Flexible filaments open up a world of possibility for your prints. You can print a range of objects with flex materials, and if you have a dual or multihead extruder you can print some pretty amazing things. Bespoke flip flops, stress ball-heads, or just vibration dampeners for your printer, to name a few.
With flexi filaments part of your printing arsenal – it really makes the most of your 3D printer.
But just a few years ago when they first became available there just wasn’t much imagination to use them. Then you tried them in your printer and you realized they were a bit of a pain to print.
This is because of a few factors; but primarily early flexible filaments were just soft. Too soft – this might sound stupid, considering you wanted a soft, flexible filament but when you ran them through your printer they just didn’t print very reliably. This happened because of the ‘pushing string effect’ in most extruders in 3d printers – you push something with no rigidity through a nozzle and it will bend, twist and fight against it.
Additionally, they were a bit too grippy (almost like rubber). Which when you need your filament to slide through the nozzle smoothly, doesn’t help the extrusion process.
Furthermore these soft TPE materials were challenging to extrude with good tolerances. And poor tolerances mean jams and extrusion problems.
Luckily, there’s now a range of bendy and soft filaments, some even with elastic properties and varying levels of softness. Here at rigid.ink, we’ve experimented with our fair share of soft pla, TPE and TPU materials – so we know a thing or two about the differences; what works best for what, and a good filament when we see one.
One main way flexible materials are graded are by a scale or soft/hardness. The scale commonly used in 3d printing is the Shore A scale. Typically 3d printer flexible materials are gauged between 100A and down to around 75A. With 100A being much less flexible (think the rubber on a shopping cart wheel) – and 75A being more or less the softest limit you can print using current FDM printers. Stiffer materials tend to be easier to print, while the very soft materials can be problematic.
Let’s take an impartial look at the best flexible filament available on the market today. After all, flexi materials like TPE filament or flexible pla filament tend to cost a bit more than standard 3d printing materials – so it pays to know what you’re getting first.
First, think about what’s important to you with your filament. What features or qualities really matter to you, to what you’re printing, or your business? Are you looking for reliability in supply, reliability in printing? Perhaps you need to know layer adhesion is uncompromised, ensuring your finished prints are durable and last? Are you looking for a material with high elasticity, or are you looking for a strong, vibrant range of colours?
Is customer service important to you, or will you likely just order once to experiment and not need to worry about excellent service later?
And then there’s price, how much are you willing to pay. TPE, TPU and flexi pla filaments are often more expensive to produce, so cheaper alternatives may have shortcuts in manufacturing standards or contents. You don’t want contaminants in cheap filament ruining your prints, or causing time-draining nozzle blockages.
Don’t worry; we’ve taken all this into consideration with this article.
A review of the best flexible filaments:
NinjaTek SemiFlex Filament
Ninjaflex’s first TPE filament on the scene (the original NinjaFlex) is a great flexible material, but it’s very soft. TPE stands for thermoplastic elastomer. This caused some problems in printing, in some printers more so than others. Their newer, slightly less flexible material; SemiFlex is much easier to print and produces good results. The only downside is it is actually less flexible, but this can be a benefit depending on your application.
Ninjaflex Shore Hardness is 85A whereas the Semi Flex version Shore Hardness is 98A.
Unlike regular Ninjaflex settings you’ll be able to print the semi flexible materials up to around 85mm/s. Typically the softer materials top printing speeds for regular Ninjaflex and softer materials are around 30-55mm/s depending on your printer.
Benefits of SemiFlex Filament are:
- Low friction
- Higher stiffness, easier to print
- Adheres to most regular print surfaces
- Higher tensile strength than standard Ninjaflex
Unfortunately SemiFlex is only available on 0.5KG spools, and is very expensive – especially if you need a larger quantity. Ninjaflex SemiFlex print settings are 225-235C
Polymakr Polyflex Filament
Polyflex is a TPU filament, which is similar to TPE – but it has its differences. You can view our comparison between TPU and TPE filaments here. TPU is now becoming more commonly available for 3D printing and has only recently come on the scene.
Polyflex Shore A hardness is rated at between 90A – 95A which is comparable to most other TPU based filaments. Confusingly Polymakr don’t seem to commit to a specific hardness rating, so it may be subject to conditions (temperature, humidity etc.) which is worth considering if you need specific requirements.
Generally Polyflex prints well and the service is good. It’s worth considering that it’s only available on 750 gram spools, and the colour range is very limited. PolyFlex printing settings are 220-235C.
Recreus Filaflex TPE
Filaflex is a common Ninjaflex competitor – being very similar to the original Ninjaflex, it’s very soft (the softest on this list) at just 82A. It prints well considering it’s such a flexible material, but generally if you require printing very flexible materials its worth considering using a specialist extruder with a thermal insulator and low friction PTFE lining (more on this below).
Being the softest material here, Filaflex also boasts the longer elongation to break at 700%. Useful if you need something with even more stretch, but may be overkill for most applications. 600% elongation is common among TPE and TPU materials.
FilaFlex is available in a healthy range of colours and on 250g and 500g spools. Although in a similar high price bracket to Ninjaflex, it is slightly cheaper. Print settings for FilaFlex are 210-230C.
FormFutura FlexiFil TPC
This is an interesting material – it’s a Co-Polyester 3D Printer Filament very similar to PolyFlex and SemiFlex, but it’s partially made from bio-oils. Oddly FormFutura use a different scale to measure hardness, the Shore D scale. Converting their 45D rating to Shore A means a hardness compared with the other materials in this report as between 92-94A.
Sold only on 0.5KG spools, and priced similar to other flexi materials in this guide. We found their range of colours to be very limited. Mostly because the colours were different from expected, given their names. As an example, Red is more of a light Browny/Orange. This isn’t so much as a criticism, just worth noting.
Also their recommended printing temperature is very broad. FlexiFil print settings are advertised as 220C-260C. It’s worth considering that it must be printed very slowly (10-20mm/s) as it can buckled very easily in your extruder. Adding a tiny amount of WD-40 to the filament can aid extrusion. Nice material if you’re slightly more environmentally cautious and are able to wait longer for your prints.
Who chose the name for this? Try saying PCTPE Filament sober, let alone after a few drinks (while we don’t advocate drinking and operating 3D printers, we can’t deny we’ve not had a tipple while burning the midnight oil, checking that long print).
So what does this mean? PCTPE stands for "Plasticized Copolyamide TPE", or in English; a chemical co-polymer of Nylon and TPE. This essentially creates a less flexible, less elastic version of TPE which naturally prints a little more easily. Nylon is a very durable material, so if you need something that is more flexible than Nylon then this is a great filament. But it’s borderline whether it can truly be classed as a flexible filament as when printed solid infill has very limited flex.
Shore A hardness rating is not advertised for this filament, but it’s estimated to be around 100A+. Prints slightly faster than most flexi materials as expected, but you must use a dried weak PVA slurry to aid bed adhesion and is prone to warping. Printing temperature for PCTPE is around 235-242C
MatterHackers Soft PLA
There’s not much information as to what exactly makes MatterHacker’s PLA soft, but it’s a material we wanted to mention as it’s different to the other thermoplastic elastomers.
First, it’s a biopolymer which means it’s created from (at least mostly) natural materials. Also, flexible PLA doesn’t have the same elongation abilities as co-polymer flexi materials. It is however a great advancement over regular, often brittle PLA.
Extrusion temperature is around 220-235C, and you’ll want to print very slowly as some reviews mention is jams easily. Printing flexible materials too fast can cause them to expand too quickly in the nozzle, leading to reduced extrusion or even blocking.
Shore hardness is 92A. Comes in 0.75KG spools in both 1.75mm and 3.00mm sizes.
What is a PTFE Hotend Liner?
If you’re experiencing too much friction, causing extrusion issues with your flexi filaments, it may be worth investing in a Hot-End with a low friction PTFE liner.
However, PTFE can’t get much hotter than 220C+, so positioning and temperature you print at are worth considering before using them.
How to print flexible filament:
- Print slow:
It’s important to make sure you print slowly, usually 20-40mm/s is a starting point for most flexi materials. Stiffer materials can be printed faster.
You can also print faster with specialist extruders, that have lower friction linings or reduced space for the ‘pushing string’ effect. Typically direct drive extruders work more effectively, and Bowden tubes can cause extra friction. But this can be overcome using lower friction flexible filaments.
- Check your temps:
As with any filament, ensure you’re using the right printing temperatures. Check the extrusion temperature and start in the middle of the range. If your filament is under extruding, turn the temp up a little. If it’s over extruding and oozing all over your print, turn it down a little.
- Retract, retract!
Talking of oozing, ensure you’re using the correct retraction settings. This might need to be a little more than standard filament retraction as flexi can leak a little more between extruding points. If you’re getting excess material, or wispy thin strands then adjust (increase) your retraction in the Slicer.
Another benefit of retraction is it prevents the pressure building and causing the material to expand and clog in the hot end (usually caused by excess friction).
- Bed Surface:
Soft filaments typically adhere well to beds. Often you don’t need a heated bed, as they don’t tend to warp, but we do recommend heated beds for those first layers at least.
Forget the hairspray, blue painters tape or an even, thin (dry) coating of glue stick should give great results. Some surfaces like PEI can stick a little too well, so be wary of that.
We hope this has cleared up some ambiguity 3D printing with flexi, and allow you to start experimenting with more exciting options available to you. If you’d like to view our selection of Soft, flexible PLA you can do so here. It’s low friction so works well in Bowden tubes too (like Ultimakers).
Alternatively, our own brand of TPU is available here (and in new colours). This is a Shore hardness of 94A, low friction and excellent layer adhesion. Meaning your prints print reliably and are near-as unbreakable.
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