PolyJet-Printed Bellows Actuators: Design, Structural Optimization, and Experimental Investigation

Abstract

Pneumatic bellows actuators are exceptionally suitable for Additive Manufacturing (AM) as the required geometrical complexity can easily be obtained and their functionality is not affected by rough surfaces and small dimensional accuracy. This paper is an extended version of a previously published contribution to the RoboSoft2018 conference in Livorno, Italy. The original paper (Dämmer et al., 2018) contains a simulation-driven design approach as well as experimental investigations of the structural and fatigue behavior of pneumatic multi-material PolyJet TM bellows actuators. This extended version is enhanced with investigations on the relaxation behavior of PolyJet bellows actuators. The presented results are useful for researchers and engineers considering the application of PolyJet bellows actuators for pneumatic robots.

Design of an Inkjet-Printed Rotary Bellows Actuator and Simulation of its Time-Dependent Deformation Behavior

“…The AM of suitable actuators for lightweight robots seems to be particularly challenging but the use of printed pneumatic bellows actuators presents a promising approach and could become a decisive factor for the success of pneumatic lightweight robots in the long-term. Bellows actuators overcome some of the difficulties in printing conventional pneumatic actuation systems ( MacCurdy et al, 2016 ) which require tight tolerances and smooth surfaces and the structural behavior of bellows actuators can easily be modified by varying shape and material ( Dämmer et al, 2019a ). In bellows actuators, actuation results from expansion of a deformable chamber due to pressurization.…”

“…Programming parallel deposition of droplets of different materials allows 3D multi-material objects to be produced ( Schmitt et al, 2018 ). These may consist of materials with different physical properties, such as color ( Scharff et al, 2018 ), hardness ( Stratasys, Ltd., 2017 ; Dämmer et al, 2019a ) and electrical conductivity ( Saleh et al, 2017 ); even ceramic-filled inks for abrasion-resistant components are being developed ( Graf et al, 2020 ). However, 3D inkjet printing is currently used predominantly to produce monolithic multi-material parts with soft and rigid features.…”

Leveraging Geometry to Enable High-Strength Continuum Robots

“…Utilizing endo- and exo-skeleton designs has been shown to prevent buckling and improve overall strength ( Fishman et al, 2017 ; Castledine et al, 2019 ). Bellows, which have high torsional rigidity in comparison with its flexural rigidity, have also been used in pneumatic ( Drotman et al, 2017 ; Dämmer et al, 2019 ) and concentric-tube robots ( Childs and Rucker, 2020 ) which can drastically improve the torsional strength of the overall robot. Origami-inspired structures show great promise as many of these designs can be tuned from geometric parameters and can be made on a wide range of scales ( Liu et al, 2018 ; Rus and Sung, 2018 ; Santoso and Onal, 2020 ).…”

Investigations on the Processing of Ceramic Filled Inks for 3D InkJet Printing

“…For example, when it comes to printing ever smaller structures [10,11] or simplifying the process by using physical conditions to meet economic requirements [12,13]. 3D inkjet printing differs from the above-mentioned production methods in that it allows several materials to be deposited in one process step, which could enable the production of fully functional and complete components in one printing process [14][15][16]. Layer by layer, a low-viscosity material is usually dispensed from a drop-on-demand print head via piezoelectric actuation.…”

“…To further increase the potential of 3D inkjet printing, the technology is moving from rapid prototyping to rapid manufacturing [14,15]. This creates a demand for components with suitable mechanical properties.…”