3D Printing Basics: Transparent Prints

One of the many classes of filament you can 3D print with is transparent filaments. These filaments come transparent, and it may seem as simple as just printing with them to get a transparent print. Unfortunately, things are not that simple.

Requirements for transparency

To get a transparent part you need to ensure that light can pass through it with minimal redirections. There are techniques to achieve transparency in the Z-axis, the X- and Y- axis and in all axes. Depending on what you’re trying to print, your techniques may have to change. It is also generally easier to make transparent pieces that are flat, rather than curved. A curved surface not only redirects light somewhat but it’s also more difficult to post-process.

Z-Axis transparency

In a process pioneered by FennecLabs, you can get Z-axis transparency ideal for lenses or transparent surfaces with a standard FDM printer. To do so you will need to use:

• The highest nozzle temperature within the transparent filament’s range
• 100% infill
• A 108% flow rate
• A slow print speed of 20 to 30 mm/s
• A disabled print cooling fan
• A high-temperature print bed around 100°C

Printing at such a high temperature ensures reliable fusing of the plastic which is crucial for a transparent print. The piece will likely have some excess plastic that will need to be removed with a craft knife. You’ll also need to sand the print down with sandpaper ranging from 400 to 4000 grit until it becomes transparent. If you’re using a glass print bed, you won’t need to sand the bottom as this will already be smooth.

X- and Y- axis transparency

Large layer heights help when wanting X- and Y-axis transparency, ideally you want these layers to be as round as possible rather than flattened and wide. For the best results you will want to:

• Print slowly, at roughly 25% of your normal speed
• Use thick layers with a large nozzle
• Print at 70-90% of the nozzle diameter

Using these settings will help ensure minimal reflection and refraction of light travelling through the print, giving a clear result. You shouldn’t even need to do any post-processing to achieve transparency with these settings.

Surface treatments

Some transparent filaments can be post-processed with a solvent such as ethanol to be made transparent. Make sure to do your research before doing so, however, as most solvent smoothing processes result in the material fogging up not becoming transparent. There are also some coatings you can add such as spray-on polyurethane that smooth the surface and increase transparency.

SLA resin dipping

Normally when transparent resins are used with an SLA printer, you can get a translucent but not clear print. Formlabs pioneered a technique, however, where the resulting print is then dipped in the clear resin again, then left to drip dry. This smooths out any imperfections in the surface finish. Once the dried print has been cured under UV light, the result is an optically transparent print suitable for use as a lens.

Are you planning on making a transparent print? We’d love to hear what you’ve got in mind down below.