Weird bumps cylindrical hole

Question

Not quite sure what's happening here. I printed it as a single ball and had this effect. I thought it might be a cooling issue so I printed 4 at once but the issue still occurred. If I size the ball up, the problem reduces.

Note that the hole is supposed to be a cylinder.

Answer 1

It looks like possibly a combination of too high of extruder temperature and poor retraction.

1. First, try reducing your extruder temperature. PLA ideal extruder temps range from about 185C to 225C; depending on purity, quality, and climate. This can help prevent additional oozing and clogging. If your extruder clogs easily, you probably have too high of temperature.
2. After you've verified you have correct extrusion temperature. Try finding/adjusting retraction settings in your preferred slicing engine. Here's a good troubleshoot page from Simplify3D's website.

Answer 2

In order to exclude a cooling issue, you could try printing a larger object alongside the spheres. Something that has a constant cross-section and is at least as high as the spheres.

I have had issues when printing objects with a sharp tip, even printing 8 at once the total amount printed on the top layers was not enough to let the material cool before the next layer.

Answer 3

It looks like it is trying to fill in what might be small gaps and is putting blobs down because the gaps to too small of a detail to accurately fill.