Contraction in diameter when printing cylinders

[ryanmandell 0]

Hi everyone. I've had my Ultimaker 2 for over a month now, but am just now pulling myself away from it long enough to join the users group. In general, I have to say that I'm very happy with the machine.

I have noticed an interesting phenomena on the lower portion of some of my prints and wonder if anyone has any suggestions as to what might be going on. When printing cylindrical forms a contraction occurs in the diameter of the cylinder at just about a 1/4" above the build plate (.1 layer height) and lower when printing at thinner layer heights. This is the case with both PLA and ABS.

Here are some pictures, I hope they load correctly (I'm new at this):

 

 

Any feedback would be greatly appreciated.

 

[illuminarti 16]

I think it's related to the fan coming on fully - you might try changing the fan settings in Cura's Expert Settings to start earlier or later, and see if that makes a difference. Also, try lowering the bed temperature a bit - the default temp for PLA is 75; several of us find that a bit too hot; try reducing that to 60ºC.

 

[ryanmandell 0]

That makes sense, I'll give it a shot. Thanks for the help.