Flexible Filament for 3D printers

Properties, characteristics and uses of the flexible filament for 3D printers

The flexible filament (Elastomer or Thermoplastic TPE) is a material resulting from a combination of plastic and rubber, also known as thermoplastic elastomers.

Within the variety of flexible filament, there are mainly 2 types, but before you decide to buy one type or another of flexible filament, you must take into account that the concepts “Flexible” and “Elastic” are not the same.

This type of filament can be used in a normal 3D FDM (Fused Deposition) or FFF printer.

An elastic filament will allow you to stretch the piece, while a flexible filament will allow the curvature of the printed piece.

If you want to know a little more, we will detail these concepts and the different types of flexible filament materials below.

The main problem of printing Flexible Filament

The biggest disadvantage you may encounter is retraction. Unlike other more rigid materials such as PLA, the flexible filament is very weak, like a rubber that does not return to its original state.

Therefore, when there is retraction in printers with Bowden systems, the filament can get stuck when retracted.

There is a solution to the problem of shrinkage with flexible filaments, and it is simply to change the guide tube to a PTFE one, like the Capricorn XS bowden tube, which helps to reduce the friction of the filament and the shrinkage.

You can also deactivate the shrinkage in printers with a bowden system.

On the other hand, on 3D printers with direct extrusion system this is less likely to happen.

Material Shore Hardness Grades

All materials have a hardness, in the case of flexible ones this becomes even more important. You can find different grades:

• Hardness 70A Ultra elastic: only available in 3.00 mm
• Hardness 82A Good elasticity: it is the most common flexible filament.
• Hardness 95A Semi-flexible: compatible with all Bowden system printers and less elastic than 82A.

On the other hand, the brand Fillamentum commercializes spools with hardness 92A and 98A, which are differentiated by their elasticity (92A more elastic than 98A).

Things you should know before buying Flexible Filament:

1. The printing temperature of the flexible filament can be around 230 ºC. We say it can be around, because depending on the manufacturer of the filament, it will recommend one or another temperature. If you print without retractions you can raise the temperature.
2. The Flexible Filament does not need a hot bed
3. It is quite difficult to warp, as the flexible filament adheres perfectly in the first layer to the bed. There are also some TPUs that do need warm bedding to avoid the small warping they can generate. For this we always recommend checking each of the manufacturer’s specifications.
4. Use a layer height no greater than 0.2 mm
5. No need for a coating fan
6. Printing speed, from 10 mm/s – 20 mm/s Again we have to make the clarification, because many users print at speeds of 50 – 60 mm/s. But if you are just starting out or are looking for the best results, we recommend low print speeds.
7. The shrinkage configuration is very important: it will also depend on the type of flexible filament you are using, but we recommend a configuration of between 3 and 4.5mm for bowden systems and less than 1mm for direct systems.
8. The retraction speed is about 35-40 mm/s, and not exceeding 50 mm/s.
9. This material does not give off odours and is resistant to solvents
10. FilaFlex brand Filaments are both elastic and flexible, to a greater or lesser extent depending on the degree of hardness.

As the filament is softer and presents less resistance to friction than others. If possible, insert the flexible filament directly into the extruder, without using a feed tube. Ideally from above, and the higher the better.

Conservation

Conservation recommendations. The flexible filament is hygroscopic, i.e. it absorbs a lot of humidity from the environment. As always, we recommend keeping the filaments in cool and dry places.

If your filament has been in use for a long time, and has absorbed humidity in such a way that when printed it looks like bubbles, then you should put the flexible filament in the oven for about 5-6 hours at about 180 ºC.

Starting: the first layer with the flexible filament

The 3D printing of the first layer is complicated, and requires a little extra attention. You must check that it adheres correctly to the bed, and that the residue does not stick to the nozzle. The flexible filament is sticky, so the nozzle must be cleaned before and after each print.

Sections 1.75mm and 3mm

Flexible filament spools can be purchased in both 1.75mm and 3.00mm

Remember that when we talk about 3.00 mm coils we also refer to 2.85 mm.

One consideration: in the case of flexible filaments, it is better to print in 3.00 mm format. Why? Well, it is basically because of the previously mentioned issue of shrinkage and extruder thrust.

When the filament tends to bend, it is more difficult to bend the filament with greater thickness.

But don’t worry, you will be able to print it perfectly with a thickness of 1.75mm in 3D printers with Bowden system using a quality PTFE tube or choosing a flexible material with a higher hardness, for example, between 95A and 98A which is easier to extrude.

Filament color range

Although this material is relatively recent, there is a wide range of colors to choose from, with the main ones being

White
Different shades of green
Blue
Sea water (very clear blue)
Different shades of yellow
Transparent
Skin
Red
Gold
Black
Purple

Weight or Size

These spools can be found in different sizes:

• S size rolls of 0.25 kg – 0.3 kg : depending on the brand that sells them, you can find them of 0.25 or 0.33 kg.
• M size rolls 0.5Kg – 0.75Kg: Also depending on the brand you can find them of 0.5 kg or 0.75 kg.
• 1kg rolls: This is the largest size for flexible filament coils.

Range of materials in Flexible Filaments

When buying a flexible filament, we must take into account the different types of materials that exist: TPU, TPE and PCTPE. There are no filaments with effects, as in the case of PLA, which we can find marble, wood, metallic effects, etc..

TPE Filament (More Elastic)

The TPE (Thermoplastic Elastomer) filament is characterized by its shock absorption, it resists breakage, it recovers its original shape when the material is finished stretching and it is also recyclable.

The filament can lose elasticity if temperatures are higher than indicated.
The use of pieces printed on TPE filament makes them lose elasticity over time.

TPU Filament (More Flexible)

TPU (Thermoplastic Polyurethane) material is slightly more rigid (less elastic, more flexible) than TPE. It is also a material resistant to cold, chemical agents and sun rays (UV).

PCTPE (Nylon) Filament

Within the Nylon filaments, there are some with greater felxibility. This is the case of PCTPE, but these materials are still Nylon.

Flexible Filament Brands

Perhaps the most famous brand is FilaFlex, however, today several brands are marketed, among which we highlight:

• ESUN
• Fillamentum
• FilaFlex (Recreus)
• FormFutura
• Polymaker (PolyFlex)
• Sakata 3D
• Smart Materials 3D (SmartFil)

En la gama de filamentos flexibles, puedes encontrar precios muy competitivos dependiendo de la marca y el peso que elijas.