Drafting with 3D Printing in Mind

Posted by LGM | Friday, September 20th

These 3 considerations should be in your mind while drafting for 3D printing

To produce a set of printed 2D construction drawings, certain preparation must be made; layouts arranged, sheets put in order, print jobs configured, etc. Similarly, to 3D print a model, certain steps must be taken to ensure a successful outcome.

Tolerances  If it is too small for the 3D print technology you choose, it will break.

The first order of consideration is referred to in the industry as print tolerance. Tolerance, as it applies to 3D printing, is how small a detail can successfully be 3D printed and survive the process. Every 3D printer has a different tolerance, so there is no definitive rule for how small a detail can be on a 3D printed part. There are several factors in determining the appropriate adjustments to make to a model to get the tolerances right such as level of detail desired, scale of printed model, the model's native CAD format, and printing technology, to name a few. Almost always, smaller details on the digital model must be enlarged so that they can survive the 3D printing process and be visible at a physical model scale. See the sections on Size/Scale, Thin and Tapered Surfaces, and Wall Thickness.

Holes and Gaps  3D printers require "water-tight" models, no holes in the exterior surface.

Once tolerances have been correctly accounted for, the model must be checked for openings. To 3D print a model, the input file must be one continuous, solid object, usually in the STL file format. The printer must be able to clearly distinguish between the inside and outside of the object it is printing. There cannot be holes or gaps in the model, because the 3D printer will not be able to tell what is inside the object and what is outside. This applies quite literally to a house - the exterior of the building must be sealed. There are tools that can help identify an close holes and gaps, like CADspan, but the majority of these areas should be found and closed within the original CAD model for best results.

Creating a printable file  A 3D printable file is a single, solid, model, typically in .STL format.

Once the model's tolerances have been adjusted and the major holes and gaps have been closed, the next step is to generate a 3D printable file. This can be achieved a number of ways. Depending upon the CAD application in which the model exists, the "best" method differs. Many programs offer an STL exporter, however users should be aware that JUST BECAUSE YOU HAVE AN STL DOES NOT MEAN YOU ARE READY TO 3D PRINT. To successfully 3D print an object, the STL file must be one single, solid shell. The mesh resurfacer from CADspan can be used to "shrinkwrap" your model and output a single object as a solid STL. This tends to be the easiest approach. Alternatively, STL repair programs like Magics or Netfabb can help with solidifying a poor STL file.

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