The Maker’s Guide to Flexible FilamentBeau Kuhn
Types of Flexible Filament
While there are several materials on the market that have flexible properties, the two major types of flexible filament are Thermoplastic Polyurethane (TPU) and Thermoplastic Elastomer (TPE). Both of these are made from thermoplastic elastomers which are derived from a blend of hard plastic and soft rubber. While terminology is often mixed, thermoplastic polyurethane (TPU) is the most commonly used flexible material within the 3D printing industry.
How is Flexible Filament Measured?
What sets many flexible filaments apart is the degree of flexibility they offer. Most materials are measured on a “Shore Hardness/Durometer” scale which is the measure of the resistance a material has to indentation.
Typically, the durometer of a flexible material is denoted as being on either the Shore A or Shore D scale. Softer materials such as flexible filament for 3D printing are measured on the Shore A scale, while Shore D is reserved for harder rubbers.
The Flexx™ Flexible TPU by Keene Village Plastics, which is now available directly through our store, comes in 3 different varieties:
- SemperFlexx98 (98 Shore A Hardness)
- SummaFlexx50 (50 Shore D Hardness)
- VexiFlexx70 (70 Shore D Hardness)
Printing Flexible Filament – Things to Consider
Printing with flexible filament can be a delicate balancing act. To achieve great results, your printer needs to be a finely tuned machine along with using a good high-quality filament and perfecting the settings in your slicing software. Here are five things to consider when printing flexible material. Remember, changing any of these can drastically change the print.
Due to the nature of flexible TPU filament and the potential to kink or buckle when being pushed through the hot end, it is highly recommended that you hit the brakes on your print speeds and slow them w-a-y down. Typical print speeds for non-flexible filaments can range from 30mm/second all the way up to 90mm/second. For flexible, slower is better so we recommended starting around 30mm-40mm/second and see what works best in your particular printer.
A direct drive extruder will work best when trying to print flexible TPU. However, you can print flexible on a Bowden-type extruder but with some increased difficulty. We are currently working on flexible extruder adapters that will allow you to print TPU easier on a printer with a Bowden-type extruder. If your printer is not equipped with a Bowden tube, then adding one to help guide the filament can give you a better chance of avoiding filament buckling.
Flexible TPU is especially sensitive when it comes to the temperature of your hot end. We recommend that with our material you start at 220°-245°C and fine-tune your settings for the best results. This will reduce the oozing material from the print head that can create messy or stringy prints.
Your retraction settings will also play a big part in getting good results and avoiding stringy prints. Retraction is when the extruder motor moves in reverse ever so slightly to avoid extrusion when moving across a gap in a printed design. Too little retraction and you will be left with cobwebs of material all over your print. Too much retraction will leave you with blobs of filament when the print head starts its next segment of printing.
Proper bed adhesion is key to any successful print but with flexible TPU, it is even more crucial. We recommend that you only try printing flexible on a printer with a heated bed with the temperature range set between 45°-60°C. Check out our article on bed preparation for more information.
Once you’ve prepped your printer with the right settings & selected your preferred filament, you’ll be ready to make all kinds of flexible prints!