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Transparent 3D Printing – 4 Ways to Create Transparent Parts

Picture of Benjamin Goldschmidt
by Benjamin Goldschmidt
Aug 2, 2019
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Have you ever wanted to 3D print a see-through part? Look no further, as we'll discuss a few different methods to achieve transparent 3D printing!

Transparent 3D Printing What Is It?

Nearly transparent 3D prints can be created to make prisms and other types of objects.
Nearly transparent 3D prints can be created to make prisms and other types of objects. Source: fenneclabs.net

As you might have guessed, transparent 3D printing is printing a plastic part that you can see through. Applications of this technique vary from see-through vases to optical elements like prisms, art, or decorative pieces. While this might seem simple to achieve (buy transparent filament and print it), the reality is a bit more complicated. Before going into methods, we’ll need to learn about some of the science behind what makes something transparent: What is transparency?

Transparency, or the ability to see through an object, is controlled by how light passes through it. If light passes through an object without being redirected in a significant way (i.e. through a pane of glass), the object will appear to be transparent. In glass, the material is homogenous and clear, meaning that you can easily see through it. To mimic this property in a 3D printed object, we must adhere to the following rules:

  • Plastic material must be transparent to start with
  • Printing must limit the introduction of air bubbles into the part
  • The part should have a smooth surface in the desired transparent area
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Transparent 3D Printing A Little... Clarification

Getting transparency across a print, as in this example, requires large layer heights to reduce cloudiness.
Getting transparency across a print, as in this example, requires large layer heights to reduce cloudiness. Source: 3D Print - Tech Design / Youtube

In order to achieve transparent 3D printing, you need to decide what transparency type you want.

Do you need transparency perpendicular to the Z-axis, in the XY-plane, or complete transparency? For making a transparent vase, you most likely will only need transparency in the X- and Y-axes (across it). For making a flat window, you only need transparency through the Z-axis. For complete transparency, you’ll need transparency in all axes.

An additional consideration is that most 3D printed objects are not entirely flat. 3D printing a transparent flat part is easier than printing a transparent curved part since the curve redirects light.

Of course, if you are interested in nailing transparency without having to go through all the fuss yourself, there is always the option of using a professional 3D printing service. Through Craftcloud, All3DP’s 3D printing and price comparison service, you can easily find the best service and the best price for your needs!

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Transparent 3D Printing Z-axis Transparency (FDM)

3D printed lenses can be achieved using transparent filament.
3D printed lenses can be achieved using transparent filament. Source: fenneclabs.net

FennecLabs has created a method to 3D print transparent lenses using a standard FDM 3D printer. The key to achieving this involves the following steps:

  • The highest nozzle temperature (in this case, 255 °C ) within the filament’s range (ensuring fusing of the plastic)
  • 100% infill
  • Flow rate above 100% (in this case, 108%)
  • Print speed at half of what you’d normally use (in this case, around 20–30 mm/s)
  • Fan/print cooling disabled
  • Increased build plate temperature to ensure fusing on the bottom of the print (in this case, 100 °C)

The printed part will look like the image above with some overextended plastic left on the part. This isn’t an issue since it can be removed during post-processing by cutting it off with a craft knife. After removal, the part should be sanded with sandpaper from 400 to 4000 grit until the part becomes transparent. If printed on glass, the bottom will not need to be sanded as it will already be made smooth.

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Transparent 3D Printing X-axis and Y-axis Transparency (FDM)

The more cylindrical a layer, the better the transparency.
The more cylindrical a layer, the better the transparency. Source: taulman3d.com

Achieving transparency in the X- and Y-axes requires large layer heights relative to the nozzle size used. Larger, more spherical layers tend to refract less light, thus leading to a more see-through 3D printed part. Generally, printing at 70–90% of the nozzle diameter results in more transparent prints. Overall, the following settings can improve transparency in this technique:

  • Print slower (25–30% of your normal print speed)
  • Print thicker layers by using a larger nozzle
  • Print at 70–90% of the nozzle diameter to obtain a structure that refracts less light

Once the part has been printed, no further post-processing is needed. This technique is used for vase mode prints and single layer prints that do not significantly refract light passing through them.

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Transparent 3D Printing Complete Transparency (FDM)

Here, the surfaces have been melted with a solvent to smooth out the layer lines.
Here, the surfaces have been melted with a solvent to smooth out the layer lines. Source: The 3D Print General / YouTube

For complete transparency, surface treatment is required to smooth out the surface in order to create a transparent 3D print. There are two separate methods to achieve this.

Method #1

The first method involves using a solvent to smooth the print in order to remove the appearance of layer lines. For instance, PolySmooth filament, a filament type designed specifically for models which are intended to be transparent, can be smoothed using ethanol. The ethanol is sprayed onto the print and left to dry. After several reapplications, the part will turn transparent, but the part may lose dimensional stability as a result of the application of a solvent to the print.

In addition, it takes a long time (days) to dry completely. Finally, only PolySmooth filament can be used this way. Other forms of solvent finishing tend to fog up other plastics such as acetone smoothing on transparent ABS.

Method #2

Another method involves coating the print using either XTC 3D or a spray-on polyurethane coating. These coatings are applied several times until the surface of the print becomes smooth and transparent. This is similar to painting an object; like the solvent method, however, it can change the dimensions of the part.

Both of these methods work by smoothing the surfaces of the print until the part becomes transparent. The only difference is whether material is added or removed.

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Transparent 3D Printing Bonus: Complete Transparency (SLA)

Resin dipping using a standard SLA printer can create optical quality lenses ready for real use.
Resin dipping using a standard SLA printer can create optical quality lenses ready for real use. Source: formlabs.com

Formlabs has pioneered a method to make transparent 3D printed parts using SLA technology. Normally, when optically clear resin is printed, the resulting print is somewhat translucent, but not exactly transparent,  as shown in the figure.

But it gets even better: Their process for achieving optically transparent prints involves dunking the resulting print in resin after it has been printed. This smooths out any surface imperfections and makes it transparent. Once the part has dripped dry, the resin is cured using a standard UV lamp. As you can see from the figure, this method works extremely well and gives pretty clear results due to the fact that the internal cavity of the print does not typically contain air in SLA printing.

Overall, this method tends to result in the best optical clarity among all the techniques. Formlabs was even able to make a fully 3D printed camera using this technique.

Feature image source: taulman3d.com

License: The text of "Transparent 3D Printing – 4 Ways to Create Transparent Parts" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.

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