Grundfos : Gearbox for Hydronic Valve (A Practical Setup)

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The design enables effortless assembly and reassembly along the Z-axis. To ensure concentricity and alignment remain intact even after multiple setups, the enclosure box features precision-engineered extrusions that guide components into place with minimal adjustments required.Stepped Planetary gear was chosen for its superior reduction ratio per gearbox width compared to two-stage planetary transmission. Furthermore, ring gear fasteners can share the radial stress of 300 N on the shaft, a load that would otherwise be borne alone by the bearing. Additionally, Stepped Planetary gear is more efficient, precise and compact than simple spur gear reduction.Gear ratio is 597:1, taking into account 5% losses at each spur gear mating and an overall 5% loss in the planetary set.The primary objective of the design was to minimize possible vibrations in shafts and gears. To achieve this, several strategies were implemented, including positioning the gearbox as close to the base as feasible (in our case, limited to 35mm out of the allowed 50 mm from the base), providing sufficient bearing support to the shafts, and eliminating keys by integrating gears directly onto shafts.The design assumes that the enclosure box lacks sufficient strength to secure components using threads. Threaded inserts have been incorporated into the design to hold components in place. Depending on production quantity and equipment availability, these can be added either before molding (Insert Molding) or after using heated shafts.