Exploring the performance of 3D-printed custom piston-cylinder systems

Abstract

Background Pneumatic actuators are widely used in applications like (medical) robots, or prosthetics. They require tight tolerances to keep them leakage-free. Over the last decade 3D-printing, or additive manufacturing, has emerged as a cost-effective production method in these applications.
Objective The goal of this research is to study the possibility of creating a pneumatic linear actuator with additive manufacturing. The focus is on finding sealing mechanisms which can have a positive influence on preventing leakage and friction force in the 3D-printed actuator. Furthermore we aimed to use the advantage of 3D-printing to create pneumatic actuators with a non-circular cross-section.
Methodology To evaluate the performance of a 3D-printed pneumatic actuator, a test setup is designed to measure the leakage and sliding friction force. Furthermore, we designed two pneumatic actuators with a non-conventional cross-sectional shape and validated their performance.
Results The choice for the optimal sealing mechanism in 3D-printed pneumatic actuators depends on the application in mind. For low-pressure situations the single-acting cup-shaped NAPN sealing is recommended, with a measured friction force of 6.7 N at a pressure of 0.1 MPa for one entire movement cycle (extending and retracting stroke together). For high pressure situations the double acting KDN sealing shows the lowest friction force while remaining leakage-free (13.5 N for the entire stroke at a pressure of 0.7 MPa). Furthermore, we have proven it possible to print pneumatic cylinders with a non-cylindrical cross section.
Conclusion We demonstrated a method to create leakage-free pneumatic linear actuators with additive manufacturing. For low pressure applications we showed first steps towards 3D-printed pneumatic actuators with non-circular cross-section of the piston, allowing more design freedom for these actuators.