[Solved] spiderweb-like strings nylon with no movement between parts

[johnse 31]

I printed a simple open container with nylon. Walls are 1.6mm thick (.4 nozzle, 4 walls--no infill), so the nozzle never moves over open space--the usual culprit for stringing.

 

I'm wondering what might be causing this. I'm attaching the Cura project as well. This was printed on a UM3 with Ultimaker Nylon.

 

In further processing it, I noticed that there was a fair amount of "hair" on the outside as well. Also, the first time I printed this model, the same kind of webbing appeared, but it also did occasional infils--just on the apex of the corners and in just a portion of the walls. I'm including that project file as well (the -nofill project is the one shown here). The one printed with no infil has poor adhesion between the inner walls. The inner-wall to outer wall seems fine.

 

So in the case of the one where fill is not turned off, I'm wondering why it only did the infill in very limited portions of the walls. The model was created in Fusion360 by creating a solid with the correct outer shape and then using the "shell" command so the walls should be consistently 1.6mm thick.

 

UM3_suetmold-nofill.3mf

UM3_suetmold.3mf

Edited June 19, 2019 by johnse

[johnse 31]

This was one of two issues (or a combination of both).

 

My nylon may have gotten a little damp. I store it in a drybox, but haven’t yet built one I can print from. RElative humidity in the house sits around 50%. So I dried the filament overnight sitting on the build plate at 90c with a towel over it. I used the towel to pick up the roll and put it directly to the drybox to cool.

 

i also realized that we had some warm days that caused the AC to kick on. There is a vent in the ceiling right above my printer. I recalled reading how drafts can be a problem with nylon.

 

So I made a front cover and put a box over the top. The print came out beautifully! No hairs and very consistent finish.