6 Degree of Freedom (DOF) Robotic Arm

Introduction

This 6 DOF robotic arm designed from the ground up with a focus on ease of manufacturing. By designing the robotic arm to be easy to manufacture, the costs of such 6DOF robotic arm should be reduced significantly and improves accessibility for everyone. 

4 Major Pieces of 6DOF Robotic Arm

Table of Contents

Figure 1. A fully assembled shoulder.

The Shoulder

The shoulder is the first major piece of 6DOF and anchors the entire arm to a robust foundation below. The shoulder experiences some of largest forces and moment and need to be robust and stiff. It is designed with customized and integrated cycloidal drives double layer of ball bearings to improve stiffness. It also has an integrated cycloidal drive that provides the required torque to rotate the arm around axis #1. 

Assembling The Shoulder

The structural bracket is fixed onto the rolling plate, in between a constraint plate. Rolling plate is spliced between two layers of ball bearing and allow for free rotation of the structural bracket while enabling good stiffness, both in compression and tension direction.

Figure 3. The remaining parts that are attached to the thin wall bracket below.
Figure 2. A exploded view of different parts that are connected to structural bracket.

The ball bearing are held in place by constraint plate at the top and load transfer plate at the bottom. Both pieces are fixed in place, onto a 3Dprinted thin wall bracket below. 

Figure 5. A fully assembled 48:1 cycloidal drive.
Figure 4. An inside look into 48:1 cycloidal drive.

Cycloidal Drive 48:1

The rotation at the shoulder is driven by a cycloidal drive with an amplification ratio of 48:1. It is designed to be compact with a 15mm thickness and can be hidden inside the shoulder. 


If you are curious how cycloidal drive works, do check out my article below on what, why and how a cycloidal drive works.

The What, Why and How a Cycloidal Drive Works

by BengLoon 2 comments

Assembling The Cycloidal Drive

The cycloidal drive is designed to be easy to assembled. This achieved by ensuring the parts serve multiple functions. For example the casing do more than simply shield the drives from dusts but used for mounting NEMA17 stepper motor, hold dowel pins, have threads for screwing top cover down and as well as an anchor point to the main body. Similarly, the top cover serves as a protection against dust and to keep the parts together. 

 

There is a video below detailing the assembly procedure of the cycloidal drive. 

Figure 6. The first half of parts needed for the cycloidal drive.
Figure 7. The second half of parts needed to form the torque extractor.