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Inf@Vis!

The digital magazine of InfoVis.net

3D Printing
by Juan C. Dürsteler [message nº 49]

To what extent can touching information help us to visualise it? In the near future stereolithography will help us to clarify this point. 

As you know, stereolithography is the process of building, layer by layer, 3D objects from the specification of a virtual model of the same.

The basic idea is the decomposition of the model in a set of sections and to produce them one after the other. Once a section is finished the next one is built onto it and the process is repeated until the object is completed.

Nowadays 3D printers are able to produce models in resin, metals, ceramics and elastomers and even paper with precision up to 1/1000 of an inch.. Some systems produce the object from a liquid monomer bath that solidifies by polimerisation through the energy of a laser that follows the interior of each section that is to be built. Once a section has been solidified, it sinks just enough to polimerise the next section on top of it. The process is repeated until the completion of the object.

Other systems solidify (sinterise) powder with a similar process in which the laser melts the powder, metallic or not, layer by layer. Examples are the systems of 3D Systems.com or Stratasys. The Massachusetts Institute of Technology (MIT) has also a very interesting 3D printing laboratory.

The Japanese company KIRA produces machines that cut the sections out of paper sheets that are stacked to produce the final model . A high-pressure lamination process makes the object 25% harder than wood.

By its very nature, this layer by layer process makes the complexity of the object almost irrelevant since you can build objects with internal holes, inlets and outlets virtually without limitation. The time required to build the object depends on its volume and is in the range of a few hours.

But what has all this to do with Information Visualisation? Quite a lot, indeed. Engineers developing complex pieces or objects can obtain much more information on the model having it in their hands and testing its behaviour rather than simply looking at a projection onto the computer screen. The so-called rapid prototyping allows you to produce a functional prototype in a fraction of yesteryear's time.

But beyond this evident application arise others like the biomedical ones that use these systems to build replicas of the organs that are to be operated. See for example the attached images that depict some of the biomodel applications. Multimodal visualisation (visual, tactile) of the operation field constitutes a source of information and understanding of the reality that provides a great help in preparing surgical interventions.

Figure 1
Manufacturing in a UV curable monomer tank.

Fig 1: Example of the manufacturing process 
  1. The laser polimerises slices of the skull over a platform. 
  2. The platform sinks just to allow the liquid to be solidified by the laser with the shape of the next slice. 
  3. The process is repeated slice by slice.
  4.  The finished result. 
Fig. 2:  Finished model of a human skull of a specific patient. Magnetic Resonance data are used to create a virtual model that is then manufactured following the process of Fig 1. In red you can see the pathology to be surgically removed.

Images courtesy of Biomodel

BiomedSLitog.gif (144668 bytes)

Figure 2. 
Model of a human skull affected of a pathology (in red)
(Click on the image to enlarge)

Similar techniques are used to build matrices where cellular tissue can grow in order to repair organs (see for example the interesting abstracts on several biomedical applications)

This set of techniques has evolved spectacularly since 1987 and the last generations represent a leap in precision and versatility. 3D printers are a sophisticated way of visualisation since they let you see, touch and even test the behaviour of virtual objects in reality

When prices drop, 3D printing will become more ubiquitous. Just as we print charts today to better understand the evolution of the stock exchange or the illness of a patient, in a few years from now we will print 3D models that maybe will help us to understand more complex problems even better.

Links of this issue:

http://www.3dsystems.com/  
http://www.stratasys.com/  
http://web.mit.edu/afs/athena.mit.edu/org/t/tdp/www/index.html  
http://www.kiracorp.co.jp/EG/pro/rp/RP_process.html  
http://www.biomodel.com/  
http://www.msoe.edu/reu/Biomed_abstracts.shtml  
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