Liquid composite moulding of Lactam 12 monomer and activating system (APLC12) into satin weave carbon fabrics is investigated, with emphasis on minimising the void content in the final part. The main sources for void formation are identified. The solidification shrinkage is quantified to account for at most 9% in the matrix. Optimal flow conditions are determined to minimize void content during liquid moulding. Finally, as the monomer is kept under Nitrogen prior to processing, diffusion and solubility of Nitrogen in the monomer are characterized, to indicate that Nitrogen coalescence during injection is a major cause of voids in the final part. The average void content is reduced from initially 15% to below 1% in polyamide 12 based composite plates with optimised process conditions.