Wednesday, 9 October 2013

7 reasons why plaster beats Nylon for making architectural concept models.

Nylon is better than plaster. Right?

Here are 7 reasons why plaster is better than Nylon for making architectural concept models:
  1. Nylon parts (SLS) cannot show the surface features achievable with plaster. For 2 reasons, first the economics of SLS bureaus dictate they print with the thickest layer they can get away with and second the laser spot size physically prevents printing features smaller than about 0.5mm. This makes the plaster based machine better for printing architectural facade models at scale.
    Part printed on ZPrinter 650 at Lee 3D showing 0.3mm surface detail.
  2. Plaster parts do not shrink or warp. Nylon parts are created at melt temperature which means they shrink as they cool. If the cooling is not even the parts warp and distort. Plaster parts do not warp. Model makers who know the technology have strategies for dealing with warp but it can be a problem when a model arrives for a meeting and the walls are bowing. 
  3. Plaster printing is probably 4 to 5 times faster than Nylon. That is 3 to 4 days that could be better spent designing. We often print same day jobs for clients in plaster which would simply not be possible in Nylon.
  4. Plaster printing can be full colour. Nylon can be dyed and that looks really nice - but it is a single colour. 
  5. Plaster is less wasteful. Now here is contentious issue. I really do not know the facts but if you think that a typical refresh rate applies to an SLS build of 25 - 30% then there may well be a good case for this assertion. Refresh rate means that 25 - 30% of the powder must be replaced after each build either used in a part or thrown in the bin. With the plaster system we reuse pretty much everything that does not go into a printed part.
  6. SLS is very sensitive to geometry. With the ZPrinter you can print multiple, intersecting and touching shells and sharp triangles with no loss of quality to the part. With SLS these can cause double passes of the laser that mark the surface of printed part. If you print a part with sharp triangles these appear on the surface of the part even if it should be flat.
  7. As a consequence of #6 it is much easier to model for a plaster printer. Ever tried getting rid of sharp triangles? 
In summary I would like to remind the reader that these points are made in reference to making architectural concept models.  A concept model by its nature is made quickly at a very early stage in the design process when it is often desirable to show simplified design geometry. Conversely are many reasons that model makers use SLS parts for making presentation models.

Certain technologies fit certain tasks. Nylon is not better than plaster and neither is plaster better than Nylon. Each material has its own characteristics which inform the choice of technology. I have deliberately not included cost in these points but this too will need to be part of the equation.

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  1. I'd like to believe that if the material science improves steadily enough, then one day architects & designers will be more confident in 3D printing final presentation models using plaster-based technology over that of laser sintering.

    Personally, I think the three consumables which exist in the ZPrinter (HP print head, plaster powder and binding solution) could all be refined to the point where post curing stages are not needed. Imagine a binding solution that's as tough as Araldite and fluid like water. Can Hewlett Packard print more stuff through even smaller holes? It feels to me like it could be a lot easier to develop this type of technology over that of lasers and melting points. Maybe I'm wrong?

  2. I don't think 3D printed models will ever make high end presentational models, due to the infinite number of material representations. We should leave that to the modelmakers of this world.

    After working alongside with EOS Nylon printers I can tell you that nothing beats the quality, strength and detail of these printers. I would personally disagree with all reasons but number 4 and maybe number 6, as the plaster printers can be extremely forgiving to such details. But if the file is fixed to a higher standard this is generally not a problem.

    It would be great to see such a machine one day Paul, until then we'l just settle with copious amounts of super glue...

  3. Marc

    Would be great if you could give reasons for dismissing all but 4 and 6.

    You really think an P100 is as quick as a ZPrinter?