Preliminary Research and Documentation

The following research and documentation is meant to get this project started. Please consider this a work in progress. Significant work is needed to move this project forward.

A concrete 3D printer comprises of the following:

• 3D design software
• Concrete as a 3D print material
• Gantry 
• Extruder

3D Design Software

A 3D software application is used to create the design of  the structure. This is then sent to the 3D printer for printing. 

 

Concrete as a 3D Print Material

Concrete is a mixture of cement, sand, crushed stone, Portland cement mixed with water. Water in the concrete acts as a binding agent. The aggregates (sand and crushed stone) in the mixture are bound together by cement. The size of these aggregates is an important factor to consider when creating concrete. 

Water in concrete activates the cement, which acts as the binding agent. Aggregates (coarse and fine) in the mix are bound together by the cement. Mixes that use larger aggregates tend to be stronger than those with finer aggregates.

Collaborators need to research on the exact amount of aggregates and cement mixtures to ensure that the structure is long lasting.

 

Extruder

An extruder is a component that lays concrete layer by layer to build the structure. The extruder must be capable of printing objects of different sizes. The extruder consists of 2 parts. A base and a dispenser nozzle. The base is connected to the raining system on the gantry. The dispenser nozzle is screwed to the the base and dispenses the right amount to concrete depending on the design.

When printing larger objects like walls, a 6-inch nozzle is more suitable than a 1-inch nozzle, When printing thinner surfaces like platforms or pathways, a 1-inch nozzle is more suitable. The nozzles dispensers must be designed for different applications.

 

Gantry

The printer is mounted on the 3D printer gantry . The gantry has a railing system that allows the extruder to move horizontally and vertically while dispensing concrete layer by layer.

 

The 

following 

 

 

 

 

 

  

Figure 5 - 3D printing a concrete wall.

 

Extruder rails

Extruder rails are rails that move vertically and horizontally depending on the values computed by the application software. The vertical movement allows them to be placed above and below the child base plates depending on the 3D model. The horizontal movement allows them to print the 3D model. These rails are controlled from the application software and operate on connected motors, similar to the base plates.

Figure 6 - Extruder rails

 

3D Printer Extruder

The 3D printer extruder is fitted to the extruder rails and can move horizontally while printing. The print medium is fed to the extruder from tubes connected to the chassis. Each extruder may have different properties depending on the print material. Here are a few examples of 3D extruders and print material.

Print material	Extruder and Description
Plastic and polycarbonate	Standard 3D extruder that is currently used in regular 3 printers. The extruder has an option of controlling the aperture and flow of material depending on the object. For example, consider printing a rod and a pipe that have a diameter of 2 inches and a pipe. The same extruder's must be capable of adjusting the size and shape of the printed object.
Clay and concrete	An extruder for clay of concrete is different from the usual printer. A construction 3D printer extruder is used for these. An example application of this extruder is building walls and platforms. When constructing a wall with spaces for doors and windows the software application must program 2 base plates.  For more information, see this video.
Calcium carbonate	Similar to the extruder for clay and concrete, the extruder for calcium carbonate can print minute details based on the 3D design. This extruder will be mostly used to print coral reefs. For more information, see this video.
Other	TBD

The following image is an illustration of a sample extruder.