As 3D printing rubber is not possible, flexible filaments are the next best alternative for stretchy, elastic parts. Flexible filaments are still very elastic – their elasticity depending on the type of filament used – mixing plastic polymers and rubber to create hybrid materials.
All flexibles are made from TPE – thermoplastic elastomers – though there are a number of different types that are best for different types of 3D printing. We explain each type of flexible filament in depth below. The most common flexible filament is TPU.
- We also have a separate guide to TPU 3D printing.
Properties of flexible filaments
Different blends of flexibles vary in their elasticity, depending on the exact chemical formula used. Some flexible filaments are designed to be only moderately flexible, instead prioritizing other properties such as strength and chemical resistance, whereas other flexibles can mimic the elasticity of a rubber band, and can be stretched extremely wide without snapping.
Types of Flexible Filament
TPU combines the advantages that both thermoplastics and elastomers offer within one flexible filament. It’s very flexible and elastic, and very soft, making it perfect for vibration dampening applications as it can handle large shocks and impacts.
TPU flexible filament is also great for resisting chemicals such as oil, and can withstand low and high temperatures well. It’s also recyclable, which is a plus for makers who want to recycle their prints and who are environmentally minded.
TPU is probably the easiest flexible filament to 3D print, making it a favorite among makers, and is the most used flexible filament. It typically prints at between 210-250C, sticks well to painter’s tape as a great build surface to use, and works well with a heated bed of up to 60C.
TPU is used commonly in creating insoles, as well as in the latest wave of 3D printed shoes. The flexibility and ability to cushion runner’s feet to retain energy is key in creating the next generation of running shoes and sneakers.
TPU flexible filament we recommend includes:
- Hatchbox TPU filament on Amazon
- MH Build Series TPU on Matterhackers
- NinjaTek NinjaFlex TPU on Matterhackers
- 3DJake UK & Europe flexible filament range
Also known as TPA filament and commonly used in the production of golf balls, PCTPE filament is a mix of TPE and Nylon, combining Nylon’s durability with TPE’s more flexible nature. PCTPE has good heat resistance and great layer adhesion, leading to solid flexible 3D printed parts.
Use a heated bed at a lower temperature, of between 30-50C, and an extruder temperature of between 235 and 250C, with 240C+ often working best.
Sold by Taulman as PCTPE rather than TPA, PCTPE is capable of large impacts and very high tensile forces without breaking, and is a strong and flexible filament owing to its combination with Nylon.
Soft PLA is as the name suggests, a flexible filament combining PLA with TPE or TPU to make it less brittle and prone to shattering, adding strength and durability.
You can print Soft PLA flexible filament at around 230C, and consider going 5-10C higher if necessary, with a heated bed of 30-45C.
Short for Thermoplastic Copolyester, and often sold as FlexFil by FormFutura, TPC is a more industrial flexible filament, with mostly engineering applications such as in parts for cars and other types of automotive.
TPC has lower elasticity than other flexible filaments like TPC, but it is notably stronger and with extremely good chemical and heat resistance, able to withstand temperatures of up to 150C. To print TPC, you’ll need a higher heated bed temperature of up to 110C, and as with all flexible filaments you should only print at a maximum speed of 30mm/s.
Not generally considered a flexible 3D printer filament, but PLA+ is more of a general brand name given by filament companies to an upgraded, premium version of standard PLA filaments.
Most PLA+ filaments are mixed with TPU to reduce their brittleness and make them more durable and impact resistance. Therefore, though they may not be geared especially towards flexible filament users, PLA+, like Soft PLA, has been treated to make it more flexible.
However, check the PLA+ for this before purchasing, and only consider it for a flexible 3D print if you have tried Soft PLA and other flexibles, but struggled to get results.
- We also have an article explaining the differences between PLA vs PLA+.
- eSun PLA+ filament available here
- Kodak PLA+ filament available here
- ColorFabb PHA / PLA+ available here
Flexible filament melting point & printing parameters
Depending on the type of flexible filament, you may need an extruder temperature of between 220C and 260C. Softer TPEs will be fine 3D printing at 220C, whereas for filament like PCTPE, it is better to 3D print at 240-250C. TPU filament and Soft PLA filaments are fine between 220C and 250C.
For a heated bed, it can be optional for filaments like TPU, though we highly recommend using one for better layer adhesion. In general, around 40-60C will work well, printing at the higher end of that scale for TPU.
As for a closed chamber or enclosure, you do not require a heated chamber for flexible filaments, so any open printer such as Prusa can work fine.
Best Flexible Filament 3D Printers
|Name & Brand||Build volume (mm)||Price||Best price available at:|
|Creality Ender 3||220 x 220 x 250||$215||Amazon here|
|Creality Ender 5 Pro||220 x 220 x 300||$400||Amazon here|
|Qidi Tech X-Pro||230 x 150 x 150||$588||Gearbest here|
|Flashforge Creator Pro||227 x 148 x 150||$600||Amazon here|
|Pulse XE||250 x 220 x 215||$999||Matterhackers here|
|Qidi Tech X-Max||300 x 250 x 300||$1,199||Gearbest here|
Flexible filament 3D printing guide and tips
- Print slowly: at high speeds, the 3D printer can jerk, causing the soft filament to kink and jam. We recommend a max speed of 30mm/s, with 20mm/s also being fine for conservative makers who don’t mind waiting longer for a print that won’t fail.
- Direct drive extruders: this is not as absolutely necessary as a few years ago, as a well set up Bowden extruder can print flexible filaments without much issue. But if you are using a Bowden extruder, ensure that the entire feed distance is firm and tight from gear to hot end, otherwise the filament can become damaged, kink, and cause prints to look worse or fail.
- Spool above printer: If you have a printer like a FLSUN QQ-S, this is the default way of holding the spool. However, if not, try to place your spool above your printer so that when printing the spool is pulled downwards, putting the least pressure on the filament and minimizing the chance that the filament will become damaged from being pulled.
- Retraction: minimize / turn off any retraction to avoid any sudden jerky movements that could damage or affect the flexible filament during 3D printing. These quick movements can cause jams and the coiling of filament.
- Optimize travel movements: because of the lack of retraction, it is possible that you will see a small amount of stringing – though this can be minimized with good print settings. If you set your print settings to only print within the boundaries of your print, you prevent any visible stringing from occurring.
- Ensure filament is dry: flexible filaments are hygroscopic, meaning that left out too long they will absorb moisture and worsen their 3D printing properties. Therefore, always store in dry and preferably airtight conditions (we recommend how to do this further down) and you can also heat any “wet” filament in an oven at a reasonable temperature for a few hours to dry the filament again. The print results from wet vs dry flexible filaments is very noticeable, with wet filaments containing more bubbles and less fine detail.
Advantages and disadvantages of flexible filaments
Benefits of Flexible Filaments
- Flexible (obviously): 3D printed parts can stretch if necessary, will never have an issue with being brittle, and have a wide range of engineering and other fun applications.
- Good heat resistance: Not only can flexible filaments handle high temperatures, but they also hold their structure and properties well at temperatures as low as -30C.
- Great impact resistance: Due to their elasticity, flexible filament printed parts can take powerful impacts well. As a result, they are often used in applications like phone cases and running show midsoles, as well as in vibration dampening.
Disadvantages of Flexible Filaments
- Must be 3D printed carefully: To ensure your flexible 3D printed parts won’t fail due to jams and clogging, it is important to print slowly, at the correct temperatures, with an accurately calibrated print head and print bed.
- Will string if not planned for: It is important to optimize your 3D printer’s travel movements, as due to the lack of retraction, more stringing can occur during 3D printing. However, these strings can easily be dealt with in post-processing.
- May struggle with a Bowden extruder: if you do not properly ensure that the entire travel distance for your flexible filament is firm and tight, you risk damaging and breaking the filament with a Bowden extruder. Take extra care in these cases.
- Hygroscopic: needs to be carefully stored and dried if left out for a long time.
Flexible filament applications
Flexible filaments are commonly used where preventing impact damage is key, such as in phone and other electrical casings. They are also used in vibration dampening applications, and in a wide variety of automotive parts.
Increasingly flexible TPEs are used in 3D printed shoes, with brands such as Adidas and Reebok using flexible filaments to create 3D printed midsoles in recent sneaker releases, such as in the Adidas Futurecraft 4D.
How to store flexible filaments
TPU and other flexible filaments are hygroscopic, and should only be stored in dry conditions in airtight storage or it will swell and worsen for 3D printing properties.
We recommend the following containers: