ABS Warping

The two types of plastic commonly used in 3D printing are PLA and ABS. PLA is more brittle and hence a little less strong than ABS, which is what LEGO bricks are made of. Working with ABS, however, has a few more issues than PLA.
The biggest issue is the thermal contraction of the plastic after extrusion. As an example, consider the part shown here (a SmartPhone tripod mount).

Printing with PLA is no problem, but printing with ABS yields a part that is curved like a banana. The photo shows the PLA part (back) and the ABS part (front).

You can see that the plastic on the bottom layers has separated from the printing platform due to the stress of the cooling plastic in the layers above it. It's the same reason that leaves curl up when they dry out. There are a number of ways suggested to fight warping and curling. Most sites suggest a heated bed, which is an extra cost, non-standard item for the Ultimaker. Maybe later.

I first wanted to try design with mouse ears. This only works if you have the source file and not just the STL file so you can manipulate the solid model. This is one of my pet peeves with Thingiverse, most things only have the STL files. I predict that in 3 years, Thingiverse will be considered a junk yard and obsoleted by a site that requires solid models. But I digress.

Adding small ears to the part, and it looks like this.

This only ameliorates the problem. The part edges still lift from the bed while printing.

Oh well. Back to PLA I think.