Flexible filaments
Most flexible filaments are based on TPU (Thermoplastic Polyurethane) and have a Shore hardness of 95A. This is a common and popular standard, as these filaments usually work equally well in both direct-drive extruders and Bowden-style extruders. In addition to TPU, there is also TPC (thermoplastic copolyester) and mixtures such as PEBAX, or PEBA from the chemical company Arkema. In principle, flexible filaments can be processed with almost all 3D printers (Ultimaker, Prusa, Creality, Anycubic and Flashforge etc.). However, there may be a need to reduce the printing speed and the model cooling fans if necessary.
In the world of 3D printing materials there are of course also various flexible, soft filaments and synthetic resins that can be processed. Flexible materials can sometimes be a little more difficult to print. Especially with Bowden Style Extruders in the FDM field it can be difficult to print on soft materials. Therefore we recommend to always pay attention to the so-called shore hardness of the filament. Shore hardnesses are usually indicated by a letter (A. B, C, or D). The lower the value, the softer the filament is. It is important to remember that the different measuring methods (A, B, C, D) are not directly comparable with each other if you take it very precisely.
Flexible materials are mostly based on TPU (thermoplastic polyurethane). This material is available in various gradations and variations. You can find exact data in the technical data sheet of the respective product.
The situation is similar with flexible synthetic resins, for example for Formlabs 3D printers or EnvisionTEC printers. Here too, flexible resins are somewhat more difficult to process, as they are already soft when printed and of course yield slightly. This means that the support structures have to be made considerably larger and more generous. This of course also increases the time in the post-processing.