Re: [rp-ml] STL settings

From: Delft Spline Systems <>
Date: Mon Sep 20 2010 - 14:23:39 EEST

Hi Bill,

The size of the STL file (in MB) does not mainly depend on the size of the part (in mm/inch).
It is the required accuracy (as you say the triangle size) that has most influence.

The file size in most cases will anyway be much larger than when saved in the CAD programs format.
Reason is that STL is not really efficient. Extreme example: a sphere can be represented in the CAD program as four numbers: X, Y and Z for the center plus the Radius R. In STL the sphere's surface will be described as (approximated by) many triangles on the surface of the sphere: much more information to store.

The number of triangles depends on the required precision and surface smoothness: in any CAD program you can select a precision in the export options for STL. So the STL filesize for a very small sphere that needs to be very smooth (like in jewelry) may be larger than for a large sphere where the smoothness does not matter.

You can use an STL file viewer for a visual check of the surface smoothness.
Note that you will need a viewer that does not apply anti-aliasing but instead shows the real STL geometry.
The free trial version of the DeskProto 3D CAM software works OK for this aim.

Best Regards,

Lex Lennings.

At 20/09/2010, you wrote:
>Can anyone point me to an online tutorial for setting triangle sizes in
>STL files?
>I seem to manage to produce very large files for small physical
>objects. Me gut feeling is that I could reduce the file size, but I
>need a handle on just how far I can go without compromising the quality
>of the finished object.
>Bill Bedford
>"Man is an animal suspended in webs of significance he himself has spun"
>-- Clifford Geertz

Delft Spline Systems, The Netherlands.
We offer DeskProto: affordable Rapid Prototyping using CNC milling. --- website:
Received on Mon Sep 20 14:16:34 2010

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