Design Example: Open Hub (3D Printed)

This sample is a single-axis rotating ball-bearing hub with an open center suited for passing through wiring or other structure. The hub is built around a single ball bearing of type 6707, 35x44x5 mm. The inner and outer hubs have snap-fit tabs to grip the inner and outer races. Holes are provided for press-fit inserts which accept M3 screws. In this view, the lower half has a 60 mm outer diameter (OD) and the upper half has a 72 mm OD. The assembled hub is 20 mm thick. The design could be easily adapted for other bearing sizes or to include additional features such as gear or timing belt teeth.

The hub parts are sensitive to printing orientation. The snap-fit tabs need to flex during assembly and will tend to break off unless some of the print fibers run along the long axis of the tab (e.g. parallel to the bearing axis). This leads to printing the hub parts ‘on-edge’.

An alternate version of the parts without snap-fit features is available as a SolidWorks configuration. This is simpler to print, but the axial constraint to pulling the halves apart is only frictional.

The SolidWorks model files and STL 3D printing fabrication files may be found in the SolidWorks/open-hub-demo folder, or may be downloaded as a single file as open-hub-demo.zip.

Other Views

Section view of the open hub showing the snap-fit tabs gripping the bearing.

The hub with all inserts and screws installed. The intent is for the hub to be screwed between two panels.

Layout for fabricating both hub parts in a single 3D printer job. The parts fit within the 120 mm bounding box of the IDeATe Stratasys. Note the ‘on-edge’ orientation for bending strength in the snap-fit tabs.

Alternate version of the hub without the snap-fit tabs. This is simpler to print and can be successfully printed in a horizontal orientation. The limitation is that the hub parts are only held together by friction.