Object structure changes depending on the geometry, possibly Cura problem

[musti 0]

Hi all,

I am using a home built ultimaker with E3D print head, using ABS from reprap.cc printing at 230deg with 10% infill and 2mm walls.

All the objects I am printing appear to have the following problem:

Surface finish is significantly degraded, some small gaps and blobs appear, when the object does not have a continuous circumference on the layer. As you can see on the very simple object shown in pictures, first 10mm of the object have a very nice finish, because the base is a solid rectangle, with a gap in one side when higher then 10mm. Having such a gap causes the beforementioned problem.

This is consistent with the geometry properties, is not random and appears with different spools of material.

Any ideas how to solve it?

 

[gr5 898]

There could be many things causing this and I'm not sure which it is, but a lot of the time you can get a better surface by slowing down.

Try printing 1/2 speed you are printing now to see what happens. The bowden tube tends to store pressure like a spring. So when the print head slows down, and the extruder slows down at a corner, the printer tends to overextrude approaching the corner and underextrude just past the corner. So this is one possible cause.

Another possibility is that even though you asked for 2mm walls, in certain areas with those holes running through the corners, Cura may have been confused about how to fit 5 passes around the holes and another 5 passes along the side. It usually handles this just fine - I've even asked for 100mm skin and it usually works fine. But still. Try another slicer. Possibly Cura 13.04 which has a completely different slicing engine (but mostly the same settings so there is almost no learning curve). Or kisslicer.

Older Cura's here:

http://software.ultimaker.com/old/