Repurposing Portland Stone Waste with the Novi 3D Printer

Background

Dealing with the waste in this world is now, more than ever, of crucial importance. In the limestone quarrying industry, for instance, it has been suggested that valuable waste is around 80% to 90%. In an effort to sustainably deal with this high amount of valuable limestone waste, Jack Biltcliffe, in collaboration with ASTUDIO and the Portland Sculpture and Quarry Trust, developed Novi, a 3D printing mechanism that has been designed from the ground up to work with the extrusion of limestone slurry. This project was developed as part of a major project for an undergraduate degree at Brunel University London.

Quarrying Limestone – An Inefficient Process

The architecture industry, which is the primary market for quarried limestone, has set high quality standards and requirements for limestone. Inefficiencies which cause waste during the quarrying and masonry stages are largely due to the fact limestone is a natural material which contains many natural faults. For the quarries it is not economical to cut around these faults and so extracted stones with faults in them are often wasted. The whole masonry process produces waste at such a fast rate it seems impossible to keep up, and so vast areas are needed to store and process waste. When a large enough quantity has accumulated the waste stone can then be transported to a crusher to be turned into aggregates.

Working with the Isle of Portland

The Isle of Portland has been built around the limestone quarrying industry. Portland Stone is some of the most sought after limestone, notable buildings such as St Paul's Cathedral (London, UK) use it as a building material. Through contacts on the Isle of Portland such as the Portland Sculpture and Quarry Trust (PSQT), this project has been able to collaborate with quarries and become involved with the exciting regeneration project happening on the island. The objective of this project is to reuse the waste material produced during the quarrying in a manner that will help with the regeneration project on the Isle of Portland through a sculptural piece.

Limestone Paste Extrusion Development

Through a series of iterative experiments, a limestone paste extrusion process was developed as part of a major project for an undergraduate degree at Brunel University London. Initially, it was observed that a fine grain of Limestone would mix with coolant during the stone cutting process to create a limestone slurry. This slurry can be left to dry out, then hardens completely and is bound together. The process of drying out slurry can be exploited for paste extrusion and ultimately 3D printing purposes.

Material Development

Testing of the pure limestone prints presented many challenges. For instance, once the printed object comes into contact with water it disintegrates back into slurry again. Structural testing also showed the pure limestone parts were extremely weak in tension. Material development through the addition of external compounds into the mix has been ongoing, with positive results so far.

3D Printer Development

The first physical experiments involving 3D printed limestone objects involved hacking a ‘Mendel90’ desktop 3D printer to use a 10ml syringe, as a form of controlled paste extrusion. After optimizing the syringe setup and managing to successfully print in limestone, it quickly became apparent that safely extracting prints was a problem because of the long drying time. The small scale test objects had to dry for over 12 hours before they could be handled or removed from the build plate. This means the 3D printer cannot be used for long periods of time while a print dries. To combat the need for waiting on prints, further research into tri axial movement mechanisms was conducted. A version of a robotic arm seemed a great fit because of its versatile nature. Further research into robotic arms found that one of the simplest mechanism, giving all 3 axis of movement required, is the SCARA mechanism. The SCARA robot is traditionally used as a pick and place robot in assembly line operations. The two arms work together to recreate the XY positional values. Unlike conventional 3D printers it is not constrained to a self contained build plate, instead any flat surface can become a build plate and the printer can move to a new build plate. A custom developed SCARA robotic arm called ‘Novi’ was designed and developed as part of the project with 3D Printing specifically in mind.

Larger Scale Extruder

A larger format paste extruder was developed alongside ‘Novi’, to allow for larger prints. The new extrusion system builds upon the previous system, a larger format syringe with a capacity of 200ml was chosen to fit on the end of the arm. The benefit of continuing to use syringes at this stage is ease of use and the ability to buy in multiple syringe bodies which can be filled with different material mixes and used as a cartridge drop in drop out system.

Application

The hope for this project is that it will help with the regeneration happening on the Isle of Portland through the creation of sculptural pieces. Further development is underway to build more ambitious designs and to also explore other practical applications that could impact the architectural industry.

Please visit the Made in Brunel student showcase 16-19th June to see the printer in action!