What is a 3D printer in construction?
A 3D printer in construction is a machine that builds elements up layer by layer, with a computer-controlled head extruding a bead of mortar, concrete or polymer along a path taken from a digital model. The technique is also called additive manufacturing or, for the most common variant, 3D concrete printing. The essential difference from conventional concrete work: no formwork is needed, because the mortar holds its own shape while it sets.
How it works
- Digital model — the element is modelled in 3D and cut into horizontal layers (slicing)
- Print path — software converts the model into the path the print head follows
- Printing — a gantry robot or robot arm lays down mortar in beads typically a few centimetres wide and 1 to 3 cm high
- Reinforcement — added during or after printing: post-tensioning cables in printed ducts, placed bars, or fibres in the mix
- Finishing — filling the voids, connections, surface treatment
The mortar has to satisfy two contradictory demands: stay readily pumpable in the hose, and be shape-stable immediately on leaving the nozzle so it can carry the next layer.
Application in practice
- Housing. Project Milestone in Eindhoven is a collaboration involving Eindhoven University of Technology, Van Wijnen, Saint-Gobain Weber Beamix, Vesteda and the municipality. The first 3D concrete printed house, with around 94 m² of floor area, was occupied at the end of April 2021 and meets Dutch building regulations.
- Bridges and civil works. Printed cycle and footbridges exploit the shape freedom to put material only where the forces run.
- Precast elements. Permanent formwork, noise barriers, facade elements and street furniture in complex shapes.
- Restoration. Printing moulds or replacement pieces for ornament.
Advantages and limits
Advantages: no formwork cost, considerable shape freedom (a curved wall costs no more than a straight one), material saving by placing material only where it is needed, and few manual operations on the print floor.
Limits: reinforcement remains the hardest problem, because printed concrete, like any concrete, is weak in tension. Print mortars cost more per cubic metre than ordinary concrete, horizontal spans cannot readily be printed without support, and each project still requires a bespoke case for demonstrating compliance with building regulations.
Related terms
- Concrete
- Formwork
- Precast
- Reinforcement
- 3D laser scanner
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.