Abstract
Purpose This study aims to investigate the potential of using polymer multi-material additive manufacturing (MMAM) to produce miniature hydraulic piston actuators combining rigid structures and flexible seals. Such actuators offer great potential for medical robots in X-ray and magnetic resonance environments, where conventional piston actuators cannot be used because of safety issues caused by metal components. Design/methodology/approach Hydraulic pistons with two different integrated flexible seal shapes are designed and manufactured using MMAM. Design 1 features a ring-shaped seal made from a flexible material that is printed on the surface of the rigid piston shaft. Design 2 appears identical from the outside, yet an axial opening in the piston shaft is added to enable self-reinforced sealing as fluid pressure increases. For both designs, samples with three different outer diameters are fabricated leading to a total of six different piston versions. The pistons are then evaluated regarding leakage, friction and durability. Findings Measurement results show that the friction force for Design 2 is lower than that of Design 1, making Design 2 more suitable for the intended application. None of the versions of Design 2 shows leakage for pressures up to 1.5 MPa. For Design 1, leak-tightness varies with the outer diameter, yet none of the versions is consistently leak-tight at 1.5 MPa. Furthermore, the results show that prolonged exposure to water decreases the durability of the flexible material significantly. The durability the authors observe may, however, be sufficient for short-term or single-use devices. Originality/value The authors investigate a novel design approach for hydraulic piston actuators based on MMAM. These actuators are of particular interest for patient-specific medical devices used in radiological interventions, where metal-free components are required to safely operate in X-ray and magnetic resonance environments. This study may serve as a basis for the development of new actuators, as it shows a feasible solution, yet pointing out critical aspects such as the influence of small geometry changes or material performance changes caused by water absorption.
Highlights
Image-guided surgery is an emerging medical field, in which imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI) are used to provide intraoperative guidance during minimally invasive procedures such as tissue biopsies or tumor destructions (Monfaredi et al, 2018)
Printing process The pistons are produced with an Objet Connex350 3D printer using the PolyJet technology (Stratasys Ltd, the USA), which is based on photopolymerization
The aim of this work was to evaluate whether the capabilities of multi-material additive manufacturing (MMAM) technology can be exploited to design and produce hydraulic actuators with integrated seals for medical robots
Summary
Image-guided surgery is an emerging medical field, in which imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI) are used to provide intraoperative guidance during minimally invasive procedures such as tissue biopsies or tumor destructions (Monfaredi et al, 2018). The current issue and full text archive of this journal is available on Emerald Insight at: https://www.emerald.com/insight/1355-2546.htm. Because of the limited space available inside the scanner bore (usually a diameter of 60 cm), remote robotic manipulators.
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