PVA/PLA material changes causing rough surface

[erind 0]

Hi guys,

I am having a few issues with the finish of my prints when using the dual extruder on the Ultimaker 3 Extended.

I have found that a small amount of material is left on the back right of the print as the head moves to change materials, leaving a rough finish which needs to be sanded off. As I will be doing a large amount of printing for this particular project, I would prefer to iron out any issues in the printing stage rather than doing tons of post-processing.

I am printing with Rigid.Ink's PLA and PVA, which works great on the main print. I have tried to print a tower to resolve the issue, but the PVA does not seem to want to stick to the PLA layer, leaving me with large strings of both filaments when the tower begins to fail. I get the same rough finish when printing without a tower in two PLA's.

Please see images for detail.

I am printing at:

AA & BB 0.8 print cores at 0.4 mm layer height.

PLA: Temp - 200, Speed - 35mm/s, Fan - 100%, Retraction - 7mm

PVA: Temp - 220, Speed - 25 mm/s, Fan - 100%, Retraction - 7mm

Bed: 60

Thanks in advance!

Erin