Axial piston pumps have several pistons that are arranged parallel to the drive shaft. They are available as either variable pumps or constant pumps.
Axial piston variable pumpsoperate, for example, according to the swash plate principle. They adjust the geometric output volume from maximum to zero. As a result they vary the flow rate that is provided to the consumers.
Axial piston constant pumpsoperate according to the bent axis principle. They have a constant output volume and therefore deliver a constant flow rate at a specific rotation speed.

Axial piston pump according to the swash plate principle

Axial piston pump according to the swash plate principle (source: HAWE Hydraulik SE)

Axial piston pump according to the bent axis principle

Axial piston pump according to the bent axis principle (source: HAWE Hydraulik SE)
When designing an axial piston pump, it is not only the functional principle that comes into play, but also whether the equipment is to be used in an open circuit or closed circuit.