Separation of layers in middle of print  

RE: Separation of layers in middle of print

A few possible causes:

1. Excessively high layers for your nozzle size. Ideally, you want to keep layer heights below 80% of your nozzle size. Any higher and you start to get extrusions with a circular cross-section and little squish with the layer underneath. This can result in poor inter-layer adhesion. I can't make out what layer height you're using from the pic, but it's worth verifying.
2. Excessive speed. The filament needs some time to fully bond with the underlying layers. This may be accompanied by under-extrusion on long straight extrusions.
3. Excessive cooling/insufficient heat.  Try reducing cooling first. Increasing heat can also introduce stringing, but adding 5-10C may help.

Those are the things I usually check. If you save your part & settings off in a 3MF project file, zip it up, and attach it to a reply here, we can check other settings for possible suggestions.

RE: Separation of layers in middle of print

@bobstro

Thanks. I will try to reduce cooling and slow the speed. I don't think it was a layer size issue, since I was doing 0.2mm layers with a 0.4mm nozzle. But to be honest with you, I also suspect the filament. I've been having other weird things happen with this filament that I haven't seen in the past.