Minibuilders – How to 3d print big structures with small robots

Written by: admin@makezilla


Minibuilders from STEREOTACTIC on Vimeo.

There has always been a close relationship between architecture and technology. However, recently architecture has stagnated and the construction industry has been slow to adopt technologies that are already well established in other fields. Whilst we design digitally we still construct manually.

Robotics offers great potential towards innovation within the construction industry. However, in their current form applied to the architectural field, in particular construction robotics, these systems all share a specific limitation: the objects they produce are linked to and constrained proportionally to the size of the machine. This methodology of production and construction is not scalable. In this sense, to create a house, using current construction robotics, the machine needed must have a work envelope as large as the house itself.

Hence, the project here below elaborated aims to address this particular limitation through the creation of a technology that is both scalable and capable of fabricating structures using tools that are independent of the final product’s shape or size. The Team explored and investigated the potentials of additive manufacturing (3D Printing) applied to the architectural scale.

Substituting one large robot for number of smaller more agile robots, we developed a family of small-scale construction robots, all mobile and capable of constructing objects far larger than the robot itself. Moreover, each of the robots developed was to perform a diverse task, linked to the different phases of construction. Working together as a family towards the implementation of a single structural outcome.

Minibuilders is a family of three robots, each robot linked to sensors and local positioning system. These feed live data into custom software allowing control over the robots movement and deposition of material, an fast setting artificial marble.

Current research focuses on 3D printing for the FDM (Fused Deposition Modeling). Which means that three dimensional objects may be produced by depositing repeated layers of solidifying material until the shape is formed. Material adheres to the previous layer with an adequate bond upon solidification, may be utilized. 

The positioning device, the small robots all equipped with the print-head nozzle, move in a predefined path depositing material in layers. Each layer base is defined by the previous layer, and each layer thickness is defined and closely controlled by the height at which the tip of the print-head is positioned in relation to the previous layer. Controller, material supply and power sources are connected externally.

Step 1: Base robot

The first robot, the Base Robot, lays down the first ten layers of material to create a foundation footprint. Sensors mounted inside the robot control direction, following a predefined path. Traveling in a continuous path allows for a vertical actuator to incrementally adjust the nozzle height for a smooth, continuous, spiraling layer. The advantage of laying material in a continuous spiral is that it allows for constant material flow, without having to
move the nozzle up at intervals of one layer.

The foundation robot size 26*35*37 cm, weights 2.05kg.

Tools and materials:

-Makerbeam with bearings and bolts and nuts

-QTR-8RC reflectance sensor array

-Electronic tape

-Waterjet aluminum gears

-T2.5 timing belt and pulley

-Laser cut acrylic

-Motor, Axle and wheel mount (aluminum or 3d printed)

-9/4/4mm bearings

-4mm metal shaft

The base robot is mobile, with a vertical CNC moving the nozzle up in Z, incrementally while the robot moves along a predefined path. This creates a continuous spiraling toolpath for the nozzle laying the material on top of each layer previously printed.

All the three robots make use of Makerbeams for their frames, giving flexibility within the prototyping process. Makerbeams are reusable and relatively easy to adjust using the T-slot bolt system. The CNC is also made using the makerbeam bearing kit. You can learn from projects listed here.

The connection between the wheels, chassis and motors is simple using a bearing to support the wheel shaft attached with self locking nuts. The stability of the shaft is reliant on the size and spacing of the bearing set. This solution created a more stable platform for printing than a soft suspension system.

For the robot to follow the predetermined path we used a basic QTR-8RC reflectance sensor array. This allows the robot to follow a predefined path. When testing outside we found that the sensor would lose the track of its path under strong direct sunlight. The simple solution we found to this was to shade the sensor from the sun.
The Arduino and Processing file can be found in step 4 software section.