The development of exotic filaments, including flexible filament, is driving advances in the applications of 3D printing technology. Thanks to these new materials, we can now print an increasingly complex and diverse array of 3D designs. With any new material, comes a new set of challenges to get the best prints possible. In this article, we will go through some different types of flexible filament, some common challenges, and the top 5 tips for successful results with flexible filament.
5 Types of Flexible Filament
Flexsolid is a high strength flexible filament with good elasticity. This is a great filament to use for anything that will require high durability — like mechanical items that will be handled a lot or sporting equipment. Highly detailed prints may come out stringy so this filament is best used for simple prints that would require a lot of strength and flexibility. The filament is fairly easy to print compared to others.
NinjaFlex is a thermoplastic elastomer (TPE) and is softer than FlexiFil™. It’s also a very strong material to print with (on par with FlexSolid). NinjaFlex has a low friction exterior, which helps reduce buckling and speeds up printing. It has fairly good reviews from the online community, but some people have challenges with feeding. It requires low heat to stick to the print bed (30-50 celsius).
They also released a new product called SemiFlex which (surprise, surprise!) is semi-flexible but not as soft as their regular line.
This material is made from Thermoplastic Co-Polyester (TPC) and is also quite flexible. It is resistant to high temperatures and is strong. If being environmentally friendly is important to you, it is partially made out of renewable carbon content (bio based oils). One challenge with this filament is that it can get clogged in the extruder (we provide some tips below to help you avoid this).
Fila Flex is made from the same material as NinjaFlex (TPE) and has similar properties but is not as strong as Ninjaflex. It’s very soft and is highly adhesive so layers stick together well. This material is more elastic than NinjaFlex and is good for prints that need a lot of stretch, but also makes it one of the most difficult to print with. Since it is so soft, however, it may have a tendency to come out stringy or clog your nozzle. This filament will print on a cold bed.
This is a polyester based filament and is firmer than NinjaFlex and FlexiFil. It also has a lower melting point which is meant to make it easier to extrude. One fun feature is you can adjust your print by running it under hot water to re-shape it. It is stiffer than FlexiFil™ and has a nice iridescent glossy finish. Challenges are it is sometimes difficult to feed without tangling. Recommended settings are found on the Makerbot website.
6. Flexible Resin
Flexible resin will only work for SLA 3D printers. However because SLA is not a feeding system, flexible resin doesn’t come with many of the challenges that flexible filament does. If you own an SLA 3D Printer, flexible resin is a useful material that is great for printing tactile designs. Check out this collection of designs by Formlabs on things you could 3D print with flexible resin.
The Bottom Line
Those are just a few of the flexible filaments on the market. Your decision on which filament to use for the best print will depend on what you are printing, your budget, and what type of extruder you are using. Every filament will have different recommended settings for optimal print so it’s best to check with the supplier.
4 Challenges of printing with flexible filament
Although flexible 3D printing filament can be very useful, all new technology has its hiccups. Here are the main challenges you may face when printing with flexible filament.
1. Feeding filament through the extruder: Flexible filament is much softer than regular filament and can be difficult to feed through the extruder and can cause jams. To successfully feed the filament from the drive gear through to the hot end, it needs a direct path. This is usually not a problem with regular filament because it is stiff, but with flexible filament, it can get deformed and stuck.
2. Material buckling: Due to the nature of flexible filament, pressure in the nozzle will sometimes cause the material to buckle when pushed through the hot end. This is usually caused by printing too quickly or not having a tight and narrow pathway between your extruder and your hot end. This is described by one user who tested a few different materials. Material buckling can also cause jams.
3. Difficulty sticking to build plate: To avoid shrinkage and get the best adhesion to your print bed, the print bed temperature may need adjusting. Usually the culprit is cold print beds or bad levelling.
4. Messy or stringy prints: A symptom of pressure build up in the extruder is extra filament will ooze out and create a messy print. This is caused by a number of factors, including temperature, speed, and retraction settings.
5 tips for successfully printing with flexible filaments
1. Print slowly:
In general, recommended speeds for flexible filament is between 30mm – 40mm/second for optimal print quality and timing. If you’re printing with FlexiFil™, they recommend 10-20mm/s. Print speed can be set as low as 5mm per second for precise prints. Yes, we know – it’s really slow! Printing slowly will increase your chances for a successful print because it helps you avoid pressure build up in your extruder which can lead to messy prints.
2. Use a direct drive extruder:
To avoid filament jamming in the extruder, it is best to reduce the space between the cold end and the nozzle by using a direct-drive extruder. According to Fenner Drives, the makers of Ninjaflex, bowden extruders are not recommended for printing with flexible filament. Though it’s not impossible to do, it’s more challenging.
If you are printing with a bowden extruder, Thomas Sanladerer made a great video tutorial below on how to print NinjaFlex with a bowden extruder.
3. Keep temperature hot…but not too hot:
Heating up your extruder temperature allows filament to flow more easily through your nozzle. The downside of this is it can cause oozing and stringy, uneven prints. Every printer and type of filament will require slight adjustments in temperature settings for the best print. Makezine’s flexible filament guide includes a great chart with recommended temperatures for different flexible filaments, which can be seen below.
4. Adjust retraction settings:
Retraction can relieve the pressure from the hot end and keep filament from being pushed through the nozzle when the extruder isn’t printing. You can adjust your retraction settings depending on the problem you are experiencing. If your extruder is clogged, you will want to lower your retraction. Some have had success with flexible filaments at retraction of zero. You want to find the minimum amount of retraction necessary to reduce the extra stringiness in your print. If you are experiencing extra material coming out of your nozzle, you will want to increase your retraction distance or speed.
5. Adjust hot bed temperature & use tape:
Hairspray is great to keep hair in one place for those sweet 80’s hair styles. It is not necessarily the best solution for keeping your filament on the print bed (though sometimes it works for that too!). Flexible filament should stick quite well to Kapton tape or regular blue painters tape. For your hot bed, temperature settings may vary depending on what type of printer and filament you are using. Most companies recommend between 40-50C but for the best results we recommend referring to the filament guide for the product you are using.
In addition to flexible filament, you might want to try some other materials for your next project. We’ve got you covered with our exotic filament guide by 3DSupplyGuys, which describes the different properties of these filaments and what they are best used for. Check it out!