Talpadk’s Blog

October 10, 2013

3D printing using Ninja Flex filament

Filed under: 3D Printing — talpadk @ 7:53 pm
Tags: , ,

Yesterday I received some of the relatively new “Ninja Flex” filament sold by http://www.fennerdrives.com/ 

As the internet doesn’t seem to overflow with print reviews / settings for it yet I decided to post some words about it.

NinjaFlex Sapphire 1.75mm

NinjaFlex Sapphire 1.75mm

The Filament

It is always difficult to measure a soft material but using my caliber I measured the diameter to be 1.75mm as it is supposed to.
The filament also seems to be nice and round.

I ordered the “sapphire” version of the filament, and it has a nice (mat) blue color  which turns glossy when printed.
It is also slightly translucent when printed thinly.

The filament is very flexible (I can tie a tight knot on it without it breaking)
The filament is also elastic but not as much a a regular rubber band… perhaps 5-8 times harder if I should make a guess.

The material is not known to me, but I strongly suspect it to be polyurethane (PUR) with a surface coating/treatment to make it less sticky.
Fennerdrives already produces PUR belting  which have been used in 3D printing prior to this material appearing and due to the mat to glossy change.
(Update: it has been confirmed that it is polyurethane)

The Fennerdrives recommended settings are:

Recommended extruder temperature: 210 – 225°C
Recommended platform temperature: 30 – 40°C

The filament isn’t exactly cheap I would say roughly 3x the cost of PLA/ABS including shipping compared to the cheap PLA/ABS I normally buy.
Then again soft/specialty filaments doesn’t seem to come cheaply normally.
(Actually a lot of the cost comes from the somewhat expensive USP shipping)

Fennerdrives does ship both from the US and the UK, living in Denmark (inside the EU) this is a big plus for me.

3D model for the rubber feet

3D model for the rubber feet

The test prints

As I’m currently designing and building a tabletop CNC mill I thought that I might as well print some rubber feet for it.

The print isn’t necessarily the simplest one to print due to the outwards sloping unsupported  walls.
However the angle is quite close to vertical and wouldn’t normally be causing problems.

The 3D model was created using FreeCAD which is my preferred open source CAD package.

I used Slic3r for generating the G-code.

And my printer is a RepRapPro Huxly which has a bowden extruder which might actually not be ideal for extruding a soft and springy filament.

Print 1

Was done using my regular PLA/ABS profile.

I had to abort the very first attempt as the filament wasn’t printed continually.

  • I increased the extrude temperature from the low temp that felt right while manually extruding the filament
  • Reduced the speed using the M220 command
  • And upped the heat bed temperature to 85 deg C

Much to my amazement the rubber foot actually printed sort of  okay.
It was however sticking so hard to the “Kapton” tape that removing it actually pulled the tape off the print bed!

Prints 1 though 4

Prints 1 though 4

Print 2

I then tried to create a specific profile for printing the rubber filament.

  • Reduced the printing speeds to avoid having to scale them using the M220 command
  • Removed the “Kapton” tape as it had become wrinkled any way
  • Printed without having heat on the bare aluminium print bed.

It printed with roughly the same quality at the first print but was very very easy to remove.

Print 3

I noticed that the hot end seemed quite “laggy” probably caused by the flexible nature of the filament and i therefore made some additional changes.

  • All print speeds were set to 15 mm/s to avoid having the extruder changing speed
  • Retract was disabled, again to keep a constant pressure in the hot end
  • “Skirt loops” was increased to 4, to give the hot end more time to build up a constant pressure.
  • Infill was reduced from 50% to 0% to see if the vibrations caused the surface defects
  • The hot bed was set to 40 deg C

Just after starting the print I realized that setting infill to 0% would cause some parts to be printed in mid air with nothing supporting them from below.
Out of curiosity I did however allow the print to continue.

The printer managed to print the part despite the fact that is was “unprintable”…
Also the surface finish was very satisfying.

Due to the 0% infill the part was slightly softer as was to be expected

Print 4

I don’t like printing the impossible as it may or may not succeed I made one small change

  •  I changed the infill back to 50%

I’m pleased to report that the surface finish seems to be just as good as before.

Printer settings

Please keep in mind that  printer settings varies from printer to printer and that the one described here may not be optimal even for my own printer.

The following list is semi sorted by what “I think is probably the most important settings”

  • No retract
  • Uniform print speed (of 15 mm/s)
  • Multi loop skrit (4 loops)
  • Hot end temperature 240 deg C
  • Print bed temperature 40 deg C
  • Travel speed 100 mm/s
  • Extrusion width 0.5 mm with a 0.5 mm nozzle
  • First layer 50% (might actually be a bad idea)
  • Layer height 0.3 mm

Again while reading this keep in mind that I haven’t played very much with the temperatures.

I had some undocumented failures after print 1 where the extruder/hot end seemed to jam and I haven’t dared reducing the temperature again as I needed/wanted some functional prints.
The problems may however be related to too fast extrusions, filament loading and or the filament being deformed by the retracts.

My prints was stringing slightly internally lowering the temp may be able to reduce this…



  • It has been confirmed by the friendly customer support at Fennerdrives that the material is actually polyurethane.
  • Even without any heat on the hotbed it still sticks very very well to “Kapton”

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