Research Experience for Undergraduates
I spent summer 2022 in the National Science Foundation's Research Experience for Undergraduates, and I was placed in the in the Additive Assembly Lab at Boston University. In my time there, I was tasked with optimizing their printing process by integrating the pressure system with the NPAQ controller. The experience concluded with a psoter session, where I was able to create and share a scientific poster that outlined all of the work that I achieved in my time there.
Evan 2022 REU Poster.pptxAbstract
Direct Ink Writing (DIW) is an additive manufacturing technique which uses viscoelastic material to selectively print 3-dimensional(3-D) structures via layer-by-layer deposition. These 3-D structures can have detailed features down to the micro scale. However, when printing at the micro scale, any deviation from the intended printed filament leads to low fidelity prints. One factor that causes deviations is ink accumulation, which is caused by lack of synchronization between ink extrusion and print head movement. In this work, I synchronize the ink extrusion and movement of the printhead with Position Synchronized Output(PSO) to increase print fidelity. To achieve this, I wrote custom functions that set PSO pulses to fire at specific intervals which turn ink flow on and off during nozzle motion. By implementing hardware, I was able to use the PSO pulses to control ink extrusion, leading to precise printing. To evaluate this method, I compared traces that were printed with PSO and without PSO. Traces printed with PSO showed no accumulation, and yielded traces with more uniform trace width, as compared to non-PSO traces. These results indicate that PSO-based printing is better suited for micro scale printing than non-PSO counterparts.
10mm_traces_control2.aviPrinting without PSO at 25 mm/s at 15 psi
How it Started
This video displays the original process of direct ink writing. As you can see, the nozzle:
Moves to the desired position
Starts printing
Starts moving
Stops moving
Stops printing
This creates an unwanted accumulation of material at the ends of lines. The problems caused by this includes the fact that:
Material is wasted
The stoppage time adds up when printing many lines
Lines cannot be printed close to each other without risk of touching, which is detrimental when printing with conductive material that would short circuit
Improvements Made
At the end of the summer program, I got the nozzle to print based on position rather than from the sequential code. This way, the nozzle would not need to stop to begin/finish printing. This resulted in printing traces that did not have accumulation of material at the ends, eliminating all 3 of the problems defined in the previous section.
Skills Gained
G-Code
Read through G-code manuals, communicated with controller distributer, and experimented with codes in order to implement PSO functionality
Matlab
used Matlab to analyze the dimensions of the printed traces
Arduino skills
Coded in arduino to control nozzle manifold for multi-material printing
Soldering
Soldered wires and transistors onto PCB for multi-material printing
pso_trace.movPrinting with PSO at 25 mm/s at 15 psi
Further Improvements
While much progress was gained, the process still has room for improvement that I did not have time to get to during my 10 weeks at BU. Further improvements would include:
Getting more uniform thickness of the traces
Starting printing before the nozzle gets to the printing zone
getting the length of the printed trace to be more accurate
This could be done with further experimentation, and creating a function that accounts for nozzle velocity, material viscosity, nozzle diameter, yield stress of the fluid, printing pressure, and consistency index to define when to begin printing in order to print a trace of a desired length and get it in a precise location.
This graph displays the width of a trace along a trace that is desired to be 10 mm long and 0.2 mm wide.