Strange shrinkage issue

[Andrew G 0]

I have been a home printing hobbyist for some time but I am new to the world of Ultimakers. My company recently purchased an Ultimaker 3, mostly for printing enclosures for electronics and mounting brackets, and we've been having some strange issues with shrinkage near the base of our prints. The shrinkage seems to occur only for the thickness of the "roof" of the enclosure. I have experienced shrinkage and adhesion issues before and in my experience they are usually coupled together, but in this case we haven't had any adhesion problems nor curling at the corners. This particular part was printed in Hatchbox PLA at 215 C with a bed temperature of 80 C (though I get the same effect at 60 C). Layer height is 0.1 mm, perimeter thickness is 1.2 mm, 20% infill, all printing moves were done a 40 mm/s. I also ramp up the fan speed from 0 for the 1st layer to 100% for the 4th layer. I've tried altering the print temperature between 200 and 220, but that doesn't seem to affect the results. Has anyone had this problem and know how to fix it?

[fbrc8-erin 270]

Can we get a picture of the STL for comparison? I haven't printed with Hatchbox PLA but my initial thought is that 80 C is too high for PLA on the bed. 

[Andrew G 0]

Here is an image of the STL. I am running another print at 55 C bed temperature today to see if that shows any improvement.

[geert_2 557]

In addition to lowering the bed temp, also check if the cooling fans do come on correctly? Not on the first layer, but then they should gradually start, and blow full power after a couple of layers (at least, that is what they do on my UM2, and this works well).

 

[Andrew G 0]

Dropping the bed temperature to 55 C seems to have fixed the problem.