Emmy: The Picker Upper

tldr:

Designed and prototyped a picker upper manipulator kit for a third year mechanical engineering course as my primary co-op project. Designed parts on AutoCAD and SolidWorks which were manufactured using a laser cutter and FDM printers.

What:

As co-op students at a rapid prototyping clinic at the University of Waterloo, other than running the clinic, my coworker and I had to complete a major project. We helped with restructuring a third year mechanical design course by putting together a kit that students can use to start off their design.

From what I have heard from upper years, third year is the most challenging academic year for the mechanical engineering program. The goal of the kit is to give students a head start in their design process. The kit contains servo and stepper motors, STL files, DWG files and other components that students think may come in help.

*Also we named the picker upper 'Emmy' because it was for the ME 380 course. Get it? "M-E" : "Emmy" lol

Assembled CAD Model of Emmy (only one side pictured)

Why:

We created a viable solution for the third year mechanical design course problem. The design was flexible enough to be compacted into a kit and allowed the versatility to let students to improve on the design or change the design objectives.

Our design objective was to optimize efficiency by minimizing energy/effort required by the manipulator to transport as many objects as possible. We achieved this by creating a symmetrical dual claw system that allows two objects to be picked up and delivered simultaneously.

How:

Since we worked with 3D printers all day, our design was heavily inspired by a 3D printer and a laser cutter. We wanted free movement in the x and y axis and at least 3 inches of movement in the z axis (problem constraint). We divided the project into three parts: The claw, the frame and the rotating base. I primarily focused on the claw and rotating base

Claw CAD Model

Frame CAD Model

Rotating Base CAD Model

After going through several design iterations of the claw and its servo mount, I settled on a working prototype.

However, I realized the movement in the z axis was very restricted. The claw moved approximately 3/4 of an inch in the z axis. It was necessary to devise another mechanism to allow further movement in the z axis.

We settled on a scissor lift mechanism that was controlled by a servo. Since we had to add an extra servo, we had to modify the frame to create a mounting spot for the new servo motor.

As my coworker was working on the frame, I continued to move onto the last part: the rotating base. The anatomy of the base consists of

i. internal gear lid

ii. stepper motor + gear

iii. top plate

iv. motor mount

The mechanism is quite simple, the gear lid rests inside the cylinder and the stepper motor gear spins the gear lid as it rotates. I had to be very mindful of the dimensions and the tolerance of each piece. This prototype only worked when the gear lid was snug, yet should still rotate with minimal resistance.

As part of testing, I learnt how to control stepper motors and servo motors using Arduino. I also improved on my writing skills since I had to create documentation of assembly, kit contents and recommendations. I also learned how to source parts online efficiently with consideration of the budget.

What did I learn:

Prototyping with 3D printing generates a lot of waste. A LOT. Since we had open access to 3D printers, we went full ham on printing prototypes with the smallest different design iterations. What we should have done, is take a bigger look at all the problems in the design so that we would print less prototype iterations. In the end, we had to throw out a lot of 3D printed waste.
Material selection is very important: both for 3D printing but other components as well. One flaw of our final design was the material of the frame. The weight of the claws and motors caused a lot of cantilever force on the frame and acrylic sheet used for the frame wasn't the ideal choice.
I learnt A LOT about optimal 3D printing techniques

What's next:

We will not be going back to the project for any improvements as this was a co-op project. However, we did include a list of considerations and what we would change in the documentation. Some changes include:

Replacing acrylic to wood or aluminum as the primary material for the frame.
Redesigning the servo mount to reduce the dead zone
etc.

Hopefully, the third years will enjoy working and improving on our design.

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