Extrusion resistance abnormal automation

While printing TPU, many extrusion resistance abnormal errors occur due to how soft the material is being pushed. (Even using HF nozzles, dry material, exclusively using only TPU though the nozzles, it’s inevitable to get the errors)

This is normally fixed easily if you are at the printer, by going into manual extrusion buttons and going up, then down. Repeating this until it flows freely, then resume print.

While away from the printer, it is much more difficult. You have to be careful not to extrude up too far, losing the filament completely. The buttons don’t give you any indication whether they are working up or down, and how much. And you can’t see the camera while operating the buttons. It still can be achieved sometimes by this method, but improvements to make the manual method better would be great.

Even better though, would be an automation that would kick in when the extrusion resistance abnormality occurs. It could be much more precise and controlled if it were automated. Even if it only tried for a number of times or minutes. But since the printer knows when resistance is there, it should also be able to tell when it’s extruding and resistance is normal, that printing can be resumed.

Using extrusion resistance as the indicator that it’s time to kick in isn’t the solution; by the time there’s resistance pressure will already have dropped in the nozzle and underextrusion will be occurring. It’s just not the right feedback signal.

Consider why extrusion issues happen with TPU in the first place, whereas other filaments have no issues. It’s the high tensile strength of the filaments; the extruder can pull the filament and overcome a lot of friction in the feed path. With TPU, the filament is too stretchy, and rather than pulling through the filament just gets stretched to the point of necking or breaking entirely. The solution is to overcome the feed resistance issues, not just keep pulling via the extruder motor until it feeds properly again.

Based on that don’t think a software-based solution is ever the right answer.

Check out the TPU assist module, it is a good solution to this problem, although it does have some shortcomings as well.