Anyone who has fought a clogged hotend knows the drill: you run a cleaning filament, hope for the best, and never really see what is happening in there. A soft pull is, according to the maker, a good way to clear buildup inside the hot end, and Masters of the 3rd Dimension has built a clever way to make the invisible visible. By slicing a real hotend assembly open lengthwise, the whole process can be watched from the inside, which is something I have not seen done this way before.
The build itself is nicely done. A red anodized aluminum finned heatsink sits on a metallic heater block, and the block is cut open to expose its internals. The brass nozzle is partially sliced too, revealing its cavity and threads, and a blue PTFE guide tube is split lengthwise with white filament seated inside it. A threaded metal heatbreak lined with white PTFE tubing completes the picture, and the whole assembly is held upright in a clamp on a workbench. Wires in red, yellow, and white sheathing with Kapton tape are held by a metallic alligator clip tool, a tidy touch.
The demonstration itself is the payoff. White PLA is slowly pulled at 90 degrees Celsius, and blue filament filling the cutaway nozzle and lower heatbreak chamber slightly melts and bubbles as heat is applied. The strand shows irregular diameter variations, with swollen and thin stretched sections. The maker reports the pull removed black junk even from a clean nozzle.
One open question for me: since the demo used a clean nozzle, whether a soft pull clears a truly stubborn jam is not shown. Also, 90 degrees seems quite warm for something called a cold pull.
Project by Masters of the 3rd Dimension. Watch it on their YouTube channel: