High-precision technology with negative punch clearance for the manufacturing of a cycloid pump

A high-precision technology with negative punch clearance for manufacturing a cycloid pump is proposed in this paper. Notably, the manufacturing process for this technology is similar to extrusion, except that a substantially different die and punch design was developed. Specifically, a trough engraved in a die was designed around the gear shape of a cycloid pump, and a ram with a hole through which the punch can penetrate was developed to press the billet. Thus, when the ram descends to a certain level, a portion of the billet is forced into the cave of the trough and keeps the ram from touching the bottom of the trough. In such situations, very high hydrostatic stress on the cutting edge of the die is produced. The diameter of the punch was designed to be larger than the hole of the die, but smaller than the diameter of die. Thus, when the punch descends to extrude the billet, the hydrostatic pressure around the cutting edge of the punch and die is increased; this can also substantially reduce product fracturing. An experimental test for two types of cycloid pump shapes was conducted and the results showed that a long and well-burnished product surface can be obtained within a few minutes. Notably, the mechanical clearance that effectively prevented fluid from leaking backward was measured to be less than 10 μm, which is considerably smaller than that of conventional products and verifies the potential of this technology.