Material Consuption Reduction and the Influence on the Mechanical Properties of the 3D Printed Parts for ABS Silver

The main objective was to reduce the consumption of material when obtaining 3D printed parts (different empty shapes inside) and the secondary one was to maintain the mechanical properties closer to the full printed version. In order to achieve these objectives, two internal configurations were designed a configuration with hexagonal gaps (material reduction was 30%) and a configuration with sinuous gaps (material reduction was 15%). The specimens thus obtained were tested for traction, threepoint bending and shock (resilience). Hexagonal hollow configuration has a resistance values close to those of solid specimens but with the advantage of consuming with 30% less material.

In order to improve the behavior of the material during hot extrusion, the researchers studied the possibility of introducing additives into the filament, like coupling agents, plasticizers, stabilizers, etc., to control the mechanical response to several degradation factors of the final 3D-printed polymer [5,18,19,24].
Several studies and research have been reported in the literature related to the mechanical behavior of 3D-printed structures originating from several types of filaments [20,23,24], the influence of build defects on the properties of the material or optimization of the layer height, printing duration or material consumption [21][22][23][24][25][26][27][28].
The novelty of this work resides in developing and characterizing two internal build architectures for 3D-printed materials, namely a hexagonal model structure and a sinuous architecture with an amount of materials consumed 30 and 15% less.

Samples design
In the first phase and using the Solid Works Software were designed all the specimen type. The 3D specimens were designed for mechanical tests (tensile, three-point bending and resilience) according to SR EN ISO 527-3: 2000 / AC: 2003. We started from a "full" printed test specimen, and then two variants were proposed, namely: the hexagonal gap version and the sinuous gap version.   As can be seen from Figure 3, in order not to influence the results, the gap model was applied only in the calibrated area and not in the grip area in the tensile test device.

Sample printing
Next, we proceeded to the physical obtaining of the previously designed specimens using ABS "Silver" material from Sakata3D.

Technical specifications form the producer [24]
Material: ABS "Silver" ( CreatBot DX printer A CreatBot (Zhengzhou, China) DX-3D double-nozzle printer was used to obtain samples prints with a 0.4 mm layer thickness. The printing temperature for the filament (measured at the extrusion head) was 275°C and the bed temperature 90°C, as recommended by the manufacturer.
For each type of sample, five prints were obtained at a printing speed of 30 mm/s. The placement method and the obtained specimens are presented in the Figures

Characterization methods
The tensile and three-point bending tests were done on the WDW -150 S universal testing machine. The testing machine can perform static and dynamic tests (including alternating fatigue). The test force is between 1 and 150 kN.
The toughness fracture was determined by Charpy hammer pendulum with the following characteristics: -arm length l=380 mm, m=6.784 kg and maximum measured energy W=5kpm.
Relation 1 was used to calculate the toughness.

3.Results and discussions Determination of physical-mechanical properties
For mechanical tests, a number of 5 specimens were obtained for each type of test. From the 5 values obtained, the minimum value and the maximum value were eliminated, and from the remaining 3 values the arithmetic mean was made.
Results concerning three-point bending test printing are given in Table 1.

Table1. Bending test results
No. crt.  One may remark that in the case of three-point bending test, the average resistance is almost equal compared to the reduction of material in the case of samples with hexagonal gap compared to solid ones, so it is recommended the configuration with hexagonal gaps to obtain marks required mainly for bending material consumption.

Sample
Results concerning toughness tests printing are given in Table 2.

Figure 8. Toughness strength
In the case of the toughness test, the behavior is different in the sense that the average resistance is almost the same as the reduction of the material in the case of hexagonal gap samples. At a 30% reduction of the material used, the decrease of the value of the average resistance was of 37%, instead the joint (maximum bending before breaking) decreased by 50%. In the case of corrugated vacuum samples, the maximum bending strength decreased by 70% while the deflection increased, showing that the whole assembly has a more elastic behavior. Toughness strength is the property most influenced by the reduction of material (a decrease of over 50% in strength).
Results concerning the tensile tests printing are given in Table 3.  The maximum tensile strength (average) in the case of samples with hexagonal gap decreases by 50% even if the reduction of material was 30%, instead the average elongation increases compared to the samples printed in full.
In the case of samples with corrugated gaps at a material reduction of 15%, the maximum resistance to average tensile decreased by almost 70% while the average elongation by only 27% compared to the samples printed in full.
Partial conclusion: in the case of 3D printed parts subjected during tensile use, the full printed version is recommended (100%).

Conclusions
The present paper resides in developing and characterizing two internal build architectures for 3Dprinted materials, namely a hexagonal model structure and a sinuous architecture with an amount of materials consumed 30 and 15% less. From our experiments there are the following conclusions: -full specimens and two types of gaps were obtained where the reduction of material consumption was 30% for hexagonal gaps and 15% for corrugated gaps; -in the case of the tensile test, it was shown that the maximum average strength of the test piece with hexagonal gaps was 50% lower compared to that of the solid test piece but there was an increase in elongation before breaking, while in the case of with corrugated type gaps the resistance decrease was 70%. If it is desired to obtain parts with high tensile strength, it is recommended to use the full variant and only if the part is not intensely requested, the hexagonal configuration can be used; https://doi.org/10.37358/MP.21.3.5508 -in the case of three-point bending test, the average resistance is almost equal compared to the reduction of material in the case of samples with hexagonal gap compared to solid ones, so it is recommended the configuration with hexagonal gaps to obtain marks required mainly for bending material consumption; -for the parts required for toughness, only the full version is recommended. Finally, it was determined that the part with an internal configuration with hexagonal type gaps kept the mechanical properties closest to the full specimen, while achieving a saving of 30% of the material used.