surface appearance and dimensional accuracy. To achieve these properties in end products, the fine-finished surfaces of the mould cavities are required. In this paper, fine finishing over the internal tapered longitudinal and flat end EN-31 cylindrical blind hole (CBH) type mould cavity surfaces is obtained using the magnetorheological polishing (MRP) fluid with the help of present grinding wheel type magnetorheological finishing tool. This typical mould cavity used finds its usefulness in the manufacturing of plastic spray bottle cap hoods. The process parameters such as working gap, current, workpiece rotational speed, tool rotational, and reciprocation speed are optimized to achieve fine finishing on the EN-31 CBH type mould cavity. For validation of the optimized parameters, the experiments are performed over the samples. Further, the finishing is performed on the typical mould cavity where the final roughness values after MR finishing over the tapered longitudinal surface are measured as 80 nm from 350 nm and on flat end surface is 50 nm from 320 nm. The improvement in surface characteristics can be analysed from the scanning electron microscope images. Further, to investigate dimensional accuracy of its tapered longitudinal surface, the circularity test is conducted. Thus, fine finishing of both CBH type mould cavity surfaces can be achieved with the present developed MR finishing process. This type of fine-finished mould cavities can be used for the effective manufacturing of plastic parts like bottle caps, containers, etc.