This paper presents a manufacturing method for a zero-stiffness compliant mechanism to be used as a flexible head support. The manufactured design consists of two curved, thin-walled U-beams made of high strength steel. The beams are prestressed in opposite directions to obtain zero torsional stiffness so that rotation of the head is allowed. The presented manufacturing method for the beams consists of three different steps; (1)Production of a straight U-beam using a saw mill, (2)Bending the U-beam with a bending tool based on press die forming, (3)Heat treatment to increase the strength of the profile.
C75 high strength steel is used for the production of the beams. The straight U-beams with a wall thickness of 0.4 mm were produced within an accuracy of 0.03 mm. The formed U-beams in step 2 approximately follow the desired curve with a maximum lateral error of 1mm which is deemed sufficient for this application. Finally, the beams were strengthened using a standard quenching and tempering heat treatment which increased the yield strength with a factor of 4 up to 1650 MPa. A prototype was made which consists of a 3D printed lower and upper base, as well as two prestressed curved U-beams produced with the presented manufacturing method. The performance of the compliant mechanism design with the produced beams is analysed in terms of the moment-angle curve. Prestressing reduced the maximum moment between -60 and 60 degrees with a factor of about 60 to 0.015 Nm.