Stereolithography—a rapid prototyping technique for orebody modelling and mine design
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Stereolithography is a well known rapid prototyping technique in the manufacturing sector. Essentially, it is a three-dimensional printing process that produces plastic prototype parts from standard CAD files. At present, Canadian mining companies are not fully aware of the potential of rapid prototyping techniques (RPTs) for their production and mine design systems. Mining engineers and geologists attempt to visualize and understand the characteristics and layouts of orebodies on computer models, and in cases where it is decided to develop physical models, the process is time-consuming based on simplified constructions. RPTs, such as stereolithography, can facilitate engineers and geologists to quickly, and with satisfactory accuracy, visualize sections of orebodies and evaluate alternative ore extraction techniques using 3D solid models.
The research discussed in this paper is carried out by the Laurentian University Mining Automation Laboratory (LUMAL) in collaboration with Inco Limited and the Integrated Manufacturing Technologies Institute (IMTI) of the National Research Council of Canada. The main objective with this research is to evaluate the applicability of state-of-the-art RPTs to underground hard rock mining systems. RPTs can play a significant role in accelerating the design and development process of mining systems.
Rapid prototyping is a term describing a series of techniques used to create solid models based on computer drawings. Rapid prototyping is widely used in the manufacturing industry mainly due to the quick turnover and low cost compared to other modelling techniques. Stereolithography (STL) is a well known RPT that is capable of producing a physical three-dimensional object from a CAD file. Stereolithography allows anyone with CAD skills to create models that can be processed, revised, and reprocessed in a matter of hours. This is a vast improvement over some traditional modelling techniques (carving, molding, etc.) that require specialized skills and often weeks of labour with little or no flexibility in the process.
A stereolithography machine uses a computer-controlled laser to cure a photosensitive resin, layer by layer, using a special ultraviolet light (UV) source. By exposing thin layers of resin to the laser and moving the model vertically within the resin tank, a full model is constructed in a layered fashion in a few hours depending on the capabilities of the printing machine. The process allows for the rapid creation of smallscale, three-dimensional plastic models that can be utilized for conceptualization, test fitting of parts, and for display purposes. There are many levels of finishing available depending on accuracy and finishing quality (e.g. well sanded, smoothed, painted, etc). There are different formulas available for the photosensitive polymers, and with heat curing, the resin can achieve extremely high strength. As a validation tool, stereolithography is invaluable allowing components to be verified early in the design phase. This allows changes to be made in the validation stage rather than having a potentially costly redesign later in a project’s life cycle.
In this project, three models were created to demonstrate the capabilities of STL. The first model was based solely on an existing development and orebody outline at a Sudbury nickel mine in Ontario, Canada. The other two models were intended to demonstrate the possibilities of stereolithography, presented from a mine design perspective. By displaying the same orebody with different development stages, it is possible to offer a true sense of how the mine would look, rather than depending on an interpretation of a flat computer view. To this end, two mining methods that require very different development were chosen for the second and third models—sub-level caving and vertical retreat mining.
The potential of RPT for use in mining is extensive. For an orebody model, it offers an accurate geometric representation. It can also be used for the planning of development work as was done in this project. Geological features such as faults and dykes can be added to the model increasing the awareness and understanding of these features on the overall mine plan. As a visualization tool for presentations, it can have a very profound impact. RPTs can also be applied to the manufacturing aspect of mining, allowing for scale models of machinery to be created as design tools or for marketing purposes.