Design Optimization of 3-DOF Redundant Planar Parallel Kinematic Mechanism Based Finishing Cut Stage for Improving Surface Roughness of FDM 3D Printed Sculptures

Minbok Lee,Donghun Lee,Hyungjin Jeong

doi:10.3390/math9090961

Abstract

This paper describes the optimal design of a 3-DOF redundant planar parallel kinematic mechanism (PKM) based finishing cut stage to improve the surface roughness of FDM 3D printed sculptures. First, to obtain task-optimized and singularity minimum workspace of the redundant PKM, a weighted grid map based design optimization was applied for a task-optimized workspace without considering the redundancy. For the singularity minimum workspace, the isotropy and manipulability of the end effector of the PKM were carefully modeled under the previously obtained redundancy for optimality. It was confirmed that the workspace size increased by 81.4%, and the internal singularity significantly decreased. To estimate the maximum rated torque and torsional stiffness of all active joints and prevent an undesired end effector displacement of more than 200 μμm, a kinematic stiffness model composed of active and passive kinematic stiffness was derived from the virtual work theorem, and the displacement characteristic at the end effector was examined by applying the reaction force for the PLA surface finishing as an external force acting at the end effector. It was confirmed that the displacement of the end effector of a 1-DOF redundant PKM was not only less than 200 μμm but also decreased from 40.9% to 67.4% compared to a nonredundant actuation.

Highlights

To meet the demand in various fields, the global 3D printer market has grown by more than 15% annually since 2014
The singularity analysis was conducted through the isotropy and manipulability analysis of these six combinations, and 1-DOF redundancy was considered manipulability analysis of these six combinations, and 1-DOF redundancy was considered for the combination with the best singularity area removal performance
While the proposed cutting stage satisfied the required workspace of a triangular shape with an area of 0.0081 m2, the design efficiency including a weight grid map (WGM) was presented as an objective function to minimize the size of the parallel kinematic mechanism (PKM), and the optimization of the workspace based on the genetic algorithm was performed

Summary

Introduction

To meet the demand in various fields, the global 3D printer market has grown by more than 15% annually since 2014. The FDM method, which is a method for laminating industrial plastics such as PLA and ABS by heating at high temperatures, has a market share of more than 20% in the global market owing to its low cost and simple lamination technology. The FDM method has a slow molding speed and low surface roughness of the sculpture owing to the characteristics of the additive manufacturing method in which materials are stacked one by one through high heat nozzles; it is necessary to develop a technology to compensate for this [1,2].

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Results

Conclusion