Until recently I was a little sceptical about dual extruding. Why would anyone want to have two extruders on their 3dprinter or prototyping machine?
Well, there is one great reason and that is for support structure which is soluble. Stratasys FDM machines come with dual extruders and they use a soluble support material which dissolves in caustic soda!
It has been documented that PVA filament if left in the open i.e. subject to humidity the properties of it change more dramatically than PLA. The PVA support filament swells, softens and generally goes more rubbery like. So obviously it is not going to fit through the nozzle and behave like an ABS or PLA filament.
I used my roll the first time out the packet and got good results on my Orcabots. I then shelved the material (in a sealed bag with desiccant) for a while. After getting it back out and feeding it through my new rapid prototyping machine it began to get stuck.
Unfortunately after trying the PVA support filament I discovered that it did not like the type of extruder that it was going through and got all tangled up. However it did work on a simple T piece shaped test part.
Here is a photo of my artistic results so far: