Missing Filament at Layer Start after Bottom/Top Layers

[Evil Knievel]

I find a fairly strange behaviour when printing from simplify3D:

Parameters are:
Bottle model, about 240mm high, printed in 1 perimeter with 1.2mm nozzle, 20mm/s, 0.4mm Layers, but the problem also occurs elsewhere (more perimeters, smaller nozzle, smaller layer height etc.):
The part is printed with 3 bottom layers and 3 top layers, no infill, no support.
The part prints fine, retractions work fine with speed and temperature.

At some points (very small overhangs) in the middle of the bottle, simplify adds very small top and bottom layers, strange enough, but it does not bother me. But every time, after these small bottom/top layers are printed and the nozzle prints the next regular perimeter, it misses out the first 4-6mm and results in a strong gap (see pic below). I tried all retractions settings, nothing solves the problem. All normal travels between islands (there are several travels in the model) or layer change retractions work fine, as said. The problem only occurs after printing bottom/top layers.

Any ideas?

[JoeJ]

Are those gaps also present in the preview? They look like they're occurring right around your start points. Perhaps due to excessive coasting or too high of a retraction speed.

[Evil Knievel]

Yes, in the preview they are closed and yes, they are occuring around the starting points. But only, if there were these "mini top or bottom layers" printed before. Normal starting points (also after travel moves) are fine.
I believe, the important question is, if you can somewehere switch off the "mini top layers/mini bottom layers".
I attached a screenshot of these mini layers, because I believe, that this mini-printed-dots create a kind of double retraction.

[JoeJ]

Hah, yeah that does not look like a good way to print that part. You should adjust the settings to only do a single outline. There's a couple ways to do this. Post the factory file and it will be easier to give suggestions

[Evil Knievel]

Yep, I am happy to send you the factory file, but:
- I am doing this with one outline
- I can´t do a corkscrew, as I have a handle (islands), furthermore, corkscrew does not look to well with 0.4mm layers
- I need to keep bottom and top layers as a kind of "stabilizer" for the bottom of the handle, as I can not put support inside the bottle

The strangest thing about that is, that this only happens after printing top and bottom layers. It does not happen after normal travel moves.

Will send the factory file as pm.