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UCSD Automated Pick-And-Place Gripper

Background

The motivation for this project was the need to improve device consistency, to increase lab throughput, and to minimize manual labor involved in the lab-scale solar cell manufacturing process. The Solar Energy Innovation Lab (SOLEIL) headed by Professor David P. Fenning at UC San Diego recognized the value in the study and production of next-generation hybrid organic-inorganic perovskite solar cells. Emphasis is placed on the analysis of defects thatimpact device performance in an effort to develop predictive models of material processing. The work at SOLEIL seeks to advance the field of renewable energy by accelerating material development and innovation. Professor Fenning and his lab can better characterize defects by automating the solar cell manufacturing process. Implementing an automated system increases the consistency between cell production and can redirect saved time towards other pursuits. The repetitive nature of the solar cell manufacturing process is liable to introducing human error over time as lab personnel may mistime curing or damage samples. An increased consistency in turn reduces the confounding variable of sample quality and makes analysis of defects more straightforward.

Steps in the Solar Cell Manufacturing Process

Objectives

The primary objective of this project is to design and ultimately deliver a robust mechanical system to transfer glass slide substrates between fabrication stations for solar cell manufacturing. The proposed pick-and-place gripper design is meant to increase the throughput and consistency of the manufactured devices. As such, the final design should be an automated system that is able to process the devices with little to no human intervention.

Process

The first steps for this project consisted of establishing a basic idea about how the system would operate. The constraints and objectives of the system were discussed at length. The next step was risk reduction for high-risk components. In our case, this was the gripper's ability to grab solar cells without breaking the glass. After using an Instron to test the glass slides for crack propagation and complete breakage, we found that parallel gripping would be a sufficient method for picking the glass substrates. After redefining the scope of the project in light of COVID-19, preliminary designs were tested as a part of rapid prototyping. This process included several iterations of both the gripper and the translation system that it attaches to for travel. During this time, several calculations and analyses were carried out as well to ensure that our design solution could performed as required.

The video below shows the performance of the gripper mecahanism in picking up an ITO sample.

Design

The electromechanical gripper system must be able to pick and place thin glass slides without affecting the coating or breaking the glass. With these considerations in mind, we began designing a system that could pick up the slides from their sides and transfer them to different stations using only translational motion. Two primary designs for the gripper were studied: direct drive and rack and pinion. The former was chosen for its simplicity and robustness. Similarly, two designs were studied for the translational system; inspiration was taken from 3D printers and CNC machines. Ultimately, the latter was chosen for its feasibility. During rapid prototyping, it became apparent that tension springs were required to operate the gripper as intended and modifications were made to the design to fit these requirements. CADs of the gripper and translation systems as they appeared in our proof of concept are provided above. In addition to these two main components, we were tasked with providing a viable storage solution for completed solar cells that worked with our automated system. A top view of the final design solution is provided below. Detailed information on each major component is included in the Final Design tab.