Synthesis and Evaluation of A High Precision 3D-Printed Ti6Al4V Compliant Parallel Manipulator

Minh Tuan Pham,Pan Wang,Song Huat Yeo,Mui Ling Sharon Nai,Tat Joo Teo

doi:10.1088/1757-899x/280/1/012040

Abstract

A novel 3D printed compliant parallel manipulator (CPM) with θX − θX − Z motions is presented in this paper. This CPM is synthesized using the beam-based method, a new structural optimization approach, to achieve optimized stiffness properties with targeted dynamic behavior. The CPM performs high non-actuating stiffness based on the predicted stiffness ratios of about 3600 for translations and 570 for rotations, while the dynamic response is fast with the targeted first resonant mode of 100Hz. A prototype of the synthesized CPM is fabricated using the electron beam melting (EBM) technology with Ti6Al4V material. Driven by three voice-coil (VC) motors, the CPM demonstrated a positioning resolution of 50nm along the Z axis and an angular resolution of ~0.3 “about the X and Y axes, the positioning accuracy is also good with the measured values of ±25.2nm and ±0.17” for the translation and rotations respectively. Experimental investigation also shows that this large workspace CPM has a first resonant mode of 98Hz and the stiffness behavior matches the prediction with the highest deviation of 11.2%. Most importantly, the full workspace of 10° × 10° × 7mm of the proposed CPM can be achieved, that demonstrates 3D printed compliant mechanisms can perform large elastic deformation. The obtained results show that CPMs printed by EBM technology have predictable mechanical characteristics and are applicable in precise positioning systems.

Highlights

Compliant parallel manipulator (CPM), which is developed based on the merits of elastic deformation and closed-loop parallel architecture, plays an important role in high precision motion systems
This paper presents a high precision 3D printed Ti6Al4V CPM with 3-DOF out-of-plane motion
The 3D printed CPM was fabricated by electron beam melting (EBM) technology to eliminate assembly errors and several experiments were carried out to evaluate its performance

Summary

Introduction

Compliant parallel manipulator (CPM), which is developed based on the merits of elastic deformation and closed-loop parallel architecture, plays an important role in high precision motion systems. The beam-based method [12] is employed to synthesize a new design of 3-DOF (θX – θY – Z) CPM with large workspace of more than 8o and 5.5mm and the targeted first resonant mode of 100Hz. The factor of 1.27 proposed in [15] is used to correct the actual thickness of EBM printed thin features. It is observed that the C-T beams became flat and two reflecting C-T beams cut each other at the free ends to generate a V-shape flexure for each compliant limb This structure is able to provide the largest workspace and good decoupled motions for the CPM. With the Ti6Al4V material providing a yield strength of 850MPa, the synthesized CPM can deliver a large workspace up to ±5o × ±5o × ±3.5mm, which satisfies the desired requirements and much larger than the existing CPMs [11, 12, 15]

Experimental investigation and results

Conclusion