Page 54 - MSAM-3-3

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

Table 4. Peak shear load at different print and print bed Table 6. Shear strength of print bed adhesion computed with
temperatures equation I at different print and print bed temperatures
Print bed Print temperature (°C) Peak shear Print bed Print temperature (°C) Shear strength
temperature (°C) load (N) temperature (°C) (MPa)
30 220 207.4 30 220 0.843
225 376.1 225 3.013
230 541.4 230 3.884
235 739.6 235 3.436
35 220 421.2 35 220 2.163
225 660.9 225 3.071
230 745.5 230 3.601
235 965.0 235 4.615
40 220 587.0 40 220 3.181
225 810.9 225 3.084
230 Part fail 230 Part fail
235 Part fail 235 Part fail
45 220 798.6 45 220 3.819
225 Part fail 225 Part fail
230 Part fail 230 Part fail
235 Part fail 235 Part fail

Table 5. Failure areas at different print and print bed 50 mm/s closely resembles the PS of subsequent layers in
temperatures the standard ABS profile.

Print bed Print temperature (°C) Failure area It was observed that the printed rHDPE filament broke
temperature (°C) (mm ) while printing the first layer at 50 mm/s. At 15 mm/s, the
2
30 220 246.0 filament did not break, but it was sliding off the print bed.
225 124.8 At 5 mm/s, the sliding on the print bed was significantly
230 139.4 reduced.
235 215.3 Lower PSs are better suited to match the extrusion
35 220 194.8 speed, allowing time for the molten filaments to adequately
225 215.3 settle, thus reducing the breaking and sliding of printed
230 207.0 filaments. This also explains why first layers are often
235 209.1 printed at lower speeds compared to other layers, as
40 220 184.5 first layers typically have larger layer heights and lower
extrusion speeds in most MEX machines. For subsequent
225 213.2 tests, the PS of 5 mm/s is recommended.
230 Part fail
17
235 Part fail As mentioned by Sun et al., the temperature profile
of the print significantly affects bond formation and print
45 220 209.1 bed adhesion. Results indicate significant improvements
225 Part fail
at an elevated PBT of 40°C, likely due to the cooling rate
230 Part fail that allows the printed filaments to stay at an elevated
235 Part fail temperature for a longer duration, where bonds can
develop. 17
4.3. Printing at various speeds These tests establish the importance of the temperature
Parts were printed at three different PS: 5 mm/s is the profile of the print. Therefore, temperature settings,
reduced PS recommended in the literature; 14,16 15 mm/s is such as PBT and PT, are important parameters that we
the PS of the first layer in the standard ABS profile; and subsequently investigated.

Volume 3 Issue 3 (2024) 11 doi: 10.36922/msam.4084