Mouldability of various zirconia micro gears in micro powder injection moulding

The mouldability of various zirconia micro gears was investigated based on different binder systems. Temperature window for feedstock preparation and injection moulding was set up based on thermal analysis. Rheological properties of the feedstocks and injection moulded micro gears of different dimensions (200 to 900 μm) were examined to study the mouldability. Experimental results show that the micro gears below 500 μm were difficult to mould due to sticking and short-shot. As the low-molecule binder component, bee wax (BW) provided the feedstock with better fluidity and stability than paraffin wax (PW) to replicate the small mould. As the backbone polymer, a combination of ethylene–vinyl acetate (EVA) and high-density polyethylene (HDPE) was beneficial to mould filling and demoulding. The micro gears as small as 200 μm were injection moulded and sintered with shape retention using the feedstock comprising the binder system of HDPE, EVA, BW and stearic acid.