At first many 3D printer owners mistakenly believe their machine can “print anything”, but of course that’s not the case. Some shapes are definitely easier to print than others.
The first problematic geometry usually discovered is “overhangs”, where part of the object has no material underneath for support. If a cantilevered shape exceeds, say, 45 degrees or so, you may experience slumping or outright failure. Overhangs can be almost completely solved by using supports in your slicing program, but you’ll have to spend time to remove them. Depending on the slicing software, removal could be easy or exceedingly tedious.
Another problematic geometry is “thin structure”, as shown in the image above. Typically a large mass is to be supported by very small structures. Such non-robust shapes can permit wobble during printing that can sometimes lead to cracking and total failure, also evidenced above.
Read More at Fabbaloo