3D Mouse With 3D Printed Flexures And PCB Coils

3D mice with six degrees of freedom (6DOF) motion are highly valued by professional CAD users. However, the entry-level versions typically cost upwards of $150 and are produced by a single manufacturer. Colton Baldridge has created the OS3M Mouse — an open source alternative using PCB coils and 3D printed flexures.

The primary challenges in creating a 6DOF input device, similar to the 3Dconnexion Space Mouse, lie in developing a mechanical coupling that enables full range motion, and electronics capable of precisely and consistently measuring this motion. After several iterations of printed flexure combinations and trip down the finite element analysis (FEA) rabbit hole, Colton had a working single-piece mechanical solution.

To measure the knob’s movement accurately, Colton employs inductive sensing. Inductance to Digital Converters (LDCs) assess the inductive alterations across three pairs of PCB coils, each having an opposing metal disk mounted on the knob. This setup allows Colton to use a Stewart platform‘s kinematic model to calculate the knob’s relative position. Furthermore the calculations are done on an STM32, which also acts as a USB HID to send the position data to a computer. Finally for the demo, Colton created a simple C++ app to translate the position data to Solidworks API calls.

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