Holes in top layer of model, makes my students melancholy

[nmcafee]

I am running a Powerspec 3D Pro (private label clone of Flashforge Creator Pro) with 1.7 ABS, .2 layer height, 50 speed. I use maker desktop software. I am getting holes in the top of my prints. I just finished the pyramid below to check all of the flat surfaces a pyramid can offer. All of the parts print well except for the top. Things I have tried are

• Infill from 15% (my default) up to 70%
• Speed down to 30
• temperature from 225 to 240 in 5 degree increments
• minimum layer time of 15 seconds (from the default of 5)
• Cleaned nozzle to make sure there wasn't obstruction

Not much difference found from my changes. I have this problem across multiple models using multiple colors of filament. Things I have considered:

• Under extrusion. However, all surfaces other than top layer print fine.
• More fans? This model has a 40mm fan that blows on the hotend.

Any suggestions would be welcomed. Please help

.pyramid.jpg

[Alibert]

Either something strange in the STL file, or the slicer is making errors (assuming that the slicer settings are OK)?

Which slicer are you using?

[nmcafee]

Am using the built in slicer in MakerDesktop, they use makerbot slicer. I have tried different infills and layer heights to see if I could shake something loose in the slicer. Guess I could load replicatorG and see if that changes anything.

it does this on every model, not just a specific .stl file.

Nathan

[nmcafee]

Could it be something with X offset? Possibly raising the hot end between layers? Any feedback?