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Novel High-Speed 3D Printing Method Using Selective oil sintering
black particles, which cannot be eliminated. Hewlett sintering steps were repeated until a 3D structure was
Packard’s MJF PBF high-speed 3D printer contains formed. The printed objects are heated on a hot plate
a considerable amount of carbon black particles and set at 220°C for 30 min, cooled at room temperature
hence cannot be used in biomedical products because for 10 min, and then washed with soapy water to
of its toxicity. In addition, carbon black particles may remove excess oil for post-processing to complete the
be inhaled, causing secondary lung injury. Thus, the final product. The final parts were characterized using
applications of this technology are limited. Therefore, a scanning electron microscopy (SEM) and a universal
high-speed 3D printing method that is environmentally tensile machine (UTM).
friendly, nontoxic, and can be manufactured in large
quantities at a high speed is required. At present, no 3. Results and discussion
methods can print TPU, which, as a biomaterial, can Figure 2 presents the SEM images of the TPU particles
be used in biomedical products and is environmentally fused using two different fusing agents-food oil and
friendly. The difference between the two types of 3D carbon black. As illustrated by Figures 2A and C, the
printing is that the oil droplet can directly define the energy of the hot oil was sufficient to melt the powder,
printing area and heating, while the MJF needs to define leaving no porosity (red circle in Figure 2C). When
the area first and then illuminate and heat it. Therefore, carbon black was used (Figures 2B and D), no melt
the oil droplet is used as a 3D printing method and only tracks were formed because carbon black does not
one step is required for the printing speed. SOS’s 3D cover the particle surfaces uniformly and the heat of
printing speed must be faster than MJFIn this study; we the IR absorber is insufficient to melt the powder and
developed a novel fusing agent (i.e., food oil) that does solidify it onto the substrate. Moreover, the resulting
not require photo absorbers. The oil covers the particle pore size was approximately 90 in diameter (red circle
surface uniformly, and the heated oil droplets completely in Figure 2D).
melt the powder. Moreover, when oil is used as the fusing Differential scanning calorimetry (DSC) was
agent, the powder can be directly fused, and the printed used to determine the melting and crystallization
area can be accurately defined with heated oil droplets. temperatures of the TPU particles. A DSC8000
Moreover, this method can print TPU. instrument from PerkinElmer was used at a temperature
of 20 – 200°C, with a heating rate of 5°C/min.
2. Experimental methods Nitrogen purge gas and 0.5-mg aluminum crucibles

2.1. Materials
TPU (maximum particle size of 100 ) was supplied by
BASF. Food oil is canola oil was purchased from a local
store and used without any further purification. The
boiling point of the food oil was 250°C.

2.2. 3D printing
Figure 1 presents the PBF process of melting TPU
particles in a layer-by-layer manner using selective
hot oil sintering technology. A commercial powder
bed 3D printer (T10 3D printer, Microjet Technology
Co Ltd., Taiwan) was used in this work for spreading
the TPU micro powder. The hot oil droplets (175°C,
droplet size of approximately 2000 μm) were ejected
through a glass dropper. Using oil as a fusing agent
for high-speed 3D printing technology, all printing
processes can be completed in one step. The hot oil
can be transformed into small droplets through the
multiple glass droppers, and then through a large
number of small droplets to define the pre-printed area
and shape. The heat source moved along the X and Y
axes of the bed to which a thin and uniform powder
layer was applied. The base was then lowered based on
the thickness of one layer (0.1 – 0.08 mm), and another
powder layer was applied and sintered. The powder Figure 1. Selective oil sintering process.

160 International Journal of Bioprinting (2022)–Volume 8, Issue 2