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Materials Science in Additive Manufacturing MEX optimization printing of rHPDE from milk jugs

molten material was extruded through the die at 190°C. nozzle. To optimize the printing of rHDPE filaments,
The opening size of the hopper was 30 × 20 mm. The we investigated several parameters, including print
extrudate was cooled along a Filabot Airpath (Filabot, bed material, print speed (PS), surface roughness (Ra),
Vermont USA) (Figure 2) at an ambient temperature as well as the print bed temperature (PBT) and print
of 21.8°C before spooling. The Mitutoyo Filameasure temperature (PT).
(Mitutoyo, Japan), attached to the mechanical spooler, Due to limitations in the controls and settings of the
was used to measure and monitor the consistency of the LulzBot printer, the ABS standard profile available from
diameter of the extruded filament during the extrusion the slicer program, CURA LulzBot edition version 4.0
process. The filament would pass through the plunge (Ultimaker, The Netherlands) was used for initial testing
indicator to monitor its thickness before being pulled into to preserve the availability of rHDPE during parameter
the rotating reel (Figure 2). To produce a 3 mm-diameter
filament, a 2.85 mm-diameter die was used. evaluation, as the T range for HDPE is similar to that
g
of ABS. For the LulzBot printer, it is important to note
2.3. Optimization of MEX print parameters for that ABS prints at a higher nozzle temperature and PBT
rHDPE compared to PLA, and the favorable settings for rHDPE
The filament was 3D printed using a LulzBot MEX are likely closer to those for HDPE.
3D Printer (TAZ 5, Fargo Additive Manufacturing 2.3.1. Printing on different print bed materials
Equipment 3D; Fargo, USA), fitted with a 2.85 mm
FlexyStruder extruder head (Fargo, USA) and a 0.5-mm In this study, parts were printed on various print bed
materials recommended in the literature, 9-15 as well as
on a bare polyetherimide (PEI) print bed that is attached
to the printer. The PEI print bed was chosen for its high
mechanical strength, high rigidity, high creep resistance
over a wide temperature range, high dimensional stability,
good resistance to hydrolysis, and high permanent
operating temperature (170°C). Several other materials,
including vHDPE sheet, hot-pressed rHDPE sheet,
masking tape, double-sided tape, ABS, and paper-faced
foam core board, were applied or layered over the PEI
surface of the print bed to investigate their suitability as
a print surface for rHDPE. This experiment also involved
printing two different sample models, each with 10 layers.
The first is a 20 × 20 × 5 mm square model, and the
other is a 20 mm-diameter cylindrical model. Printing
on different print bed materials allows us to investigate
Figure 1. Collected milk jugs from Meiji Co. were washed and cleaned whether form factor affects the MEX printing process for
before use to produce filaments for additive manufacturing rHDPE.

Figure 2. Extruder setup consisting of the hopper, where cut-pieces were fed; extruder die where molten material was extruded; Airpath where extrudate
was cooled; inline filament diameter measurement device to monitor filament diameter; and spooler to spool filament into a reel

Volume 3 Issue 3 (2024) 3 doi: 10.36922/msam.4084