Wednesday, 4 October 2017

Optimising size and cost for 3D printing

The purpose of this post is to illustrate the effect of size and scale on cost in 3D printed architectural models. To illustrate this we will use the same basic model printed at three different scales as shown in the image below. 


Factors determining Size and Scale

The size of the design project being modelled will partly determine the scale. Massing of large projects can be effectively represented as scales that would make no sense for single house designs.

Size of a model is also determined by what it will be used for. A design model for internal review has a different value to a model for a planning application. A marketing model has a different value again.




Factors affecting cost

Cost of 3D printing is never directly proportional to size. 

Doubling the size of a model can mean up to 8 times more material is used. Some printers may take up to 8 times longer to print all of that material. 


When we are able to hollow models to reduce the amount of material used, typically this reduces the cost of doubling the size of a model from a factor of 8 to a factor of 4 times the cost. (See note on the maths of hollowing models at the bottom of the page.)

To illustrate the effect size or scale has on cost with some typical numbers. The models shown in the image above might cost something like:

1:100 - £100
1:75 - £200
1:50 - £600

So in the case of the facade model, hollowing is not as effective at reducing the cost. Here, doubling the size of the 1:100 model to 1:50 increases cost by a factor of 6.

Optimising size and cost

To conclude, there is often an intermediate scale that offers a good balance of size to price. 

When looking to get a model 3D printed it helps to be flexible and it pays to get a guide price early on in a project.




Typical 3D printed architectural context model with inserts


Many of the models we make are context models with inserted existing and proposed buildings, like the model shown in the image below. It can pay to make this model so that a series of inserted proposal models can be made as the design develops. 



Note on the maths of hollowing models

The cost of printing is based on the amount of material used. So as the size of the model increases cost is not directly proportional to the size. Without hollowing the cost of increasing size is inversely proportional.

To illustrate this:
A cube measuring 10 x 10 x 10cm has a volume of 1000 cubic cm.
A cube measuring 20 x 20 x 20cm has a volume of 8000 cubic cm.

Translating this to architectural models we can see that doubling the scale can mean 8x the cost for unhollowed models. 

When we hollow parts this reduces the effect of scaling on cost by about half. In the simplified illustration below we can see that the effect of hollowing significantly reduces the cost.

Hollowing the cubes with a 3mm wall thickness and leaving the underside open to remove unused material:
A hollow cube measuring 10 x 10 x 10cm has a volume of 143 cubic cm.
A hollow cube measuring 20 x 20 x 20cm has a volume of 586 cubic cm.

In this case this represents a fourfold increase in cost for doubling the size of the part.



Please note that all 3D print bureaus have different charging rates and methods. However the underlying principle that changing the size of parts has a substantial influence on cost is unavoidable.



To find out more about 3D printing for architecture and colour 3D printing please visit www.lee3d.co.uk 





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