How to Print with Flexible Filaments

Here are a few pieces of advice for getting the best results from flexible filaments:

First, to debunk a few myths.

Myth 1 – you can’t print flexible filaments with a Bowden tube system

A Bowden tube system is one in which the drive gear (that pushes on the filament to feed it to the nozzle) is contained in a separate part of the printer to the extruder nozzle, and the two are connected via a plastic PTFE tube, known as a Bowden tube.

Flexible filaments can be printed with these systems if there is a constrained path between the driver gear the extruder (this is discussed in more detail later). In fact, Bowden tube systems can sometimes be better than direct extrusion systems for printing with flexibles, as the filaments tend to soften at lower temperatures. Printers that have the drive gear close to the hot end can suffer from “heat creep”, where the filament warms up due to heat conduction from the nozzle, causing it to soften and compress, which can stall the extrusion.

Myth 2 – flexibles can’t handle overhangs

There is nothing to stop a flexible filament printing exactly the same models as PLA or ABS, if the printer has been set up correctly to optimise the print for the filament. Our F41 FLEX can handle up to 45 degrees from vertical and our F43 TOUGH can reach up to 60 degrees without support.

 

Here follow some pointers for setting up your printer for flexible filaments:

Check the filament has a constrained path

The basic function of the extruder system is to pull the filament from the spool and push it through the hot end nozzle at a controlled speed. If there are any small gaps between the pushing gear and the hot end, there is opportunity for the filament to buckle.

If your printer hasn’t been designed with a constrained path, you can probably find a model for an extruder housing or addition to enable the printing of flexible filaments.

Slow down

The quality of any print can usually be improved by slowing down the speed of print, but in the case of flexibles, the effect is even more dramatic. Printing slowly can mean the difference between success and failure.

No strings

Flexible prints can often end up with messy surfaces and strings of filament between parts of the model. The flexible filaments are generally softer and stretchier than standard printing materials, they are more likely to ooze out of the nozzle between extrusions and leave strings of plastic on the print. There are a number of printer settings that can be used to reduce this effect:

  • Retraction – set a retraction of a fraction of a millimetre between extrusions, so that the filament is pulled back into the nozzle while the print head moves between parts of the print.
  • Z-lift – this setting lifts the print head a small distance, breaking the string of filament from the surface of the print before the head moves to the next position.
  • Avoid crossing perimeters – this adds a little time to the print, but many slicer programs offer the option to keep the print-head movements within the perimeters of the print where possible, which keeps any unsightly stringing hidden inside the model.

Ready to print Flexible?

Try our high-performing flexible polypropylene! Forefront F41 FLEX is bendy and rubbery yet prints smoothly. It is completely non-toxic and releases no odours during printing. To find out more about how our materials compare to other filaments for 3d printing, including other flexible filaments, read our blog “A Comparison of Popular 3D Printing Materials”.