Micro cycloid-gear system fabricated by multi-exposure LIGA technique

In this paper, a prototype of 2 mm-diameter micro-cycloid gear system fabricated by the multi-exposure LIGA technique is presented. The entire gear system consists of a casing and three vertically stacked disks and gears. Each part is composed of three different levels. The first level, 40 mu m high, was fabricated by UV-lithography, and the second as well as the third level, 195 mu m and 250 mu m high respectively, were processed by aligned deep X-ray lithography (DXL). The alignment error between two DXL-processed layers was measured, and the results have turned out to be within +/-5 mu m range. As a result of the height control process by the mechanical surface machining, the deviation of structural height has been maintained within +/-3 mu m range for the UV-lithography-processed structures, and +/-10 mu m for the DXL-processed structures. Further the tests of gear assembly were implemented with 125 mu m-diameter glass fiber,by using a die-bonding machine with vacuum gripper under stereo-microscope. Finally the dynamic tests of the gear system were successfully conducted with the mechanical torque input by an electrical motor. A proper rotational speed reduction was observed in the operational input range of 3 to 1500 rpm with the designed gear ratio of 18.