μRIGS – Ultra-light Micropositioning Robotics for Universal MRI Guided Interventions

Performing minimal invasive interventions under real-time image guidance proves problematic in a closed-bore magnetic resonance imaging scanner. To enable better usability in MRI guided interventions, robotic systems could be used for additional assistance. However, the integration of such devices into the clinical workflow relates to many technical challenges in order to increase precision of the procedure while ensuring the overall safety. In this work, an MR compatible, compact, ultra-light and remotely controllable micropositioning system called μRIGS is presented. The instrument positioning unit can be operated in a 5-DoF range within a working volume of 2100 cm3with an instrument feed of 120 mm. The kinematics are actuated with a combination of non-metallic Bowden cables and electric stepper motors from a safe distance inside the scanner room, while their control is initiated from the control room via a custom-fitted GUI. Thereby, the precision of the positioning reproducibility of the respective DoF can be achieved with a mean deviation of 0.12 °. Furthermore, a feed force of 14 N can be provided to puncture various soft tissue.

XYZ Micropositioning System Based on Compliance Mechanisms Fabricated by Additive Manufacturing

This article presents the design and implementation of a micropositioning system actuated by three piezoelectric stacks to control its displacements on XYZ axes. The use of conventional piezoelectric buzzers allows us to reduce fabrication costs. The working or mobile platform is the base for objects that will be manipulated, for example, in automated assembling. The micropositioner can be integrated into a microgripper to generate a complete manipulation system. For micropositioner fabrication, at first, Polylactic Acid (PLA) was chosen as the structural material, but after simulation and some experimental tests performed with a micropositioner made of Acrylonitrile Butadiene Styrene (ABS), it showed larger displacement (approx. 20%) due to its lower stiffness. A third test was performed with a positioner made with Polyethylene Terephthalate Glycol (PETG), obtaining an intermediate performance. The originality of this work resides in the geometrical arrangement based on thermoplastic polymer compliance mechanisms, as well as in the use of additive manufacturing to fabricate it. An experimental setup was developed to carry out experimental tests. ANSYS™ was used for simulation.

Electropolishing of surfaces in metallic parts obtained by Additive Manufacturing

In this paper a study of the process of Electropolishing (EP) to be applied to metallic parts obtained by Additive Manufacturing is presented. The roughness of parts obtained by Additive Manufacturing is not acceptable in many applications and consequently they require a postprocessing stage to improve the surface roughness of these parts. If the material hardness is very high, like in Stainless Steels, the process of mechanical grinding is not suitable, since there is an important wear in the tool and residual stresses can be generated in the part. EP is a process in which the roughness required is obtained without tool-part contact. The conditions for this process in 17-4PH and 316 Stainless Steel parts with a Tungsten or Lead electrode are worked out in order to achieve a fast and effective smoothing process. DC voltage and an electrolyte of H3PO4 and H2SO4 are used between the tool, which acts as the cathode, and the part, which is the anode. A micropositioning system is used to set the interelectrode gap to the optimum value. Decrease in roughness Ra from 12 m to values about 3 m with this process was achieved.