Passive Chatter Suppression of Thin-Walled Parts by Means of High-Damping Lattice Structures Obtained from Selective Laser Melting

Abstract

Chatter vibrations arising during machining operations are detrimental for cutting process performance, since they may cause poor surface quality of the machined part and severe damages to machine tool elements. Passive approaches for chatter suppression are based on the integration of special mechanical components with high-damping properties within the machining system. They represent a good solution to this problem thanks to their intrinsic simplicity. Recently, the application of metallic lattice structures inside 3D printed parts obtained from the Selective Laser Melting technology have proven superior damping properties with respect to the same full density material. Here, this idea is further explored by considering the novel configuration where the unmelted powder grains are retained inside the lattice structure by an external shell, acting as a multiplicity of microscopic mechanical dampers. This concept is applied for passive chatter suppression of thin-walled parts that are of particular relevance for industry. Preliminary experimental investigation was first carried out on simple beam-like specimens, and then on thin-walled benchmarks that were identified through modal analysis and tested under real cutting conditions. The main conclusion is that the novel proposed configuration (lattice plus unmelted powder) has higher damping properties with respect to the full density and lattice alternatives. Accordingly, it may be successfully applied for passive chatter suppression in real machining operations.

Influence of the Experimental Setup on the Damping Properties of SLM Lattice Structures

“…The latter was found to be the most effective against mechanical vibrations, both during modal analysis and cutting tests. No significant differences were found between the first and second configuration, contrary to the expectations derived from [32]. A possible explanation of this behaviour will be provided in this work.…”

“…According to the results of the previous experimental campaigns [31,32], SLM lattice structures can be very effective for mechanical energy dissipation, especially when unmelted powder filler is retained within the lattice porosities. However, this behaviour was not confirmed by all the experimental data, likely because of the influence of some external additional dissipative phenomena.…”

“…The beam-like shaped specimens are representative of structural elements and members of mechanical systems, robotic mechanisms and tools, while the blade-like shaped ones are representative of slender structures such as turbine blades, parts for aerospace applications and thin mechanical components in general. The beam-like and blade-like geometries were designed by means of SolidWorks Simulation and ANSYS Mechanical APDL FEA [31,32] in order to satisfy different objectives and constraints:…”

“…The blade-like specimens had a lower base designed for mechanical clamping on machine tool table, a central section embedding the same lattice structure of the beam-like specimens (with and without metal powder) and an upper base where a sacrificial sample could be clamped. All the geometrical details of the blade-like specimens can be found in [32]. In the current case, the upper base was used for the application of the external force.…”

“…These results inspired an innovative method for passive vibrations suppression in milling of thin-walled parts [32]. In that work, three similar blade-like fixtures were 3D printed by means of SLM and then compared in terms of their dynamic behaviour: a full density blade, a blade embedding a given lattice structure and a third configuration having the same lattice structure filled with unmelted metal powder.…”