JPChauvel

So I’ve had my UM3 for a few weeks now and love it but have had a few clogs using the PVA material in the BB 0.4 print core. This became exceptionally annoying when printing something like Gyro the Dodo which takes days. One thing I noticed when the core clogs is that the PVA turns from a more translucent white color to a more opaque yellow and sometimes even brown color, clogging the nozzle and turning the PVA into an almost sandy grit. So I decided to look into the chemical properties of PVA and to my surprise I found that partially hydrolysed (reacted with water from the air) PVA will begin pyrolysis (chemical decomposition from high temperatures) at temperatures above 200 C and the UM3 default setting print temperature for PVA is 215 C. Since it would be a hassle to try to constantly keep the PVA dry even during printing I simply lowered the print temperature and have had pretty good luck with 205 C print temperature. There doesn’t seem to be any indication of under extrusion and the filament flows better and creates cleaner lines. According to the TDS for UM PVA filament it actually has a melting temperature of just 163 C but I think extrusion issues may result from temperatures lower than 195 C especially with higher print speeds.