Temperature Compensated 3D Printed Strain Sensor for Advanced Manufacturing Applications

Additive Manufacturing, has evolved beyond prototyping to manufacturing end-products. The authors are involved in developing a large-scale extrusion-based 3D printer to print mining equipment - a Gravity Separation Spiral, and embedding sensors to monitor the operational conditions re-motely. This paper presents a temperature-compensated strain sensor that can be 3D printed inline within large-scale 3D printed equipment. The sensor is printed using conductive carbon filament and embedded in a Polylactic acid (PLA) base. A half-bridge setup is proposed to reduce the impact of temperature variations. Temperature-controlled tests have been conducted with the proposed half-bridge and compared with a non-temperature compensated quarter-bridge setup. Results show that the half-bridge configuration reduces the temperature impact on the strain measurement significantly (68%) compared to the quarter-bridge, in the range of 25-40 °C. Deflection testing conducted on the printed sensor shows a near-linear relationship between bending strain and voltage. Multiple bending cycles have shown that there is no significant hysteresis. ANSYS simulations are used to accurately estimate the internal temperature since embedding a temperature sensor would affect the structural integrity. Although carbon black material is naturally brittle, steps have been taken in the design to avoid undesirable cracking. Results from laser microscopy analysis of the printed traces showed no crack defects.