In case of manufacturing hexahedral ABS (Acrylonitrile Butadiene Styrene) plastic components using a FDM (Fused Deposition Modeling)-based 3D printer, undesirable shape errors occur in the product due to heat shrinkage. This paper experimentally ob-served the influence of the bed temperature change on the deformed shape errors of a hexahedral specimen of 100 × 50 × 50 mm3 produced by using a 3D printer. During printing work, the head nozzle temperature was kept at 240?C and the head speed was set at 50 mm/s. The chamber was enclosed with a PC-plate. 3D printing was conducted at four different bed temperatures; 50?C, 70?C, 90?C, and 110?C. After the produced specimens naturally cooled down to room temperature, their deformed shape errors were measured. As a result, the higher the bed temperature, the lower the deformed shape errors of the specimens were. However, if the bed temperature had exceeded 120?C, laminating adhesion became poor. That seems to occur because of the material phase change and can make 3D printing work very hard as a consequence. Results of this study can be helpful to set optimum bed temperature condition in FDM additive manufacturing.
When FDM (Fused Deposition Modeling) [
The percentage shape errors caused by the heat shrinkage are X, Y and Z percentage errors, each of which is defined as follows.
X percentage error:
Y percentage error:
Z percentage error:
1) 3D printer for specimen fabrication
To fabricate the ABS specimens with 3D printing, an FDM 3D printer was built as in
Meterial Specification | Value |
---|---|
Specific Gravity (GMS/cm3) | 1.05 |
Tensile Strength (Mpa) | 34 |
Elongation (%) | 50.00 |
Softening Point (˚C) | 104 |
Cura, an open source tool offered by Ultimaker, was used [
2) 3D printing experiment
First, for the AM, Inventor program for 3D CAD modelling [
For the 3D printing, the ABS filament material was fed into the head at a rate pre-set by the slicer. The incoming filament was fused and heated at a pre-set temperature in the head before being extruded by the nozzle. The fused filament from the nozzle tip was layered on the bed. While being layered, the extruded filament material was transferred by the 3-axis stage through the pre-set channel to mold the layer surface. This AM process was repeated to fabricate the final specimens.
During the FDM-based 3D printing, the nozzle diameter, temperature, speed and layer height were set at 0.8 mm, 240˚C, 50 mm/s and 0.3 mm, respectively. Also, the infill percentage was set at 100%, where the material shrunk most. The platform adhesion type was not used. The mean outside air temperature was maintained at 27˚C during the experiment. It took 6 hours and 16 minutes to fabricate the specimens, including the printing but excluding the time spent on the 3D printer setup. Upon completion of the 3D printing, the specimens were naturally cooled down for 2 hours at room temperature. Then, the shape errors caused by heat shrinkage were measured.
For considering the phenomenon that the ABS filament layers fail to settle on the bed due to the temperature difference between bed and ABS filament [
Case 1: Bed temperature 40˚C, Case 2: Bed temperature 50˚C, Case 3: Bed temperature 70˚C, Case 4: Bed temperature 90˚C, Case 5: Bed temperature 110˚C.
Case of experiment | Bed temp. (˚C) | Chamber temperature at (˚C) | Heat shrinkage shape errors (%) | ||||
---|---|---|---|---|---|---|---|
Top | Mid | Bottom | X-percentage error | Y-percentage error | Z-percentage error | ||
1 | 40 | 32.5 | 31.3 | 28.7 | Fail in AM | Fail in AM | Fail in AM |
2 | 50 | 33.2 | 30.9 | 29.3 | 93.7 | 94.2 | 14.0 |
3 | 70 | 37.2 | 32.5 | 30.6 | 80.9 | 84.6 | 7.9 |
4 | 90 | 38.0 | 33.6 | 31.6 | 74.1 | 72.1 | 6.0 |
5 | 110 | 45.8 | 34.1 | 31.2 | 3.44 | 4.0 | 0.24 |
cated at different temperatures inside the chamber.
As shown in
The present experimental observation of the effects of bed temperatures on the shape errors caused by the heat shrinkage of ABS specimens in the FDM-AM shed light on the following.
It was impossible to fabricate the specimens on account of the inter-layer separation resulting from the heat shrinkage in the AM of ABS in 3D printing when the bed temperature was 40˚C, which was lower than that of the softening temperature (104˚C) of the ABS by over 60˚C.
When the bed temperature increased within the range from 50˚C to 90˚C, the shape errors caused by the heat shrinkage of the ABS specimens decreased in proportion to the difference between the bed temperature and the ABS’ softening temperature. When the bed temperature was 110˚C, approaching the ABS’ softening temperature (104˚C), the specimens manufactured hardly showed the shape errors ascribable to the heat shrinkage. When the bed temperature was set at 110˚C close to the ABS’ softening temperature (104˚C), the inter-layer adhesion improved following the extrusion of ABS because the ABS material was subjected to a slow phase transformation from the liquid phase to solid phase, and thus hardened slowly.
Therefore, to minimize the shape errors attributable to the heat shrinkage in ABS specimens fabricated with the AM (Additive Manufacturing), the temperature of the bed needs to remain close to the ABS’ softening temperature throughout the AM process. Then, upon the AM being finished, the specimens should be cooled down. The present findings will benefit the temperature settings for manufacturing precision products with FDM 3D printing.
The present paper concerned an experimental manufacturing of hexahedral specimens. Further studies should explore the fabrication of diverse specimens of different shapes and build on the experimental findings to develop a theoretical model for prediction.
This work (Grants No. S2176447) was supported by the technological convergence R & D program funded by Korea small and medium business administration in 2014-2016.
Choi, Y.-H., Kim, C.-M., Jeong, H.-S. and Youn, J.-H. (2016) Influence of Bed Temperature on Heat Shrink- age Shape Error in FDM Additive Manufacturing of the ABS-Engineering Plastic. World Journal of Engineering and Techno- logy, 4, 186-192. http://dx.doi.org/10.4236/wjet.2016.43D022