Phantom Solid Layers??

[theturtle32]

This is turning out to be a problem I'm encountering with some frequency. It seems to be related to something about the mesh that Simplify3D doesn't like, as often times Cura and/or Slic3r will work with the same STL file just fine and – usually – running the STL through the online netfabb mesh repair service solves the problem.

The specific behavior I'm seeing is that S3D will generate – seemingly at random – solid layers where no such surface exists in the model. Usually this results in filament being extruded into thin air, sometimes bridging quite some distance. It creates a diaphragm (as a bridge) where none existed in the model.

I've seen this behavior with models that I've created and exported from Autodesk's 123D Design software, but today I'm seeing it with the stock, unmodified STL for 3dbenchy obtained from thingiverse.com.

I tried to run the 3dbenchy STL through the Netfabb repair service today but couldn't because it seems to be down. Tried using the repair options available in Netfabb free and meshlab to no avail.

Changing the layer height modifies where and whether the phantom diaphram bridges are generated, but eliminating them in this way is a trial-and-error process of guessing random numbers, and is really just obscuring the actual problem.

I've attached my factory file. I'm running Simplify3D 3.0.2

I've found one other report of this issue in the forum here: viewtopic.php?f=9&t=3444, but no true technical explanation of the exact nature of the problem, and no real solution (outside of the Netfabb service) provided.

Here are some screenshots:

[ianlee74]

I'm also seeing this quite regularly and its making some prints unprintable due to the weak layers where this is happening. The most recent example is when I try to print the "Heatwave" vase. With the spiralize option turned on, I get a weird base where it prints about half of a layer and then tries to print the other half of it in air in the next layer. I'm finding it harder to use S3D while this problem exists.

@theturtle32 - thanks for the tip on using Netfabb to repair. I'll give that a try.

[dkightley]

Here's my theory:
viewtopic.php?f=9&t=4995&p=21574#p21574

As for 3DBenchy......all you need to do is change the layer thickness from 0.2500 to 0.2501 and all is well.

[Paul M Smith]

I have used Microsoft 3D STL repair service to clean the STL and then had a close look at my settings. I was using multiple processes so it is easy to get a setting wrong. I seems S3D sometimes thinks it has to print a Top or Bottom layer into a void. Off course this is incorrect - but by tweaking my process settings - the 'bridge' is gone.

It raises the issue of better 'bridge' control. I am trying to print large (300 x 300 x 280) PLA models for Investment casting where material reduction is preferred but I want good quality surfaces. The close to horizontal surfaces are problematic with out a speed change AKA bridging unless i use infill - which is not required for structure or function here.
I would like to an auto bridging option that applied to surfaces within a user definable angle range. e.g. I want t to print ot take more care on those harder to print sections.
I do not see any way this can be done at present?
But I would be pleased to learn...