One very common mistake that happens during the print may not actually be an issue with the printer or software – it may be with the model itself. Since we are often sent files that we did not design, it is mandatory that every model be checked for the ability to be printed.
One extremely common model error is having a wall too thin or non existant. A printer will only print the wall of a print if it is thicker than the nozzle diameter. And with that said, we always suggest walls be at least 3 times thicker than the diameter of the nozzle. It is best to figure out if this is going to be a problem while in your slicing program. Take the print layer by layer to make sure there are no gaps. The same is true for the thickness of the bottom and top walls.
Holes in Model
Individuals will often try to save time by converting a 2D object into a 3D field and expect this to print properly. While these 3D objects look good to the eye, the printer will not recognize the walls as anything but non-printable 2D faces. One easy way to tell if this problem exists on your print is to drag into a program like Netfabb and check for anything highlighted red that can be repaired.
There can also be actual holes in the model just as there are flat faces. Often these can be very hard to notice on a slicing program and you won’t even know until the printer head gets to that section.
Angles and Limitations
As explored in Understanding Limitations, there are some things that are just not printable on an FDM 3D printer. A mostly enclosed structure that requires support may not have an exit for that support material to be removed. Extreme angles and lack of flat surface touching the build plate can cause ugly surface quality on most materials.