Transparent or translucent materials suit a number of applications.  In medical, such materials let physicians see anatomy and are useful in surgical planning. help In automotive, clear materials often are used for headlights. In fluid research, clear materials let engineers see within to better analyze fluid flow.  Many vendors offer transparent materials for 3D printing / additive manufacturing. Here are tips and guidelines on working with these materials in 3D printing.

Objects built on 3D printers can have varying degrees of translucency, ranging from translucent to relatively transparent.  Multiple factors contribute to this range, including the object design, the type of 3D printer used, 3D printing settings, the material, and any post-production treatment.

Design

If a design will have facets, angles, walls, and curves, know that those features will refract or redirect light, which may deliver less of the desired clarity.  Careful design can eliviate this result. For walls, one tip is to use the thinnest walls you can, taking into account 3D printing guidelines. Thick walls tend to disperse light, leading to an opaque appearance.

3D printing technology

FDM/FFF:

Because filament-based 3D printing is a layer-by-layer process, small gaps can form between the layers. In addition, this process often results in visible lines because of the layering. Both the gaps and the lines can affect transparency as they both tend to disperse light.

The settings on the chosen FDM/FFF 3D printer affect transparency as well.  Depending on the printer and the material, the settings to adjust include material extrusion temperature and flow rate, print bed temperature, printing speed, layer height thickness, and nozzle diameter.

Stereolithography (SL):

SL technology is a good choice for transparent or translucent parts. It can deliver thinner layers than other additive technologies. Thus, this technology can deliver good results for transparency.  Depending on the design, however, support structures may be involved. If not removed, supports will affect transparency. But SL parts can be post processed for a more transparency.

Polyjet technology:

Polyjet 3D printing is a third option for 3D printing transparent or translucent objects. UV curable resins with varying degrees of transparency are available. Parts made from this process are usually dimensionally accurate and smooth.

Materials for transparency  

Most 3D printing materials are not naturally optically clear.  Post processing can improve the finish, but it depends on the application.  The choice of material will depend on the 3D printer and the object design and purpose.

FDM/FFF offers the widest range of materials for transparency.  These materials include:

Polylactic acid (PLA) filaments. PLA comes in a variety of colors and transparencies, as well as filament quality.  PLA does tend to have a yellowish tinge.

Acrylonitrile butadiene styrene (ABS) is not naturally clear, so it is often blended with an additive for better clearness.  Post processing can enhance its transparency.

PMMA prints rather clearly when compared to other materials and is available in a range of colors.

Polycarbonate (PC) is a clear 3D printing filament with a glossy sheen.

Polyethylene terephthalate glycol (PETG) is a very clear 3D printing filament.

Stereolithography users have a number of options, as many resins offer varying degrees of transparency. And, in many cases, post-processing can enhance clarity.

With Polyjet systems, the available clear resins can be polished to give a more transparent finish.

Post-production 

Once made, a 3D printed part can be sanded, dipped, coated with epoxy, and smoothed using acetone and polishing.

Sanding can improve optical transparency.

Resin dipping is used on flat SL objects. The part is submerged in resin and then allowed to dry, resulting in a clear and smooth finish.