<p>Additive manufacturing (AM) can
be an advantageous substitute to various traditional manufacturing
techniques. Due to the ability to
rapidly create products, AM has been traditionally used to prototype more
efficiently. As the industry has progressed, however, use cases have gone
beyond prototyping into production of complex parts with unique
geometries. Amongst the most popular of
AM processes is fused deposition modeling (FDM). FDM fabricates products through an extrusion
technique where plastic filament is heated to the glass transition temperature
and extruded layer by layer onto a build platform to construct the desired
part. The purpose of this research is to
elaborate on the potential of this technology, while considering environmental
impact as it becomes more widespread throughout industry, research, and
academia.</p>
<p>Although AM consumes resources
more conservatively than traditional methodologies, it is not free from having
environmental impacts. Several studies have shown that additive manufacturing
can affect human and environmental health by emitting particles of a dynamic
size range into the surrounding environment during a print. To begin this
study, chapters investigate emission profiles and characterization of emissions
from FDM 3D printers with the intention of developing a better understanding of
the impact from such devices. Background work is done to confirm the occurrence
of particle emission from FDM using acrylonitrile butadiene styrene (ABS)
plastic filament. An aluminum bodied 3D printer is enclosed in a chamber and
placed in a Class 1 cleanroom where measurements are conducted using high
temporal resolution electrical low-pressure impactor (ELPI), scanning mobility
particle sizer (SMPS), and optical particle sizer (OPS), which combined measure
particles of a size range 6-500nm. Tests
were done using the NIST standard test part and a honeycomb infill cube. Results from this study show that particle
emissions are closely related to filament residence time in the extruder while
less related to extruding speed. An
initial spike of particle concentration is observed immediately after printing,
which is likely a result of the long time required to heat the extruder and bed
to the desired temperature. Upon conclusion of this study, it is theorized that
particles may be formed through vapor condensation and coagulation after being
released into the surrounding environment.</p>
<p>With confirmation of FDM
ultrafine particle emission at notable concentrations, an effort was
consequently placed on diagnosing the primary cause of emission and energy
consumption based on developed hypotheses. Experimental data suggests that
particle emission is mainly the result of condensing and agglomerating
semi-volatile organic compounds. The
initial emission spike occurs when there is dripping of semi-liquid filament
from the heated nozzle and/or residue left in the nozzle between prints; this
supports the previously stated hypothesis regarding residence time. However,
the study shows that while printing speed and material flow influence particle
emission rate, the effects from these factors are relatively insignificant.
Power profile analysis indicates that print bed heating and component
temperature maintaining are the leading contributors to energy consumption for FDM
printers, making time the primary variable driving energy input.</p>
<p>To better understand the severity
of FDM emissions, further investigation is necessary to diligence the makeup of
the process output flows. By collecting exhaust discharge from a Makerbot
Replicator 2x printing ABS filament and diffusing it through a type 1 water
solution, we are able to investigate the chemical makeup of these compounds.
Additional exploration is done by performing a filament wash to investigate
emissions that may already be present before extrusion. Using solid phase
micro-extraction, contaminants are studied using gas chromatography mass
spectrometry (GCMS) thermal desorption. Characterization of the collected
emission offers more comprehensive knowledge of the environmental and human
health impacts of this AM process.</p>
<p>Classification of the
environmental performance of various manufacturing technologies can be achieved
by analyzing their input and output material, as well as energy flows. The unit
process life cycle inventory (UPLCI) is a proficient approach to developing
reusable models capable of calculating these flows. The UPLCI models can be connected to estimate
the total material and energy consumption of, and emissions from, product
manufacturing based on a process plan. The final chapter focuses on using the
knowledge gained from this work in developing UPLCI model methodology for FDM,
and applying it further to the second most widely used AM process:
stereolithography (SLA). The model created for the FDM study considers material
input/output flows from ABS plastic filament.
Energy input/output flows come from the running printer, step motors,
heated build plate, and heated extruder. SLA also fabricates parts layer by
layer, but by the use of a photosensitive liquid resin which solidifies when
cured under the exposure of ultraviolet light. Model material input/output
flows are sourced from the photosensitive liquid resin, while energy
input/output flows are generated from (i) the projector used as the ultraviolet
light source and (ii) the step motors. As shown in this work, energy flow is
mostly time dependent; material flows, on the other hand, rely more on the
nature of the fabrication process. While a focus on FDM is asserted throughout
this study, the developed UPLCI models show how conclusions drawn from this
work can be applied to different forms of AM processes in future work.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/15067803 |
| Date | 28 July 2021 |
| Creators | Timothy Simon (9746375) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/A_Study_of_Additive_manufacturing_Consumption_Emission_and_Overall_Impact_With_a_Focus_on_Fused_Deposition_Modeling/15067803 |
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