Giovanni Totis

Cutting force measurement plays a fundamental role in machining research and industrial applications, but existing dynamometers present important trade-offs between cost, stiffness, and dynamic bandwidth. Strain gauge devices are inexpensive but too flexible for high-speed operations, whereas piezoelectric systems provide excellent accuracy and bandwidth at prohibitive costs. This work presents the design, construction, and validation of a novel plate dynamometer based on polyvinylidene fluoride (PVDF) sensors, aimed at providing an effective alternative having an intermediate cost and suitable for advanced milling applications. The device integrates eight symmetrically arranged PVDF films in a stiff steel structure, complemented by four accelerometers for inertial compensation. A finite-element analysis confirmed favorable stress distribution at the PVDF contact surfaces and high resonance frequencies (under ideal clamping conditions). Modal tests demonstrated that uncompensated PVDF signals offer limited bandwidth, but the application of the Universal Inverse Filter (UIF) extended the usable bandwidth to 5 kHz along direct directions and up to 0.3–4 kHz along cross directions, approaching the performance of piezoelectric reference devices. Milling tests under diverse cutting conditions further validated the new device. Overall, the proposed device bridges the gap between low-cost strain gauge and high-performance piezoelectric dynamometers, offering a versatile and promising solution for both laboratory research and industrial applications.

Laser based-powder bed fusion (LB-PBF) enables fast, efficient, and cost-effective production of high-performing products. While advanced functionalities are often derived from geometric complexity, the capability to tailor material properties also offers significant opportunities for technical innovation across many fields. This study explores the optimization of the LB-PBF process parameters for producing Ti6Al4V titanium alloy parts with controlled porosity. To this end, cuboid and lamellar samples were fabricated by systematically varying laser power, hatch distance, and layer thickness according to a full factorial Design of Experiments, and the resulting specimens were thoroughly characterized by analyzing envelope porosity, surface roughness and waviness, surface morphology, and surface area. A selection of specimens was further examined using small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) to investigate the atomic structure and nanometric porosity of the material. The results demonstrated the possibility to finely control the porosity and surface characteristics of Ti6Al4V within specific LB-PBF process ranges. The pores were found to be mostly closed even for thin walls, while the surface roughness was recognized as the primary factor impacting the surface area. The lamellar samples obtained by exposing single scan tracks showed nearly an order-of-magnitude increase in both surface area and pore volume, thereby laying the groundwork for the production of parts with optimized porosity.