- 3D printed houses require different design considerations than traditional construction, like print path strategies, rounded corners, and avoiding overhangs.
- Object sizes must fall within printer build volumes, which currently max out around 12x3x3 meters for the largest 3D construction printers.
- Wall thicknesses, layer heights, and nozzle sizes influence strength and print time. Typical values are 30-80mm for wall thickness and 5-15mm for layer height.
- Support structures or thickened base layers are needed to prevent collapse of overhangs and spans during printing.
- Orienting prints vertically can provide better strength along load paths. Horizontal, stepped, and non-planar layering strategies enable different geometries.
- Large prints can be segmented into elements that are assembled post-printing. Sectioning is also useful for transporting elements.
- Electrical and plumbing systems need to be modeled integratedly or planned for post-print insertion via channels.
- Topology optimization and simulation tools help refine structural performance digitally before printing.
How to Design 3D Printed Houses
3D printing with concrete is an innovative technology that enables on-site automated construction of houses and buildings by depositing material layer-by-layer. However, it requires adapted design guidelines to ensure the planned geometry can be successfully printed. Here are key considerations:
Printable Object Size Limits
The maximum printable object dimensions are constrained by the build volume and weight capacity of the 3D construction printer.
Printer Build Volume Limits
The largest 3D concrete printers like those of Cobod or COBRA have build envelopes around 12x3x3 meters (LxWxH). Smaller mobile printers may have reduced envelopes under 5 meters in some dimensions.
Any housing design should fit within these dimensional limits or be sectioned into smaller components. Exceeding the build volume is not feasible as the gantry cannot reach beyond its frame.
Printer Weight Limits
Most large 3D construction printers have a maximum object weight capacity of 1-3 tons. Heavier elements risk compromising the printer itself.
Home or building designs should avoid exceeding these weight restrictions in a single continuous print. Sectioning the structure strategically into lighter sub-components can help overcome weight limits.
Optimizing Wall Thickness and Layer Height
Two key parameters influencing print time, material use, and structural strength are:
- Wall thickness – Outlines the number of perimeters or shells printed for each wall section. More shells increase strength but also print time.
- Layer height – The vertical resolution and thickness of each deposited material layer. More layers mean higher resolution but slower overall printing.
Typical values are:
- Wall thickness: 30-80 mm
- Layer height: 5-15 mm
Thinner walls and lower layer heights generally produce finer resolution and details but are slower. Finding the right balance for the design requirements is important.
Strategies for Print Path and Layer Orientation
3D printing builds up structures through continuous extrusion of material beads along a toolpath. This requires different design strategies than traditional construction:
Closed Loop Printing
The most common technique is using closed loop toolpaths, where each layer is printed in a single continuous loop path before moving upwards. This allows non-stop extrusion for faster printing.
Open Loop Printing
Open loops can also be used where layers are printed back-and-forth in alternating directions. However, this may increase printing time. Open loops should be minimized where possible.
Some designs may call for adjacent layers to intentionally overlap each other, like for interlocking bricks or stairs. The overlapping depth should be at least 5-10mm.
Orienting Layers Vertically
Orienting the print direction vertically provides maximum strength along vertical load paths. This is ideal for walls, columns, etc. Horizontal layering can be used for floors and roofs.
Avoiding Unsupported Overhangs
A core constraint is avoiding any overhangs, spans, or cantilevers that are unsupported below. As layers are deposited, they need a solid base to build upon or they will collapse under their own weight.
Table: Typical Overhang Angles in Function of Layer Height and Extrusion Width
Maximum Overhang Angle
As a rule of thumb, most printers can only bridge overhangs up to 10 degrees from vertical depending on factors like layer height and nozzle size. Anything beyond this limit requires additional supports during printing.
Combining with Traditional Elements
In some cases, segments with long unsupported spans can be constructed traditionally, then interfaced with the printed components. Hybrid designs provide more flexibility.
Thickened Base Layers
Proper design should minimize unsupported spans through techniques like thickening lower layers or using sloped geometries to transfer loads directly downwards.
Sectioning Large Designs Into Printable Elements
Models exceeding printer build volumes or weight limits can still be realized by strategically segmenting the structure into smaller printable elements.
These elements can then be assembled together on site after printing using traditional 3d construction methods. Sectioning also facilitates transporting printed elements from printer to site and can solve overhangs.
When sectioning, overlapping interlocking interfaces between sections should be designed to ensure proper alignment and load transfer. Adhesives or fasteners may be required for bonding.
Optimizing 3D Printed House Designs for Performance
3D printing technology enables new design freedoms for houses, but engineers must optimize the geometry, structure and materials for performance. Here are key strategies:
- Simulate designs digitally with finite element analysis to validate structural integrity under load conditions like wind, seismic forces, etc. Iteratively refine the geometry to improve stress distribution.
- Optimize wall thicknesses, internal lattices, and reinforcement for structural stability, insulation, and weight limits. Balance strength vs print time.
- Orient the print direction strategically for maximum axial load bearing capacity. For multi-story buildings, optimize print orientation per layer.
- Design complex organic shapes with curves and contours to enhance earthquake resilience and dampening. Avoid simple block-like forms, long unsupported straight walls.
- Use topology optimization algorithms to iterate hollowed out shapes that minimize mass and material usage while preserving strength.
- Carefully design how printed components will interface with non-printed features like windows, doors, utilities. These connections are vulnerabilities.
- Collaborate with materials scientists to develop custom printable concrete composites reinforced with polymers and nanomaterials for superior strength and ductility.
- Validate designs via industry standard tests for buckling, vibration, impact, fatigue, and simulated environmental conditions.
Integrating Electrical and Plumbing Systems in 3D Printed Houses
Plumbing and electrical integration must be considered early when designing 3D printed homes. Strategies include:
- Model required conduit routes, outlets, fixtures etc. directly into the 3D CAD design files. This enables conduits to be placed into the structure.
- Plan vertical shafts and channels for easier post-print installation of wiring and piping if embedment is not possible.
- Optimize conduit diameters and routes for efficient space usage within printed walls and floors.
- Print removable ports for utilities access. This aids maintenance and alterations down the road.
- Explore printing with conductors like carbon fiber or graphene to enable embedded circuitry.
- Partner with HVAC and plumbing engineers to develop ductwork and pipes suited for 3D printing integration methods.
- Create library of modular electrical and plumbing components that can be inserted into prints.
- Seek feedback from contractors, inspectors and tradespeople on best practices for interoperability of 3D prints with finishing utilities.
Validating Designs Digitally via Simulation
Advanced topology optimization and finite element analysis tools enable validating the mechanical performance of designs digitally before printing:
- Simulate structural integrity under predicted load cases like wind, seismic, snow, etc.
- Identify and remediate areas of high stress concentrations within the geometry.
- Optimize wall thicknesses, infill densities, and reinforcement layouts for best strength-to-weight ratio.
Thorough simulation and optimization minimize costly design iterations and print failures by verifying designs perform as intended.
The integration and automation advantages of 3D printing must be balanced with adapted structural design principles tailored for layer-by-layer additive construction. Following the guidelines outlined here will help architects successfully transition designs from concept to physical reality. Expert input from structural engineers is also recommended when pushing the boundaries of new geometries and capabilities unlocked by 3D printing technology. With thoughtful design tuned for production, 3D printing can usher in the next generation of resilient, affordable and sustainable housing.