Abstract: A mold construction system is presented for use in additive manufacturing of a metal object. The system comprises: at least one mold provision device controllably operable to form one or more mold regions defining one or more respective object regions in a production layer, and configured to receive molten metal deposited to each object region; and a control system operating each mold provision device in accordance with a predetermined building plan. The mold provision device, in accordance with said predetermined building plan, creates each mold region of each production layer with at least one metal-facing zone configured to define at least one cavity forming the object region to receive the molten metal therein. The metal-facing zone comprises a predetermined arrangement of spaced-apart sites of relatively weak mechanical properties relative to spaces between said sites within said mold material.