3D Printed Three Piston Axial Water Pump

I built this compact axial three-piston water pump as a hands-on 3D printing project because I wanted to see if I could fit a fully functional positive displacement pump into something the size of a coffee mug. It uses a rotating swash plate to drive three pistons in sequence, which keeps the water flowing smoothly. The whole pump fits inside a 6-inch cube, so it’s perfect for experimenting on a desk or dropping into a small system.

I made it partly just for the fun of tackling the design challenges—getting the sealing right, making the pistons move smoothly, and preventing backflow—but also because I like building projects that show how mechanical systems actually work.

The supplies I used for this project was primarily my Bambu A1 3D printer with PLA and TPU filament, some small 16mm OD O-rings, 30mm steel screws to join everything together, and some lithium grease to make the pistons run smoothly in the bores.

First, I planned and modeled the pump. I started by sketching an axial three-piston layout and modeled it in AutoCAD. I decided on having a 15° swash plate angle, a 3 piston bore design that was sealed with O-rings and lithium grease to prevent any air leakage, and a gear driven crank. In then moved to CAD software where I designed the housing, cylinder block, pistons, swash plate with the internal spline, and valve tubing, making sure to leave 0.1–0.2 mm clearance for sliding fits such as the pistons.

Next, I printed and prepared the parts on my Bambu A1. I used PLA for this prototype, printing at a 0.2 mm layer height with thick walls and high infill. I then pieced together the model and made sure to sand and polished the piston to the right tolerance as well as apply a light coat lithium grease to the O-rings for proper lubrication. Also, I printed the valve tubing with TPU filament so that I could fit a ball check valve inside for one way water flow.

Finally, I tested and tuned the pump. After greasing the seals, I pieced together my piston pump by attaching to two halves of the housing together making sure the pistons were fit into their grooves as I was doing so. When I tested it however, I didn’t quite get it fully working—it just needs more tuning to improve suction and adjust for backflow—but the core mechanism operated as designed, and with those adjustments, I hope to get it up and running as intended.