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Week-17 Wildcard week

Week-17 Wildcard week

This is my 17th week at FabAcademy. This week we had the wildcard so I learnt about designing and fabricating something completely new: 3D printing concrete. The assignment of the week consisted of:

  • Design and produce something with a digital process (incorporating computer-aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it.

Design and fabrication workflow of 3D printed concrete.

I visited a different technological center from my university: Center for Technological Innovation in Construction and Civil Engineering (CITEEC) https://www.udc.es/citeec/index-en.html and with the support of their staff I leanrt about printed concrete, which was completely new to me. Hereafter I documment the design process workflow I learnt which includes the main steps necessary for printing concrete. After this section I documment my first ever fabricated piece of printed concrete.

  1. Design with Grasshopper (Rhino 3D)

The process begins by creating a parametric model of a cylinder (or any shape one wants) using Grasshopper within Rhino 3D. Steps:

Define the base circle and extrude it to the desired height.

Apply any patterns or structural modifications as needed.

Ensure the model is a closed, watertight mesh suitable for 3D printing.

Export the model in STL format.

Note: Maintain a minimum wall thickness of 30 mm to ensure structural integrity during printing.

  1. Slicing with Cura

Import the STL file into Cura slicing software to generate the G-code for the printer.

Configuration:

Layer Height: Set between 10–15 mm.

Wall Thickness: Minimum of 30 mm.

Infill: Typically set to 0% for concrete printing.

Print Speed: Adjust according to printer specifications.

Nozzle Diameter: Match with the printer’s nozzle size.

Export the G-code file and transfer it to the Be More 3D printer via USB or network connection.

Here you can see an illustration of the design in Cura of the first test we did:

  1. Concrete Mix Preparation

Prepare a concrete mix optimized for 3D printing, focusing on properties like pumpability and buildability.

Components:

Cement: Use Portland cement or a suitable alternative.

Aggregates: Fine aggregates with a maximum particle size of 4 mm.

Admixtures: Include superplasticizers to enhance flow and setting agents to control curing time.

Water: Adjust to achieve the desired consistency.

Note: The mix should be cohesive enough to retain its shape post-extrusion yet fluid enough to pass through the pump and nozzle system.

Here you can see our mix just some minutes ago ready to go to the printer:

  1. Printing Process

With the G-code loaded and the concrete mix prepared, proceed to print.

Setup:

Ensure the printer is calibrated and the build platform is clean.

Load the concrete mix into the printer’s hopper.

Initiate the printing process via the printer’s control interface.

Monitoring:

Continuously observe the extrusion process to detect any anomalies.

Ensure consistent layer deposition and address any issues promptly.

Post-Printing:

Allow the printed structure to cure as per the mix’s specifications.

Implement any necessary post-processing steps, such as surface finishing or structural reinforcement.

Safety Note: Always wear appropriate personal protective equipment (PPE) and follow safety protocols during the mixing and printing processes.

Here you can see a picture of the computer that controls the machine with the setting of all printing parameters which are read from the gcode:

And here the machine printing:

Design and fabrication of a printed cylinder.

By reproducing the workflow described above, I designed a simple concrete cylinder for printing. The cylider was 17,5 cm in diameter and 25 cm height. In the following I inlcude an extract of the code, which can be downloaded in full in the download section.


;FLAVOR:Marlin
;TIME:1800
;Filament used: 0.000000m
;Layer height: 0.5
;Generated with Cura_SteamEngine 5.4.0
M140 S0
M105
M190 S0
M104 S0
M105
M109 S0
G92 E0
G28 ;Home
G1 Z2.0 F3000 ;Move Z Axis up
G1 X0.1 Y20 Z0.3 F5000.0 ;Move to start position
G92 E0
G1 F1500 E-6.5
G1 F3000
G92 E0
; G-code for concrete 3D printed cylinder
G21 ; set units to millimeters
G90 ; use absolute positioning
G92 X0 Y0 Z0 ; set current position as zero
M82 ; use absolute distances for extrusion
G28 ; home all axes
G1 X72.50 Y0.00 Z0.00 E1.20 F1200
G1 X71.40 Y12.59 Z0.00 E2.40 F1200
G1 X68.13 Y24.80 Z0.00 E3.60 F1200

...

G1 X46.60 Y-55.54 Z245.00 E2214.00 F1200
G1 X55.54 Y-46.60 Z245.00 E2215.20 F1200
G1 X62.79 Y-36.25 Z245.00 E2216.40 F1200
G1 X68.13 Y-24.80 Z245.00 E2217.60 F1200
G1 X71.40 Y-12.59 Z245.00 E2218.80 F1200
G1 X72.50 Y-0.00 Z245.00 E2220.00 F1200
G1 Z255.00 ; lift nozzle
M104 S0 ; turn off extruder
M140 S0 ; turn off bed
M84 ; disable motors

Here you can see the resulting printed concrete cylinder:

Files for download and replication

Here you can download the full gcode file used for printing the simply concrete cylinder: GCODE_Concrete_cylinder.