My class is attempting to print parts for a prosthetic hand for the hand challenge. We have already printed two complete hands and are currently attempting to print our third. This print has worked in the past but now we are having issues. In the center specifically, the plastic that was already extruded is getting caught by the nozzle as it passes through resulting in bubbles in the print. We have calibrated the printer multiple times but every time something gets caught. We thought maybe the nozzle was too high, the plate wasn't hot enough but the same thing keeps happening. How can we fix this?
We have the Ultrimaker 2+ and are using PLA filament.