For the week of September 20th-26th, I continued our Iteration 1 CAD design of our 6DoF robotic arm in SolidWorks. After some discussion with the team, we decided to base our structural requirements on an already established and tested design instead of choosing every dimension from scratch.
We selected the Universal Robots UR3e (which is widely used in different industries), since it was essentially the lightest and smallest model from their catalog. It fulfilled all our design specifications as it contained 6 joints and thus 6 axes of rotation and some safety functions we could take inspiration from.
I used it as our reference and imported its STEP model into SolidWorks, which I used to note down its link lengths, joint placement, proportions, reachable workspace, and then used those measurements as a starting point for our arm. The design will not be an exact copy of the UR3e because it needs to fit to our selected actuators, 3D-printed parts, PSU, and end effector (pen gripper)– however, the reference model would give us a more dependable baseline since they’re already validated dimensions.
This week, I recorded some of the UR3e geometry, specifically its physical limits in CAD and how many degrees of freedom it had for six joints. For our robot, the joint limits need to not collide with themselves or block anything and still let the end effector to reach the object inside of our 0.4m x 0.4m x 0.4m workspace. This work is still in progress since the limits depend on the dimensions of our selected servos and the mechanical design of the 3D printed links.
My Iteration 1 CAD along with the joint simulations and surface modeling (which I’ve modeled as a simple cylindrical surface already), and physics work is scheduled through October 3rd, so I’m currently in progress and on track. What’s still remaining is finalizing joint limits by also finalizing what hardware we’re purchasing, build out the Iteration 1 CAD and run it in the workspace with torque simulations/calculations.
For next week, I plan to:
1. Finalize our hardware parts with their physical limits and calculate the range of motion for all six joints
2. Run a SolidWorks Motion simulation to record the arm’s reachable workspace, I need to figure out how to exactly simulate the physics to see if the weight of the arm is also low enough to sustain the end effector without falling over
3. Determine whether our arm’s shoulder needs a stronger actuator, or some sort of counterbalance (I was thinking of accommodating the design for a vise to hold it down)
4. Update the Iteration 1 SolidWorks assembly based on the simulation results and prepare the CAD files for printing