A method of manufacturing a separation panel (1) comprising:- producing by injection moulding two semi-panels (101；102) comprising:o a sidewall (110) comprising an inner surface (111) and an outer surface (112)；o a pair of parallel longitudinal walls (120)；o a pair of parallel traverse walls (130)；and wherein at least one semi-panel (101) further comprises a plurality of longitudinally and/or traverse partition walls (140) delimitating inside cavities (150) in said semi-panel (101), and wherein one or more of said partition walls (140) comprise respective openings (141)；- arranging said two semi-panels (101；102) one against the other, thereby forming a closed structure (2) with a plurality of inside cavities (150) connected along the longitudinal direction (3) and/or along the traverse direction (4) through said openings (141)； and- welding said two semi-panels (101；102) together, thereby forming said separation panel (1).
