Development and Analysis of a Multimaterial FDM 3D Printed Capacitive Accelerometer

Nowadays quick fabrication of mechanical spare and replacement has become more and more necessary. This is the main reason why rapid prototyping and additive manufacturing has spread in several fields, including sensor manufacturing. In this work, we propose a Fused-Deposition-Fabricated Electro-Mechanical System (FDFEMS) accelerometer sensor. As the name suggests, it was implemented with Fused Deposition Modelling (FDM) additive manufacturing and material switching capabilities of the E3D ToolChanger motion platform. Fabrication process is based on insulating plastic to implement the mechanical structure of the device, conducting plastic to manufacture the actual differential capacitance sensing element and soluble material for sacrificial scaffolding. Together with the accelerometer, we also propose a novel fully differential interface circuit for differential capacitive sensors, based on the autobalanced bridge theory where capacitive sensor variations are balanced through voltage-controlled impedances placed in the bridge branches. Measurements from the sensor system were compared to theoretical values, showing good agreement. Furthermore, these measurements were repeated with different sensors and different test masses, to determine variations of the parameters evaluated. Specifically, measured sensitivity, damping factor and quality factor, with a fill factor of 100%, have resulted equal to 0.201 V/g, 0.055, and 9.042, respectively. It was then observed that the decrease of the proof mass fill factor led to a higher sensor resonant frequency, hence a wider flat band region in the frequency response, with decreased sensitivity and resolution. Mainly, this paper aims to evaluate and discuss the feasibility of the 3D printing Fused Deposition Modelling technique for manufacturing accelerometer sensors and classify sensor parameters as a function of its internal density, that is an easily selectable parameter for this kind of modelling.