General 3D printing design rules

Why 3d printing design rules is crucial ?

When 3d printing, we must keep in mind that there are some things that it, or the materials, can’t do. When you start to design your own models, you must consider the constraints carefully. Models must also be able to lie flat on the build plate or be supported, and your model must fit within your printer’s build volume. In a word,we must consider the 3d printing design rules to get a 3d printable model.

Must be solid bodies, not surfaces

3D printing cannot print surface models; you must submit a solid body model. The walls can be thin, as low as 0.4mm (above 1mm to be safe), but they cannot have zero thickness. The minimum wall thicknesses will be different due to different material and technology. If you have drawn in surfaces to create a model, you must ensure that all faces are closed. Recommended minimum wall thickness : FDM-0.8mm; SLA/DLP-0.5mm; SLS-0.7mm; MJ-1mm; BJ-2mm; DMLS/SLM-0.4mm.

3d printing design rule-solid

No Sharped edge

Your CAD model cannot contain any shared edges between objects. It is ok to have a gap between the parts, or an overlap if the parts are joined together.

Normals

Normals are perpendicular reference points to surfaces on 3D models. They define whether the surface is an inside or outside face (closed set of edges). An inverted normal is a normal that is pointing in the wrong direction, telling the computer that an outside face is actually an inside face when it isn’t. If you have a hollow design, an inverted normal can be indicated as you have both surfaces facing in and out in the same model.

Watertightness

Sometimes when you are designing, your model may have some tiny holes. In theory if you fill your model with water it would leak. Every 3D model that is intended for 3D printing should be completely manifold (watertight): every edge should be connected to exactly 2 polygons and the model must include no holes. A non-manifold 3D model might cause inconsistent layers, holes or other errors, making the object unprintable.
Non-manifold issues are often not visible at the modeling stage. The simplest way to check whether a model is printable is to use an analyzer software, like Netfabb or Meshmixer.

Delete auto-intersections

As we create 3D model, there may be a point where two or more volumes cut into each other. These intersections create an ambiguous model with uninterpretable volumes. 3D Modeling software often have a function that can merge these elements, rendering a singular object.

Design for your Material

Depending on the intended use of your printed piece, your choice of material can affect certain aspects of your design, and needs to be taken into account for the best results.

There are some tools that you can use to check your 3d model <Offline tools to repair STL files for 3d printing>. With these software packages, you can ensure the models meet the 3d printing design rules.

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