PSI - Issue 68

374 A. Ceci et al. / Procedia Structural Integrity 68 (2025) 372–378 A. Ceci et al. / Structural Integrity Procedia 00 (2025) 000–000 3 ( , , ) = (2 ) + (2 ) + (2 ) + ∙2 (2 )∙ (2 )3 + (2 ) ∙ (2 )+ (2 ) ∙ (2 ) + = 0 (1) With parameters a=0.5 and b=0.8, Figure 2 shows the unit cell and the structure obtained by linear repetition in three directions (7 cells in the x and y directions, 3 cells in the z direction).

z

x

y

Fig. 2 : a) side view of the unit cell, b) isometric view of the unit cell, c) structure to be produced.

Once the CAD model is designed, the PLA model is created through 3D printing. For a high-quality metal model, slicing with the correct print parameter settings is essential. The key parameters include print speed, extruder temperature and print bed temperature. After the PLA model is completed, the plaster mold is created. Venting channels were made using plastic pipes connected to the structure and successively the entire assembly was placed in a steel container and covered with a mixture of water and plaster. The plaster used is a special investment casting one. Additionally, weights were placed on the PLA model, serving both to hold the model in position within the plaster and to form the pouring channels. The plaster mixture is left to dry for 24 hours, after that the weights are removed. The next step is the burnout process, where the plaster mold is placed in a cold muffle furnace and heated up to 900°C. The PLA completely degrades, leaving a negative imprint on the structure of the plaster. A skectch of the whole process is reported in Fig. 3. PLA MODEL

a) Model with CAD

b) Slicing

c) 3D prin:ng of the PLA model

PLASTER MOLD

d) Model prepara:on

e) Plaster cas:ng

f) PLA burnout

METAL STRUCTURE

g) Quenching

h) Metal removal

i) Final structure

Fig. 3 : a)-i). Sketch of the processing steps of the reticular structure. a) Model with CAD, b) Slicing, c) 3D printing of the PLA model, d) Model preparation, e) Plaster casting, f) PLA burnout, g) Quenching, h) Metal removal, i) Final structure.