RP methods

1 Introduction

With rapid prototyping (RP) tools becoming more and more inexpensive and with the software used is increasingly design to be more and more user-friendly a wide range of applications which initially was not the target group for RP-tools is emerging. Some of those applications are architecture and arts.

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2 RP methods presently applied in arts and architecture

This section looks at how the rapid prototyping tools have impacted the fields of architecture and arts. It is being used for a wide range of applications, which will be examined one by one.

2.1 Sculptures

Until recently fine art sculptures would never had dreamed of using computers as a tool for creating their art. Rapid prototyping seems to be a misleading word when it comes to sculpturing because the outcome will most likely be considered has the artist finale product and not a prototype.

As of yet there are still only a few sculptures who have ventured into the realms of TP. This is partly because of the steep learning curve in 3D software and the still relatively expensive machinery needed for RP. But with the price decreasing ant new powerful real-time rendering systems in CAD programs which make the use of CAD more intuitive and fun to use for artists. Brown is anticipating a sudden and massive demand for RP from fine artist sculptures. Below are some of the current examples of sculptures using RP

2.1.1 Using ready-made open source models.

More and more free 3D models are being put on the World Wide Web for anyone to use. Artists use this as a sort of junk-art [Brown] where they merge different kinds of 3D models to create a personal or political statement. These virtual objects can then be output to a rapid processing device and becoming a tangible object.

2.1.2 Exploring the forms of the virtual world

A lot of the present sculptures are made to explore the virtual world. Such works include Keith Browns own sculpture that is creating from the classical 3D form - the torus. The torus is twisted and deformed beyond recognition in order to create something with knife-sharp edges and crazy turns, which would not be possible to create without the use of RP. Brown's intention was to use the RP-model as a step towards making a bronze sculpture. For as he says: ”… I did not consider any of the RP materials as having any particular aesthetic qualities but saw them simply as a means to another end.” But after seeing the final result of the RP-model he changed his mind: “It was NOT just a prototype as I had expected.”

2.1.1 Data-to-form sculptures.

Another interesting method to create sculptures is the use of other kinds of data such as the work of Helena Swatton who uses a sound-waves and a revolve feature to create a unique sculpture visualising the words “come to me”. Another example is James Hutchinsons Berlin London sculpture that combines satellite photos of Berlin and London to create a political sculpture of a new intersected city.

2.2 Reverse engineering and RP benefit artists

With the advancement of scanning technology, reverse engineering software and rapid prototyping, the artists and engineers can work together to expand the boundaries of art.

2.2.1 The Millennium Sculpture

The word “Millennium” here means that the sculpture is representative of the development of rapid technology in the turn of the millennium. The original 400mm high model created by historical sculptor Anthony Padgett would go through certain processes after which a 2 metres high bronze will stand in Birmingham's National Exhibition Centre (NEC).

The basic process is like this. First, the original model was cut to eight pieces so that varied scanners and RP machines can be applied to different components depending on their respective requirement. Then the details of the model were captured by a 3D scanner and the data was fed to CopyCAD, a software from Delcom, to generate the digital model. After scaled to final size, the model was subjected to another Delcom's software, TriFix, to produce a watertight object, ready for RP.

Among these eight pieces the head was scanned by a laser stripe scanner from 3D Scanner's ModelMaker. Rover Group used its SLA machine to produce the final component in one build. The other seven pieces were scanned by a contact scanning system “Cyclone” produced by Renishaw. These parts of the statue were created by Rover Group's laminated object modelling RP machine and high speed machining.

The final work, with such a high level of quality and accuracy, is a true inspiration to artists and engineers.

2.2.2 The Tate Gallery Project

The DIY retailer Homebase and London's well-known Tate Gallery decide to mass producing designs from sculptors and sell them through the Homebase chain, to make this form of art more accessible.

They used Renishaw Cyclone to scan a trowel and fork set design by Tony Cragg, and the physical parts were returned to Tate Gallery. The scanned data were then read into CopyCAD to generate a triangle model. Another Delcam's software, PowerSHAPE, was introduced to help the designers to add holes on the surfaces and additional reinforcing ribs.

In the examining period, some rendered pictures were sent to Mr. Cragg to verify the perfection of the computer model. Moreover, for the final check, the prototype of trowel was produced by LOM and the prototype of fork took the form of a Z corp model.

After it was confirmed that this design can be moulded successfully, the data was processed by Delcam's PowerMILL to generate the tool path. At last, the mould was machined, the parts were moulded and assembled.

The significance of this project is that, it took only two months from the original model to selling the final products. In this situation, the artists can expect receiving a considerable payback on their talents in short time.

2.3 Architectures

Unlike artists, architects have a long history using various kinds of models to assist their work. Based on a paper written by Ryder et al., there are three levels of architectural modelling, which are feasibility model, planning model and final project model. Each level corresponds with a stage of the design project, and consumes different amount of time and money.

With an inherent nature which is flexible, RP can be applied to all three levels. Simply defining different parameters like precision, scale etc will satisfy most of the conditions. But of course, there are also limitations of RP when used in architecture design. This will be discussed in next chapter.

2.4 A curtain-wall project

NBBJ, a Seattle-based company, designed a curtain-wall which has components sloping at multiple angles. First the company acquired digitized information of a pre-built cardboard model. The information was then fed back to the computer to refine the virtual model. After that the computer model was sent to RP machine to make the stereolithography model. According to Patrick Mays, a principal with NBBJ, this model helped them in many aspects, e.g., examining the design iteration, understanding how components were integrated.

One interesting fact is that at the beginning the contractors' bids for this project varied enormously, but after they obtained the access to the RP model and other information, the bids were closer in range. The stereolithography model was even used by the curtain-wall manufacturer as a reference in building a full-scale sample section.

2.4.1 Multiple-unit development project, compound curves and other applications

For many residential and commercial building projects, architects often design a major structure and make minor modifications to give the buildings similarity in function and performance and some difference in appearance. The benefit of using RP in the modelling process will be tremendous.

In many situations of architectural design, the modelling is time consuming and difficult to build with traditional techniques. For example, when compound curves appear in a design, the CNC milling machine is unable to produce this detail, and hand-modelling will cost a lot of time. But RP can easily meet the architect's requirement. Other design details such as trusses are also better achieved by RP.

2.4.2 Case studies from “RPT_1” (temporary name)

Given below are some models built using RP techniques. Figure 1 is a space frame model consists of 3 parts. Because of the requirement of high accuracy, it's hard to construct manually in spite of its simple geometrical form. At first this model was finished with FDM process, but the vertical poles were so thin that the model couldn't stand its own weight. After switching to SLS process, the model was sturdy enough to assemble. This design was proposed to demonstrate the load-bearing structure, and other details like the linkages were not the focal point. For this reason, the link features could be scaled to more suitable dimension for RP process. In future, these linkages could also be built using different scaling factors.

The material of the next model is SLS Duraform nylon (Figure 2). The designer created this rotunda model to show the relationship between different rooms. In comparison with the first model, it is more conventional, both in shape and design. And the SLS process is more appropriate here, since each component was of controllable size and can easily fit into the build envelope. The structure of this model was traditionally injection moulded, so most RP methods could be suitable in this situation. Although this part was more solid in nature, building it as a hollow one can reduce distortion during the build process and shorten the processing time. A serious of rotunda model with different scales was also constructed using 3DP. The largest model shown in Figure 3 is similar to that in Figure 2, but with lower quality and is of structural integrity. As the models reduce in dimension, features become less distinct, like the scrollwork at the top and the steps. When the design requires the angled roof of the entrance to be tiled, it's in fact very time consuming to generate the tile texture on the CAD model, so the computer model used a rectangular hatch texture instead. This act made the production easier and unless observed closely, it was acceptable.

3 Advantages and disadvantages
4 Conclusion and future work
5 References

[Brown]

Found in Overview of architecture and art applications Chris Ryall and Julia McDonald

Sculpture for the new Millennium Keith Brown

The Manchester Metropolitan University, Faculty of Art and Design, Department of Fine Arts, Manchester, UK

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