Warping, poor bed adhesion, or both.
Cheerio,
RE: Bad top layer
That had not occurred to me. Would the mechanism be that the lower left corner raised up a little and the hot end is plowing through the previous layers? It looked like improper extrusion to me.
Yes, that would do it.
The first effect on warping is that the area of the upper layer reduces slightly and the filament for the intended area has to ripple up to fit ... then if the warping increases you do get plowing. If the curl gets high enough it can cause a head crash which might knock the print off the sheet - or it might cause the print head to lose it's position resulting in layer shift.
Cheerio,
RE: Bad top layer
Thanks for your help!
RE: Bad top layer
Redo with a full coat of glue stick came out fine. You were right.
Warping, poor bed adhesion, or both.
Cheerio,