Using parametric design way, water hydraulic axial piston pump's main internal parts include piston, slipper and valve plate were designed, which improves the design efficiency and quality.

One reason for the slipper piston is that, on the short-stroke, over square engine, the piston skirt had to be cut away to make room for the counterweights on the crankshaft.

A lot of study showed that the friction of the ball friction coupling between piston and slipper obviously affected the life-span and the performance of the axial piston pump.