First 5 mm trashed, but pristine after that

[roki]

Whatever I try to print, z=0..5 mm is always trashed, but after that the print is really nice. It doesn't matter whether I'm printing something small or big. My printer is a CR-10S with BondTech direct drive extruder & hot end upgrade. I'm using Atomic Filament CARBON FIBER Extreme Black PETG, with layer height 0.14, full part cooling fan starting on second layer.

This example is a box that is 45x30x20 mm.

Any ideas about where to start looking?

Thanks in advance!

[S3D-Alex]

Does this only seem to happen with this model or with other parts as well? Could you please post a Factory File so we can look into this more?

[roki]

Here is the factory file. BTW, I looked at the gcode, and the extrusion rate in the bad zone is the same in as in the good zone. Strange problem!

[roki]

I tried printing the same model with PLA and got the same result:

I figured it had to be something mechanical. The machine is on a low table, so I got a mirror and looked under the hot end. Here's what the sock looked like:

That blob of PETG & carbon fiber is about 5 mm tall. I pulled it off, and it prints like new again.

This reminds me of a problem I had with my MakerBot Rep 2 years ago. It was screwing up a print on only one side of a model because it had a blob on just that side of the nozzle. Anyway, I guess I need to get a little inspection mirror and keep it with the printer.