Fused filament fabrication and transparent prints! No, surely you mean SLA prints. And true you can get excellent transparent prints effectively using SLA however consumer-grade fused filament fabrication can be mistaken for glass when correctly created with the right materials. Going into this understand that both SLA and FFF 3D printing requires serious time spent post-processing to get the best result. Here is a link to a range 3D printing filament.
Let us dive head-first into transparent materials. This will explore which filaments give the best result to create see-through components and outline different slicer and printer settings to improve transparency results with different material types of transparent filament. We will also explore different post-processing options to improve clarity. The contents of this tutorial can be seen below.
- Material Choice
- Slicer and Printer Settings
- More Technical Slicer and Printer Settings
- Post Processing Methods
Transparent materials are the most fun when you light them up with a light source. Being able to see the 3D printed material with all its layer lines radiating out light can be spectacular. That or creating transparent clamshell cases where you can see all the electronics and wires connected and secure inside. Transparent filament is a great method also to iron out any niggling 3D printing issues be it of the 3D printer, the slicing program or in the actual CAD design. By being able to see through the model it makes it very easy to see internal issues that need addressing. For instance, if there are any missing internal lines or undesired empty spaces in your model you will be able to see and locate them clearly. Or if there are internal burn marks you will be able to see them clearly inside the print inside the model. These all cause weaknesses in the final product which would otherwise have gone unnoticed as the opaque, coloured filament would be laid down on top. The only other way to be aware of these issues would be to employ a very watchful eye or nose. Perhaps a tiny smoke sensor running alongside a 3D print would be handy.
The slicer settings will be focused with Cura however any slicing program worth its salt will have similar settings named something similar. There is an Ultimaker Cura Overview Guide which is a great reference point if this is your first time encountering Cura and you want to hit the ground running. Put simply Ultimaker Cura is a software which allows you to turn the computer file of your design into a recipe for a 3D printer to follow. It is available online and is a completely free software used by over a million users worldwide.
If you like what you see here give our Instagram post on Why Your 3D Prints Aren't Perfect a look too. If you have got any questions, queries or things to add to this topic please let us know your thoughts!
Material Choice
Naturally, material which allows light to travel through it to get the best transparency results. So, choose filament materials with the name Transparent or Natural somewhere in the name. I have been using CPE Transparent and getting interesting results off the build platform a combination of milky and translucent. CPE is a great material in terms of strength and toughness properties but if your goal is glass prints Polymaker Polysmooth is the way to go. The clearest most glass-esque result material to use currently for glassy final results is Polymaker PolySmooth Transparent. Below is a component made using Polymaker Polysmooth and the results speak for themselves. These are prints done by 3D Print General who has done great videos on this particular material both in regards to printing and post-processing.
Polysmooth transparent is a PVB material. PVB (polyvinyl butyral) is soluble in alcohol. This means after a liberal and repeated sprays/mists of alcohol over the model you can hide all the layer lines and smooth out the final piece. It is similar to how ABS is soluble to acetone and you can smooth out the layer lines with acetone. Polishers work but the best results can come from using a mist spray. I am properly excited to try to replicate it. PVB is normally used as a bonding layer in laminated safety glass, that is where you will see through it the most. It is proper amazing the materials you can 3D print.
Or if you have serious cash to burn you could also just 3D print glass sidestepping this whole process. See below for an image of glass being 3D printed by a machine from MIT. The machines they have tucked up there in MIT are proper amazing. But let us get back plastic filaments.
Slicer and Printing Settings
If you use fresh transparent filament of some description and get the settings right, you will end up with translucent milky material like what you can see in the image below left of Budda lit up. Air bubbles and layer lines are the two main enemies to clear and transparent 3D printed parts. Ignoring these factors lead to 3D prints that are fully milky, white or at the worst opaque (not letting light through). Air bubbles give the light an opportunity to bounce around inside the material. Layer lines effectively act as a lens which bounces light around inside them. Below to the right is a great image demonstrating this.
So, first and foremost, general settings to improve the transparency of any 3D Print with transparent filament. The process of printing layers makes the transparency turn cloudy and air bubbles amplify this, so the following settings have to do with minimising both these factors.
- Print Realy Slowly. 20mm/s or 15mm/s are good speeds. Even when the nozzle is travelling from one location to another slow down the speed and better results will follow naturally.
- Increase Flow Rate of the material coming out of the nozzle. Normal flow rate is at 100% and better results will occur by cranking it up to around 105% - 107%. I have even heard of people pushing it all the way to 115%. This will prevent any air-pockets or air bubbles forming inside the material. This will also increase the strength of the material. This will improve transparency particularly when printing fully filled (100% Infill) parts.
- Increase the Nozzle Temperature of your extruder nozzle by 5+ degrees and increase degree by degree until you get the best result. A higher temperature enables the layer lines to fuse together better.
- When printing parts that can be hollow make them hollow. Otherwise have a very, very low infill percentage, less than 5%.
- Bed Surface. Take advantage of a mirror-like finish that a properly calibrated and dialed in print platform can achieve. This makes the bed surface lines less visible. This creates a material which has an oblong surface which has less refraction and is easier to look through.
More Technical Slicer and Printer Settings
Improving transparency from certain directions can result in other orientations becoming more opaque. Much how 3D printed components are stronger in a certain direction than others - there are different orientations that allow for better transparency than others when 3D printing with filaments. This section will focus on how to improve transparency results from different planes when looking at them perpendicularly. These planes are the Z plane (ergo the transverse plane) and the from X plane/Y plane (ergo coronal plane/sagittal plane) and any combination of these two. See the image below for clarification of these planes (when consider 3D printed components in relation to below assume the feet of the man below are printed on the bed surface and the head is the last part to be printed).
This is because of the way a 3D printer lays down extruded filament. Below is a real-life example of this transparency change between planes using the motif of 3D printing the flexible T-rex model printed using CPE transparent. The subject can be seen from two different orientations demonstrating differences in translucency. On the bottom left is the orientation that the T-rex was printed in, thus we are looking at the transverse plane of the subject. The bottom right is a view of the same subject from the coronal plane. So the interesting point to note is in this subject the transverse plane allows more light to get through the material than the coronal plane. 
Improving Transverse Plane Translucency. This will go into the settings to alter whilst retaining a functional sturdy component. The method taken is to minimise all potential for little air bubbles or gaps to exist (like before) and crucially preventing internal scratches to occur. Also desired are a top and bottom surface that is oblong (see above picture) as this lets the light through un-harrassed.
Thus, to improve transparency when printing to improve transverse plane do the following (Note - this will result in a piece which is very cloudy when viewed from the Sagittal Plane or Coronal Plane). All applicable previous settings apply.
- Use a fine layer height (something like 0.1mm). This is to ensure no gaps are left in corners where a thicker line would not be able to get to.
- Avoid Printed Parts when Travelling. This is a checkbox which will prevent the nozzle from scratching across the transverse plane surface whenever possible
- Z Hop whenever retracting and increase Z Hop amount. This means when there is no choice but for the nozzle to travel across the printed part, it will lift itself up and avoid scratching the transverse plane surface.
- Fine layer height (0.1mm) to ensure no gaps are left in the corners where a larger line would not be able to get to (see issues with smaller prints in improving 3D printed models).
- Combing Mode set to off which will stop it from travelling inside already printed areas to prevent scratches on the transverse plane surface
- Retraction Distance - Increase this value by 1-2mm increments until the nozzle no longer leaks during travel movements. CPE is a material particularly prone to stringing (caused by nozzle leaks) and to prevent that some tinkering of the Retraction Speed is also necessary (which I increased by 5mm/s increments). This is to prevent stringing from building up which can then cause burn marks if the nozzle of the printer goes across it. Stringing is a surface blemish which you can learn a lot about at the guide Improving 3D Printed Models. This also a very important factor to control to prevent burn marks. Below are two examples of 3D transparent prints with CPE with some burning marks seen on a clamshell case to the right. Stringing builds up over multiple layers like a fine spiders web and if the hot nozzle swings past and runs into them they burn very quickly. This is the most common cause of the burn marks on 3D printed modes. If the nozzle is repeating similar paths over multiple layers this burn mark can become quite intense. Also, different retraction settings produce vastly different transparency results the model on the left was printed with lower retraction.
Improving Sagittal or Coronal Plane Translucency. Now when it comes to creating single line vases or objects where the desired translucency is in the X or Y plane and strength is not necessary I use different Cura settings which you can see below.
- Increasing the nozzle diameter on your machine by swapping it out. A great explanation of the effects of changing nozzle diameters can be found in Print Nozzle Installation and Overview.
- Increase the Line Width and Layer Height Values. In Cura, this can be done easier by just using the Fast print profile. The goal is to make large cylindrical lines. This will minimise the layers and minimise internal reflections. See below of an image of a vase 3D printed by Aidan using 1.2mm layer heights, t-glase filament and the MOARstuder.
Changing these settings will lower the overall resolution of the print. Keep in mind post-processing is going to do this as well, so compromises have to be made. This budda from above was printed using a fast profile with a 0.4 mm nozzle with 2 line wall thickness and a triangle infill of 5%. No post-processing has been done to it. Thanks to the British Museum for the CAD files, linked right here.
Post Processing Methods
ABS material you can use Acetone to smooth out layers to improve transparency. With the Polysmooth PVB material you can use Alcohol to smooth out the layers. A spray or mist bottle is the best way to apply these solvents which you can see below. Spray once every couple of days for two weeks, the longer you take doing this the better the result. When you have done it do not touch the model until it is completely dry unless you want fingerprints to be all over the subject). I want beautiful glass prints so I am experimenting currently with this.
I had an idea with CPE as it is a very strong material. So why not Sand and Buff it? Making sure to use that buff wax material I whipped out the Dremel and a plastic buffing kit. Now This is processes is both very labour intensive and prone to apprentice marks but I will say it does improve the top surface finish. However, a correctly dialed in printer produces a bedside surface which is superior to what I have been able to achieve with polishing plastic to improve transparency so far. So as a worthwhile future endeavour I don't think so. See below for an image of some of these apprentice marks, kind of looks like the layer lines have been smeared.
