Key SALEM considerations for ​CalEarth

A project log for SALEM - Construction 3D Printing

Suspended Additive Layer Extrusion Manufacturing - 3D Printing extremely large multi-storey structures.

jon.knuttonjon.knutton 08/07/2020 at 23:440 Comments

This Log is to better highlight the main considerations, advantages and adaptations applicable to SALEM for the CalEarth humanitarian foundation.

There are currently around 1.6 billion people who do not have adequette access to shelter and 1.9 billion who are considered severely food insecure. This is the fundamental driving force for why SALEM exists and why it is open source. In modern society no one should have to go to sleep hungry and without a roof over their head. it's unnacceptable and deeply troubling that humanity could achieve such monumental feats of engineering and technological progress and yet still allow 1/5 of its people to go without the most basic of needs.

When fully realised SALEM will allow for the cheap, rapid and labour light construction of structures of virtually any size in some of the hardest to reach locations on the planet and beyond. 

One of the key design requirements of the printer was that it would be compactable, modular and for each subassembly to weigh no more than the manual handling limit of a two person lift. It was also designed to need no heavy machinery to be assembled. This is to ensure that it could be used to service the housing needs of individuals that do not have the benefit of a fully infrastructured environment, making it an ideal concept for use in humanitarian missions.

The setup process of the printer demands no prior knowledge of architectural or engineering principles and is simple and easy to learn and teach with no technical steps (beyond basic computer knowledge) or requirement for careful accuracy (see section 2.7.0 of the proposal for a step by step detail). The print envelope is entirely relative and does not require a set up that is perfectly square or a ground that is levelled to any great degree. Calibration steps can be integrated into the software to automatically calculate the shape, area and ground slope/displacement to remove virtually all need for accuracy in setup and preperation. 

The printer was also designed with the intention of printing with materials that can be readily found on site. For humanitarian efforts in arid regions, this could be as simple as a soil slurry. For wetter and seismically active regions clay can be refined on site out of the surrounding soil using a basic old method called wet clay harvesting. When the clay slurry has been extruded and has dried, a fire can be lit inside the structure to cure it for a long lasting weather resistant finish. To improve the structural integrity of the prints the soil/clay slurry could also be mixed with a small amount of lime or cement (2-10%)

Construction 3D Printing naturally lends itself to the architectural ethos of CalEarth of utilising the power of the curve to produce stronger structures as this form negates the need for pausing the print to fit lintels and other supports. 

As SALEM was designed with the intention of use for applications both small and very large it is also possible to set up the printer once for a large print envolope and produce multiple habitats in one print in much the same way you would stack multiple components onto one print with desktop 3D Printers to save time. This means that the build crew can be very small. needing only an initial crew of two people to assemble the printer and then one to feed additional building mix into the mixing tank as required.

One pain point of this solution for humanitarian work is that there is a labour cost associated with creating the slurry. It is not expected that in the earliest versions of SALEM that the printer will be well enough engineered to manage large stones or other big impurities in the slurry consistency meaning the soil to be used will need to be siphted before being mixed with water and cement/lime in the mixing tank.

For this reason, this technology would be most beneficial in proactive humanitarian missions wherein the community can prepare the soil or clay mix ahead of the printers arrival as opposed to producing the build materials in tandem with the printing process. For reactive missions (such as emergency relief) where you would want to rapidly produce simple temporary structures without any preperations the CalEarth sandbag method is likely still favourable.