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This final project report details the design evaluation and tests the Liquitronics team conducted on the 96 well plate robotic liquid handler. The team was able to create a prototype that reflects the most important aspects the team set out to accomplish. The main focus of the semester was completing a functioning chassis and movement system along with the pipette mechanism.

The following tests were completed: z-axis positional accuracy, x/y-axis positional accuracy, tip discard test, plunger actuator test, fluid volume test, sustained power draw test, and a size and weight test.

Both positional accuracy tests passed without significant issues. The z-axis needed to be within 0.5 millimeters of the location for every trial, and the trial with the largest error had an error of 0.1 millimeters. Similarly, the x/y test needed each trial to be within 1 millimeter and the greatest error measured was only 0.6 millimeters. The tip discard test proved that the prototype could eject a pipette tip without fail. This test also gave the time a relationship between the voltage supplied to the linear actuator and the speed at which it moved. These results will aid in determining the working voltage for the prototype’s actuators and electronics.

Unfortunately, there were two tests that did not meet their acceptance criteria. The final design is limited to a four foot wide and 2 foot deep space. The current prototype is currently 2.23 feet in both directions. However, after speaking with the project sponsor, it was agreed that the size limit was more flexible than originally stated and thus the current dimensions do not present any practical issues. Additionally, the prototype is well under the 500 pound weight limit measuring at 34 pounds.

The second unsuccessful test was the sustained power draw test. This test is meant to prove that the circuitry of the prototype can run for extended periods of time without any components failing. Without any of the motors running, the prototype was drawing just over 300 milliamps. This was lower than what was expected. Also, the voltage regulator began to burn out, and 2 of the 9 stepper motor drivers stopped working. The reason for these failures is not yet known, but the team is currently brainstorming ideas for how to pinpoint the solution, and ensure that it will be fixed.

Future improvements will be focused on getting a fully automated prototype. For this to happen, assembly of the mechanical parts must be completed, a full code must be written, and the power draw problems must be addressed.


Sponsor: Dr. Adam Urbach

Advisor: Dr. Eliseo Iglesias

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