A Method for 3D Printing a Construction, a 3D Construction Printer System, and a Printing Unit for Use in a 3D Construction Printer System

A 3D construction printing system configured for printing using a printing material, the 3D construction printing system comprising:

• a printing unit, comprising:
• a hopper;
• a printing head;
• and
• a rotary element;
• a gantry system;
• a material pump;
• a flexible tube;
• and
• an additive system, comprising:
• a control mechanism;
• an additive outlet;
• and
• a control unit;
• wherein:
• the gantry system is configured for moving the printing unit in a three-dimensional space;
• the material pump is configured to receive a precursor printing material comprising binder, water, and sand and pump the precursor printing material towards the printing unit via the flexible tube forming a flow of the precursor printing material in a material transport direction;
• the hopper is arranged downstream of the material pump in the material transport direction and upstream of the printing head;
• the control unit is operationally connected to the control mechanism of the additive system for controlling an amount of additive added to the precursor printing material;
• and
• the additive outlet of the additive system is located upstream of the hopper in the material transport direction and provides a connection for fluid between the control mechanism and the flow of the precursor printing material downstream of the material pump, and the control unit is configured to control the control mechanism to form a flow of the first additive to the flow of precursor printing material, whereby a flow of printing material is formed for extruding via a nozzle opening of the printing head.

A printing unit for use in a 3D construction printing system wherein the printing system is configured for printing using a printing material comprising a precursor printing material and a first additive, the precursor printing material comprising a binder, water, and sand, said printing unit comprising:

• a material inlet;
• a hopper configured for accommodating a quantity of the printing material;
• a printing head configured for extruding the printing material, said printing head being arranged downstream of the hopper in a material transport direction;
• a rotary element configured for moving the printing material in the material transport direction from the hopper to the printing head;
• and
• an additive outlet, wherein the additive outlet is located upstream of the hopper in the material transport direction.