Can excess filament cause curl?

I've been printing these models successfully for some weeks, 2.8mm PLA on a simple blue tape on glass bed, unheated. ( Prusa mendel, 3mm J-head)
This is the way it is supposed to look These are going to be used as focal points in a high-stakes fundraising campaign being run by a local Knight (I kid you not, checkout medicinemondiale.org , Infant Incubator )




Last night - they started crashing out horribly.

It has started curling up at the front end - sufficiently to pull up the blue tape. I've never run into that in several months printing.
As it curls, the nozzle starts running into the previous layer down that end, and in the overnight print pictured below dragged the glass plate sideways..

This was on a new roll of PLA - now it has always been very consistently 2.8mm from this supplier, but on a hunch I measured it,
and it's now about 2.95mm on multiple measurements.
So I'm guessing that it was not only the curl that caused the head to run into the previous layer, but excess plastic that caused a buildup.

I've re-sliced with adjusted filament Diameter - but it's a 3 hour print (I guess an hour before I'll know if it's going to curly fatally or not)

So I thought it worth getting the question out there - could that excess plastic contribute to making the curl strong enough to tear up the blue tape? (which on the many of the same model I've printed over the last few weeks, it has not done so)

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How it's not supposed to .look.



The base few mm that start to crash the nozzle





Edited 5 time(s). Last edit at 07/06/2012 09:37PM by nb99.