shoe rubber

Printing With Flexible Filaments

Being able to print with flexible filaments can open the possibility of being able to print things like phone cases, watch straps, footwear, rubber tires and many other everyday objects.  Since flexible filaments have such unique properties, they can be a bit confusing to get started with.  Here are a few tips and tricks to help with printing flexible filaments. 

Choosing a filament

Most flexible filaments are some form of TPU.  Different brands of TPU filaments can have very different levels of flexibility.  This level of flex is usually rated as a score on the Shore harness scale.

The Shore hardness scale has a few different classes of hardness but for 3D printing plastics almost all fall within the Shore A rating class.  In this class, the plastics can be rated from levels 0-100 with 0 being very soft and 100 being very hard.   Here are a few examples of where household objects fall on this scale:

Shore A 20 – Rubber band

Shore A 40 – Pencil Eraser

Shore A 70 – Rubber tire tread

Shore A 95 – Shopping cart wheel

For 3D printing filaments most seem to stay in the range of Shore A 60-95.  While this rating is very important to consider for overall flexibility, your parts geometry will also have a major effect on how your part feels.   For example if you are printing a very thin part it may still feel fairly flexible despite being printed with a fairly hard material.  On the other hand, if you are printing a large wide part with the same material it may not feel like there is much flex at all. A couple of very popular brands of TPU filaments to get started with are Sainsmart TPU and NinjaTek. Both are available from Amazon.   If you are interested in learning more about other types of 3D  printing filaments check out our filament selection article here.


Printer Selection

When printing with flexible filaments, the type of extruder on a 3D printer can be very important.  In general, there are two types of extruders used on 3D printers.  

Direct Drive Extruders

Machines that have the extruder mounted directly on the print head just before the hot end.  With this type of machine, plastic is pulled directly to the hot end with no tubing between them. This setup puts a bit of extra weight on the print head which can slow things down, however  it also helps to prevent filament jam ups in the bowden tube leading up to the head. An example of a printer that comes with direct drive is the flashforge creator pro.

Bowden Extruders

With a bowden extruder style machine the extruder is mounted further away from the head, typically on one of the printers upright frame rails.  While this helps to keep the print head lighter, it also means that after reaching the extruder the filament is being pushed through the bowden tube towards the hot end. An example of  a printer with a bowden style extruder is the Creality Ender 3.

For most filaments, either extruder style works well.  However for flexible filaments, having the extruder far away from the hot end (as it is with the bowden style extruders) can cause issues.  Since the material is so flexible and being pushed up to the hot end for some distance it makes it very difficult for the extruder to accurately feed the filament to the hot end. Another way to think of it is like a rope.  Rope is very easy to control when pulling it from the end, but nearly impossible to control if trying to push it from further back.  For this reason it is best to print TPU on direct-drive printers.

Print Settings

Different types of TPU can require very different settings and it’s usually best to start with the filament manufacturers recommended settings.  To give you an idea of general settings, here are some print settings which were very successful when using Sainsmart TPU on a Flashforger Creator Pro printer. One key thing to note is the low sprint speeds.  You will need to slow your print speed down significantly to get the best results when printing with TPU.

Speed – 20mm/s base speed, 65mm/s travel speed

Layer height – 0.12mm, 0.3mm first layer height

Temperature – 210C Extruder, 55C bed

Retraction – 0mm 


1 thought on “Printing With Flexible Filaments”

  1. An intriguing discussion is definitely worth comment. I think that you should publish more about this topic, it might not be a taboo subject but generally people do not speak about these subjects. To the next! All the best!!

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