How To Print Flexible Filament

If you want to venture into the world of flexible, durable, tactile printed parts, then you came to the right place. Here is where you’ll learn to print flexible filament fast and easily print the softest filament on the market.

Using the Flexion To Print Flexible Filament

This article focuses on how to print flexible filament with the Flexion Extruder. If you do not already use the Flexion Extruder, then go get one and come back here. Right out of the box, Flexion produces fast (60mm/s), clean, void-free prints with TPU, TPE, Ninjaflex, and other flexible filaments. Angus (aka Makersmuse) even uses it to test flexible filament: Review of Flexible Filaments (with X60!). Flexion eliminates the typical problems you encounter when you print flexible filament: jamming, buckling, and oozing. Read on to find a few tips to optimize your settings and produce perfect prints with your flexible filament.

Software Settings

Here’s an example of the extrusion settings we use with a soft TPU such as Ninjaflex (about 85 Shore A). These settings are valid for speeds up to 60mm/s. A few things to note:

  • The extrusion multiplier above 1.0 – when the drive roller and idler squeeze the filament, they effectively reduce the diameter of the filament. This requires more extrusion. As you increase tension you may need to increase extrusion as well
  • Extrusion width lower than the nozzle diameter – this helps create gap-free upper layers. However, it can also make overhangs difficult. You will need to balance these factors to optimize your own prints
  • Retract high and fast – this keeps the nozzle from oozing and makes clean prints. Longer drive paths (Bowden drive, E3D hotend, Mk11 extruder), may require even longer retractions.

We recommend that you increase outline overlap above 75% to ensure a good connection between outlines and infill. Other settings will be similar to what you use for other materials.

Hardware Settings

First, adjust tension. Hold the filament between your fingers and load filament., then turn the adjust screw to maximize the pull-force on the filament. Most printers have a function to load filament automatically. If yours does not, then try this load/unload “print”.

The photo below depicts two identical prints (one still has support material attached). The print on the left was made with a perfectly-functioning Flexion extruder. The one on the right had a small hardware issue that caused pressure buildup and “blobbing”.

So how to fix this issue?

  • Blobs/strings/pressure buildup – if the barrel (see the exploded view for part name reference) is not pushed all the way up into the mounting block, then the PTFE will be able to float between the nip point and the nozzle, allowing the accumulation of material between the PTFE and the nozzle. This is a problem that can manifest over time. You may get some number of “good” prints before seeing this effect. The best way to fix it is to disassemble your hotend, remove any material, and reassemble. Ensure that the barrel is seated on its shoulder against the bottom of the mounting block. Make sure to tighten the nozzle when it is at temperature to get a good seal.
  • Bumpy surfaces/inconsistent extrusion – this can be caused by bad settings. Before you consider hardware issues, adjust temperature and extrusion up and down. If that doesn’t help, you may have an under-powered extruder motor. This can “cog” toward a stable magnetic position when it should be micro-stepping, causing visible areas of over- and under-extrusion. To operate the Flexion, we recommend a minimum of 250N-mm of torque. Most Nema17 motors achieve this, but some drivers do not deliver enough current. This happens most often on Wanhao (and similar) printers, specifically one batch that shipped in early 2017. To adjust current, follow the guide here. You can also find replacement motors on Amazon.

Design Considerations

Here are some quick tips to optimize prints for flexible filament:

  • Keep overhangs at 40° or less
  • Design in peelable support wherever possible (see Ninjaflex Support Material here)
  • Use slicer-generated support and remove with side-cutters. This works better than you might imagine

We hope this helps you print flexible filament with the Flexion Extruder. If you have any questions, we are always here to answer them! Just send a message through our contact form.

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