Construction and manufacturing of a microgearhead with 1.9-mm outer diameter for universal application

Many new applications in medicine, telecommunication, automation systems etc. require powerful microdrives. Speeds up to 100.000 rpm and output torques in the (mu) Nm-range are typical characteristics of electromagnetic micromotors with diameters of a few millimeters. To accomplish a powerful microdrive, these micromotors have to be combined with micro gearheads of the same outer diameter. For such a micro gearhead with toothed wheels manufactured by use of the LIGA process a multi-stage planetary gear has many advantages. Many stages with different gear ratios can be combined to achieve a great number of different transmission, but manufacturing tolerances and a clearance for assembly must be respected. Therefore besides the selection of a reliable gearhead type and a suitable manufacturing process the optimization of the tooth profile is the key to the implementation of powerful micro gear systems with high output torques and efficiencies. The involute profile is the most suitable toothing, but many calculations and simulations are required to find the right modulus, total depth of teeth, profile offset etc. In a joint project Dr. Fritz Faulhaber GmbH and Co. KG and the Institut fuer Mikrotechnik Mainz GmbH developed a powerful microdevice with an outer diameter of only 1.9 mm.