Extruder Tension Control (for TPU printing)

thingiverse

2020-03-18: Minor upgrade for Creality CR-10S V2: On the V2 upgrade, the filament sensor has been placed rather close to the extruder, not leaving enough space for a normal knurl screw. Therefore I created my own. I cut of a piece of M5 thread (use 10-14mm) and created my own thin knurl cap for it, which fits in the gap. I directly glued the thread into the cap, but if you have a screw with hex head or uncertain if you can glue it in exactly perpendicular, I also created a cap with hex hole where a nut or screw can just be squeezed in without any extra glue. (In case of a nut, you have to glue the thread into it, though). Actually while testing the new printer I realized, that the screw isn't really required to **successfully print TPU with Bowden extruder**. Just putting on the bracket seems to be good enough to avoid squeezing the soft TPU. (With PLA/PETG the clamp without screw just lies loose on the extruder, with TPU it grips already without screw, i.e. it limits squeezing of filament.) --- Update: added a version with cable guide (not required for CR-10V2) Initially I had problems printing flexible *TPU* filament on my CR-10S printer. It liked to ravel between extruder wheel and PTFE/Capricorn tube, especially after frequent retracts. The problem with soft filaments is that frequent back and force pulling will squeeze the filament making it more flat and wider, so that eventially it can not be pushed back into the PTFE tube and forms a ravel/clew. There are several solutions to mitigate that problem 1. control/reduce pressure of extruder wheel (this thing) 2. tune rectract parameters, pull and especially push back filament slower (normal fast pull/push will only strech-compress filamnet potentialy creating ravel when pushing into bowden tube) 3. cool the stepper motor of the extruder to avoid making filament even softer (I used a simple little USB fan for that) Actually after controlling extruter tension (avoid squeezing) and keep it cool I have **no more issues with flexible/TPU filament. And much slower (but longer) retracts also avoid stringing**. The tension control reuires a simple M5x10mm (knurled) screw + nut