I said I would update this thread with info about how this issue manifests with Cura. So here it is.
First off, the following models are one-half the linear size of the previous ones. The layer height is the same. But the 50% scale makes the blobbiness look worse than it is. I had to do it to cut the print time. But it’s going to be the relative quality that’s important.
Looking at the G-code generated by Slic3r and Cura, it looks to me like Cura makes a more continuous extrusion path, with fewer retracts and less non-extruding distance travelled. That’s good, and it shows. Here is the flower pot. Remember, in comparison to the previous pictures, the general surface quality looks worse than it is.
So you see some blobs here and there (not the holes), but not many. I think that’s because the extrusion path is so continuous that there are very few retracts. And when there are retracts/advances, half the time the advances are on an inner perimeter, and (because Cura really optimizes the path) the move before the advance is short.
But look what happens when you put four copies on the print bed.
I changed nothing in the Cura settings (except to print four). Now you see lots of blobs. That’s because each layer has a retract, followed by a long move to the next island, followed by an advance. Half the time Cura puts the advance on an inner perimeter. But that still makes a lot of blobs. Unfortunately, Cura doesn’t have an option for setting which perimeters you print first, inner or outer.
But Slic3r does. So compare the last picture (Cura) to Slic3r’s G-code for 4-up on the bed:
I tried to match the parameters (layer height, retraction distance, speeds, it’s basically the ABS fine config). But Slic3r gives you the option of printing exterior perimeters last. So that puts the blobs next to the infill where you can’t see it. The result is much cleaner, and although the pictures exaggerate the effect, you really can tell the difference with your naked eye.
So, I’m still hoping that somebody will chime in with “you dope, you’ve got your ________ set too _________,” and that will make all the blobs go away. But really, any ideas about this would be greatly appreciated! Thanks!