Abstract
In this paper, fundamental research is performed on membrane type actuators made out of 316L stainless steel, manufactured with Laser powder bed fusion (LPBF). A total of six membranes with membrane thicknesses ranging from 0.6 mm up to 1.2 mm were scanned using a high precision metrology system to measure the membrane for displacement at different actuating pressures. The membranes were furthermore investigated for roughness, porosity and thickness. This showed that the thinnest membranes skewed in the print direction when actuated. The remaining membranes achieved higher specific displacements than finite element simulations (FES) predicted, due to surface roughness and porosity. Membrane type actuators can be used for precise actuation within the micrometre range. LPBF allows the creation of internal pockets and membranes in a single metal piece. In opposition to the more commonly used polymers for membrane-type actuators, LPBF steel printed parts offer high stiffness and actuation force. However, due to limitations of the LPBF process on thin walls, large deviations from FES occur. In this paper, a CAD and FES compensation strategy is suggested, which makes future, more complex and effective, designs possible.
Highlights
Accurate micro-positioning of a heavy load remains challenging
And at the side of each colour map, the specific displacement of a 1 mm wide section, as indicated with fine black lines, in the print direction (y-axis, vertically) and perpendicular to the print direction (x-axis, horizontally) is plotted on the charts. These two cross-sectional views reveal a correlation between skewing of the membrane and the print direction of the Laser powder bed fusion (LPBF) process, especially with the thinner membranes (Figure 5d,f)
Simulations predicted that thinner membranes would offer large strokes and large specific expansions, membranes thinner than 0.6 μm are deemed unfavourable for making actuators with current LPBF technologies
Summary
Accurate micro-positioning of a heavy load remains challenging. XY-crosstables can be used for precise micro-positioning; their maximal load is limited up to about several 10 kg. Even specialised heavy duty XY-cross-tables struggle to carry loads over 200 to 300 kg and only achieve so while increasing the size and weight of the table to a hulking presence. In addition to the challenge of micro-actuating heavy static loads, dynamic loading of XY-tables is not possible. A micro-positioning device would be backlash free and extremely stiff while actuating and while holding. The stiffness allows for a high static load with minimal deflection. There is the possibility for high dynamic loads with a neglect-able amplitude
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