Dynamic response optimization of a portable robotic cell for hybrid manufacturing processes
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Date
2023-10
Authors
Μανιτάρας, Δημήτριος
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Abstract
Hybrid Manufacturing (HM) is defined as the combination of two or multiple manufacturing processes in a single machine tool. The most common combination is the integration of additive manufacturing with machining, enabling manufacturing of unique complex components but most importantly allowing repair of components in a single machine. Such approaches can be integrated on top of robotic cells, offering flexibility and allowing them to be easily transported, allowing repair in the field. However, the design of the load-bearing structure is a challenge because the weight of the structure limits its transportability. On the other hand, the stiffness of the frame plays a crucial functional role under dynamic loads and affects the product quality. Finding the right balance between weight and stiffness requires accurate boundary conditions and an effective design.
Of the processes involved in HM, machining is the one that has the greatest impact on the load-bearing structure. The cutting forces are determined through a machining process model and, through a multi-body simulation of the robot arm, the vibrations at the base of the robot are defined and used as boundary conditions in the dynamic finite element analysis.
The increase of the stiffness on the supporting structure will change its natural frequencies in order to reduce the likelihood of resonance. Since the platform consists of beams, the layout optimization method is used to find the arrangement of beams with the smallest volume. Layout optimization is a numerical approach that is used by a powerful software tool. Then by analyzing the response, the best responding structure is selected as the final design.
The proposed method achieved approximately an order of magnitude reduction in the displacement along the cutting frequency in the y-axis of the cell, as well as better accuracy for the drilling process and a 17% weight reduction compared to the non-optimized design. At the end of this thesis, the reader will have an overview of the design stages of a robotic cell with optimization, which is based on a closed-loop design, because it uses the forces generated by the machining operations as input to the final dynamic response analysis.
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Keywords
Hybrid manufacturing, Mechanical design, Layout optimization, Machine frame design, Dynamic analysis