Geometry Restrictions in 3D Printing

Introduction

In 3D printing process, we should consider the size and geometric restrictions in manufacturing process, and determine whether 3D models are suitable for 3D printing technology. These considerations are widely apply to any CAD designs, form basic mechanical parts to complex architectural pieces.

Physical Size

We summarize the normal build size of most common 3D printing technology. We should notice that large parts printing will apply industrial machines, this will increase the overall cost typically. There is an alternative solution, split part into 2 or more pieces, then print these pieces separately and assembly later.

3D printing technologyTypical build size
FDMDesktop Machine: 200×200×200mmIndustrial Machine: 900×600×900mm
SLADesktop Machine: 145×145×175mmIndustrial Machine: 1500×750×500mm
SLS300×300×300mm
MJF380×250×200mm
Binder Jetting400×250×250mm
DMLS250×150×150mm

Minimum Wall Thickness

Normally, designers can create elements with infinitesimal thickness in 3D models. However, thin features are unable to produce unless their sizes are larger than the minimum printable feature sizes of each technology. We summarize the minimum wall thickness for most 3D printing technologies. In some special case in SLA, we recommend to contact with our engineering team.

3D printing technologyMinimum wall thickness
FDM0.8mm
SLA0.5mm
SLS0.7mm
MJF1.0mm
Binder Jetting2.0mm
DMLS0.4mm

Water-tightness

We should notice that every 3D models for 3D printing should be complete water-tightness and manifold, every edge should connect to 3 polygons and no holes in model. Models without manifold will be misinterpreted by software in 3D printer instructions. The non-manifold 3D models will make the object unprintable in reason of inconsistent layers, holes or other errors.

Our engineering team will check whether your design is printable by automatic tools.

Curved Surface

In most CAD software, we apply non-uniform Rational Basis Splines to display 3D model surfaces. One export to STL file format for 3D printing, we should use adequate number of polygons to represent surfaces, in order to final parts can be printed with smooth surfaces.

Once 3D model is exported without adequate polygons, the connecting edges will be visible in final 3D parts. This issue will be more prominent in large models more than 300mm, the polygons is easy to see on curved surfaces.

Once 3D models is exported with too many polygons, the file size will be extreme large and difficult to operate. However, there is no effect on final parts quality, because the tiny details cannot be printed.

In Runsom, our modeling software have preset with adequate number of polygons in exporting process, in order to guarantee final smooth 3D parts. We can adjust export setting once higher polygon number are required.

Conclusion

We recommend design suitable build area in available size of 3D machines, and add wall thickness for small details. Upload your 3D model, and our engineering team will check it for you.